Cranial cavity ( Department of Anatomy)

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1. Presented by : Tarun K. Ubhu CRANIAL CAVITY Department of Anatomy

2. Introduction to Cranial Cavity Cavity present in cranium of skull is known as Cranial Cavity . It contains brain , meninges , venous sinuses, all cranial nerves , four petrosal nerve , part of internal carotid artery and a part of vertebral artery besides the special senses. The anterior branch of middle menengial artery lies at the Pterion and is prone rupture in extra dural haemorrhage .

3. CRANIAL FOSSAE Anterior cranial fossa accommodates the anterior lobe of brain. Middle cranial fossa is much wider than the anterior cranial fossa and contains the 2 temporal lobes of brain. Posterior cranial fossa is much shallower and wider than the middle cranial fossa and it accommodates the occipital lobes of the brain .

4. Anterior Fossa Boundaries Anteriorly and laterally Frontal bone Floor: Orbital plate of frontal bone, ethmiod cribriform plate , anterior border of sphenoid’s lesser wings and crista galli Posteriorly : Posterior border of lesser wing of sphenoid, anterior clinoid process and sulcus chiasmaticus . Crista galli It is a sharp upward projection of ethmoid bone in the midline, for the attachment of falx cerebri . Foramen cecum Small aperture between the crista galli and the crest of the frontal bone

5. Middle Fossa Boundaries Anteriorly Post border of the lesser wings of sphenoid, anterior clinoid processes and sulcus chiasmaticus . Posteriorly Superior borders of petrous part of temporal and sphenoids dorsum sella . Laterally Squamous part of temporal and some part if parietal and greater wings of sphenoid. Floor Greater wing of sphenoid and petrous and squamous parts of the temporal bone. In the centre, floor is formed by the sella tursica of body of sphenoid.

6. Posterior Fossa Boundaries Anteriorly Superior border of the petrous part of temporal bone and dorsum sallae . Posteriorly Internal surface of squamous part of the occipital bone. Floor Basilar, squamous & condylor parts of the occipital bone & mastoid part foramen magnum forms the central part of the floor.

7. DURAMATER The duramater is the toughtest and thickest membrane in our body Develops from the mesoderm surrounding the neural tube This is conventionally described as two layers: the endosteal layer and the meningeal layer. These are closely united except along certain lines, where they separate to form venous sinuses.

8. The outer layer is highly vascular whereas the inner layer is more fibrous and has little blood supply . Vault is supplied by middle meningeal artery. Anterior cranial fossa by anterior ethmoidal , posterior ethmoidal and opthalmic meningeal branches of arteries. Middle cranial fossa by middle meningeal , accessory meningeal and internal carotid arteries. Posterior cranial fossa by meningeal branches of vertebral , opthalmic and acending pharyngeal arteries . BLOOD SUPPLY OF DURAMATER

9. NERVE SUPPLY OF DURAMATER The dura of the vault has only a few sensory nerves which are the opthalmic branches of trigeminal nerve The dura of floor has rich nerve supply and quite sensitive to pain. The ACF is supplied mostly by the anterior ethmoidal nerve and partially by maxillary nerve. The MCF is supplied by maxillary nerve in the ant. Half , and branches of mandibular nerve and from the trigeminal ganglion. The PCF is supplied chiefly by recurrent branch from 1 st , 2 nd and 3 rd cervical spinal nerves by meningeal branches of 9 th and 10 th cranial nerves.

10. Layers of Dura Mater The endosteal layer periosteum covering the inner surface of the skull bones. Does not c ontinuous with the dura mater of the spinal cord. The meningeal layer is the dura mater proper, covering the brain Continuous with the dura mater of the spinal cord. It provides tubular sheaths for the cranial nerves. Outside the skull, fuse with the epineurium of the nerves.

