Functions and disease of the Heart

Functions and disease of the  Heart

Heart is a central pumping organ.It receives pumps out blood to the whole body.
1.Shape:Conical or roughly heart shaped.
2.Size:12cm from base to apex.
        6cm antero-posteriorly.
 
Situation:Situated in the middle mediastinum in between the two lungs,obliquely placed behind the body of sternum and the cartilages:about one third of it is on the right side and two third of it on the left side on the middle.

Explain:During diastole of heart,cardiac muscles are relaxed,intramural tension decreases and coronary blood vessels are less compressed.So,blood can easilyenters into coronary vessels and supply blood.On the other hand,during systole,due to increase cardic muscular tension,coronary vessels are compressed.So,heart gets its blood supply during diastole

Fuction of valves:Valves help in the flow of blood in one direction.Prevent regurgitation of back flow of blood by their direction during opening and closure.They are concerned with the production of heart sound.

Syncytium: It means a group of cells in which the protoplasm of one cell is continuous with that of adjoining cells such as the mesenchyme cells of embroys, striated muscle fibre.Heart muscle cells are large and branching.They are connected to each other by angulated dark areas crossing the cardiac muscles fibre are called intercalated discs; however, they are actually cell membranes that separate individual cardiac muscle cells from each other. That is cardiac muscle fibres are made up of many individual cells connected in series with each other the intercalated disc exerts a very little resistance, which resembles that there is no membrane fuse with each other and from very permeable junctions that allow relatively free diffusion of ions.
Therefore,from a functional point of view,ions move with ease along the axes of the cardiac muscle fibres so that action potentials travel from one cardiac muscle cell to another, past the intercalated dises, with only slight hindrance.Therefore, cardiac muscle is a syncytium.The heart is composed of two separate syncytiums; the atrial syncytium that constitute the walls of two atria and the ventricular syncytium that constitute the wall of two venticule.      

Heart sound:The vibration of the taut valves immediately motion of heart produced during the different events of cardiac cycle conducts through the structure surrounding the heartand produces special audible sound called heart sound. Classification of heart sound:Heart sound is classified into four in number

First heart sound:It is a low,slightly prolonged lub caused by vibrations set up by the sudden closure of the mitral and tricuspid valves at the start of ventricular systole.
Duration:About 0.15 second.
Fequency:24-45 Hz.
It is soft when the heart rate is low,beacuse the ventricles are well filled with blood and the leftlets of the AV valves float together before systole.The vibrations travel through the adjacent tissues to the chest wall,where they can be heard as sound by the stethoscope.

second heart  sound:It is a shorter,high-pitched dup caused by vibration associated with closure of the aortic and pulmonary valves just after the end of ventricular systole.
Duration:About 0.12 second.
Frequency:50 Hz
It is loud and sharp when the diastolic pressure in the aorta or pulmonary artery is elevated,causing the respective valves toshut briskly at the end of systole.The interval between aortic pulmonary valve closure during inspiration is frequently long anough for the second sound to be reduplicated.

Third heart sound:A soft,low -pitched third sound is heard about one-third of the way through diastole in many normal young individuals.It coincides with the period of rapid ventricular filling and is probably due to vibration set up by the inrush of blood.
Duration:The third sound has a duration of 0.1 second.

Fourth heart sound:It can sometimes be heard immediately before the first sound when atrial pressure is high or the ventricle is stif in conditions such as ventricular hypertrophy.It is due to ventricular filling and is rarely heart in normal adults.

What is heart block?

Occasionally transmission of the impules throgh the herat is blocked at a critical point in the conduetive system is called heart block.

Classification or types of heart block:There are three types of heart block-
1.Sinno-atrial heart block.Atrio-ventricular (A-V) heart block.Bundle branch block and hemi block.

Describe A-V type of heart block
Definition:When comduction of impules between atria and ventricle is blocked.
cause:Localized damage depression of A-V node..Excessive stimulation of vagus nerve..Localized destruction of AVbundle as a result of coronary infract.Pressure on the AV bundle by arteriosclerotic paques.Depression caused by various drug. Dgrees of AV heart block :First dgree heart block:All atrial impulses reaches the ventricle  but the P-R interval is abnormaly long. 2nd degree heart block:Not all atrial impulses are conducted to ventricles.There may be,for example,a ventricles brst following every second or every third atrial beat.Complete heart block:When no impules passes from atria to ventricle.It causes the"droped beat".Here the atrial rate is faster then the ventricle,for this reason, ventricle escape from the control of atria.  
Stokes Adams syndrome:When AV block occurs that is, when the cardiac impulse fails to pass from the atria into the ventricles through the AV nodal and bundle system-the atria continue to beat at the normal rate of rhythmof the sinus node, while a new pacemaker develops in the purkinje system does not minute at a new rate somewhere between 15 and 40 beats per minute.After a sudden block, the purkinje system does not begin to emit its rhythmical impulses until 5 to 30 seconds later because, before the blockage, the purkinje fibers had been ''overdriven'' by the rapid sinus impules and consequently, are in a suppressed state .
During these 5 to 30 seconds, the ventricles fail to pump blood, and the person faints after the first 4 to 5 seconds because of lack of blood flow to the brain.This delayed pick up of the heart beat is called stokes adams syndrome. If the delay period is too long it can lead to death.   


In bundle branch block:The duration of QRS is more than 0.11 second.Ppresence of RSR(in V1) pattern denotes right bundle branch block.Whereas a slurred and broad QRS in V5 and V6 denote left bundle branch block. Bundle of his block: Here the conduction of impules from AV node to bundle of his is impaired.It may be right or left bundle block.

SA Heart block :Here SA node fails to generate or fail to transmit the impules from SA node to the atrial muscle.
Causes:1.Over vagal stimulation.Vasovagal syndrom.Severe myocardial diseases.           

Blood pressure

Blood pressure

It is lateral pressure exerted by the moving column of blood on the vessel wall per unit area by(sq. mm) by its contained blood while flowing through it.
Blood pressure=Cardiac output x peripheral resistance.

Importance of blood pressure :
1.It is essential for the flow of blood through the circulatory tree.
2.It provides motive force for filtration at the capillary bed which is essential for-
a.Tissue nutrition
b.Formation of urine
c.Formation of lymph
d.For venous return.

Lateral pressure

It is that pressure when forces is exerted at right angles to the direction of flow as any point within a tube filled with a circulation fluid.

Basal blood pressure : It is lowest pressure necessary in main-taining blood flow sufficient for needs of the body.

Causal blood pressure:Any pressure that is recorded under ordinary circumstance of life is known as the causal blood pressure.

Physiologial variation of blood pressure
   1year: 80/40  mm  of  Hg
 3year:100/60   mm  of  Hg
20year:120/80  mm  of  Hg
45year:145/90  mm  of  Hg
70year:170/95  mm  of  Hg

sex:In female,the blood pressure is slightly lower(5 mm of Hg),cause is unknown.After enopause,it reaches male lavel .

Exercise:In strenuous exercise, the systolic pressure rises,even up to 180 mm of Hg. In moderate exercise, it slightly rises.Posture:During  standing, diastolic pressure is slightly higher;systolic pressure low.In recumbent position,this condition is reversed.    
During sleep:During deep sleep, there is fall of blood pressure by  15-20 mm of Hg.
Emotion and excitement:Raises systolic pressure considerably.                

What is shock?

It is an abnormal physiological condition resulting from inadequate propultion of blood to the aorta thus causes inadequate blood flow perfusing the capillaries of tissues and organs.
Tissue necrosis in severe shock : Not all cells of the body are equally damaged by shock because some tissues have better blood supplies than others . For instance, the cells adjacent to the arterial ends of capillaries receive better nutrition than the cells adjacent to the venous ends of the same capillaries. Therefore, one would expect more nutritive deficiency around the venous ends
of capillaries than elsewhere. For instance necrosis in the center of a liver lobule, the portion of the lobule that is last to be bathed by  the blood as it passes through the liver sinusoids. Similar punctate lesions occur in heart muscle, although here definite repetitive pattern, such as occur in the liver, cannot be demonstrated. Neverthless, the cardiac lesions play an importent role in the leading to the final irreversible stage of shock. Deteriorative lesions also occur in the kidneys, especially in the epithelium of the kidney tubules, leading to kidney failure and occasionally uremic death several days later. Deterioration of the lungs also often leads to respiratory distress and death several days later - called the shock lung syndrome.     

Haemorrhage : It means abnormal internal or external discharge of blood. It may be arterial , venous or capillary.Arterial blood is bright red ; flows in spouts . Capillary blood is of a reddish colour ; exudes from tissue. Venous blood is dark red ; flow is continue.    

Hydrostatic pressure : Hydroststic pressure is the pressure which is caused by the effects of gravity ona a fluid filled system i.e it occurs as a result of the weight of the blood in the vessels.

Vascular endothelium : The walls of the blood vessels are made up of a single layer of endothelial cells. Endothlium occupies a stategic interface  between blood and body. The endothelial lining varies from organ to organ.

