Week 12 - Special Sense Part 1

Question 1

What are the accessory structures of the eye

Answer 1

• eyelids
• conjunctiva
• lacrimal apparatus

Question 2

what are the eyelids and how are they accessory structure to the eye

Answer 2

• Eye lids with lashes at their leading edges
• Eyelash hair follicles innervated by nerve endings – trigger reflex blinking
• Help to prevent particles landing on eye
• Protect eyes, reflex blinking via eyelash receptors.(abrasion)

Question 3

what is the conjunctiva

Answer 3

Mucous membrane lining eyelids and sclera.
- Mucous membrane on the inside surface of the eye lid
- Extends over sclera (not cornea) connecting the eyelids to the eyeball
- Oily secretions from tarsal glands lubricate eyelids and eye

Question 4

What is the lacrimal apparatus

Answer 4

Produces and drains tears; contains lysozyme, mucus, and antibodies.

• Lacrimal glands release a dilute saline solution into superior part of conjunctival sac
• Blinking spreads fluid across eye
• Fluid drains into lacrimal sac, then nasolacrimal duct and empties into nasal cavity
• Fluid contains mucus, antibodies, and lysozyme – it cleans and protects the eye surface as it moistens and lubricates
• Spillover (tears) happen when eyes are irritated or when emotionally upset

Question 5

What are the 3 layers of the eyeball

Answer 5

1. Fibrous tunic (outer)
2. Vascular Tunic (middle)
3. Neural Tunic (inner)

Question 6

what are the parts of the fibrous tunic (outer)

Answer 6

• sclera
• cornea

Question 7

what is the sclera

Answer 7

• part of the fibrous tunic (outer)
  White, protective. Layer that covers 5/6 of the eyeball’s surface excluding the cornea.

Question 8

What is the cornea

Answer 8

• part of the fibrous tunic
  Transparent, refracts light. Cover the anterior part of the eye allowing light to enter and bend for focusing

Question 9

What are the parts of the vascular tunic (middle)

Answer 9

• choroid
• ciliary body
• iris

Question 10

what is the choroid

Answer 10

Connective tissue that supplies blood to the eye ball
- part of the vascular tunic (middle)

Question 11

what is the ciliary body

Answer 11

Controls lens shape. – thickened ring of tissues that encircles lens and modifies lens shape for focusing
- part of the vascular tunic (middle)

Question 12

what is the iris

Answer 12

Adjusts pupil size. – overlaying ciliary body, smooth muscle that open or closes the pupil, regulating light entry
- part of the vascular tunic (middle)

Question 13

What is apart of the neural tunic (inner)

Answer 13

retina

Question 14

what is the retina

Answer 14

Contains photoreceptors for light detection. – delicate nervous tissue (developed from brain extension) for photoreception; neural and pigmented layer

Question 15

the internal chambers are divided into what segments

Answer 15

• anterior cavity
• posterior cavity

Question 16

what is the anterior cavity

Answer 16

• Filled with aqueous humour
• Divided by iris into anterior and posterior chamber

Question 17

what is the function of aqueous humour

Answer 17

• Aqueous humour forms and drains at the same rate to maintain constant intraocular pressure
• Supplies nutrients and oxygen to lens and corneas; carries away metabolic waste

Question 18

what is the posterior cavity filled with

Answer 18

Filled with vitreous humour

Question 19

what is the function of vitreous humour found in the posterior cavity

Answer 19

• Forms in embryo and lasts a lifetime
• Transmits light
• Support posterior surface of lens and hold retinal layers together
• Contributes to intraocular pressure

Question 20

explain image formation

Answer 20

where Light bends mainly at cornea, then focused by lens onto retina.

Question 21

Images focus on what part of the retina

Answer 21

Fovea Centralis

Question 22

what is accommodation

Answer 22

where Lens shape changes for focus on objects at different distances

Question 23

what is the lens accommodation for distant vision

Answer 23

lens flattens

Question 24

what is the lens accommodation for close vision

Answer 24

lens bulges

Question 25

what is myopia

Answer 25

- common vision defect - nearsighted - corrected with diverging lens

Question 26

What are causes for myopia

Answer 26

- lens too strong - eye too long both results in the light bending too early and not hitting the retina correctly

Question 27

what is hyperopia

Answer 27

- common vision defect - farsighted - corrected with converging lens

Question 28

What are causes for hyperopia

Answer 28

- Lens too weak - eye too short Both result in the light not bending soon enough

Question 29

what are the 2 main photoreceptor cells

Answer 29

- rods - cones

Question 30

what are rods responsible for

Answer 30

- peripheral and night vision - also motor detection - very sensitive to light (1000x more sensitive than cones) - no colour (black and white) information - concentrated in the peripheral retina

Question 31

what are cones responsible for

Answer 31

- central vision - vision in bright light - detects colour - responsible for high resolution images - most concentrated in the fovea (central region of the retina - no rods here)

Question 32

what do rods contain

Answer 32

stack of membrane bound discs that contain the photosensitive pigment rhodopsin

Question 33

what do cones contain

Answer 33

photo sensitive pigments (photopsins) in infoldings of the cell membrane

Question 34

what are the 2 parts of rods and cones

Answer 34

- outer segment - inner segment these 2 parts are connected by stalks

Question 35

what is the outer segment of rods and cone

Answer 35

photoreception region containing photopigments

Question 36

what is the inner segment of rods and cones

Answer 36

common cell organelles and connects to cell body with nucleus

Question 37

Why is there a blind spot in the eye

Answer 37

It's where the optic nerve exits the eye