HPV causes cancer. Help protect your kids.
The eye is the organ of sight (vision). A person has 2 eyes located below the forehead and eyebrows at the front of the face, within the eye socket area of the skull. One eye is located on either side of the bridge of the nose. Only about one-sixth of the eyeball can be seen – the rest is protected by bone and surrounding tissue of the eye socket (orbit).
The eye is made up of 3 main parts:
The main part of the eye is the eyeball (also called the globe). Each eye is sphere-shaped and is about 2.5 cm (1 inch) in diameter. The eyeball is rich in blood vessels. The inside of the eyeball is filled mostly with a clear, jelly-like fluid called vitreous humor. Vitreous humor fills the back (posterior) part of the eye. It helps support the internal structures and maintain the shape of the eye.
The outer part of the eyeball is called the wall of the eye. It can be divided into 3 layers (or tunics): an outer, middle and inner layer (from the outside to the inside of the eye).
The outermost layer or covering of the wall of the eye is made up of the sclera and cornea and is called the fibrous tunic.
The middle layer of the wall of the eye is called the uvea or vascular tunic. The uvea has 3 main parts:
The innermost layer of the wall of the eye is made up of the retina or neural tunic. The retina is the thin layer of cells at the back of the eyeball and works like the film of a camera. It is made up of nerve cells that are sensitive to light. These cells are connected to the brain by the optic nerve, which sends information from the eye to the brain and allows us to see.
The lens is a transparent structure in the inner part of the eye, which lies directly behind the cornea and iris. The lens changes shape to allow the eye to focus on objects. The lens focuses light rays on the retina.
The orbit (eye socket) is a bowl-shaped cavity made up of bone formed from the skull that contains the eyeball and the connective tissues surrounding the eyeball. The bone and connective tissues cushion and protect the eye. Muscles attached to the eyeball make it move in different directions. These small muscles attach to the sclera near the front of the eye and to the bones of the orbit at the back. The orbit also contains nerves, fat, blood vessels and a variety of connective tissues.
The accessory (adnexal) structures of the eye include the eyelids, conjunctiva, caruncle and lacrimal (tear) glands.
The eyelids (palpebrae) are folds of skin that cover and protect the eye. Muscles raise and close the eyelids.
The conjunctiva is a clear mucous membranemucous membraneThe thin, moist layer of tissue that lines some organs and body cavities, including the nose, mouth, lungs, airways, vagina and gastrointestinal (GI) tract. that lines the inner surface of the eyelids and the outer surface of the eye. The conjunctiva secretes mucus to lubricate the eyeball and keep it moist.
The caruncle is the small, pinkish portion of the innermost corner of the eye (or inner canthus) that contains oil and sweat (sebaceous) glands and conjunctival tissue.
The lacrimal gland (tear gland) is the almond-shaped gland located at the upper, outer corner of each eye.
The eye is the organ that works with the brain to provide us with the sense of sight. It works much like a camera. The main function of the eye is to collect light and turn it into electric signals, which are sent to the brain. The brain then turns those signals into a visual image or picture for us to see. We have 2 eyes, so 2 pictures are usually created. If we lose the vision in one eye, we continue to see most of what we could see before.
When light enters the eye, it first passes through the cornea. The light then passes through the pupil, where the iris adjusts the amount of light entering the eye. The light then passes through the lens of the eye. The lens focuses light rays onto the retina, where it is changed into a signal that is transmitted to the brain by the optic nerve. The signal is received and interpreted by the brain as a visual image.
The Canadian Cancer Society’s peer support program is a telephone support service that matches cancer patients and their caregivers with specially trained volunteers.