Chapter 2 - Anatomy And Physiology

Question 0

Name the four primary structures included in the adnexa.

Answer 0

The orbit
extraocular muscle
eyelids
tear draining lacrimal apparatus

Question 1

Briefly describe how the eye converts light rays to a perceived image, naming the principle structures involved in the process.

Answer 1

Because the vitreous is optically transparent, light rays focus by the cornea and lens can pass through it unaffected to produce an image on the inner back surface of the eye, the retina. the light-sensitive cells of the retina convert the image to electric impulses that are carried to the brain by the optic nerve. the electric impulses are integrated up in the brains visual cortex to produce the sensation of sight.

Question 2

Describe the structure and function of the orbit.

Answer 2

The structure is pear shaped, bony cavity in the skull. has seven bones, that houses the globe, extraocular muscles, blood vessels and nerves.

Question 3

Medial rectus muscle

Answer 3

Inward rotation

Question 4

Lateral rectus

Answer 4

Outward rotation

Question 5

Superior rectus

Answer 5

Incyclotorsion - down an inward

Question 6

Inferior rectus

Answer 6

Excyclotorsion - up and outward

Question 7

Superior oblique

Answer 7

Upward rotation

Question 8

Inferior oblique

Answer 8

Downward rotation

Question 9

What are the three functions of the eyelids.

Answer 9

Protects from injury, excludes the light, aids in the lubrication of the ocular surface.

Question 10

Name the three layers of the eyelids.

Answer 10

The outer layer - skin
middle - fibrous tissue and muscle
Inner layer - conjunctiva

Question 11

Give two reasons why tears are important to functioning of the eye.

Answer 11

Clears vision and nourishes the eye.

Question 12

Endothelium

Answer 12

Maintains proper fluid balance

Question 13

Epithelium

Answer 13

Serves as first line of defense against infection and injury

Question 14

Bowman’s membrane

Answer 14

Acts as anchor for epithelium

Question 15

Descemet’s membrane

Answer 15

Contributes rigidity

Question 16

Stroma

Answer 16

Main body of the cornea, contributes rigidity also.

Question 17

Name the five layers of the corneal tissue

Answer 17

Endothelium 
epithelium 
Bowmans membrane 
Descemet's membrane 
stroma

Question 18

What is the relationship between the lacrimal gland, lacrimal sac and nAsolacrimal duct?

Answer 18

They are the Orbital structures of the lacrimal apparatus that produce tears and the ducts that drain the excess fluid from the front of the eyes into the nose.

Question 19

Name the 3 layers of tear film and their functions.

Answer 19

Lipid layer - helps prevent evaporation of moisture from the middle layer
Aqueous layer - supplies moisture, oxygen, and nutrients to nourish the cornea.
Mucin layer - innermost layer composed of mucinous fluid that promotes an even spread of the tear film over the cornea

Question 20

What is the principal function of the cornea.

Answer 20

Focus light rays reflected to the eye. It contributes 2/3 if the focusing power of the eye.

Question 21

What is the main function of the sclera?

Answer 21

Protects the intraocular contents.

Question 22

Why is a balance between the inflow and outflow of aqueous humor important?

Answer 22

It maintains the intraocular pressure and is extremely important to the proper function of the eye. If drainage of aqueous fluid is impaired, pressure inside the eye rises, increasing the rush for glaucoma. Increased pressure in the eye can damage the optic nerve, leading to vf loss and eventually blindness if appropriately treated.

Question 23

Describe the course of aqueous humor into and out of the eye, naming the principal ocular structures involved.

Answer 23

The aqueous humor is a clear, transparent fluid found in the anterior chamber. The aqueous humor is produced by the secretary tissue behind the iris. As the fluid is produced, it flows across the back of the iris, through the pupil, and into the anterior chamber. The aqueous fluid leaves the eye at the junction of the cornea and iris , called the anterior chamber or filtration angle.from there it passes through the trabecular mesh work, a spongy structure that filters the aqueous fluid and controls it’s rate of flow out of the eye. After passing through the trabecular mesh work, aqueous humor drains through a conduit in the sclera called the canal of schlemm, then through collector channels called aqueous veins and lastly into the venous vessels in the conjunctiva to return to the general circulation.

Question 24

Name the 3 main structures that make up the uveal tract?

Answer 24

Iris, ciliary body, and choroid.

Question 25

Describe how the pupil dilates and contracts, naming the muscles involved.

Answer 25

The iris controls the amount of light entering the inner part of the eye. The dilator muscle stretching from the pupil to the boundaries of the iris contract to widen (dilate) the pupil in reduced light conditions. The sphincter muscle that encircles the pupil contracts to make the pupil smaller in response to bright light.

Question 26

What is the function if the ciliary process?

Answer 26

Secretes the aqueous humor that fills the anterior and posterior chambers.

Question 27

What is the main function of the choroid?

Answer 27

Supply nourishing blood to the outer layers of the retina.

Question 28

Which structure besides the cornea provides the eyes focusing power?

Answer 28

The lens

Question 29

What is the physiologic process and purpose of accommodation?

Answer 29

The curvature of the lens can change in order to focus images of object that are close to the eye, which is called accommodation. This occurs with the help of muscles of the biliary body. When the ciliary muscle contracts, the zonules relax, permitting the lend to become rounder and increasing it’s focusing power. The purpose is to focus images of objects that are closer to the eye.

Question 30

The lens is attached to the ciliary body by transparent fibers called..

Answer 30

Zonules

Question 31

What is the main function of the vitreous?

Answer 31

This substance acts as a shock absorber and maintains the spherical shape of the globe.