Cranial Cavity Question And Answers

Question 1. Enumerate dural venous sinus. Describe the cavernous sinus in detail. (or)
Classify dural venous sinuses. Describe in detail its position, contents, tributaries & applied aspect of cavernous sinus. (or)
Describe the relation, tributaries, position, contents & connections of cavernous sinus. Add a note on applied anatomy. (or) Cavernous sinus, its relations & tributaries
Answer:

Dural Venous Sinuses:

• These are venous spaces whose walls are formed by duramater
• There are 23 venous sinuses- 8 paired & 7 unpaired

Read And Learn More: BDS Previous Examination Question And Answers

Cavernous Sinus:

Position:

It is situated in the middle cranial fossa on either side of the body of sphenoid bone

Boundaries:

• Floor- endosteal dura mater
• Lateral wall, roof & medial wall- meningeal dura mater

Extend:

• Anteriorly- upto medial end of superior orbital fissure
• Posteriorly- upto apex of petrous temporal bone

Relations:

1. Structures outside the sinus:

1. Superiorly
   • Optic tract
   • Optic chiasma
   • Olfactory tract
   • Internal carotid artery
   • Anterior perforated substance
2. Inferiorly
   • Foramen lacerum
   • Junction between the body & greater wing of sphenoid
3. Medially
   • Hypophysis cerebri
   • Sphenoidal air sinus
4. Laterally
   • Temporal bone with uncus
5. Anteriorly
   • Superior orbital fissure
   • Apex of the orbit
6. Posteriorly
   • Apex of petrous temporal bone
   • Crus cerebri of the midbrain

2. Structures in the lateral wall of the sinus:

3. Structures passing through the center of the sinus:

• Internal carotid artery with venous & sympathetic plexus
• Abducent nerve

Tributaries:

1. From the orbit

• Superior ophthalmic vein
• Branch of inferior ophthalmic vein
• Central vein of the retina

2. From the brain

• Superficial middle cerebral vein
• Inferior cerebral veins from the temporal lobe

3. From the meninges

• Sphenoparietal sinus
• Frontal trunk of the middle meningeal vein

Communications:

Applied Anatomy:

• Thrombosis of the cavernous sinus may be caused by sepsis in the dangerous area of the face, in nasal cavities & in the paranasal air sinuses
• The following symptoms occur.

Question 2. Describe the pituitary gland in detail. Mention its blood supply, development & relation
Answer:

Pituitary Gland:

• Pituitary gland is a small endocrine gland
• It is often called master of endocrine orchestra as it produces a number of hormones which control the secretion of many other endocrine glands of the body

Location:

• It is situated in relation to the base of the brain
• It lies in the hypophyseal fossa or sella turcica or pituitary fossa

Size:

• 8 mm- anteroposteriorly
• 12 mm-transversely

Relations:

1. Superiorly

• Diaphrama sellae
• Optic chiasma
• Tubercinerum
• Infundibular recess of the third ventricle

2. Inferiorly

• Irregular venous channels
• Hypophyseal fossa
• Sphenoidal air sinuses

3. On each side

• Cavernous sinus

Blood Supply:

1. Arterial Supply:

2. Venous Drainage:

Question 3. Tentorium cerebella
Answer:

• It is tent shaped fold of duramater forming the roof of the posterior cranial fossa
• It separates cerebellum from the occipital lobes of the cerebrum
• It divides cranial cavity into supratentorial & infratentorial compartments

Margins:

1. Anterior free margin

• U-shaped margin ends of which are attached anteriorly to the anterior clinoid processes
• It bounds the tentorial notch

2. Outer attached margin.

• It is convex
• Transverse & superior petrosal venous sinuses are present along this margin
• Trigeminal or Meckel’s cave is also present

Attachments:

• Both these margin cross each other near the apex of the petrous temporal bone
• Anterior to it, there is presence of triangular area forming the posterior part of the roof of cavernous sinus

 

