HBS Eye Anatomy

tapetum definition

Blue reflective layer behind retina (aids in night vision of some animals), reflects light back through the eye

speech, audio, touch

Describe at least three specific ways that we communicate with the outside world and at least three ways (other than sight) in which the world communicates to us.

1. The eye sees good food and signals the nervous system to be happy and hungry, 2. The eye sees that you are underwater and signals to the respiratory system to hold your breath. 3. The eyes see a gnat and signal to the muscular system to swat it. 4. The eye sees something gross and signals to the digestive system to vomit. 5. The eye sees a dog and signals to the skeletal system to pet it.

Describe how what you see can impact other human body systems. Provide at least five specific examples of how your communication with the outside world through your eyes initiates a response in another body system.

Cow eyes have a tapetum, which reflects light so that the cow can see in the dark. Humans do not have a tapetum because they are not nocturnal. Cow eyes also have oval shaped pupils so that they can see more. Cows have eyes on the side of their head, so the pupils need to be larger to accustom to not being able to see a full 360 degrees like humans, who have round pupils.

Describe two ways in which the cow eye and the human eye differ? How are these differences linked to function?

Allows the eye to move up, down, and to the side

Find muscle attached to the side of the eye. Why is the human eye surrounded by six different muscles? What roles do these muscles play?

It is cloudy blue and dark

Find the cornea, the covering over the front of the eye. When the cow was alive, the cornea was clear. Describe the membrane now.

It is used for strength because it is a protective coating for the eye

Find the sclera, the tough outer covering of the eye also called the "whites" of the eye. Feel the sclera. Is this structure is designed for strength or clarity? Why?

Allows light to pass through the eye

Given what you observed, state the function of the pupil.

To protect the eye from foreign substances

If the eyelid is still present, note its structure and the presence of eyelashes. What is the function of the eyelid and eyelashes?

Reflex 1) Light goes through the eye 2) The retina processes the light rays into impulses 3) The impulses are sent to the optic nerve 4) The optic nerve brings the impulse to the brain stem 5) The brain stem sends another impulse to the pupil to dilate it.

Is the response of your pupil a reflex or a voluntary action? Describe how this response is controlled by the nervous system.

To speed up the signals that are being sent from the eye to the brain

Locate the optic nerve. You may find this spot by locating a patch of white goop. This goop is the myelin around the neurons of the optic nerve. What is the function of this myelin?

Circular

Look through the cornea and see the iris, the colored part of the eye. Note the pupil, the dark oval in the middle of the eye. What shape is the pupil in a human eye?

The blood vessels obstruct vision and the function of the cornea is to allow the person to see and it bends light

Note that the cornea does not have any blood vessels. Given the function of the cornea, why do you think it is important that the cornea is clear and free of blood vessels?

The retina wouldn't be pushed up against the eye, permitting a person from because able to see because the eye can't make an image

Note that the retina is the sensory layer of the eyeball which contains receptors for sight, called rods and cones. The eye uses light coming in to make an image, a picture which lands on the retina. Seeing the state of the retina after removing the fluid, what would happen to the retina if this fluid was not present? How would this affect vision?

To cushion the eye from the bone in the skull that holds the eye

Observe the fat attached to the outside of the eye. Remember the fat pads you built behind the eye of your Maniken®. What purpose do you think this fat serves?

This helps animals see in the dark, night vision, and humans don't have night vision

Observe the iridescent layer of the inner eyeball behind the retina. This is the tapetum. Humans do not have this layer in their eyes. Based on the function of this structure, why don't we see a tapetum in the human eye?

Magnifies the words

Put the lens down on your paper and look through it to words on the page. If you are using a preserved eye, you may need to shine a light on the lens to see the words. What do you notice?

retina definition

The light sensitive layer within the eye that converts images into electrical signals, detects images focused by the cornea, lens, and aqueous humor

cornea definition

The outermost lens of the eye that focuses light into the inner eye by bending it and protects it from harmful matter

1)Enters cornea, which bends the light. 2)Light passes freely through pupil in the iris. 3)Light passes through vitreous humor. 4)Retina captures light rays, processes them into impulses. 5) Impulses sent to optic nerve via nerve fibers. 6)Optic nerve transmits message to the brain.

Trace the path of light from the time it enters the eye to the time it leaves for the brain.

aqueous humor definition

Watery liquid inside the anterior (front) chamber of the eye that helps maintain pressure and shape.

vitreous humor definition

Watery liquid inside the posterior (back) chamber of the eye that helps maintain pressure and shape.

sclera definition

White outer covering of the eye that provides protection

The pupil dilates when the light is shown

With a flashlight or penlight, carefully shine a stream of light into your partner's eye. Watch what happens to the pupil. Take the light away and observe this reaction. Switch positions and allow your partner to observe these changes. Describe your observations below.

pupil definition

changes size to allow light into the inner eye

iris definition

controls how much light enters the eye

blind spot definition

place where the optic nerve leaves the retina

optic nerve definition

the bunble of nerve fibers that carry information from the retina (electrical signals) to the brain

lens definition

the transparent orb within the eye that refracts light to the retina of the eye, makes an image on the eye's retina, focuses on objects