External features of the eye

Question 1

Eyelashes

Answer 1

Barriers to keep out dust and debris from entering the eye.

Prevents injury, infection, and obstruction to vision.

Produces sebrum.

Question 2

Limbus

Answer 2

Junction between the cornea and sclera of the eye.

Question 3

Lateral canthus

Answer 3

General area where the temporal upper and lower lids meet.

Provides an anchor point that allows the eyelids to close completely over the eye.

Question 4

Iris

Answer 4

Controls the size of the pupil to control the amount of light entering the eye.

Pupillary light response.

Radial dilator muscle opens the pupil from the inside out. Sphincter is a circular muscle that controls closing the pupil.

Question 5

Lower eyelid

Answer 5

Protects the eye from foreign objects and excessive sunlight.

Spreads the tear film.

Inside surface is lined with conjunctiva.

Question 6

Eyebrow

Answer 6

Can prevent sweat, rain, dust and pollen from entering the eyes.

Arch shape directs light and sweat around the eyes and to the side of the face.

Protects from bright lights (provides shade) and irritants.

Question 7

Upper eyelid

Answer 7

Protects the eye from foreign objects and excessive sunlight.

Spreads the tear film.

Inside surface is lined with conjunctiva.

Moves in association with vertical eye movements - adjusts position when you change your gaze.

Generally covers the superior limbus when eyes are open and looking straight ahead.

Question 8

Palpebral fissure/aperture

Answer 8

The space between upper and lower eyelids when eyes are open.

Generally covers the superior limbus when eyes are open and looking straight ahead.

Question 9

Pupil

Answer 9

Black opening in the centre of the iris allowing light into the eye.

Size controlled by the iris according to the amount of light, avoids damage to the retina.

Gives aqueous humor a pathway to the front of the eye.

Question 10

Caruncle

Answer 10

Small, pink, globular nodule located at the inner corner of the eye (medial canthus) in the palpebral fissure.

Contains modified sebaceous and sweat glands.

Source of white secretion which constantly collects there.

Can become irritated and swollen with pollen.

Question 11

Medial canthus

Answer 11

General area where the lateral (nasal) upper and lower lids meet.

Provides an anchor point that allows the eyelids to close completely over the eye.

Question 12

Sclera

Answer 12

White of the eye acting as the eye wall.

Protects and provides structural support for the inside of the eye and gives its shape.

Coated by the conjunctiva.