Regulation of blood pressure:Two major types of arterial pressure control system in the body-
1.Nervous mechanism.
2.Humoral mechanism.

1.Nervous mechanism :
Has two different types-
a.Short terms regulation: Occurs within seconds to minutes.

Mechanism occurs within seconds:

*Baroreceptor feed back mechanism.
*Chemoreceptor feed back mechanism.
*Central nervous system ischemic mechanism.

Mechanism occurs within minutes:

* Renin angiotensin vasoconstrictor mechanism.
*Capillary fluid shift mechanism.
*Stress relaxation changes in vasculature.

b.Longterm regulation:
1.Renal body fluid mechanism.
2.Renin angiotensin mechanism.

Humoral regulation:
a.Epinephrin-norepinephrin mechanism.
b.Vasopressin vasoconstrictor mechanism.
c.Renin angiotensin aldoterone mechanism.


Hypertension:
Definition: Hypertension is a clinical condition characterized by persistance rise of blood pressure  above
the normal range in respect of age and sex.Hypertension occurs when diastolic pressure is great than 90 mm of Hg and systolic pressure is above 150 mm of Hg. Hypertension is an increase in mean blood pressure that is usually chronic and is common in humans.Hypertension can result in serious health consequences if left untreated. The majority of hypertension is of unknown cause, but several gene mutations underlie rare forms of the disease and are informative about mechanisms that control the dynamics of the circulatory system and its integration with other organs.     

Type: Hypertension are two types-
1.Primary or essential hypertension.
2.Secondary hypertension.

Essential hypertension: When arterial blood pressure persistently exceeds 150/90 or 160/100 mm of Hg.Its causes is unknown.It is of two types-
a. Benign form: In the early stages the hypertension is moderate, e.g. 210/110 mm of Hg.
b.Malignant form: The condition is so named because death occurs within months to 2 years of its first ecognition.The BP is much higher than in the benign form e.g. 260/150 of Hg.

Secondary hypertension: It is due other diseases, as renal diseases,phaeochromo-cytoma, by excess secretion of  glucocorticoids or aldosterone, by coarctation of aorta.Volume loading hypertension:Hypertension occurs due to excess extracellular fluid volume .It is due to excess salt intake or salt retension from kideny.Vasoconstrictor hypertension: It is due to continuous infusion of vasoconstrictor agent into blood or by  excessive secretion of  vasoconstrictor from endocrine gland.The vasoconstrictors are-
1.Angiotension-II
2.Norepinephrine.
3.Epinephrine.  

The cranial cavity

 The cranial cavity

Cranial cavity, the highest placed cavity, contains the brain, meninges, venous sinuses, all cranial nerves, four Petronella nerves parts of internal carotid artery and a part of the vertebral artery besides the special sense. The anterior branch of middle meningeal artery lies at the criterion and is most likely to be ruptured resulting in extramural hemorrhage. The convex upper wall of the cranial cavity is called the vault. It is uniform and smooth. The base of the cranial cavity is uneven and present three cranial Fosse ( anterior, middle and posterior ) lodging the uneven base of the brain. The  cranial cavity contains the brain and meninges; the outer dura mater, the middle arachnoid mater, and the inner Pia mater.The Duran mater is the thickest of the three meninges. It encloses the cranial venous sinuses, and has a distinct blood supply and nerve supply. The dura is separated from the arachnoid by a potential subcultural space. The arachnoid is separated from the Pia by a wider sub arachnoid space filled with cerebration fluid (CPS). The arachnoid, Pia Subaru arachnoid  space and CS F are dealt with the brain; the aura is described here.

Tentorium cerebellar : The tentorium cerebellar is a tent-shaped fold of dure mater, forming the roof of the posterior cranial Foss. It separates the cerebellum from the occipital lobes of the cerebrum, and broadly divides the cranial cavity into supranational and extraterritorial compartment, in other words,is the posterior cranial Foss containing the hind brain and the lower part of the mid brain. The tentorium cerebellar has a free margin and an attached margin. The anterior free margin is U-shaped and free. The ends of the 'U' are attached anterior to the anterior to the anterior Clinton processes. This margin bounds the territorial notch which is occupied by the mid brain and the anterior part of the superior vermin. The outer or attached margin is convex. Collaterally, it is attached to the lips of the transverse Dulci on the occipital bone,and on the posteroinferior angle of the parietal bone.Collaterally it is attached to the superior border of the troupes temporal bone and to the posterior Clinton processes. Along the attached margin there are the transverse and superior Petronella venous sinuses. The germinal or mackerel's cave is a recess of dare mater present in relation to the attached margin of the tentorium. It is formed by imagination of the inferior layer of the stentorian over the germinal  impression on the troupes temporal bone.It contains the germinal ganglion.The free and attached margins of the stentorian cerebellar cross each other near the apex of the troupes temporal bone. Anterior to the point of crossing, there is a triangular area which forms the posterior part of the roof of the cavernous sinus, and is pierced by the third and fourth cranial nerves.

Straight sinus : The straight sinus lies in the median plane within the junction of flax cerebra and the stentorian cerebellar. It is formed anterior by the union of the inferior Sagittarius sinus with the great cerebral vein, and ends at the internal occipital protuberance by continuing as the transverse sinus usually left.In addition to the veins forming it,it also receives a few of the superior cerebellar veins. At the termination of the great cerebral vein into the sinus, there exists a ball valve mechanism, formed by a sinusoidal plexus of blood vessels, which regulates the the secretion of CSF.

Other sinuses

The occipital sinus is small, and lies in the attached margin of the flax cerebellar. It begins near the foreman magnum and ends in the confluence of sinuses.The phenobarbital sinuses, right and left lie along the posterior free margin of the lesser wing of the spheroid bone, and drain into the anterior part of the cavernous sinus. Each sinus may receive the frontal trunk of the middle meningeal vein. The superior Petronella sinuses lie in the anterior part of the attached margin of the stentorian cerebellar along the upper border of the troupes temporal bone. It drains the cavernous sinus into the transverse sinus.The inferior Petronella sinuses right and left lie in the corresponding petrol-occipital fissure, and drain the cavernous sinus into the superior bulb of the internal jugular vein. The Basil plexus of veins lies over the Clausius of the skull.It connects the two inferior Petronella sinuses and communicates with the internal vertebral venous plexus. The middle meningeal veins form two main trunks, one frontal or anterior and one parietal or posterior, which accompany the two branches of the middle meningeal artery. The frontal trunk may end either in the pterodactyl plexus through the foreman oval, or in the phenobarbital or cavernous sinus. The parietal trunk usually ends in the pterodactyl plexus through the fore- men Spinoza. The meningeal veins are nearer to the bone than the arteries, and are, therefore, more liable to injury in fractures of the skull. The anterior and posterior inter cavernous sinuses connect the cavernous sinuses. They pass through the diaphragms Sella, one in front and the other behind the incunabulum.

Middle meningeal artery          
The middle meningeal artery is important to the surgeon because this artery is the commonest source of extramural hemorrhage,which is an acute surgical emergency. The artery is a branch of the first part of the maxillary artery, given off in the infra temporal Foss. In the infra temporal Foss, the artery runs upwards and medially deep to the lateral pterodactyl muscle and superficial to the mandibular ligament.Here it passes through a loop formed by the two roots of the horticulturalist nerve.It enters the middle cranial Foss through the foreman Spinoza.In the middle cranial Foss,the artery has an extramural course, but the middle meningeal veins are closer to the bone than the artery. Here the artery runs forwards and laterally for a variable distance, grooving the squamous temporal bone,and divides into a frontal and parietal branch.The frontal or anterior branch is larger than the parietal branch.First it runs forwards and laterally towards the lateral end of the lesser wing of the spheroid. Then it runs obliquely upwards and backwards, parallel to, and a little in front of the central succubus of the cerebral hemisphere. Thus after crossing the criterion,the artery
is closely related to the motor area of the cerebral cortex. The parietal or branch runs backwards over, or near,the superior temporal calculus of the cerebrum, about 4 cm above the level of the zygotic arch. It ends in front of the posterior angle of the parietal bone by dividing into branches.

