Lens Introduction

Lens Introduction - LENS Anatomy Copy of power point...

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LENS Anatomy Copy of power point presentation of lecture taken for Junior Final year students By Dr Sanjay Shrivastava
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December 24, 2011 Prof Sanjay Shrivastava 2 Lens It is a highly organized transparent asymmetrical oblate spheroid structure that has evolved to alter the refractive index of the light entering in the eye. It does not posses nerve, blood vessels or connective tissue. Biconvex shape results from the anterior surface being less convex then posterior surface.
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December 24, 2011 Prof Sanjay Shrivastava 3 Anatomical Considerations Biconvex Lens Diameter varies from 8.8 to 9.2 Lens grow in size continuously throughout life. Its weight is about 65 mgm at the birth and up-to 258 mgm by 80 years of age. Antero-posterior thickness changes with accommodation. Thickness is 4.75 – 5 mm (un-accommodated) in adults. Circumference is known as equator
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December 24, 2011 Prof Sanjay Shrivastava 4 Lens Lens is suspended in eye by Zonules which are inserted on anterior surface and equatorial lens capsule and attached to ciliary body. Zonular fibres are series of fibrillin rich fibre.
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December 24, 2011 Prof Sanjay Shrivastava 5 Lens - Anatomy Histologically lens consists of three major components: 1. Capsule – is a thick collagenese basement membrane which is transparent, elastic acellular envelop, thick at anterior pre-equatorial region (21 micron m), thinnest at the posterior pole (4 micron m). Anterior pole is approximately 14 micron m thick. It contains the epithelial cells and fibres as a structural unit and allows a passage of small molecules both into and out of lens
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December 24, 2011 Prof Sanjay Shrivastava 6 Lens - Anatomy 2. Lens Epithelium – It is a single layer of cells lining the anterior capsule and extends to the equatorial lens bow. Zone of epithelial cells: a. Central – cells do not actively divide, they divide under pathological conditions only. b. Pre-equatorial germinal zone : cells rarely divide.
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December 24, 2011 Prof Sanjay Shrivastava 7 Lens - Anatomy c. Germinal zone: constitute of the stem cell population. The newly formed cells from germinal zone are forced into transitional zone where they elongate and differentiate to form mass of the lens. The lens capsule secretes the lens capsule and also regulate the transport of metabolite, nutrients and electrolytes to the lens fibres.
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December 24, 2011 Prof Sanjay Shrivastava 8 Lens - Anatomy 3. Lens substance : It constitute the main mass of the lens. It is divide into- a. Nucleus b. Cortex Nucleus: consists of (i) Embryonic nucleus (it contains primary lens fibres that are formed in lens vesicle)
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December 24, 2011 Prof Sanjay Shrivastava 9 Lens - Anatomy (ii) Fetal nucleus: it contains embryonic nucleus and all fibres added to the lens before birth (iii) Infantile nucleus: it contains embryonic , fetal nucleus together with all the fibres added up-to the age of 4 years. (iv) Adult nucleus: composed of all fibres
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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Lens Introduction - LENS Anatomy Copy of power point...

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