Tri B - The Special Senses

Question 1

Describe the eyeball

Answer 1

2.5cm diameter
Inner 5/6ths are protected by bony orbit and peri-orbital fat

Question 2

What are the 3 layers of the eyeball?

Answer 2

Outer - fibrous tunic
Middle - vascular tunic
Inner - retina

Question 3

Describe the outer layer of the eyeball

Answer 3

Avascular
Contains:
1. Anterior cornea - Focuses light rays
Transparent
2. Posterior sclera - white of the eye
Dense connective tissue - adds rigidity
3. Scleral venous sinus - Junction of 1&2
Aqueous humour drains into sinus

Question 4

Describe the extrinsic eye muscles

Answer 4

3 pairs - insert into sclera
Superior and inferior rectus
Lateral and medial rectus
Superior and inferior oblique

Question 5

Describe the vascular layer of the eyeball

Answer 5

Choroid - Posterior, highly vascular, provides nutrients to sclera
Ciliary body - ciliary process, folds internally, capillaries secrete aqueous humour, zonular fibres attach to lens, ciliary muscle
Iris

Question 6

Describe the retina

Answer 6

Surface is the only area where blood vessels can be viewed directly
3 landmarks:
Optic disc
Macula lutea
Fovea

Question 7

Describe the 2 layers of the retina

Answer 7

Pigmented layer - Melanin in epithelium, absorbs stray light
Between choroid and neural layer
Neural layer - 3 zones; photoreceptor layer, bipolar cell layer, ganglion cell layer

Question 8

Describe the Macula and fovea of the retina

Answer 8

Contains only cones
Area of maximum visual acuity
Rods are more plentiful towards periphery

Question 9

Describe the optic disc of the retina

Answer 9

No rods or cones
Images that strike the optic disc cannot be processed - the blind spot

Question 10

Describe photoreceptor cells

Answer 10

Convert light rays to nerve impulses
- Rods - only show greys, dim light vision
- Cones - colour vision
Both contain photopigments

Question 11

Describe the structure of the lens

Answer 11

Numerous layers of protein fibres, crystallins
No blood vessels

Question 12

What is the function of the lens in the eyes

Answer 12

Focuses light onto retina to produce clear images
Accommodation -lens changing size to adjust for distance or close vision - younger people
Loss of transparency - cataract

Question 13

Describe the Anterior and posterior chambers of they eye

Answer 13

Filled with aqueous humour
Intraocular pressure from humour, filters out of blood capillaries

Question 14

Describe the vitreous cavity of the eye

Answer 14

Contains ‘vitreous body’ – jelly like substance - holds retina flush against choroid
Does not replenish
Phagocytic cells remove debris

Question 15

Describe the accessory structures of the eyes

Answer 15

Eyelids - Thin mucus membrane
Shade eyes during sleep, protect eyes from light and foreign objects
Eyelashes/eyebrows - protect eyes from foreign objects, perspiration, direct rays of sun

Question 16

Describe the lacrimal apparatus

Answer 16

Structures that produce and drain lacrimal fluid
Function - to protect, clean and moisten eyeball
Lacrimal gland - secretes fluid
Lacrimal ducts - empty fluid onto conjuctiva
Lacrimal puncta - Fluid drains into puncta

Question 17

Describe the auricle of the ear

Answer 17

Flap of elastic cartilage
Sound directed into external auditory canal

Question 18

Describe the external auditory canal

Answer 18

Curved tube - ~2.5cm
Lined with skin
Hairs and earwax prevent foreign objects

Question 19

Describe the tympanic membrane (eardrum)

Answer 19

Thin, transparent membrane
Separates outer from middle ear
Covered by epidermis
Connective tissue

Question 20

Describe the middle ear

Answer 20

Small, air filled cavity
Lined with epithelium
Separated from inner ear by thin bony partition
Mastoid antrum - chamber connecting to mastoid cells
Opening that leads to auditory tube

Question 21

Describe auditory ossicles

Answer 21

Smallest bones in body
Malleus (hammer) - attaches to surface of eardrum
Incus (anvil) - articulates with head of malleus and stapes
Stapes (stirrup) - Footplate fits into oval window

Question 22

Describe the inner ear

Answer 22

Bony outer labyrinth
- Surrounds membranous labyrinth
- Contains fluid - perilymph
Membranous inner labyrinth
- Series of sacs and tubes
- Lined with epithelium
- Contains fluid - endolymph

Question 23

Describe the semi-circular canal

Answer 23

Semi-circular ducts - Portions of membranous labyrinth
Contain receptors for epithelium
3 bony canals - each lies at 90*
At one end - enlargement - ampulla
Communicate with utricle of vestibule

Question 24

Describe the vestibule

Answer 24

Oval central portion of membranous labyrinth
2 sacs - utricle, saccule
Contains receptors for epithelium

Question 25

Describe the cochlea

Answer 25

Bony spiral canal
Almost 3 turns round central bony core - modiolus
3 channels
Partitions are Y shaped

Question 26

Describe the 3 channels of the cochlea

Answer 26

Scali vestibuli - Communicates with oval window
Contains perilymph
Scala tymphani - Communicates with round window
Cochlear duct - Contains spiral organ, relays auditory information

Question 27

Describe the nose

Answer 27

Organ of sense of smell
Olfactory region in superior nasal conchae
Lined with mucus membrane
Bipolar nerve cells
Fibres from olfactory bulb pass to temporal lobe

Question 28

Describe the tongue

Answer 28

Function - sense of taste, speech, swallowing
Papillae concerned with sense of taste

Question 29

Describe the sense of taste

Answer 29

Sensitive to temperature, pain, touch