Pestrosal nerves
The greater Petronella nerve carries gustatory and parasympathetic fibers.It arises from the gesticulate ganglion of the facial nerve, and enters the middle cranial Foss through the hiatus for the greater Petronella nerve on the anterior surface of the troupe temporal bone. It proceeds towards the foremen lace rum, where it joins the deep Petronella nerve which carries sympathetic fibers to from the nerve of the pterodactyl canal. The nerve of the pterodactyl canal passes through the pterodactyl canal to reach the interpolation ganglion. The parasympathetic fibers relay in this ganglion.Post ganglionic parasympathetic fibers arising in the ganglion ultimately supply the lacrimal gland and the mucosa glands of the nose, palate and pharynx.The gustatory or testes fibers do not relay in the ganglion and are distributed to the palate.The deep Petronella nerve,sympathetic in nature,is a branch of the sympathetic plexus around the internal carotid artery. It contains post ganglionic fibers from the superior cervical sympathetic ganglion. The nerve joins the greater Petronella nerve to from the nerve of the pterodactyl canal.The sympathetic fibers in it are distributed through the branches of the interpolation ganglion. The lesser patrol nerve, parasympathetic in nature, is a branch of the tympani plexus, deriving its ganglion parasympathetic fibers from the tympani branch of the pharyngeal nerve.It emerges through the pharyngeal nerve.It emerges through the hiatus for the lesser Petronella nerve, situated just lateral to the hiatus for the greater Petronella nerve, passes out of the skull through the foreman ovals, and ends in the optic ganglion. Post ganglionic fibers arising in the ganglion supply the Pavarotti gland through the horticulturalist. The external Petronella nerve, sympathetic in nature is an inconstant branch from the sympathetic plexus around the middle meningeal artery to the gesticulate ganglion of the facial nerve.

Dissection : Detach the cranial neurosis if not already done laterally till the inferior temporal line. In the region of the temple, detach the temporal is muscle with its overlying fascia and reflect these downwards over the pinny.Draw a horizontal line across the skull 1cm above the orbital margins and 1cm above the union. Saw through the skull. Be careful in the temporal region as skull from the fused endmost and Duran mater. To remove the brain and its enveloping meninges; the structures leaving or entering the brain through various for amine of the skull have to be carefully detaching flax cerebra from the Crista galls. Put 2-3 blocks under the shoulders so that head falls backwards. This will expose the olfactory bulb, which may be lifted from the underlying anterior cranial Foss. Identify optic nerve,internal carotid artery,incunabulum passing towards hypothesis cerebra. Divide all three structures. Cut through the locomotion and cochlear nerves in relation to free margin of stentorian cerebellar.  

The eye ball

The eye ball

Sense of sight appreciated through retina of the eyeball is one of the five special senses. Its importance is obvious in the varied ways of natural protection. Bony orbit, projecting nose and various coats protect the precious retina. Each and every component of its three coats is assisting the retina to focus the light properly. Lots of advance have been made in correcting the defects of the eye. Eyes can be donated at the time of death, and a ''will'' can be prepared accordingly.Eye sees the out side world. The inside of the eyeball can be seen through the ophthalmologist where by health of small vessels can be visualized in normal subjects, in diabetics and in hypertensive individuals. About 75% of afferent reach the brain through the eyes. Adequate rest to eye muscles is important.Could a good place for rest be the classroom where palpable part of orbicular is oculist closes the eyes gently? The eyeball is the organ of sight. The camera closely resembles the eyeball in its structure. It is almost spherical in shape and has a diameter of about 2.5 cm. It is made up of three concentric coats. The outer of fibrous coat also called the uveal tract consists of choroid, the cilia body and the iris. The inner or nervous coat is the retina. Light entering the eyeball passes through several refracting media. From before backwards these are the cornea, the aqueous humor, the lens and the vitreous body.             

Scleroses

The sclera (skleros=hard) is opens and forms the posterior five-sixths of the eyeball. It is composed of dense fibrous tissue which is firm and maintains the shape of the eyeball. It is thickest behind, near the entrance of the optic nerve, and thinnest about 6 mm behind the sclerocorneal junction where the recti muscles are inserted. However,it is weakest at the entrance of the optic nerve. Here the sclera shows numerous perforations for passage of fibres of the optic nerve. Because of its sieve-like appearance, this region is called the lamina cribrosa (crib=sieve).The outer surface of the sclera is white and smooth, it is covered by tenon's capsule. Its anterior part is covered by conjunctiva through which it can be seen as the white of the eye. The inner surface is brown and grooved for the ciliary nerves and vessels.It is separated from the choroid by the perichoroidal space which contains a delicate cellular tissue, termed the suprachoroidal lamina or lamina fusca of the sclera. The sclera is continuous anteriorly with the cornea at the sclerocorneal junction or limbus. The deep part of the limbus contains a circular canal known as the sinus venosus sclerae or the canal of schlemm. The aqueous humour drains into the anterior scleral or ciliary veins through this sinus.   

Iris

This is the anterior part of the uveal tract. It forms a circular curtain with an opening in the centre, called the pupil. By adjusting the size of the pupil, it controls the amount of light entering the eye, and thus behaves like an adjustable diaphragm. It is placed vertically between the cornea and the lens, thus divides the anterior segment of the eye into anterior and posterior chambers, both containing aqueous humour. Its peripheral margin is attached to the middle of the anterior surface of the ciliary body and is separated from the cornea by the iridocorneal angle or angle of the anterior chamber. The central free margin forming the boundary of the pupil rests against the lens.The anterior surface of the iris is covered by a single layer of mesothelium,and the pigmented cells which are continuous with those of the ciliary body. The main bulk of the iris is formed by stroma made up of blood vessels and loose connective tissue in which there are pigment cells. The long posterior and the anterior ciliary arteries join to form the major arterial ciecle at the periphery of the iris.From this circle vessels converge towards the free margin of the iris and join together to from the minor arterial circle of the iris.The colour of the iris is determined by the number of pigment cells in its connective tissue.If the pigment cells are absent, the iris is blue in colour due to the diffusion of light in front of the black posterior surface. The iris contains a well-developed ring of muscle called the sphincter pupillae which lies near the margin of the pupil. Its nerve supply (parasympathetic) is similar to that of the ciliary muscle. The dilator pupillae is an ill-defined sheet of radial muscle fibres placed near the posterior surface of the iris. It is supplied by sympathetic nerves.

Inner coat/retina

This is the thin, delicate inner layer of the eyeball. It is continuous posteriorly with the optic nerve. The outer surface of the retina (formed by pigment cells) is attached to the choroid, while the inner surface is in contact with the hyaloid membrane (of the vitreous) Opposite the entrance of the optic nerve (inferomedial to the posterior pole) there is a circular area known as the optic disc. It is 1.5 mm in diameter. The retina diminishes in thickness from behind forwards and is divided into optic,ciliary and iridial parts. The optic part of the retina contains nervous tissue and is sensitive to light. It extends from the optic disc to the posterior end of the ciliary body. The anterior margin of the optic part of the retina forms a wavy line called the ora serrata. Beyond the ora serrata, the retina is continued forwards as a thin, non-nervous insensitive  layer that covers the ciliary body and iris, forming the ciliary and iridial parts are made up of two layers of epithelial cells. The depressed area of the optic disc is called the physiological cup. It contains no rods or cones and is therefore insensitive to light,i.e it is the physiological blind spot. At the posterior pole of the eye 3 mm lateral to the
optic disc, there is another depression of similar size, called the macula lutea. It is avascular and yellow in colour. The centre of the macula is further depressed to from the fovea centralis. This is the thinnest part of the retina. It contains cones only, and is the site  of maximum acuity of vision. The rods and cones are the light receptors of the eye. The rods contain a pigment called visual purple. They can respond to dim light (scotopic vision). The periphery of the retina contains only rods, but the fovea has none at all. The cones respond only to bright light ( photopic vision ) and are sensitive to colour. The fovea centralis has only cones. Their number diminishes towards the periphery of the retina. The retina is supplied by the central artery. This is an end artery. In the optic disc, it divides into an upper and a lower branch, each giving off nasal and temporal branches. The artery supplies the deeper layers of the retina up to the bipolar cells. The rods and cones are supplied by diffusion from the capillaries of the choroid. The retina veins run with the arteries.

Aqueous humour             
This is a clear fluid which fills the space between the cornea is front and the lens anterior segment. This space is divided by the iris into anterior and posterior chambers which freely communicate with each other through the pupil. The aqueous humour is secreted into the posterior chamber from the capillaries in the ciliary processes. It passes into the anterior chamber through the pupil. From the anterior chamber, it is drained into the anterior ciliary veins through the space of the iridocorneal angle or angle of anterior chamber and the canal of schlem. Interference with the drainage of the aqueous humour into the canal of schlemm results in an
increase of intraocular pressure ( glaucoma ). This produces cupping of the optic disc and pressure atrophy of the retina causing blindness. The intraocular pressure is due chiefly  to the aqueous humour which maintains the constancy of the optical dimensions of the eyeball. The aqueous is rich in ascorbic acid, glucose and amino acids, and nourishes the avascular tissues of the cornea and lens.

