Lymphoid Tissues

Lymphatic Vessel Anatomy

Lymphatic vessels are like dead ends instead of a cul-de-sac like blood capillariesThe smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues..  These dead ends can be called lymphatic capillaries and they are interwoven with the blood capillary beds.  These lymphatic vessels are anchored to the surrounding tissue with specific anchoring filaments that attach mostly to collagenA structural protein in the dermis that provides strength and elasticity..  When the tissue swells with fluid, the venule side of the capillary bed is unable to reabsorb it. The anchoring filaments move away from each other. This movementA fundamental property of life involving motion of the body or its parts. opens these intercellular clefts.  The excess fluid then enters into the lymphatic vessel.  Much like the large veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge of the legs, lymphatic vessels have valves, which are infoldings of the epithelial cellsThe basic structural and functional units of life..  These valves ensure one way flow of lymph fluid.

Lymphoid Nodes

Fluids from lymphatic capillaries can enter into the lymph node through many afferent vessels. However, there is only one efferent vessel. It is usually larger than each individual afferent vessel. Nevertheless, it does not compare to the cumulative diameter of all afferent vessels. This setup causes a bottleneck of fluid. It allows more B&T cells to come into contact with the fluids. They inspect them for any pathogens. You may think of pair when I say the term follicle. However, a follicle is just usually some spheroid type structure of organized cells. In a lymph node, there are primary lymphoid folliclesStructures in the ovaries that contain developing oocytes. composed mostly of B cells. There is also a secondary lymphoid follicle. It contains mostly T cells and macrophages. This follicle also has a germinal center containing mostly lymphoid stem cells.

Mucosa
Associated
Lymphoid
Tissue

We have observed malt tissue in various locations. These include the tonsils and the peyer’s patches of the small intestine. Malt is like an unencapsulated lymph node. A proper lymph node has a much more organized structure. It consists of follicles that house mostly B cells. Other surrounding tissue in the lymph node houses T cells and macrophages. The primary tissue within a lymph node is reticular connective tissue. This tissue was a loose connective tissue. It also included areolar and adipose connective tissues. Reticular connective tissue as its name implies had only reticular fibers in it with no collagen and no elastin.