WEEK 3: Gross Anatomy of the Globe, EOM and Sclera

Question 1

What connective tissue lines the oribital margin ?

Answer 1

Periorbita, continous with the periosteum covering the bone of the face
at the optical canal is continous with the periosteal layer of the dura mater, however thickens at the common tendinous ring

Question 2

What are the 12 cranial nerves?

Answer 2

1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abduces
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Accessory
12. Hypoglossal

Question 3

Describe somatic nervous system

Answer 3

Regulates the voluntary movement of the body
covers skeletal muscles and sensory stimuli
afferent (towards) division - sensory: pressure, heat, pain
efferent (away) division - motor: sketetal muscle. Neurotransmitter is acetycholine.

Question 4

Describe autonomic nervous system

Answer 4

Regulates involuntary movement of the body
Covers bodily function such as respiration rate, heart rate, urination, digestion, sexual arousal, pupil response.
innervates: smooth muscle, cardiac muscle and glands
autonomic: not consciously directed, afferent and efferent nerves
neurotransmitters are acetycholine and norepinephrine
sympathetic (fight/flight) and parasympathetic (rest/digest) division

Question 5

Sympathetic nervous system (fight and flight) reaction within the eye

Answer 5

Ocular innervation of the following structures:
- iris dilator
- ciliary muscle (small, slow inhibitory input)
- superior tarsal muscle (muller’s muscle): maintain elevation of upper eyelid
- lacrimal gland
- choroidal and conjunctival blood vessels
Sympathetic ganglion is the Superior Cervical Ganglion
Beta 1 : Adrenergic receptors: neurotransmitter is epinephrine and norepinephrine

Question 6

What is parasymapathetic nervous system (rest/digest) reaction within the eye?

Answer 6

Ocular innervation of the following structures:

1. iris spinchter
2. Ciliary muscle
3. Lacrimal gland

the Parasympathetic ganglion is the cliary ganglion
muscarinic receptors, neurotransmitter is acetycholine

Question 7

What is the pathway for CN2?

Answer 7

Optic Nerve
Sympathetic afferent pathway (towards)
carries sensory nerve impulses from the retinal ganglion cells (RGCs) towards the cortical and sub-cortical visual centres in the brain
RGC axons become myelinated in the optic nerve
Surrounded by cranial meninges, does not join with brainsteam

Question 8

What is the function of CN3?

Answer 8

Oculomotor nerve
Sympathetic efferent pathway
motor control of eye movements

Question 9

What muscles does CN3 innervate?

Answer 9

Inferior rectus
Inferior oblique
Medial rectus
superior rectus
levator palpaebrae superioris
iris sphincter (parasympathetic innvervation)
ciliary body (parasympathetic innervation)
Origin in midbrain at level of superior colliculus

Question 10

What is the function and innervation of CN4?

Dysfunction?

Answer 10

Trochlear nerve
innervates the superior oblique
long intracranial course: high risk of dysfunction due to trauma and IC pathology
Function: intorsion, depression and abduction
Dysfunction : impaired depression on downward gaze (vertically and in adducted positions)

Question 11

What is the pathway, innervation, function and dysfunction of CN6?

Answer 11

Abducens nerve
innervates the lateral rectus muscle
long intracranial course: high risk of dysfunction due to trauma and IC pathology
also: innvervates contralateral medial rectus to enable co-ordinated lateral movement
Function: movement of the eye laterally
Dysfunction: eye cannot move laterally and may turn in in primary gaze position

Question 12

What are the layers of the sclera?

Answer 12

Episclera - outer most layer, connected to tenon’s capsule
Sclera stroma - can stretch and lenghten
Lamina fusca - brown due tp melanocytes

Question 13

What is cn5?

Answer 13

Trigeminal nerve - afferent pathway

Question 14

What are the 3 division of the trigeminal nerve?

Answer 14

Opthalmic, maxillary and mandibular

Question 15

What are the 3 division of the opthalmic nerve and their function?

Answer 15

Prior to entering the orbit through the superior orbital fissure, it divides into 3 main branches

• lacrimal - sensory innvervation of the lacrimal gland, upper eyelid and conjunctiva. Contains parasympathetic and sympathetic efferents to lacrimal gland
• frontal - passes beneath the roof of the orbit on the upper surface of the levator palpaebrae muscle. halfway in the orbit divide into large supraorbital branch - travels through supraorbital notch and supplies the skin and conjunctiva of the upper eye lid, skin of forehead and scalp and mucus membrane of the frontal sinus and small supratrochlear branch - travels above the superior oblique muscle trochlea then leaving the orbit through the orbtial septum and supplies skin and conjunctiva of the upper eyelid and skin of the medial forehead
• nasociliary

Question 16

What is the innervation and function of maxilary nerve trigeminal afferent pathways?

Answer 16

Infraorbital nerve - sensory fibres from cheek, upper lip, lower eyelid, lateral aspect of noes
Zygomatic nerve - sensory fibres from temporal region, cheek and lower eyelid
posterior superior alveolar - sensory to teeth, maxillary sinus

Question 17

What is the innervation and function of mandibular nerve trigeminal afferent pathways?

Answer 17

has both a sensory (afferent) and a motor (efferent) root
Sensory - teeth, gum of mandible, skin of temporal region, lower lip, lower part of face
Motor: muscles of mastication

Question 18

What in the innervation of the facial nerve?

Answer 18

Efferent pathway
2 roots
large motor root - innervates facial muscles
smaller sensory root - from superior salivatory nucleus: containing parasympathetic secretomotor fibres to sublingual, submandibular and lacrimal glands and sensory fibres from solitary nucleus involved in taste (anterior 2/3 of tongue)