Lens            
The lens is a transparent biconvex structure which is placed between the anterior and posterior segments of the eye. It is circular in outline and has a diameter of 1 cm. The central points of the anterior and posterior surfaces are called the anterior and posterior poles. The line connecting the poles constitutes the axis of the lens, while the marginal circumference is termed the equator. The chief advantage of the lense is that can very its dioptric power. It contributes about 15 dioptres to the total of 58 dioptric power of the eye ( A dioptre is the inverse of the focal length in meters.A lens having a focal length of half meter has a power of two dioptres ).The posterior surface of the lens is more convex than the anterior. The anterior surface is kept flattened by the tension of the suspensory ligament. When the ligament is relaxed by contraction of the ciliary muscle, the anterior surface becomes more convex due to elasticity of the lens substance. The lens is enclosed in a transparent, structureless elastic capsule which is thickest anteriorly near the circumference. Deep to capsule, the anterior surface of the lens is covered by a capsular epithelium. At the centre of the anterior surface, the epithelium is made up of a single layer of cubical cells, but at the periphery, the cells elongate to produce the fibres of  the lens substance. The centre (nucleus) of the lens is firm, where as the periphery is soft and is made up of more recently formed fibres.                                                                                     

The human brain

The human brain

The appearance of Dulci and gyro increases the surface area for the neurons many times, without increasing the size of the brain. There are specific areas on the brain for specific functions. Thalamus integrates sensory, motor and visceral activities. Hypothalamus controls various visceral and vasomotor activities. It maintains a biological clock for our body. Parkinson ism occurs due to lesion of corpus stratum. There is reduction in speed or bradykinesia,i.e. slow movement or akinesia, i.e. no movement with muscle rigidity. There is free flow of information in the central nervous system, between two hemispheres through the commissariat fibers;
between various parts of one hemisphere through the association fibers and between upper and lower parts through the projection fibers. Internal capsule contains lots of fibers packed in its ''limbs''. It is supplied by the ''end'' of the human being concerned, if not treated properly.The cerebrum is made of two cerebral hemispheres which are incompletely separated from each other by the median plane by the corpus callous. Each hemisphere contains a cavity, called the lateral ventricle.

Dissection

Keep the cerebrum so that the longitudinal fissure faces superiorly. Identify the convex strong band of white matter, the corpus callosum binding parts of the medial surfaces of the two cerebral hemisphers. Define splenium as the thick rounded part of corpus callosum. Divide the corpus callosum in the median plane starting from the splenium towards the trunk, genu and rostrum. Inferior to the trunk of corpus callosum extend the incision into the tela choroidea of the lateral and third ventricles, and the interthalamic adhesion connecting the medial surfaces of two thalami.Identify the thin septum pellucidum connecting the inferior surfaces of corpus callosum to a curved band of white matter-anterior column of the fornix. Look for the anterior commissure just at the anterior end of the anterior column of fornix. Turn the brain upside down and identify optic chiasma. Divide the optic chiasma, anterior communicating artery, infundibulum and a thin groove between the adjacent mamillary bodies, posterior cerebral artery close to its origin. Carry the line of division around the midbrain to join the two ends of the median cut. Separate the right and left cerebral hemispheres. In the two hemisphere, identify the three surfaces, four borders, three poles. Identify the central sulcus, posterior ramus of lateral sulcus, parieto-occipital sulcus and preoccipital notch and demarcate the four lobes of the superolateral surface of each cerebral hemisphere. Strip the meninges from the surfaces. Identify the vessels on the surfaces of hemisphere surface, medial surface and inferior of hemisphere. Make thin slice through the part of the calcarine sulcus, posterior to its junction with the parieto-occipital sulcus. Identify the stria running through it. On cutting series of thin slices try to trace the extent of visual stria. 

Motor areas 

Primary motor area : It is located in the precentral gyrus, including the anterior wall of central sulcus,and in the anterior part of paracentral lobule on the medial surface of cerebral hemispheres. This correspond to area 4 of brodmann. Electrical stimulation of primary motor area elicits contraction of muscles that are mainly on the opposite side of body. Although cortical control of musculature is mainly contralateral, there is significant ipsilateral control of most of the muscles of the head and axial muscles of the body. The contralateral half of the body is represented as upside down, except the face. The pharyngeal region, tongue are represented in
the most ventral and lower part of percentral gyrus, followed  by the face, hand, arm, trunk and thigh. The remainder of leg, foot and perineum is on the medial surface of hemisphere in the paracentral lobule. Another significant feature in this area is that the size of the cortical area for a particular part of the body is determined by the functional importance of the part and its need for sensitivity and and intricacy of the movements of that region. The area for the face, especially the larynx and lips, is therefore disproportionately large and a large area is assigned to the hand particularly the thumb and index finger. Movements of joints are represented rather than individual muscles.

Premotor area :This area coincides with the brodmann's area 6 and is situated anterior to motor area in the superolateral and medial surfaces of the hemisphere. The premotor area contributes to motor function by its direct contribution to the pyramidal and other descending motor pathways and by its influence on the primary motor cortex.In general,the primary motor area is the cortex in which execution of movements originates and relatively simple movements are maintained. In contrast, the premotor area programmes skilled motor activity and thus directs the primary motor area in its execution. The premotor and primary motor areas are together
referred to as the primary somato-motor area. Both these areas give origin to corticospinal and cerebellum after relay in ventral intermediate nucleus of thalamus.

Sensory areas               

First somesthetic : The representation of the body in this area corresponds to that in the motor area in that contralateral half of the body is represented upside down except the face. The area of the cortex that receives sensations from a particular part of the body is not proportional to the size of that part, but rather to the intricacy of sensations received from it. Thus, the thumb, fingers, lips and tongue have a disproportionately large representation. The different sensations,i.e. cutaneous and proprioceptive are represented in different parts withinsensory area. The ventral posterior nucleus of thalamus is the main source of afferent fibres for the sensory area. This thalamic nucleus is the site of termination of all the fibres of the medial lemniscus. Most of the fibres of the spinothalamic and trogeminothalamic tracts carrying fibres for cutaneous sensibility end in anterior part of area and those for deep sensibility end in the posterior part. Somesthetic cortex is mainly in the superior parietal lobute on the precuneus on the medial surface. It coincides with areas 5 and 7 of brodmann. This receives afferents from first sensory area and has reciprocel connection with dorsal tier of nuclei of lateral mass of thalamus. Data pertaining to the general sense are integrated, permitting a comprehensive assessment of the characteristic of an object held in hand and its identification without visual aid.

Areas of special sensations
Vision : The visual area is located above and below the calcarine sulcus on the medial surface of occipital lobe. It corresponds to area 17 of brodmann. The visual area is also called the striate area because the cortex here contains the line of gennari, which is just visible to the unaided eye. The role of the second and third visual areas includes among other complex aspects of vission, the relating of present to past visual experience, with recognition of what is seen and appreciation of its significance. The three areas are linked together by association fibres. The visual areas give efferent fibres which reach frontal eye field.

Hearing :The auditory area (acoustic area) lies in the temporal lobe. Most of it is concealed as it lies in that part of superior temporal gyrus which forms inferior wall of the posterior ramus of lateral sulcus. It corresponds with areas 41 and 42 of brodmann. The medial geniculate body of the thalamus is the principal source of fibres ending in the auditory cortex with these fibres constituting the auditory radiation. The auditory radiation does not only end in the first auditory area but extends to neghbouring area as well, that is known as auditory association area or second auditory area. This area lies behind the first auditory area in superior temporal gyrus. It corresponds to area 22 of brodmann on the lateral surface of superior temporal gyrus. This region of the cortex is also known as wernicke's area and is of major importance in language functions. 

Corpus callous                
The corpus callosum is the largest commissure of the brain. It connects the two cerebral hemispheres. Since it is the neopallial commissure, it attains enormous size in man (10 cm long). The corpus callosum connects all parts of the cerebral cortex of the two sides, except the lower and anterior parts of the temporal lobes which are connected by the anterior commissure.The rostrum is directed downwards and backwards from the genu, and ends by joining the lamina terminalis, in front of the anterior commissure. It is related superiorly to the anterior horn of the lateral ventricle,and the longitudinal striae. The trunk or body is the middle part, between the genu and the splenium. It is overlapped by the gyrus cinguli and is covered by the indusium griseum and the longitu- dinal striae. The inferior surface is concave from before backwards and convex from side to side. It provides attachment to the septum pellucidum and the fornix, and forms the roof central part of the lateral ventricle. The splenium is the posterior end forming the thickest part of the occipital pole. Its lies 6 cm in front of the occipital pole. The superior surface is related to the inferior sagittal sinus and the falx cerebri. Posteriorly, it is related to the great cerebral vein, the straight sinus and the free margin on the tentorium
cerebelli.

Internal capsule
Gross anatomy : The internal capsule contains fibres going to and coming from the cerebral cortex. It can be compared to a narrow gate where the fibres are densely crowded. Small lesions of the capsule can give rise to widespread derangements of the body. When traced upwards, the fibres of the capsule diverge and are continuous with the corona radiata. When traced downwards, its fibres converge and many of them are continues with the crus cerebri of the midbrain.

Food

Food

Foods are those chemical substances which an individual takes, digests, assimilates and provides the nutritive requirements of an individual to maintain growth and physical well being. Food supply energy for production of heat and for all types of activities. It essential for growth of human body. It essential for the repair of the daily wear and tear. Protects the body from various types of diseases. In general way, it is involved in the functioning of the body processes.

