Orbit and Meninges

Question 1

Borders of the orbital cavity

Answer 1

Base: Frontal, maxilla, zygomatic process, zygomatic bone
Roof: Frontal and sphenoid bones
Medial: Lacrimal, ethmoid, sphenoid and maxilla
Floor: Maxilla, zygomatic and palatine bones
Lateral: Zygomatic and sphenoid bones

Question 2

Average thickness of the skull

Answer 2

4.4 mm (4 x thicker than the thinnest part)

Question 3

Layers of the eyelid from superficial to deep

Answer 3

Skin
Subcutaneous tissue
Obicularis oculi
Orbital septum
Conjuntiva
Tarsus

Question 4

Muscle responsible for eyelid opening

Answer 4

Levator palpebrae superioris

Question 5

Muscle connecting levator palpebrae and tarsus

Answer 5

Superior tarsal muscle

Question 6

Tarsus gland

Answer 6

Modified gland that secretes oily substances

Question 7

Orbital septum

Answer 7

Continuation of the periosteal layer

Question 8

Muscle responsible for eyelid closing

Answer 8

Obicularis oculi

Has an orbital part and a palpebrae part

Question 9

Innervation of the eyelids

Answer 9

Ophthalmic nerve (sensory)
Maxillary nerve
Oculomotor nerve
Facial nerve
Sympathetic fibres

Question 10

Blood supply of the eyelids

Answer 10

Ophthalmic artery
Facial artery
Superior temporal artery

Question 11

Raccoon eyes

Answer 11

Haemorrhage of the eyes due to pooling of the blood in the potential space between the skin and the subcutaneous tissue

Question 12

Obicularis oculi innervation

Answer 12

Frontotemporal branch of the facial nerve

Question 13

Levator palpebrae superioris innervation

Answer 13

Oculomotor nerve

Question 14

Superior tarsal innervation

Answer 14

Postganglionic sympathetic fibres

Question 15

Horner’s syndrome

Answer 15

Damage to sympathetic ganglion resulting in ptosis, miosis and anhydrosis

Question 16

Common tendinous ring

Answer 16

Thickening of the periosteum in the posterior part of the orbit around the optic canal and the central part of the superior orbital fissure

Question 17

Structures that pass through the common tendinous ring

Answer 17

Oculomotor nerve
Nasociliary nerve (branch of ophthalmic nerve)
Abducens nerve
Optic nerve
Also the common origin of the extraocular muscles

Question 18

Attachment of the superior rectus

Answer 18

Superior and anterior sclera

Question 19

Attachment of the inferior rectus

Answer 19

Inferior and anterior sclera

Question 20

Attachment of the lateral rectus

Answer 20

Anterolateral sclera

Question 21

Attachment of the medial rectus

Answer 21

Anteromedial sclera

Question 22

Structures that pass through the optic canal

Answer 22

Optic nerve

Ophthalmic artery

Question 23

Structures that pass through the superior orbital fissure

Answer 23

Superior ophthalmic vein
Ophthalmic nerve
Mandibular nerve
Trochlear nerve
Abducens nerve

Question 24

Structures that pass through the inferior orbital fissure

Answer 24

Inferior ophthalmic vein (if not through the superior orbital fissure)
Infra-orbital vein
Infra-orbital artery
Maxillary nerve
Sphenopalatine ganglion

Question 25

Levator palpebrae superioris attachment

Answer 25

Superior tarsal plate and skin of upper eyelid

Question 26

Facial vein drainage

Answer 26

Drains into the internal jugular vein

Question 27

Dacryocystocoele

Answer 27

Nasolacrimal duct doesn't open, visible when baby cries

Question 28

Layers of the eyeball

Answer 28

Fibrous tunic: cornea and sclera Vascular tunic: iris, ciliary body and choroid Nervous tunic: retina

