24. Peyer’s patches in the distal ileum. PPs seen in a 20-years-old man during
ileocolonoscopy. Note that PPs form a lymphoid ring in the distal ileum.
Image from - http://www.3dscience.com/3D_Models/Human_Anatomy/Male_Systems/Male_Lymphatic.php
The Lymphatic System = one of the least familiar organ systems
Primary functions:
The production, maintenance, and distribution of lymphocytes.
The return of fluid and solutes from peripheral tissues to the blood.
The distribution of hormones, nutrients, and waste products from their tissues of origin to the general circulation.
Interacts with cells and tissues of other systems to defend the body against infection and disease.
Maintaining the constancy of the fluid around each body cell is possible only if numerous homeostatic mechanisms function effectively together in a controlled and integrated response to changing conditions.
Remember the levels of organization.
The lymphatic system includes the following 4 components:
Vessels
Fluid
Lymphocytes
Lymphoid tissue & organs
Lymphatic trunks
lymphangiogram
Lymphatic vessels = LYMPHATICS
Image from -http://www.pc.maricopa.edu/Biology/pfinkenstadt/BIO202/202LessonBuilder/Immunity/index.html
Lymphoid nodules – collections of loose connective tissues and lymphocytes; example = tonsils
http://www.hindawi.com/journals/iji/2010/823710/fig1/
From Encyclopedia Britannica:
Peyer patch, any of the nodules of lymphatic cells that aggregate to form bundles or patches and occur usually only in the lowest portion (ileum) of the small intestine; they are named for the 17th-century Swiss anatomist Hans Conrad Peyer.
Peyer patches are round or oval and are located in the mucous membrane lining of the intestine. They can be seen by the naked eye as elongated thickened areas, and their surface is free of the projections (villi) and depressions (Lieberkühn glands) that characterize the intestinal wall. Usually there are only 30 to 40 patches in each individual. In young adults they may be more numerous, and as a person ages they tend to become less prominent. Their full function is not known, but they do play a role in immunologic response and contain B and T cells similar to those found in peripheral lymph nodes.
T Cells constitute 70-80% of the circulating lymphocytes.
Other T Cells reside in lymphatic organs and tissues, particularly abundant in lymph nodes, thoracic duct, and white pulp of the spleen.
B Cells constitute 20-30%n of the circulating lymphocytes.