Structure & Function of the Eye

External Features

1. Soft tissue that must be protected

2. Cells exposed to air must not be allowed to dry out

3. Should have the ability to select a direction to sample

4. Should have the ability to control the amount of light entering the eye

Structure & Function of the Eye

External Features

1. Soft tissue that must be protected

2. Cells exposed to air must not be allowed to dry out

3. Should have the ability to select a direction to sample

4. Should have the ability to control the amount of light entering the eye

Structure & Function of the Eye

External Features

1. Soft tissue that must be protected

2. Cells exposed to air must not be allowed to dry out

3. Should have the ability to select a direction to sample

4. Should have the ability to control the amount of light entering the eye

Structure & Function of the Eye

External Features

1. Soft tissue that must be protected

2. Cells exposed to air must not be allowed to dry out

3. Should have the ability to select a direction to sample

4. Should have the ability to control the amount of light entering the eye

1. Protecting the Soft Tissues

The eye is located in a bone socket.

Why is there a hole in the back of the eye socket?

1. Protecting the Soft Tissues

The _________ help filter out dust

1. Protecting the Soft Tissues

The eyelashes help filter out dust

1. Protecting the Soft Tissues

The eyelashes help filter out dust

The ______ can close and cover the eye.

1. Protecting the Soft Tissues

The eyelashes help filter out dust

The eyelid can close and cover the eye.

1. Protecting the Soft Tissues

The eyelashes help filter out dust

The eyelid can close and cover the eye.

The eye is covered by a tough thick skin called the ___________

1. Protecting the Soft Tissues

The eyelashes help filter out dust

The eyelid can close and cover the eye.

The eye is covered by a tough, thick, opaque skin called the sclera

2. Keeping the eye Moist

The ______________ lies within the orbit on the outer portion of the upper eye. The gland continually secretes ____ which moisten, lubricate, and protect the surface of the eye. Excess tears drain into __________ which empty into the __________.

2. Keeping the eye Moist

The lachrymal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes ____ which moisten, lubricate, and protect the surface of the eye. Excess tears drain into __________ which empty into the __________.

2. Keeping the eye Moist

The lachrymal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes tears which moisten, lubricate, and protect the surface of the eye. Excess tears drain into __________ which empty into the __________.

2. Keeping the eye Moist

The lachrymal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes tears which moisten, lubricate, and protect the surface of the eye. Excess tears drain into small ducts which empty into the __________.

2. Keeping the eye Moist

The lachrymal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes tears which moisten, lubricate, and protect the surface of the eye. Excess tears drain into small ducts which empty into the nasal cavity.

2. Keeping the eye Moist

The lachrymal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes tears which moisten, lubricate, and protect the surface of the eye. Excess tears drain into small ducts which empty into the nasal cavity.

Why do you think we have to blow our nose when we cry?

3. Controlling Direction

A set of 6 muscles control the direction the eye is pointed

4. Controlling the Amount of Light Entering the Eye

The _____ is the hole.

The ____ is a muscle that can be contracted or relaxed to change hole size.

4. Controlling the Amount of Light Entering the Eye

The pupil is the hole.

The ____ is a muscle that can be contracted or relaxed to change hole size.

4. Controlling the Amount of Light Entering the Eye

The pupil is the hole.

The iris is a muscle that can be contracted or relaxed to change hole size.

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 16.5b

Accessory Structures of the Eye• Lacrimal apparatus

– keeps the surface of the eye moist– Lacrimal gland –

produces lacrimal fluid

– Lacrimal sac – fluid empties into nasal cavity

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Fibrous Tunic• Most external layer of the eyeball– Composed of two regions of connective tissue• Sclera – posterior five-sixths of the tunic–White, opaque region– Provides shape and an anchor for eye muscles

• Cornea – anterior one-sixth of the fibrous tunic• Limbus – junction between sclera and cornea• Scleral venous sinus – allows aqueous humor to

drain

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Medial View of the Eye

Figure 16.7a