Chapter 14- Ocular anatomy and physiology part 1 (1)

Question 1

When light rays strike the surface of the eye, what is the first thing they encounter?

Answer 1

The tear film

Question 2

What is a tear film?

Answer 2

A thin layer of fluid

Question 3

What are the functions of the tear film?

Answer 3

1- Lubricates the eye

2- Barrier to foreign bodies and antigens (protection)

3- Ensuring a smooth refractive surface for vision

Question 4

What is the tear film composed of?

Answer 4

Mucus, serous, sebaceous substances arranged in layers.

Question 5

Tear film secretions occur from where?

Answer 5

Exocrine glands, located within epithelial tissue.

Question 6

What exocrine glands are involved with tear film?

Answer 6

1- Outer lipid layer (sebaceous)

2- Central aqueous layer (serous)

3- Inner mucin layer (mucous)

Question 7

What are the roles of the outer lipid layer (sebaceous)?

Answer 7

1- Minimises evaporation

2- Limits contamination from particles and microorganisms

Question 8

What is the outer lipid layer secreted primarily by?

Answer 8

It is secreted primarily by meibomian (tarsal) glands

Question 9

Where are the meibomian (tarsal) glands located?

Answer 9

Located within tarsal plates of upper and lower eyelids.

Question 10

What is a tarsal plate?

Answer 10

Regions of dense connective tissue located deep in the upper and lower eyelid.

Question 11

What type of gland is a meibomian (tarsal) gland?

Answer 11

A simple, multicellular exocrine gland.

Question 12

What does the tarsal plate open on to?

Answer 12

They open onto the ocular surface via pores at the eyelid margin.

Question 13

What are the roles of the central aqueous layer (serous)?

Answer 13

1- Washing away foreign bodies and contaminations

2- Nourish the avascular cornea

Question 14

What is the central aqueous layer secreted by?

Answer 14

Secreted primarily by the lacrimal gland.

Question 15

Where is the lacrimal gland located?

Answer 15

Above the upper eyelid

Question 16

What type of gland is the lacrimal gland?

Answer 16

Compound multicellular exocrine gland

Question 17

What are the roles of the inner mucin layer (mucous)?

Answer 17

1- Forms a glycocalyx over the ocular epithelium that prevents pathogen adhesion

2- Reduces friction during blinking

Question 18

What is the inner mucin layer secreted by?

Answer 18

Secreted by goblet cells

Question 19

Where are these goblet cells located?

Answer 19

Located in the conjunctiva

Question 20

What is the conjunctiva?

Answer 20

A mucous membrane covering the inner surface of the eyelid and the exposed surface of the eyeball up to the limbus.

Question 21

What type of gland is the goblet cell?

Answer 21

This is a unicellular exocrine gland

Question 22

How does the orbicularis oculi operate around the eye?

Answer 22

The orbicularis oculi runs in circular bands around the eye

Question 23

What is the function of the orbicularis oculi?

Answer 23

Involved in the closing of the eyelid

Question 24

Where is the orbicularis oculi situated?

Answer 24

Part of the muscle lies within the face and part within the eyelid.

Question 25

What happens when the orbicularis oculi muscle contracts?

Answer 25

The tears are drawn from the tear film.

Question 26

Where is the levator palpebrae superioris situated and what does it do?

Answer 26

Runs along the top of the eyeball and sends tendons down into the eyelid.

Question 27

The contraction of the levator palpebrae superioris does what?

Answer 27

Its contraction raises the upper eyelid