12 W18-CoogxUntitled document le.com/document/d/1Ds2txxIZoe2wjas iVylEr b4Cad22d

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12 W18-CoogxUntitled document le.com/document/d/1Ds2txxIZoe2wjas iVylEr b4Cad22dzcjOpN6lG0o/edit Tools Add-ons Help saved in Drive Arial activated cells divide Killer cells which secrete toxins that kill pathogens responsible for specific immunity-that is, cells can recognize pathogen- specific proteins (antigens) and target those specific pathogens for elimination TOPIC: Lymphatic Organs A. Spleen: Describe the anatomy of the spleen, including its location. What substance does the spleen filter? Describe 2 functions of the spleen. B. Thymus: Describe the anatomy of the thymus, including its location. The thymus is also an organ of the Endocrine system - explain why. Describe the major functions of the thymus. At about what age does the thymus reach its maximum size? Would you expect to find a thymus in an 80 year old patient? Why or why not? C. Tonsils: Name the 3 pairs of tonsils and describe the location of each. Describe the functions of the tonsils. D. Which of the lymphatic organ(s) listed above is/are NOT required for life? Justify your answer

Explanation / Answer

Spleen

Spleen is a large, ovoid secondary lymphoid organ located high in the left abdominal cavity. It is the largest of the secondary lymphoid organs. It is highly efficient in trapping and concentrating foreign substances carried in the blood. It is the major organ in the body in which antibodies are synthesized and from which they are released into circulation. It has two types of compartments- Red pulp and white pulp. Red pulp is the site where old and defective RBCs are destroyed and removed, whereas, white pulp forms PALS (periarteriolar lymphoid sheath) which are rich in T-cells. approximately 50% of spleen cells are B-lymphocytes; 30-40% are T-lymphocytes.

Thymus

It is a flat, bilobed organ located above the heart. It is the site where T-lymphocytes mature.

The thymus grows during childhood but gradually decreases in size after puberty. It is also responsible for growth during childhood stage. Thymus secretes hormones called thymosins that stimulate the development and differentiation of T-lymphocytes. Since they secrete hormones, they are considered a part of the endocrine system.

Tonsils

Tonsils are found in three locations: lingual at the base of the tongue, palantine sides of the back of the mouth and pharyngeal in the roof of the nasopharynx. All the three tonsil groups are nodular structures. Tonsils defend against antigens entering through the nasal and oral epithelial routes.

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