Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU THE HUMAN EYE 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU THE HUMAN EYE Our paired eyes are located in bony sockets of the skull called orbits and are cushioned in a fatty connective tissue. Each eye(also called the eye ball) is a hollow spherical structure measuring about 2.5 cm in diameter and 7gm in weight. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Schematic representation of Parts of Human Eye 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU PARTS OF THE EYE The main components of the eye are : 1. Outer Fibrous Coat: - Sclera, Cornea. 2. Middle Fibrous coat: - Choroid, Iris, Ciliary Body 3. Inner Fibrous Coat: - Retina.( Ganglion cells, Bipolar cells, Photoreceptor cells.) 4. Lens 5. Aqueous Chamber 6. Vitreous Chamber 7. Conjunctiva 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU FIRST LAYER OF THE EYE Outermost- Posterior 2/3rd opaque SCLERA Sclera : The sclera is a tough white sheath around the outside of the eye-ball. This is the part of the eye that is referred to by the colloquial terms "white of the eye". Outermost-Anterior 1/3rd transparent CORNEA: Cornea : The cornea is a strong clear bulge located at the front of the eye (where it replaces the sclera - that forms the outside surface of the rest of the eye). The front surface of the adult cornea has a radius of approximately 8mm. The cornea contributes to the image-forming process by refracting light entering the eye 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU SECOND LAYER OF THE EYE Posterior: Choroid Choroid : The choroid layer is located behind the retina and absorbs unused radiation. It is highly vascular. It is thin & Bluish in color. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU Anterior: Iris Iris : The iris is a diaphragm of variable size whose function is to adjust the size of the pupil to regulate the amount of light admitted into the eye. The iris is the colored part of the eye (illustrated in blue above but in nature may be any of many shades of blue, green, brown, hazel, or grey). 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU INNERMOST LAYER Retina : Your retina is in the very back of the eye, past the vitreous body. Though it's smaller than a dime, it holds millions of cells that are sensitive to light. The retina takes the light the eye receives and changes it into nerve signals so the brain can understand what the eye is seeing. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU Rods and Cones The retina uses special cells called rods and cones to process light. Just how many rods and cones does your retina have? How about 120 million rods and 7 million cones - in each eye! Rods and cones are most sensitive to yellow-green light. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU RODS Rods see in black, white, and shades of gray and tell us the form or shape that something has. Rods can't tell the difference between colors, but they are super-sensitive, allowing us to see when it's very dark. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU CONES Cones sense color and they need more light than rods to work well. Cones are most helpful in normal or bright light. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU LENS Lens …The lens of the eye is a flexible unit that consists of layers of tissue enclosed in a tough capsule. It is suspended from the ciliary muscles. It Is the transparent, curved front of the eye which helps to converge the light rays which enter the eye. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU OPTIC CHAMBERS Hyaloid : The hyaloid diaphragm divides the aqueous humour from the vitreous humour. AQUEOUS HUMOUR Aqueous Humour : The aqueous humour is a jelly-like substance located in the anterior chamber of the eye. VITREOUS HUMOUR Vitreous Humour : The vitreous humour (also known as the "vitreous body") is a jelly-like substance. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

FUNCTIONS OF THE FLUID IN THE TWO CHAMBERS AQUEOUS HUMOUR It provides nutrition to the posterior part of the cornea and anterior part of the lens VITREOUS HUMOUR It provides nutrition to the posterior part of the lens and anterior part of the retina. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU FOVEA CENTRALIS Fovea : The fovea is a small depression (approx. 1.5 mm in diameter) in the retina. It is the yellow pigmented spot called Macula Lutea with central pit called the Fovea. This is the part of the retina in which high-resolution vision of fine detail is possible. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU BLIND SPOT Papilla : The papilla is also known as the "blind spot" and is located at the position from which the optic nerve leaves the retina. Optic Nerve : The optic nerve is the second cranial nerve and is responsible for vision. Each nerve contains approx. one million fibres transmitting information from the rod and cone cells of the retina. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU

Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU EVALUATION WORK Answer the questions posted on the THINK QUEST site on the page Home work on the lesson EYE. Post the answers on the message board for multiple choice questions and rest of the question and answers in your home work note book and submit the same by tomorrow. Question beyond textual learning has been posted, the answer shall be discussed two days later. 9/15/2018 Mrs H R SHYAMALA, PGT BIO K V HEBBAL BENGALURU