Lymphocyte Origins

During fetal development, red bone marrow releases un-differentiated lymphocytes into the circulation. About half of these cells reach the thymus, where they remain for a time. Here, these thymocytes specialize into T lymphocytes, or T cells. ("T" refers to thymus-derived lymphocytes.) Later, the blood transports T cells, where they comprise 70% to 80% of the circulating lymphocytes. T cells reside in lymphatic organs and are particularly abundant in the lymph nodes, the thoracic duct, and the white pulp of the spleen.

Other lymphocytes are thought to remain in the red bone marrow until they differentiate into B lymphocytes, or B cells. (Historically, the "B" stands for bursa of Fabricius,

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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