The orbit and nasal cavity

Question 1

What is the shape and function of the nose

Outline its arterial and nerve supply

Answer 1

Projection from face that filters dust entering respiratory system

Nasal cavity opens into nasopharynx

Ophthalmic and maxillary artery branches

Olfactory nerve, ophthalmic (V1 and V2)

Question 2

How is the nose adapted for olfaction?

In which conditions can olfaction be disturbed?

Answer 2

Conchae help warm and moisture the air

Olfaction receptors in epithelium (lining roof and walls) secrete a mucus fluid and odoriferous gases are dissolved into the fluid then detected by olfactory nerves

Parkinsons/trauma can cause a lack of sensation of smell

Question 3

Describe the paranasal sinuses

Answer 3

They are air filled extensions of the nasal cavity. They help lighten the skull and with voice resolution

Paired frontal sinuses in frontal bone that drain through frontonasal duct

Ethmoidal cells- invaginations in the ethmoid bone and drain into middle meatus (anterior and middle) or superior meatus (posterior)
Paired maxillay sinuses in maxilla drains into middle meatus (LARGE)
**Reason why nose runs when you cry

Sphenoidal sinuses in sphenoid bone drain –> spheno-ethmoidal recess

Question 4

What is the location and function of the eye?

What are its three layers?

Answer 4

It is in orbit suspended by muscles, it contains the optical apparatus for vision

Outer: fibrous sclera and cornea
Vascular: iris
Inner: retina
** divided into anterior and posterior chambers

Question 5

Describe the embryology of the eye

Answer 5

Optic stalk grows out and lens vesicle grows in

Occurs after 4 weeks

Question 6

Name and state the function and innervation of the 7 extraocular muscles

Answer 6

OCULOMOTOR NERVE (CN3)
Levator palpebrae- Elevates upper eye lid
Superior rectus- Elevation, some adduction and medial rotation
Inferior rectus- Depression, some adduction and lateral rotation
Medial rectus- Adduction
Inferior oblique- Elevates, abducts and laterally rotates the eyeball.

ABDUCENS NERVE (CN6)
Lateral rectus- Abducts

TROCHLEAR NERVE (CN4)
Superior oblique- Depresses, abducts and medially rotates the eyeball

Question 7

State the arterial and nerve supply of the eye (+extraocular muscles)

What effects does sympathetic and parasympathetic innervation of the eye have?

Answer 7

Arterial supply: Ophthalmic, infra-orbital and central arteries

Nerve supply: CN 2,3,4,5 (v1) ,6, 7

Symp: Stimulates dilator pupillae to let MORE light in

Parasymp: Stimulates constrictor pupillae to let LESS light in

Question 8

This question relates to eye pathology.

Which nerve(s) are effected in:

1. an inability to do specific eye movements?
2. dilated pupil?
3. ptosis (drooping eyelid)?
4. abnormal pupil reflex?

Answer 8

1. CN 3,4,6 (Oculomotor, trochlear, abducent)
2. CN3 (Trochlear)
3. CN3 (Trochlear)
4. CN3 (Trochlear)

Question 9

This question relates to eye pathology.

A lesion in cranial nerve X may form as a result of?

1. X= 3
2. X=4
3. X=5

Answer 9

1. Aneurysm of cerebral artery
2. Orbital fracture
3. Cavernous sinus lesion

Question 10

Crying involves lacrimal apparatus. Describe what happens in crying

What is the nerve supply to the lacrimal apparatus?

Answer 10

Lacrimal gland (two parts, orbital and palpebral) secretes lacrimal fluid which passes across the eye and into the lacrimal papilla, lacrimal sac and to the inferior meatus via the nasolacrimal duct

It is stimulated by happiness/sadness and environmental stimulus e.g. pollen or injury

Parasymp: Secretomotor (via facial nerve-CN7)
Symp: Vasoconstrictive (superior cervical ganglion via internal carotid)