Tuesday, 7 April 2020

SENSORY ORGANS

SENSORY ORGANS

1. SCLEROTIC LAYER
 The transparent bulging, circular part of sclerotic layer which lies in the front is called cornea.
 Cornea is covered by the thin conjunctiva.

2. CHOROID LAYER
 Choroid layer starts from iris which is next to cornea. It controls the amount of light entering intothe eye.
 The circular aperture of iris is called pupil.
 Next is lens (proteinous). It is biconvex in nature.
 Space between lens and cornea is filled with a transparent watery fluid called Aqueous Humour.
 The space behind the lens is filled with Vitreous Humour.

3. RETINA
 Image of the object is formed on retina.
 Rod cells: Sensitive to dim light
 Cone cells: Color sensitive for 3 primary colors (Red, Blud and Green)
 Yellow spot (Macula Lutea): On retina, finest image is formed here.
 Blind spot: No image formation takes place here as the optic nerves innervate the eyeball here. Also the rods and cones are absent here.
 Color of eye is the color of the iris.
 Cornea is donated in eye donation
 Eyes glow in animals due to tapetum

DEFECTS OF EYE
 Myopia: Cannot see distant objects, image formed before retina, concave lens is used.
 Hypermetropia: Cannot see near objects, image formed behind retina, convex lens is used.
 Astigmatism: Curvature of cornea becomes irregular and image is not clear. Cylindrical lens is used.
 Cataract: Due to defective protein metabolism the lens becomes opaque.
Gloucoma: Due to defect in aqueous humour.
 Xerophthalmia: It is due to deficiency of Vitamin A.
 Presbiopia: In this, power of accommodation of lens decreases due to age factor and defected metabolism. Can be removed by bifocal lens.

EAR MIDDLE EAR
 It encloses 3 ear ossicles.
 Middle ear is connected to the pharynx by Eustachian tube.

INTERNAL EAR
 Various parts are there which perform 2 acts: Maintenance of balance and hearing.
 Succulus and cochlea parts are associated with hearing. It is filled with a flud, perilymph.
 In the internal ear are 3 semi-circular canals and utriculus which are filled with a fluid, endolymph. They perform the balancing act.

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