Category: Biology Second Paper

The orb is attached to the orbit by 6 muscles. Muscles are double. Rectus muscle and oblique muscle.
1. Rectus muscle: 4 rectus muscles.
(i) Lateral Rectus Muscle : It helps rotate the eyeball outwards.
(ii) Medial rectus muscle : It helps in inward rotation of the eyeball.
(iii) Superior rectus muscle : It helps the eyeball to rotate upwards.
(iv) Inferior rectus muscle: It helps the eyeball to rotate downwards.
2. Oblique muscles: 2 oblique muscles.
(i) Superior oblique muscle: It helps the eyeball to rotate along the axis between the optic nerve and the cornea.
(ii) Inferior Oblique Muscle: It acts opposite to the superior oblique muscle.

The hair above the eyelid is called eye brow. It prevents sweat from the forehead from entering the eyes.

The eyelash is called Akshipaksha. It prevents dust and germs from entering the eyes.

The transparent thin membrane covering the cornea is called conjunctiva. It protects the eyes from dust and germs. It keeps the eyes slippery and moist.

(i) Upper eyelid: The upper lid of the eye is called upper eyelid. Under it there is a line of eye lashes like hair. It is contagious. It controls the opening and closing of the eyes.
(ii) Inferior eyelid: The lower eyelid is called lower eyelid. Its free end has single eye lashes like hair. It is not contagious. It protects the eyes from dust and sand.
(iii) Nectitating screen: It is the hidden almost passive part. It is located in the inner corner of both eyes. It is a reddish flesh. Through this the lacrimal gland ducts are opened.

1. Helps light rays enter the eye.
2. Regulates internal and external eye pressure.
3. Through it the light rays are refracted and fall on the retina.

The large chamber between the lens and the retina is called the vitreous chamber. It is 80% of the eyeball. It is filled with a jelly-like fluid called vitreous humor. Vitreous humor is like egg white. Vitreous humor consists of 99% water, 1% collagen and hyaluronic acid. Vitreous humor helps in refraction of light.

The cavity between iris and lens is called posterior chamber. It is also filled with aqueous humor.

The cavity between the cornea and the lens is called the aqueous humor chamber. It is filled with a fluid called aqueous humor.

The eyeball has three cavities filled with fluid.
(i) Aqueous humor chamber: The cavity between the cornea and the lens is called the aqueous humor chamber. It is filled with a fluid called aqueous humor.
(ii) Posterior chamber: The cavity between iris and lens is called posterior chamber. It is also filled with aqueous humor.
(iii) Vitreous humor chamber: The large chamber between the lens and the retina is called the vitreous chamber. It is 80% of the eyeball. It is filled with a jelly-like fluid called vitreous humor. Vitreous humor is like egg white. Vitreous humor consists of 99% water, 1% collagen and hyaluronic acid. Vitreous humor helps in refraction of light.