11. Folds of Dura Mater

12. VENOUS SINUSES OF DURAMATER . (Venous spaces whose walls are formed of duramater ) These are Have inner lining of endothelium Have no muscles in their walls Have no valves Receive blood from brain,meninges and bones of skull. Some are also poured by CSF. They communicate with veins outside the skull throug emissionary veins. These communications help to keep the pressure of blood of venous sinuses constant. There are 23 venous sinuses: Paired venous sinuses : 8 Unpaired venous sinuses : 7

13. CAVERNOUS SINUS INTRODUCTION It is one of the paired sinuses It is a large venous space situated in the middle cranial fossa on either side of the body of the sphenoidal bone. Floor and medial walls of it are formed by the endosteal duramater and lateral walls are formed by meningeal duramater Anteriorly : extend upto medial end of the ant. orbital fissure. Posteriorly : extend upto apex of petrosal temporal bone. 2 cm long and 1cm wide on each side

14. Relations of Cavernous sinus Superiorly : optic tract, optic chiasma , olfactory tract, internal carotid artery and anterior perforated substance. Inferiorly : Foramen Lacerum and the junction of the body and greater wing of the sphenoid bone. Medially : Hypophysis Cerebri and Sphenoidal air sinus. Laterally : Temporal bone of uncus . Below laterally : Mandibular nerve. Anteriorly : superior orbital fissure and the apex of the orbit. Posteriorly : Apex of the Petrous temporal and the Crus Cerebri of the midbrain.

15. RELATION OF CAVERNOUS SINUS

16. Structures within the lateral wall ( from above downwards) Occulomotor nerve: in the anterior part of the sinus. It divide into sup. and inf. divisions which leaves the sinus by passing though the sup. Orbital Fissure Trochlear : nerve in the anterior part of sinus it crosses superficially to the occulomotor nerve and enters the orbit through sup. Orbital fissure. Opthalmic nerve : In the ant. part of the sinus. It divide into lacrimal , frontal and nasocilliary nerves. Maxillary nerve : It leaves the sinus by passing through foramen rotundum on its way to pterigopalatine fossa . Trigeminal ganglion : The ganglion and its dural cave projects into the post. Part of the lateral wall of the sinus.

17. Structures passing through the medial aspect of the sinus Internal carotid artery with the venous and sympathetic plexus around it. Abducent nerve, inferolaterally to the internal carotid artery. The structures in the lateral wall and on the medial wall are separated from blood by endothelium lining.

18. Tributaries or incoming channels FROM THE ORBIT The superior opthalmic vein A branch of the inferior opthalmic vein or sometimes the vein itself The central vein of the retina may drain either into the superior opthalmic vein or into the cavernous sinus. From the brain Superficial middle cerebral vein . Inferior cerebral veins from the temporal lobe FROM THE MENINGES Sphenoparietal sinus . The frontal trunk the middle meningeal vein may drain either into the pterygoid plexus through the foramen ovale or into the sphenoparietal or cavernous sinus.

19. DRAINING CHANNELS OR COMMUNICATIONS Into Transverse sinus through Superior Petrosal sinus. Into Internal Jugular Vein through inferior petrosal sinus and through a plexus around the internal carotid artery. Into Pterygoid plexus of veins through the emissionary veins passing through the foramen ovale , thge foramen lacerum and the emissary sphenoidal foramen. Into the facial veinn through the superior opthalmic vein. The right and left cavernous sinus communicate with each other through the anterior and posterior intercavernous sinus and through the basilar plexus of veins. ALL THESE COMMUNICATIONS ARE VALVELESS AND BLOOD CAN FLOW THROIUGH THEM IN ANY DIRACTION.

20. FACTORS HELPING EXPULSION OF THE BLOOD FROM THE SINUS EXPANSILE PULSATIONS OF THE INTERNAL CAROTID ARTERY WITHIN THE SINUS GRAVITY POSITION OF THE HEAD

21. SUPERIOR SAGGITAL SINUS It occupies the upper convex, attached margin of the falx cerebri . It begins anteriorly at the crista galli by the union of tiny meningeal veins. Here it communicates with the veins of the frontal sinus, and occasionaly with the veins of the nose ,through the foramen caecum . As the sinus runs upwards and backwards, it becomes progressively larger in size. Its triangular in crossection . It ends near the internal occipital protuberance by turning to one side, usually the right and becomes continuous with the right transverse sinus.

