Chapter 20: Lymphatic system and lymphoid organ and tissue Flashcards
lymphatic capillaries
similar to blood capillaries except they are VERY permeable (take up proteins, cell debris, pathogens and cancer cells). Anchored by collagen filaments, prevents collapse of capillaries; increased ECF volume opens mini-valves.
Collecting lymphatic vessels
Similar to vein, except they have thinner walls, with more internal valves.
Travel with superficial veins
Deep vessels travel with arteries
Nutrients supplied from branching Vasa Vasorum
Lymphatic Trunks
Formed by union of largest collecting ducts.
Lymphatic ducts
Lymph is delivered into one of the two large ducts.
The right lymphatic duct drains right upper arm and right side of head and thorax
The thoracic duct arises a cisterna chyli; drains rest of body
Source of Lymph
the lymph is formed when the interstitial fluid is collected through the lymph capillaries. It is then transported through lymph vessels to ;lymph nodes before emptying ultimately into the right or the left subclavian vein, where it mixes back with blood.
Composition of lymph
comparable to blood plasma. the lyph is formed in teh human digetive system called chyle and is rich in triglycerides (fats) and looks milky white.
Lymphocytes
main warriors of immune system. Arise in red bone marrow
T Cells (T lymphocytes)
manage immune response
attack and destroy infected cells
B Cells (B lymphocytes)
Produce plasma cell, which secrete antibodies. Antibodies mark antigens for destruction by phagocytosis.
lymphoid tissues
provide structural basis of immune system. House phagocytic cells and lymphocytes.
Lymphoid Organs
Spleen, thymus, tonsils and others
Lymphoid Tissue
Houses and provides production site for lymphocytes
Surveillance vantage point for lymphocytes and macrophages
Largely reticular connective tissue
Two main types of lymphoid tissue
Diffuse lymphoid tissue and lymphoid follicles
Diffuse Lymphoid Tissue
Tissue of lymphoid cells and reticular fibers in every body organ.
(larger collections in lamina propria of mucous membranes)
Follicular lymphoid tissues
Are solid, spherical bodies of tightly packed lymphoid cells and reticular fibers.
May form part of larger lymphoid organs
Isolated aggregations of peyers patches
Location of lymph nodes
found throughout body, but the largest groupings are found in the neck, armpits and groin areas.
function of lymph nodes
Major sites of B, T and other immune cells.
Lymph nodes are important for the proper function of the immune system, acting as filters for foreign particle and cancer cells. Lymph nodes do not deal with toxicity which is primarily dealt with by the liver and kidneys.
Structure of Lymph Nodes
small bean shaped glands or bulb that tend to occur in clusters much like grapes.
Spleen
- largest lymphoid organ.
- Served by splenic artery and vein, which enter and exit at the hilum.
- the spleen is the site of lymphocyte proliferation and immune surveillance and response.
- Cleanses blood of aged cells platelets
- macrophages remove debris
Thymus
Important functions early in life
- found in inferior neck; extends into mediastinum; partially overlies heart
- increases in size and most active during childhood
- stops growing during adolescence, then gradually atrophies
- still produces immunocompetent cells, but slowly
Tonsils
Contain follicles with germinal centers
are not fully encapsulated
trap and destroy bacteria and particulate matter
allow immune cells to build memory for pathogens
Peyer’s patches
cluster of lymphoid follicle
in wall of distal portion of small intestine
Similar structures are also found in the appendix
destroy bacteria, preventing them from breaching intestinal wall
generate “memory” lymphocytes
Types of lymphatic vessels
lymphatic capillaries
collecting lymphatic vessels
lymphatic trunks