Caloric intake and distribution

The calotic value of the dietary intake must be approximately equal to the energy expended if body weight is to be maintained. In addition to the 2000 k cal/d necessary to meet basal needs, 500-2500 kcal/d are required to meet the energy demands of daily activities. The distribution of teh calories among carbohydrate, protein,and fat is determined partly by physiologic factors and partly by teste and economic considerations.

Protein :A daily protein intake of 1 g/kg body weight to supply the eight nutritionally essential amino acids and other amino acids is desirable. The source  of the protein is also impotent. The animal proteins of meat, fish, diary products, and eggs, contain amino acids in approximately the proportions required for protein synthesis and other uses.20 to 30 grams of the body proteins are degraded and used to produce other body chemicals daily. Therefore all cells must continue to from new proteins to take the place of those that are being destroyed, and a supply of protein is needed in the diet for this purpose.An average person of protein is needed in the diet for this purpose. An average person can maintain normal stores of protein, provide the daily intake is above 30-50 grams. Therefore, individuals in economically disadvantaged countries who consume cornmeal as the principal source of protein sometimes develop the protein-deficiency syndrome called workmanship which consists of failure to grow, lethargy, depressed mentality, and edema caused by low plasma protein concentration.        
   
Fat : Fat is the most compact form of food, since it supplies 9.3 kcal/gm. However, often it is also the most expensive.Indeed,internationally there is a reasonably good positive correlation between fat intake and standard of living. In the past, Western diets have contained large amounts.The evidence indicating that a high unsaturated/saturated fat ratio in the diet is of value in the prevention of atherosclerosis and the current interest in preventing obesity may change this. In central and south American Indian communities where corn is the dietary staple, adults live without ill effects for years on a very low fat intake. Therefore, provided that the needs for essential fatty acids are met, a low-fat intake does not seem to be harmful, and a diet low in saturated fats is desirable.

Milk

Milk is an ideal food. It is unique in nutritive  value and contains all the food factors of a well balanced diet required for human body.It is easily digestible, absorb able and assimilable. Skimmed milk powder is devoid of fat and fat soluble vitamins but a good source of  protein, calcium and water soluble vitamins. Cow's milk is to be suitably changed to make it comparable to mothers milk and to make a substitute drink for young baby, even a new one. The insoluble carcinogen of cow's milk must be reduced to the level as  present in human milk, the amount of lactose must be increased to the right proportion and the resulting mixture must be pasteurized.

Energy balance

The endocrine system, like the nervous system, adjust and correlates the activities of the various body system, making them appropriate to the changing demands of the external and internal environment. Endocrine integration is brought about by chemical signals secreted by ductless glands and transported in the circulation to target cells. Some of the hormones are amines, and other are amino acids, polypeptides, proteins, or steroids. Only about 27 per cent of the energy ingested normally reaches the functional sys-
tens of the cells, and much of this is eventually converted to heat, Which is generated as a result of protein metabolism, muscle activity, and activities of the various organs and tissues of the body. Excess energy intake is stored mainly as fat where as a deficit energy expenditure eventually equals energy intake or death occurs. In athletes and laborers, energy expenditure for the high level of muscle activity may be as high as 6000 to 7000 calories per day, compared with only about 2000 calories per day for sedentary
individuals.                          

                 
   

Kidney functions and location

Kidney functions and location

Kidneys are a pair of excretory organs situated on the posterior abdominal wall, one on each side of the vertebral column,behind the peritoneum. They remove waste products of metabolism and excess of water and salts from the blood, and maintain its PH. The kidneys are kept in position by renal fascia, perinatal fat and perinatal fat. If the fat is lost drastically, as in dieting, the support of the kidneys is lost and these may descend down, leading to kinking of the ureter. So the loss of weight must be slow and steady. Kidneys are also liable to stone formation. The renal stones mostly have calcium and are easily seen on plain radiography of the abdomen. Kidney also gets affected by toxins of a particular type of bacteria responsible for pharyngitis. The condition is called acute conglomeration. The closely packed structure and numerous
functions of the kidney illustrate the beautiful workmanship of our creator. It not only applies to the kidney but to each and and every part of our body. Kidney are also called rents from which we have the derivative renal; and nephritis from which we have the terms pheromone, nephritis, etc.
     

Location,shape,size,weight,and orientation

The kidney occupy the epigastric, hypochondriac, lumbar and umbilical regions. Vertically they extend from the upper border of twelfth thoracic vertebra to the center of the body of third lumbar vertebra to the center of the body of third lumbar vertebra. The right kidney is slightly lower than the left, and the left kidney is a little nearer to the median plane than the right. The trans pyloric plane passes through the upper part of the hilts of the right kidney, and through the lower part of the hilts of the left kidney. Each kidney is about 11cm long, 6cm broad, and 3cm thick. The left kidney is a little longer and narrower than the right kidney. On an average the kidney weight 150 g in males 135 g in females the kidneys are reddish brown in color. The
long axis of the kidney is directed downwards and laterally, so that the upper poles are nearer to the median plane than the lower poles . The transverse axis is directed laterally and backwards.

Capsules or coverings of kidney

The Fibrous capsule : This is a thin membrane which closely invests the kidney and lines the renal sinus. Normally it can be easily stripped off from the kidney, but in certain diseases it becomes adherent and cannot be stripped off from the kidney, but in certain diseases it becomes adherent and cannot be stripped.
Perirenal or epinephrine fat : This is a layer of adipose tissue lying outside the fibrous capsule. It is thickest at the borders of the kidney and fills up the extra space in the renal sinus. The perinatal fascia was originally described as being made up of two separate layers. Posterior layer was called fascia of Scandalmonger and anterior layer as fascia of Gerta. These two fascia fused laterally to from lateral canal fascia. According to this view, lateral canal fascia continued collaterally behind colon to blend with parietal peritoneum. But lately it has been seen that the fascia is not made up of fused fascia, but of a single illuminated structure which is fused stereoscopically with muscular fascia of soaps major and quadratures Borglum muscles.The  
fascia then extends intermediately behind the kidney as bi laminated sheet, which divides at a variable point into thin layer which courses around the front of kidney as anterior perinatal fascia and a thicker posterior layer which continues collaterally as the lateral canal fascia. It was believed  earlier that above the supra renal gland the anterior and posterior perinatal fascia fuse with each other and then get fused to the diaphragmatic fascia, but research presently demonstrates that superior aspect of perinatal space is "open'' and is in continuity to the bare area of liver on the right side and with schizophrenic extra peritoneal space on the left side. On the right side at the level of upper pole of kidney anterior fascia blends with inferior coronary layer and bare area of liver. On the left side, anterior layer fuses with schizophrenic ligament. Posterior layer on both right and left sides fuses with fascia of  muscles of posterior abdominal wall, i.e. psoriasis major and quadrature Borglum as well as with fascia on the inferior aspect of abdominal diaphragm.

Histology : Histological, each kidney is composed of one to three million coniferous tubules. Each tubule consists of two parts which are embryo logically distinct from each other. These are as follows. The secretory part, called the pheromone, which elaborates urine. Pheromone is the functional unit of the kidney, and comprises ;
(a) Renal corpuscle or Mammalian corpuscle, (for filtration of substances from the plasma) made up of agglomerates (a tuft of capillaries) Bowman's capsule.
(b) Renal tubules, (for selective resorption of substances from the agglomerate filtrate) made up of the proximal convoluted tubule, loop of Henley with its descending and and ascending limbs, and the distal convoluted tubule. The collecting tubule begins as a junction tubule from the distal convoluted tubule. Many tubules unite together to from the ducts of Bellini which open into the minor calyxes through the renal papillae. Agglomeration apparatus is formed at the vascular pole of agglomerates which is intimately related to its own ascending limb of the Helene's loop near the distal convoluted tubule.

Arterial supply
There is one renal artery on each side, arising from the abdominal aorta. At or near the hilts the renal artery divides into anterior and posterior divisions. Further branching of these divisions gives rise to segmental arteries each of which supplies one vascular segment. The segmental arteries are end arteries, so that the vascular segments are independent units. Each segmental artery divides into lobar artery divides into 2-3 inter-lobar arteries which run on each side of the pyramid. At the corticosteroid junction  the inter lobar arteries divide dichotomous into curate arteries, which arch over the bases of the pyramids, at right angles to the inter lobar arteries.The articular arteries do not anatomist with their neighbors, but finally turn up into the cortex as additional  interocular arteries. The interocular arteries do not anatomist with their neighbors, and, therefore, are end arteries. Afferent agglomerate arterioles are derived mostly as side branches from interocular arteries. The efferent agglomerate arteriole, from most of the glimmer, divides soon to from the perambulate capillary plexus around the proximal and distal convoluted tubules. Since blood passes through two sets of capillaries, agglomerates and perambulate plexus, it forms the renal portal circulation. Arterial supply of the medulla is derived mostly from the efferent arterioles of the medulla glimmer, and party from a number of agglomerate arterioles. Each arteriole dips into renal pyramid, breaks up into 1-2 dozen of descending vase rectal which run into the outer part of medulla. These break up to form capillary plexus in the inner part of pyramids, closely related to the loops of  Henley and the collecting ducts. At the venous end the plexus gives rise to ascending vase rectal which return blood to interocular or curate veins. In the outer part of medulla, the close relation between the descending vase rectal, the venues, and the medulla portion of renal tubules and ducts provides the structural basis for the counter current exchange and multiplier system.

