Thymus and Spleen page 65

1. Thymus a. The thymus is a soft, bilobed organ located within the mediastinum.

b. It slowly shrinks after puberty.

c. It is composed of lymphatic tissue subdivided into lobules.

d. Lobules contain lymphocytes, most of which are inactive, that develop from precursor cells in the red bone marrow.

e. Some lymphocytes leave the thymus and provide immunity.

f. The thymus secretes thymosin, which stimulates lymphocytes that have migrated to other lymphatic tissues.

2. Spleen a. The spleen is located in the upper left portion of the abdominal cavity.

b. It resembles a large lymph node that is encapsulated and subdivided into lobules by connective tissue.

c. Spaces within lobules are filled with blood.

d. The spleen contains many macrophages and lymphocytes, which filter foreign particles and damaged red blood cells from the blood.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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