Question 4. Trigeminal ganglion in middle cranial fossa Answer:

• It is sensory ganglion of the V cranial nerve
• It is similar to the dorsal nerve root ganglia

Shape:

• It is semilunar in shape
• Its three divisions emerges from the anterolateral convexity
• The posterior concavity receives its sensory root

Position:

• The ganglion lies on the trigeminal impression on the anterior surface of the petrous temporal bone near its apex
• It lies at the depth of about 5 cm from the pre-auricular point
• It occupies trigeminal or Meckel’s cave

Meningeal Relations:

• The inner & outer layers of duramater lie below it
• Trigeminal cave is lined by pia- arachnoid

Relations:

Associated root and branches:

• Central processes form large sensory root of trigeminal nerve
• Peripheral processes form ophthalmic, maxillary & mandibular divisions of trigeminal nerve
• Small motor root is attached to the pons superomedially to the sensory root

Blood Supply:

• It is supplied by twigs from

1. 1. Internal carotid artery
   2. Middle meningeal artery
   3. Accessory meningeal artery
   4. Meningeal branch of ascending pharyngeal artery

Question 5. Middle meningeal artery
Answer:

It is a branch of the first part of the maxillary artery

Branches:

Related Foramen:

• It is transmitted through foramen spinosum

Supplies following structures:

• More of bone & less of meninges
• Bone & red bone marrow in the dipole
• Small branches of duramater

Course:

• In the infratemporal fossa, the artery runs upwards & medially deep to the lateral pterygoid muscle & superior to the Sphenomandibular ligament
• It enters the middle cranial fossa through the foramen spinosum
• Here it runs forwards & laterally, grooving the squamous temporal bone & divides into

1. Frontal/ Anterior branch:
   • It is larger branch
   • It runs forwards & laterally towards the lateral end of the lesser wing of the sphenoid
2. Parietal/ Posterior branch:
   • It runs backwards over, or near the superior temporal sulcus of the cerebrum about 4 cm above the level of the zygomatic arch

Clinical Importance:

It is commonest source of extradural hemorrhage

Question 6. Circle of Wills
Answer:

It is an arterial circle, situated at the base of brain in the interpeduncular fossa

Formed by:

1. Anterior & middle cerebral branches of internal carotid artery

• They are interconnected by anterior communicating artery

2. Posterior cerebral branches of basilar artery

• Middle & posterior cerebral artery are united by posterior communicating artery

Branches:

1. Cortical/ External branches
   • Runs on the surface of the cerebrum
   • Anastomose freely
2. Central branches
   • They are arranged in following groups

Question 7. Sigmoid sinus
Answer:

• It is S-shaped paired sinus
• It is direct continuation of the transverse sinus

Extend:

• From the posteroinferior angle of the parietal bone to the posterior part of the jugular foramen

Tributaries:

• Mastoid and condylar emissary vein
• Cerebellar vein
• Internal auditory vein

Applied aspect:

• Thrombosis of the sigmoid sinus is always secondary to infection of middle ear
• Spread of infection or thrombosis from sigmoid sinus to superior sagittal sinus causes impaired CSF drainage into superior sagittal sinus leading to hydrocephalus

Question 8. Inferior sagittal sinus
Answer:

It is an unpaired sinus

Location:

• Lies in the posterior two third of the lower, concave free margin of the falx cerebri superior to Corpus callosum.
• It drains to the straight sinus by joining the great cerebral veins
• It receives blood from the deep and medial aspects of the cerebral hemispheres
• It is of a cylindrical form, increases in size as it passes backwards
• It is smaller and inconstant

Question 9. Definition, attachment and sinuses enclosed by falx cerebri.
Answer:

Falx Cerebri:

• It is large sickle shaped fold of duramater.