Blood and nerve supply                     
The upper part receives branches  from the renal artery. It may also receive branches from the gonadal, or colic vessels. The middle part receives branches from the aorta. It may also receive branches from the gonadal, or ilia vessels. The pelvic part is supplied by branches from the vesicle, middle rectal, or uterine vessels.The arteries to the ureter lie closely attached to peritoneum. They divide into ascending and descending branches which first form a plexus on the surface of the ureter, and then supply it. In about 10% of cases, middle part of the ureter is supplied only by minute twigs from the peritoneal vessels. In another 2% of cases although there are several long arteries to the middle part, the upper and lower parts are supplied by short vessels. The ureter is supplied by sympathetic from T10-L1 segments and parasympathetic from S2-S4 nerves. They reach the ureter through the renal, aortic and hypo gastric plexuses. All the nerves appear to be sensory in function.

Development of kidney and ureter : Kidney develops from metamorphose, though proneness and mesospheres appear to disappear. Only the duct of mesospheres, the nephritic duct persists. Thus the nephritis of the kidney arise from the metamorphose. Parts of pheromone formed are bowman's capsule, proximal convoluted tubule, loop of Henley, distal convoluted tubule. Tuft of capillaries from the glimmer. Collecting part of kidney develops from ureter bud, which is an outgrowth of the nephritic duct. Ureteric bud gets capped by the metaphoric tissue, the ureter bud forms ureter. Soon it dilates to from renal pelvis and divides and subdivides to from major and minor calyxes and 1-3 million collecting tubules.kidney starts developing in sacral region,then it ascends to occupy its lumbar position. 
                     

Respiratory Physiology

Respiratory Physiology

Functional Anatomy: Two lungs taken together can be viewed as a trumpet having two separate zones-
1.Conducting
2.Respiratory zone.
Gaseous exchange occurs in the respiratory zone but not in the conducting zones (also called, dead space).Accordingly the respiratory zone presents a typical histological pattern conducive to the exchange. Mast cells of mucosa secrete histamine (H) when their membrane perturbed and H1 receptors are occupied by H bronchospasm.Mast cells also produce SRS-A, which causes bronchospasm.Bronchial muscles supplied by sympathetic and parasympathetic.Besides VIP secreting neurons also supply. Blood in pulmonary capillary is separated from air within alveolus by alveolo-capillary membrane.

Respiratory Tract:The organs which allow the entrans of air into the lungs and exchanges of gases with the blood in the air passages from the nose to the pulmonary alveoli.
Division of respiratory tract:
a.Upper respiratory tract: From nose (anterior nares) to the vocal fold.It consists of-
1.Nose.2.Nasopharynx.3.Oropharynx.4.Larynx upto vocal folds.
b.Lower respiratory tract:From vocal folds to the alveoli of the lungs.It consists of-
1.Larynx below the vocal folds.2.Trachea.3.Two bronchi.4.Bronchioles.5.Terminal bronchioles.6.Respiratory bronchioles.7.Alveolar duct.8.Atria.9.Air sac.10.Alveoli.

Linning epithelium of respiratory system:
a.Trachea and major bronchi: Pseudostratified ciliated columnar epithelium.
b.Bronchioles: Ciliated columnar epithelium.Onwards from respiratory bronchioles:The cilia disappear and the epithelium
becomes cubical.
c.Alveolar wall: Thin,simple squamous type. The linning epithelial cells are of two types.
1.Type I cells:Squamous cells.
2. Type II celles (also called granular pneumocytes ) are interminged with the type I cells.They secrets surfactant a substance which reduce the surface tension in the alveoli.They constitute about 10 percent of the surface area of alveoli.

Alveoli:
a.Total numbers                                                        :300 million
b.Total area of the alveolar walls in                                                                                          
   contact with capillaries in both lungs is about            :70 m2
c.Space between air and blood                                    :0.5 micro meter.
Alveoli communicate with each other by small pores called pores of khan.Accessory communation sometimes occur between fine bronchioles and their adjacent alveoli and known as Lamberts sinuses.  

Conducting and respiratory zone:

The whole lung can be divided into two major zones, conducting zone and respiratory zone.Weibel numbered each generation of  tracheobronchial tree.Thus the trachea is generation 0(zero).The two major divisions of the trachea , viz, the right and left bronchi,constitute the first generation and so on.In the 16th generation,the bronchi are called the terminal bronchiole.The 17th generation  bronchioles are the respiratory bronchioles.There are three generations of respiratory bronchiole.The alveolar sac is the 23rd and the last generation.On and from the 17th generation, few alveoli can be found on bronchioles.Although, the major portion of the O2  and CO2 exchanges occurs in the alveoli (the 23rd generation), some exchanges begin to occur from the 17th generation.Therefore the portion upto the 16th generation,is called the conducting zone, whereas on and from the 17th generation begins the respiratory zone.The two lungs taken together,can be represented as a trumpet shaped organ.The total capacity of the conducting zone is only about 150 ml whereas that of respiratory zone is about 3 liters.In short,the walls of the tracheobronchial tree in the conducting zone are thick, contain-cartilage and heavy amount of smooth muscles.Also there are glands in the submucous coat draining into the lumen.The epithelia are ciliated columnar type.No alveolus sprouts from these areas and no gaseous exchange occurs here.On  the other hand, respiratory zone is a big area containing large number of exceedingly thin walled alveoli, without any mucous secretion.Gaseous exchanges occur through the alveoli of this zone.It will be seen afterwards that velocity of air flow is high in the conducting zone, whereas it is low in the respiratory zone.These multiple divisions greatly increase the total croos-sectional area 
of the air ways-
1.Trachea       : 2.5 cm2
2.Alveoli         : 11,800 cm2.
Pleura:
The lungs are inveested by pleura which has tow layers , parietal and viceral.The parietal pleura is the outer and viceral pleura is the inner of the double layer.In between the two layers, there is therefore a potential space,called the pleural cavity.The parietal layer is adherent to the parieties, inner side of the chest wall and thoracic side of the diaphragm.Therefore, when these structures move, the parietal pleura has to move.The viceral pleura is adherent to the underlying viscus, the lung itself, therefore when the viscus (the lung) moves, it has to follow the viscus.The parietal pleura is supplied by vessels which are systemic,(that is here the blood pressure is higher) whereas the viceral pleura is supplied by vessels of pulmonary circulation and so the blood pressure in these vessels is low.In between the two layers of pleura there is a very small amount (say about 2 ml) of fluid, called pleural fluid. It is dispersed throughout the pleural cavity.

Pulmonary circulation:
pulmonary blood vessels:Anatomical peculiarities: The pulmonary vascular bed resembles the systemic, except that-
1.The walls of the pulmonary artery and its large branches are about 30% as thick as the wall of the aorta.
2.The small arterial vessels,unlike the systemic arterioles ,are endothelial tubes with relatively little muscle in their walls.
3.There are also some smooth muscle in the walls of the postcapillary vessels.
4.The pulmonary capillaries are large, and there are multiple anastomoses, so that each alveolus sits in a capillary basket.

Pulmonary blood flow:
With two quantitatively minor exceptions, the blood put out by the left ventricle returns to the right atrium and is ejected by the right ventricle, making the pulmonary vasculature unique in that it accommodates a blood flow that is almost equal to that of all the other organs in the body.One of the exceptions is part of the bronchial blood flow.As noted above there are anastomoses  between the bronchial capillaries and the pulmonary capillaries and veins, and although some of the bronchial blood enters the bronchial veins, some enters the pulmonary capillaries and veins, by passing the right ventricle.The other exception is blood that
flows from the coronary arteries into the chambers of the left side of the heart.Because of the small physiologic shunt created by  those two exceptions, the blood in systemic arteries has a PO2 about 2 mm Hg iower than that of blood that has equilibrated with alveolar air, and the saturation of hemoglobin is 0.5% less.

Pulmonary edema:
pulmonary  edema occurs in the same way that edema occurs elsewhere in the body.Any factor that causes the pulmonary interstitial fluid pressure to rise from the negative range into the positive range will cause sudden filling og the pulmonary interstitial spaces and alveoli with large amounts of free fluid.

