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.