Attachments:

Sinuses enclosed by it:

• Straight sinus
• Inferior sagittal sinus
• Straight sinus

Question 10. Falx cerebri
Answer:

• It is large sickle-shapes fold of duramater
• It occupies the median longitudinal fissure between the two cerebral hemispheres

Ends:

1. Anterior end

• It is narrow & attached to the crista galli

2. Posterior end

• It is broad & attached to the upper surface of the tentorium cerebelli

Margins:

1. Upper convex margin

• Attached to the lips of the sagittal sulcus

2. Lower concave margin

• It is free

Surfaces:

• Left & right related to the medial surface of the cerebral hemisphere

Venous sinuses present in it:

• Superior Sagittal sinus
• Inferior Sagittal sinus
• Straight sinus

Question 11. Meckel’s cave
Answer:

• It is a recess of duramater present i.r.t the attached margin of the tentorium

Formed by:

• Evagination of the inferior layer of the tentorium over the trigeminal impression on the petrous temporal bone

Content:

• Trigeminal ganglion

Question 12. Emissary vein
Answer:

• These veins connect intracranial venous sinuses with extracranial veins
• They try to relieve raised intracranial pressure

Applied anatomy:

• Infection may reach through the emissary veins into cranial venous sinuses

Various emissary veins:

• Parietal emissary vein Mastoid emissary vein Condylar emissary vein

Question 13. Tentorium cerebella
Answer:

• It is tent shaped fold of duramater forming the roof of the posterior cranial fossa
• It separates cerebellum from the occipital lobes of the cerebrum
• It divides cranial cavity into supratentorial & infratentorial compartments

Margins:

1. Anterior free margin
2. Outer attached margin

Surfaces:

• Superior convex surface
• Inferior concave surface

Question 14. Diaphragm sellae
Answer:

• It is a small circular, horizontal fold of duramater forming the roof of the hypophyseal fossa
• It has a central aperture through which the stalk of the hypophysis cerebri passes

Attachments:

1. Anteriorly

• To the tuberculum sellae

2. Posteriorly

• To the dorsum sellae

3. On each side

• Continuous with the duramater of the middle cranial fossa

Question 15. Hypoglossal nerve
Answer:

• It is the twelfth cranial nerve
• It supplies the muscles of the tongue

Functional components:

• General somatic efferent
• General somatic afferent

Nucleus:

• It lies in the floor of fourth ventricle beneath Hypoglossal triangle

Branches:

1. Branches containing fibres of the Hypoglossal nerve proper

• They supply extrinsic & intrinsic muscles of the tongue

2. Branches of the hypoglossal nerve containing fibres of nerve C1

1. Meningeal branch
   • Supplies bone & meninges in the anterior part of the posterior cranial fossa
2. Descending branch
   • Continues as upper root of the ansa cervicalis
3. Branches to the thyrohyoid & geniohyoid muscles

Question 16. Superior sagittal sinus
Answer:

• Sagittal sinus occupies the upper convex attached margin of the falx cerebri
• It begins anteriorly at the crista galli by the union of tiny meningeal veins
• The interior of the sinus shows
  • Openings of the superior cerebral veins
  • Opening of venous lacumae
  • Arachnoid villi & granulations projecting into the lacunae as well as into the sinus
  • Numerous fibrous bands crossing the inferior angle of the sinus

Tributaries:

• Superior cerebral veins
• Parietal emissary veins
• Venous lacunae
• Occasionally a vein from the nose opens into it when the foramen caecum is patent

Question 17. Middle meningeal artery.
Answer:

• It is a branch of the first part of the maxillary artery
• Refer question no 4 of short essays for
  • Branches
  • Related foramen
  • Structures supplied

Question 18. Name four emissary veins
Answer:

Question 19. Confluence of dural venous sinus
Answer:

• Superior Sagittal sinus communicates Anteriorly with the veins of frontal sinus & occasionally with the veins of nose through the foramen caecum
• Next the sinus runs upwards & backwards
• It ends near the internal occipital protuberence by turning usually to right side & becomes continuous with the right transverse sinus or sometimes with left transverse sinus
• Generally, it communicates with the opposite sinus
• The junction of all these sinuses is called confluence of sinuses