The most common causes of pulmonary edema are as follows:
1.Left sided heart failure or mitral valvular disease with consequent great increases in pulmonary venous pressure and pulmonary  capillary pressure and flooding of the interstitial spaces and alveoli.
2.Damage to the pulmonary capillary membrane caused by infections such as pneumonia or by breathing noxious substances such as chlorine gas or sulfur dioxide gas.

Each of these causes rapid leakage of both plasma proteins and fluid out of the capillaries and into both the lung interstitial spaces and the alveoli.

Broncho pulmonary segment:
Each tertiary bronchus and its ramifications and the alveoli connected with them, constitute a broncho pulmonary segment,  which is self contained, functionally independent of lung tissue. It has its own blood , lymph and nerve supply and connective tissue invesment. This is of surgical importance in dissection of a portion of the lung in diseased condition.There are ten bronchopulmonary segments in the right lung and nine in the left lung. The medial basal or cardiac segment is absent in the
left lung.

Function of the lungs:(Respiratory function):
1.Gaseous exchange:Carriage of oxygen from the lungs to the site of  tissue respiration for sub-sequent utilization and also carrige of CO2 from that site to the lung alveoli for elimination. 2.Metabolic function:Oxygen is essential for maintenance of metabolism in the tissue.Aerobic metabolism cannot take place in the abscence of oxygen. 
3.Excretion: It excretes volatile substancess like ammonia, keton bodies, essential oils etc.
4.Maintenance of acid-base balance:This is done chiefly by adjusting the amount of CO2 elimination, the normal PH of the body fluid is 7.4 any change in the PH causes alteration in the rate and depth of breathing.
5.Maintenance of water balance:600-800 ml of water  per day is lost as water vapour during expiration.
6.Maintenance of  temperature balance: When water is transformed into gaseous form , heat is absorbed, so heat is lost through water vapours. About 10% of body heat is changed in this way.
7.Homeostatic function: It helps in maintenance of homeostatic of the internal environment of the body. 

b.Non-respiratory function of lungs:
   1.Metabolic function.
   2.Excretory function.
   3.Maintenance of acid base balance.
   4.Maintenace of temprature balance.
   5.Maintenance of water balance.
   6.Role on circulation.
   7.Maintenance of homeostatic of the internal environment of the body.

Respiration:
Defnition:Respiration is a physiological process which means the transport of O2 from atmosphere to the body cell for oxydation of the ingested food materials and elemination of CO2 and other volatile metabolic end products from the cell to the atmosphere.

Types of respiration:Respiration are of two types-
1.External respiration: Intake of O2 and removal of CO2 from body is called  external respiration.
2.Internal respiration:The utilization of O2 and production of CO2 by cells and the gaseous exchange between the cells and their
                               fluid medium.


Rate of respiration:
It is the total number of respiration per unite time.It is counted in minute. The normal rate of respiration varies in accordance with age, sex, size ,work, rest and sleep.


Respiratory rate at different age groups:

..............................................................................................
: Age in years            : Respiratory rate per minute                  :
:...............................:...........................................................:
: At birth                    :         14-60                                          :
:................................:..........................................................:
: First years               :         25-35                                         : 
:...............................:..........................................................:
: 2-4 years                :         20-30                                          :
:..............................:............................................................:               
: 5-14 years              :         20-25                                           :
:..............................:............................................................:
: Adult (male)           :         10-18                                            : 
:.............................:.............................................................:
: Adult (female)        :         10-18                                            :               
:.............................:.............................................................:                                                                                                                                              

Male reproductive system organs

Male reproductive system organs

Introduction : The delicate gonads of the male lie outside the abdominal cavity as these cannot withstand the temperature of the abdominal cavity. The epidermis carrying the spermatozoa starts from the testis and continues as the vas deference. The vase deference after a course in the scrotum enters the anterior abdominal wall, crosses the pelvic brim to enter the anterior part of pelvic cavity. Seminal vesicles are placed at the vase of urinary bladder. The duct of seminal vesicle unites with vas deference to from the ejaculatory duct which opens into the prosthetic urethra. Prostate is an important gland; for its secretions help in maturation of the
sperms. It undergoes a lot of changes from birth to old age and is very vulnerable to malignant changes. Cancer prostate can metastasis even to cranial cavity as the prosthetic venous plexus. The male reproductive organs include the external and internal genitalia. The external genitalia are the penis and the scrotum. The internal genitalia on each side are the epidermis, the duct deference, the seminal vesicle, the ejaculatory ducts, the prostate, and the male urethra.

Ducts deferens

The ductus deferens is also called the vas deferens or the deferent duct. The ductus deferens is a thick- walled, muscular tube which transmits spermatozoa from the epididymis to the ejaculatory duct. It feels cord-like at the upper lateral part of scrotum.Ductus deferens has a narrow luman except at the terminal dilated part called the ampulla. The ductus deferens is about 45 cm long when straightened. The prostate lies in the lesser pelvis, below the neck of the urinary bladder, behind the lower part of the pubic symphysis and the upper part of the pubic arch, and in front of the ampulla of the rectum. It resembles an inverted cone, measuring about 4 cm transversely at the base, i.e. width 3 cm vertically, i.e. lenth, and 2 cm nteroposteriorly or thickness. It weight about 8 g.

Gross features 

 The prostate comprises an apex directed downwards ; a base;  four surfaces, anterior, posterior and two inferolateral.The apexis directed downwards surrounds the junction of prostatic and membranous parts of posterior urethra. It is separated from the anal canal bu the perineal body. The base is directed upwards, and is structurally continuous with the neck of the bladder. The junction is marked by a circular groove which lodges venules of the vesical and prostatic plexuses. The anterior surface is narrow and convex from side to side. It lies 2 cm behind the pubic symphysis, with retropubic fat intervening. Its upper part is connected
to the pubic bones by the puboprostatic ligaments. The lower end of  this surface is pierced by the urethra. The lower end of urethra emerges from this surface anterosuperior to the apex of gland. This surface is composed of fibrous tissue. The posterior surface is triangular in shape. It is flattened from side to side and convex from above downwards. It is separated from the rectum by the fascia of denonvilliers which is the obliterated rectovesical pouch of peritoneum. Near its upper border it is pierced on each side of the median plane by the ejaculatory duct. This surface lies 4 cm from the anus, and can be easily palpated on digital exa-
mination through the rectum. The inferolateral surfaces are related to this side walls of pelvis. The anterior fibres of the levator ani enclose the gland in pubourethral sling. They are separated from the muscle by a plexus of veins embedded in its sheath.                  

Blood supply and Nerve supply

The prostate is supplied by branches from the inferior vesical, middle rectal and internal pudendal arteries. Branches of these arteries from a large outer or subcapsular plexus, and a small inner or periurethral plexus. The greater part of the gland is supplied by the subcapsular plexus. The veins from a rich plexus around the sides and basa of the gland. The plexus communicates with the vesical plexus and with the internal pudendal vein, and drains into the vesical and internal iliac veins. Valveless communications exist between the prostatic carcinoma can spread to the vertebral column and to the skull. The prostatic plexus of nerves is derived from the lower part of the inferior hypogastric plexus. It contains thick nerves and numerous large ganglia. In
addition to the prostate and structures within it, the plexus also supplies the seminal vesicles, the corpora cavernosa, the corpus spongiosum, the membranous and penile parts of the urethra, and the bulbourethral glands. The prostate is supplied by both sympathetic and parasympathetic nerves. The gland contains numerous end-organs, impulses from which are relayed to the lower three lumbar and upper sacral segments. Secretions of the prostate are produced and discharged after stimulation of both the parasympathetic and sympathetic nerves.

Age changes in prostate
At birth the prostate is small in size, and is made up mainly of stroma in which a simple duct system embedded. During the first 6 weeks afterbir the epithelium of the ducts and of the prostatic undergoes hyperplasia and squamous inetaplasia, under the stimulation of maternal oestrogens. There after, up to the age of 9 years changes are negligible. Between 9 and 14 years, the duct system becomes more elaborate by formation of side buds, and the gland slowly increases in size. At puberty the male hormones bring about rapid changes in the gland. In about one year it becomes double its prepubertal size dur to rapid growth of
the follicles and condensation and reduction of the stroma. From 20 to 30 years there occurs marked proliferation of the glanular epithelium into the luman of the follicles, making them irregular. From 30 to 45 years the size of the prostate remains constant, and involution starts. The epithelial infoldings gradually disappear and amyloid bodies increase in number. After 45 to 50 years the prostate is either enlarged called the benign hypertrophy or reduced in size called the senile atrophy.

Histology and Development : Prostate is a fibromuscular glandular organ. The stroma comprises collagen fibres and smooth fibres. The columnar epithelium of acini is folded. The lumen may contain small colloid masses called amyloid bodies. The prostatic urethra, lined by transitional epithelium mayalso be seen. Prostate develops from a series of endodermal buds from the lining of primitive urethra and the adjacent portion of urogenital sinus, during first 3 months of intrauterine life. The surrounding mesenchyme condenses to from the stroma of the gland. Prostatic utricle develops in the region of mullerian tubercle similar to uterus or vagina in females. The central zone of glandular tissue is of wolfian duct system.        
                       
