THYMUS.pptx

PRIMARY LYMPHOID ORGAN

1. Primary lymphoid organ thymus Presented to DR.s.saranya Asst.prof of microbiology Sacred heart college tIRUPATTUR Presented by: v.salomi (bp211509) I m.sc microbiology Sacred heart college tIRUPATTUR

2. The thymus is an organ that sits beneath the  sternum  in the upper front part of the chest, stretching upwards towards the neck. In children, the thymus is pinkish-gray , soft, and lobulated on its surfaces. At birth it is about 4–6 cm long, 2.5–5 cm wide , and about 1 cm thick.  It increases in size until puberty, where it may have a size of about 40–50 g,following which it decreases in size in a process known as  involution . Introduction

3. Thymus The thymus is the site of T cell development and maturation . It is a flat, bilobed organ situated above the heart . Each lobe is surrounded by a capsule and is divided into lobules which are separated by strands of connective tissue called trabeculae . Each lobule is organized into two compartments-the outer compartment or cortex is densely packed with immature T cells called thymocytes whereas the inner compartment or medulla is sparsely populated with thymocytes .

4. Both the cortex and medulla of the thymus are criss-crossed by a three-dimensional stromal cell network composed of epithelial cells, dendritic cells and macrophages make up the framework of the organ and contribute to the growth and maturation of thymocytes . Many stromal cells interact physically with the developing thymocytes . Some thymic epithelial cells in the outer cortex called nurse cells have long membrane extensions that surround as many as 50 thymocytes forming large multicellular complexes .

5. STRUCTURE OF THYMUS

6. function of the thymus 1. Release thymosin hormone that will stimulate the maturation of T cells . 2. Thymus generate and select a repertoire of T cells that will protect the body from infection . 3. More than 95% of all thymocytes die by apoptosis( programmed cell death )in the thymus without ever reaching maturity . 4. Aging is accompanied by a decline in Thymic function

7. Tumors in the thymus can press on nearby structures, causing symptoms such as: Shortness of breath. Cough (which may bring up bloody sputum) Chest pain. Trouble swallowing. Loss of appetite. Weight loss . symptoms

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