Question 20. Structures passing through major openings in diaphragm
Answer:

Question 21. Name the folds of dura mater present in the cranial cavity
Answer:

• Falx cerebri- large sickle-shaped fold
• Tentorium cerebri-Tent-shaped fold
• Falx cerebelli- Small sickle-shaped fold
• Diaphragm sellae- Small circular, horizontal fold

Question 22. Trigeminal ganglion in middle cranial fossa
Answer:

• It is a sensory ganglion of the V cranial nerve
• It is similar to the dorsal nerve root ganglia

Question 23. Circle of Wills
Answer:

• It is an arterial circle, situated at the base of brain in the interpeduncular fossa

Formed by:

1. Anterior & middle cerebral branches of internal carotid artery

• They are interconnected by anterior communicating artery

2. Posterior cerebral branches of basilar artery

• Middle & posterior cerebral artery are united by posterior communicating artery

Branches:

1. Cortical/ External branches
2. Central branches

Question 24. Processes of dura mater of brain
Answer:

1. Falx cerebri

• It is large sickle-shapes fold of duramater
• It occupies the median longitudinal fissure between the two cerebral hemispheres

2. Falx cerebelli

• It is small sickle shaped fold of duramater
• It projects into the posterior cerebellar notch

3. Tentorium cerebelli

• It is tent shaped fold of duramater forming the roof of the posterior cranial fossa
• It separates cerebellum from the occipital lobes of the cerebrum
• It divides cranial cavity into supratentorial & infratentorial compartments

Question 25. Enumerate paired dural sinuses
Answer:

• Cavernous sinus
• Superior petrosal sinus
• Inferior petrosal sinus
• Transverse sinus
• Sigmoid sinus
• Sphenoparietal sinus
• Petrosquamous sinus
• Middle meningeal veins

Question 26. Duramater
Answer:

• It is the outermost, thickest & toughest membrane covering the brain

Layers:

1. Outer / Endosteal layer

• Serves as endosteum for the skull bones
• It is richly vascular

2. Inner/Meningeal layer

• Surrounds the brain
• It is folded to divide the cranial cavity into compartments
• It is more fibrous & requires little blood supply

Question 27. Falx cerebelli
Answer:

• It is small sickle shaped fold of duramater
• It projects into the posterior cerebellar notch

Question 28. Straight sinus
Answer:

• It lies within the junction of the falx cerebri & the tentorium sellae
• It is formed by the union of the inferior Sagittal sinus with the great cerebral vein
• Here exists a ball valve mechanism formed by sinusoidal plexus of blood vessels
• This regulates the secretions of CSF
• It ends at the internal occipital protuberence

Question 29. Transverse sinus
Answer:

• They are paired large sinuses
• They are situated in the posterior part of the attached margin of the tentorium cerebelli
• The right transverse sinus is continuation of the superior sagittal sinus & left sinus is continuation of the straight sinus

Extend:

• From the internal occipital protuberence to the posteroinferior angle of the parietal bone

Tributaries:

• Diploic vein
• Superior petrosal sinus
• Inferior cerebral vein
• Inferior cerebellar vein
• Inferior anastomic vein

Question 30. Sigmoid sinus
Answer:

• It is paired S-shaped sinus
• It is direct continuation of the transverse sinus

Extend:

• From the posteroinferior angle of the parietal bone to the posterior part of the jugular foramen

Tributaries:

• Mastoid & Condylar emissary vein
• Cerebellar vein
• Internal auditory vein

Question 31. Petrosal nerves
Answer:

Question 32. Differentiate between extradural & subdural hemorrhages
Answer:

Question 33. Name the venous sinuses present in falx cerebri
Answer:

Sinuses enclosed by falx cerebri:

• Superior sagittal sinus
• Inferior sagittal sinus
• Straight sinus