Clinical anatomy : Vasectomy or removing part of the vas deferens is one of the commonest operations being done for purposes of family planning. It is a minor operation which is done under local anaesthesia. A median incision is made in the upper part of the scrotum, just below the penis. Through this incision both the deferent ducts are operated. A short segment of each duct is excised,and the cut ends are ligated . The operation is reversible, and recanalisation can be doneif required . After vasectomy, the testis continue to produce the hormones normally to maintain the male characteristics. The hormones pass out through the veins. Sperms are present in a few ejaculations after vasectomy, as it is an emptying process. Newly formed sperms are destroyed in the epididymis and are removed by phagocytosis. After 50 years of age the prostate is often enlarged due to benigh hypertrophy or due to the formation of an adenome. This causes retention of urine due to distortion of the urethra. Enlargement of the median lobe not only projects into bladder,but forms a sort of valve over the internal urethral orifice, so that more patient strains, more it obstructs the passage. Urine passes when the patient relaxes. Digital examination of the rectum is very helpful in the diagnosis of an enlarged prostate. Removal of such a prostate called prostatectomy relieves the urinary obstruction. During removal, the enlarged gland is enucleated, leaving behind both the capsules and venous plexus between them.The prostate can be removed through bladder (transvesical ), through prostatic capsule (retropubic), or through perineum and fascia of denonvilliers (perineal approach) or through urethra. Inflammation of the prostate is referred to as prostatitis. It may be acute or chronic. Acute prostatitis is secondary to gonococcal urethritis and chronic prostatitis may be secondary to tuberculous infection of epididymis, seminal vesicles and the bladder.     

Gastro intestinal physiology system

Gastro intestinal physiology system

The gastrointestinal system evolved as a portal to permit controlled nutrient uptake in unicellular organisms. It is functionally continuous with the out side environment and is defended by a well developed mucosal immune system. Never-theless, the gut usually lives in harmony with an extensive commensurable micro flora, particularly in the colon. Digestive secretions serve to chemically alter the components of meals ( particularly macromolecules ) such that their constituents can be absorbed across the epithelium. Meal components are acted on sequentially by saliva, gastric juice, pancreatic juice, and bile, which contain enzymes, ions, water, and other specialized components. The intestine and the organs that drain into it secrete about 8 L of
fluid per day, which are added to water consumed in food and beverages. Most of this fluid is reabsorbed, leaving only approximately 200 mL to be lost to the stool. Fluid secretion and absorption are both dependent on the active epithelial transport of  ions, nutrients, or both. Gastrointestinal functions are regulated in an integrated fashion by endocrine, paracrine,and neurocrine mechanisms. Hormones and Paraclete factors are released from enteroendocrine cells in response to signals coincident with the intake of meals.The epicenter nervous system conveys information from the central nervous system to the gastrointestinal tract but also often can activate programmed responses of secretion and motility in an autonomous fashion. The intestine has an ususual circulation, in that the majority of its venous outflow does not return directed initially to the liver via the portal vein. A typical mixed meal consists of carbohydrates, proteins, and lipids ( the latter largely in the form of triglycerides ). Each must be digested to allow its uptake into the body. Specific transporters carry the products of digestion into the body. In the process of carbohydrate assimilation, short peptides can be absorbed in addition to amino acids. The protein assimilation machinery,which
rests heavily on the proteases in pancreatic juice, is arranged such that these enzymes are not activated until they reach their substrates in the small intestinal lumen.This is accomplished by the restricted  localization of an activating enzyme,enterokinase. Lipids face special challenges to assimilation given their hydrophobicity. Bile acids solubilize the products of lipolysis in micelles and accelerate their ability to diffuse to the epithelial surface. The assimilation of triglycerides is enhanced by this mechanism,

Key points of Gastrointestinal physiology

Whereas that of cholesterol and fat-soluble vitamins absolutely requires it. The catabolism of nutrients provides energy to the body in a controlled fashion, via stepwise oxidation's and other reactions. A balanced diet is important for health,and certain substances  obtained from the diet are essential to life. The caloric value of dietary intake must be approximately equal to energy expenditure for homeostasis.
Motility : The regulatory factors that govern  gastrointestinal secretion also regulate its motility to soften the food, mix it with secretions, and propel it along the length of the tract. Two major patterns of motility are peristalsis involves coordinated contractions and relaxations above and below the food bolus. The membrane potential of the majority of gastrointestinal smooth muscle undergoes rhythmic fluctuations that sweep along the length of the gut. The rhythm varies in different gut segments and is established by pacemaker cells known as interstitial cells of the Cajan. This basis electrical rhythm provides for sites of muscle contraction when stimuli superimpose spike potentials on the depolarizing portion of the BER waves. In the period between meals the intestine is relatively quiescent, but every 90 minute or so it is swept through by a large peristaltic wave triggered by the hormone motility. This migrating motor complex presumably serves a '' housekeeping'' function. Swallowing is triggered centrally and is coordinated with a peristaltic wave along the length of the esophagus that drives the food bolus to the stomach, even against gravity. Relaxation of the lower esophageal sphincter is timed to just precede the arrival of the bolus, there by limiting reflux of the gastric contents. Nevertheless, gastrointestinal reflux disease is one of the most common gastrointestinal complaints. The stomach accommodates the meal by a process of receptive relaxation. This permits an increase in volume without a significant increase in pressure. The stomach then serves to mix the meal and to control its delivery to downstream segments. Luminary contents move slowly through the colon, which enhances water recovery. Distension of the rectum causes reflex contraction of the internal anal sphincter and the desire to defecate. After toilet training, defecation can be delayed till a convenient time via voluntary contraction of the external anal sphincter.

Regulation of gastric secretion

Gastric motility and secretion are regulated by neural and humeral mechanisms. The neural components are local autonomic reflexes, involving choline neurons, and impulses from the CNS by way of the vague nerves. The humeral components are gastric enterogastrone. Va gal stimulation increases gastric secretion by release of gastric-releasing peptide. Other Val fibers release acetyl choline, which acts directly on the cells in the glands in the body and the fund us to increase acid and pepsin secretion. Stimulation of the vague nerve in the chest or neck increases acid and pepsin secretion but vasectomy does not abolish the secretory response to local stimuli. For convenience, the physiologic regulation of gastric secretion is usually discussed in terms of cephalic, gastric, and intestinal influences, although these overlap. The cephalic influences are vaginally mediated responses induced by activity in the CNS. The gastric influences are primarily local reflex responses and responses to gastric. The intestinal influences are the reflex and hormone feedback effects on gastric secretion initiated from the mucosa of the small intestine.                

Secretions of the large intestine
1.Mucus secretion : The mucosa of the large intestine, like that of the small intestine, has many crypts of Lieberman, but in this mucosa, unlike that of the small intestine, there are no villi. Also, the epithelial cells contain almost cells that secrete only mucus.Therefore, the great preponderance of secretion in the large intestine is mucus. This mucus contains large amounts of bicarbonate ions caused by active transport through other epithelial cells that lie between the mucus-secreting epithelial cells.
Function of mucus : Mucus in the large intestine protects the wall against excoriation, but in addition, it provides the adherent medium for holding fecal matter together. Furthermore, it protects the intestinal wall from the great amount of bacterial activity that take place inside the feces, and it plus the alkalinity of the secretion ( pH of 8.0 caused by large amounts of sodium bicarbonate ) provides a barrier to keep acids formed deep in the feces from attacking the intestinal wall.Regulation of secretion of mucus : The rate of secretion of mucus is regulated principally by direct, tactile stimulation of the mucous is regulated principally by direct, tactile stimulation of the mucous cells on the surface of the mucosa and by local
nervous reflexes to the mucous cells in the crypts of Lieberman. Stimulation of the pelvic nerves, which carry the parasympathetic innervation to the distal one half to two thirds of the large intestine, also causes marked increase in the secretion of mucus.This occurs along with an increase in motility. Therefore, during extreme parasympathetic stimulation, often caused by emotional disturbances, so much mucus may be secreted into the large intestine that the person has a bowel movement of ropy mucus as often as every 30 minutes ; this mucus contains little or no fecal material.
2.Secretion of water and electrolytes in response to irritation : Whenever a segment of the large intestine becomes intensely irritated, as occurs when bacterial infection becomes intensely irritated, as occurs when bacterial infection becomes rampant during enteritis, the mucosa secretes large quantities of water and electrolytes in addition to dilute the irritating factors and to cause rapid movement of the feces toward the anus. The usual result is diarrhea, with loss of large quantities of water and electrolytes in addition to the normal viscid solution of alkaline mucus. This acts to the dilute the irritating factors and to cause rapid movement of the feces toward the anus. The usual result is diarrhea, with loss of large quantities of water electrolytes. But the diarrhea also washes away the irritant factor, which promotes earlier recovery from the disease than would otherwise occur.