Question 29

Lacrimal apparatus

Answer 29

``` Responsible for production of tears and drainage Lacrimal gland Canaliculi Lacrimal sac Nasolacrimal duct ```

Question 30

Shapes of haemorrhages on CTs

Answer 30

Extradural: lemon Subdural: banana Subarachnoid: grapes

Question 31

Danger triangle of the face

Answer 31

``` Commissures of the mouth to the nasion Ophthalmic vein (which has valves) communicates directly with the facial vein and the cavernous sinus, providing a direction of blood flow conducive to infection spread ```

Question 32

Branches of the ophthalmic nerve

Answer 32

Lacrimal Frontal Nasociliary

Question 33

Three layers of membranes that surround the brain

Answer 33

Dura mater (outer periosteal layer and inner meningeal layer) Arachnoid mater Pia mater

Question 34

Innervation of the meninges

Answer 34

Trigeminal nerve

Question 35

Periosteal layer

Answer 35

Seals the skull from the inside and outside | Continuous with the orbital septum

Question 36

Arachnoid mater

Answer 36

Thin, avascular membrane that lines the inner surface of the dura mater Does not enter the grooves or fissures of the brain, but does send out trabeculae, forming subarachnoid spaces which contain cerebral arteries and veins

Question 37

Tentorium cerebelli

Answer 37

Partition above the cerebellum

Question 38

Diaphragma sellae

Answer 38

Membrane that covers the pituitary gland

Question 39

Falx cerebri

Answer 39

A large, crescent-shaped fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres

Question 40

Falx cerebelli

Answer 40

A small sickle-shaped fold of meningeal layer of dura mater that separates the cerebella hemispheres

Question 41

Dura mater innervation

Answer 41

Trigeminal nerve Vagus nerve Cervical nerves 1, 2 and 3

Question 42

Dura mater blood supply

Answer 42

Many arteries including the middle meningeal artery

Question 43

Venous drainage of the brain

Answer 43

Networks of small venous channels combine to give rise to larger cerebral veins which drain into dural venous sinuses and eventually to the internal jugular veins. Diploic veins and emissary veins also drain into the dural venous sinuses.

Question 44

Diploic veins

Answer 44

Run between the internal and external tables of compact bone

Question 45

Emissary veins

Answer 45

Run between the outside of the cranial cavity and the dural venous sinuses Penetrate the periosteal layer and provide opportunity for bacteria to get in from outside skull, therefore clinically important

Question 46

Where does a subdural haemorrhage occur?

Answer 46

Within meningeal layers, not between the dura and arachnoid layers Caused by tearing of meningeal layer and therefore the cerebral veins too

Question 47

Which nerve runs with the internal carotid artery?

Answer 47

The abducens nerve

Question 48

9 dural venous sinuses

Answer 48

``` Sigmoid sinus Inferior sagittal sinus Superior sagittal sinus Straight sinus Confluence of sinuses Right transverse sinus Great cerebral vein Superior petrosal sinus Cavernous sinus ```

Question 49

Clinical importance of cavernous sinus

Answer 49

Communicates with the orbital cavity via the ophthalmic vein, meaning there is a potential for sinus infection via periorbital cellulitis leading to cavernous sinus thrombosis

Question 50

6 paired structures that run in the cavernous sinus or within its lateral wall

Answer 50

``` Oculomotor nerve Internal carotid artery Trochlear nerve Abducens nerve Ophthalmic nerve Maxillary nerve ```

Question 51

4 dual partitions formed by the dura mater

Answer 51

Falx cerebri Falx cerebelli Tentorium cerebelli Diaphragma sellae

Question 52

Extradural haemorrhage

Answer 52

Blood collects between the calvarium and the periosteal layer Classically from a tear in the middle meningeal artery in the temporoparietal region

Question 53

Subarachnoid haemorrhage

Answer 53

A bleed into the subarachnoid space | Usually arterial bleeding from a ruptured cerebral artery aneurysm from the circle of Willis