22. Interior of the sinus shows Openings of the superior cerebral veins. Openings of the venous lacunae, usually 3 on each side. Arachnoid villi and granulations projecting into the lacunae as well as into the sinus. Numerous fibrous bands crossing the inferior angle of the sinus. Tributaries From Superior cerebral veins which never open into the venous lacunae Parietal emissary veins Venous lacunae, usually three on each side which first, receive the diploic and

23. TRANSVERSE SINUS These are large sinuses in which right one is larger than the left. It is situiated in the post. Part of the attached margin of tentorium cerebelli Right sinus : continuation of the superior saggital sinus Left sinus : continuation of straight sinus. Each extends from external occipital protuberance to the posteroinferior angle of the parietal bone at the base of the mastoid process where it bends downwards and becomes the sigmoid sinus.

24. Tributaries of transverse sinus Superior petrosal sinus Inferior cerebral veins Inferior cerebellar veins Diploic (posterior temporal) vein Inferior anastomotic vein.

25. SIGMOID SINUS Each sinus( left and roight ) is direct continuation of the transverse sinus. It is S-shaped and hence the name. Extends from posteroinferior angle of the parietal bone to the posterior part of the jugular foramen where it becomes the superior bulb of the internal jugular vein. It grooves the mastoid part of the temporal bone , where it is separated anteriorly from the mastoid antrum and mastoid air cells by only a thin plate of bone .

26. Tributaries of sigmoid sinuses The mastoid and condylar emissary veins. Cerebellar veins. Internal auditory veins.

27. HYPOSPHYSIS CEREBRI (Pituitary Gland) Small endocrine gland situated in relation to the base of the brain. It lies in the hypophyseal fossa or sella turcica . The fossa is roofed by the diaphragm sellae , the stalk of hypophyseal sellae peirces diaphragm sellae and is attached above to the floor of 3 rd ventricle. Often called master of endocrine orchestra because it produces number of hormones which control the secretion of many other endocrine glands of the body.

28. Relations Superiorly: Diaphragma sellae optic chiasma tubercinerium infundibular recess of 3 rd ventricle Inferiorly: itrregular venoud channels b/w the two layers of duramater lining the floor of hypophyseal fossa hypophyseal fossa sphenoidal air sinuses On each side: covernous sinus and its contents

29. RELATIONS OF PITUITARY

30. Subdivisions of hypophysis cerebri Adenohypophysis develops from the as an upward growth called the rathke’s pouch from the ectodermal roof of stomodeum . It includes pars anterior which is the largest part of the gland. pars intermedia : formed of the thin strip which is separated from the ant. Lobe by an interglandular cleft( a remenant of rathke’s pouch). pars tuberalis : an upward extension of the ant. Lobe that surrounds and form part of the infundibulum .

31. Neurohypophysis develops as an downward growth from the floor of diencephalon and is connected to the hypothallamus by a neural pathway. It includes: pars posterior : it is smaller than the ant. Lobe, lies in post. Concavity of larger ant. Lobe. infundibular stem : which contains neural connects of post. lobe with the hypothallamus .

32. BLOOD SUPPLY OF PITUITARY GLAND

33. Arterial supply of pituitary gland One superior hypophyseal artery on each side which supplies: Ventral part of the hypothallamus Upper part of the infundibulum Lower part of infundibulum through a separate long branch called as trabeculum artery. One inferior hypophyseal artery on each side which divide into medial and lateral branches which join one another to form arterial ring around the posterior lobe and also anatlomose with branches from superior hypophyseal artery. The portal vessels are of great functional importance because they carry the hormones releasing factors from the hypothallamus to the ant. Lobe where they control the secretion of the different glandular cells.

34. BLOOD SUPPLY OF PITUITARY

35. VENOUS DRAINAGE Short veins emerge on the surface of the gland and draion into the neighbouring venous sinuses. The hormones passes out the gland from the venous blood and is carried to their target cells.

36. NEURAL SUPPLY FROM HYPOTHALAMUS TO PITUITRY

37. THANKS .......... STAY TUNED