TBL14 - Lymphatic Circulation Flashcards
Where are lymphatic capillaries found? How much excess capillary filtrate enters the interstitial fluid daily? What function does the lymphatic system therefore serve?
1) Lymphatic capillaries occur almost everywhere blood capillaries are found
2) About 3 liters of excess capillary filtrate enter the interstitial fluid daily; thus, without removal as lymph by the relatively porous lymphatic capillaries, the expanded interstitial fluid volume would create massive edema
Where are lymphatic capillaries abundant? Where does lymph fluid travel within organ systems?
1) Lymphatic capillaries are particularly abundant in organ systems open to the external environment (e.g. integument and the respiratory, urogenital, and digestive systems)
2) Lymph formed in the mucosa of the organ systems traverses the porous lymphatic capillaries and is conveyed by adjoining lymphatic vessels to local lymph nodes
Where do thin-walled lymphatic vessels travel within organ systems? What ensures unidirectional lymph flow within lymphatic vessels?
1) The thin-walled lymphatic vessels course parallel with elements of the microcirculation in the stroma of the organ systems
2) Bicuspid valves of the lymphatic vessels insure unidirectional lymph flow toward the local lymph nodes
What are lymphangitis and lymphadenitis and why are these conditions potentially dangerous?
1) Lymphangitis and lymphadenitis are secondary inflammations of lymphatic vessels and lymph nodes, respectively. These conditions may occur when the lymphoid system is involved in chemical or bacterial transport after severe injury or infection
2) The lymphatic vessels, not normally evident, may become apparent as red streaks in the skin, and the nodes become painfully enlarged
3) This condition is potentially dangerous because the uncontained infection may lead to septicemia (blood poisoning)
What is lymphedema?
1) Lymphedema, a localized type of edema, occurs when lymph does not drain from an area of the body
2) For instance, if cancerous lymph nodes are surgically removed from the axilla (compartment superior to the armpit), lymphedema of the limb may occur
3) Solid cell growths may permeate lymphatic vessels and form minute cellular emboli (plugs), which may break free and pass to regional lymph nodes
4) In this way, further lymphogenous spread to other tissues and organs may occur
What do aggregations of lymphocytes within lymphatic capillaries and vessels form?
Aggregations of lymphocytes (i.e., lymphoid nodules) join the lymphatic capillaries and vessels to form mucosa-associated lymphoid tissue (MALT) in organ systems that open to the external environment
What does a lymphoid nodule mainly consist of? What do the T cells loosely dispersed among the lymphoid nodules also constitute?
1) A lymphoid nodule consists mainly of B cells
2) T cells loosely dispersed among the lymphoid nodules are also constituents of MALT
What do B cells do in the MALT? What does this result in?
1) In the MALT, B cells that selectively bind to invading bacterial antigens replicate
2) Aggregates of the B cell progeny create the lymphoid nodules
2) Some of the progeny B cells differentiate into plasma cells
What trigger a humoral immune response? What is the resulting response in a bacterial infection?
1) Synthesis and release of immunoglobulins (aka antibodies) by the plasma cells trigger a humoral immune response
2) Those antibodies that selectively bind to the bacterial antigens initiate elimination of the invading pathogen
What consistutes the pale germinal center of the lymphoid nodule?
The pale germinal center of the lymphoid nodule is occupied by plasma cells, which are derived from the activated B cells
What do cell-mediated immune responses involve? How do T cells become activated?
1) Cell-mediated immune responses involve the destruction of virus-infected cells by activated T cells
2) Activation requires T cells to selectively bind both the viral (nonself) antigen and a self-antigen; thus, a cell membrane protein of an infected cell expresses fragments of the viral antigen for dual recognition by a T cell
How do T cells destroy tumor cells?
T cells destroy tumor cells via cell-mediated responses that employ a similar recognition mechanism for fragments of tumor antigens expressed by cell membrane proteins of the tumor cells
Why can graft-versus-host disease (GVHD) occur after allogeneic bone marrow transplantation?
1) Graft-versus-host disease (GVHD) may occur after allogeneic bone marrow transplantation
2) It is caused by a mismatch of histocompatibility antigens of donor and recipient
3) GVHD develops when graft immunocompetent T cells see epithelial target tissue of the host as foreign
4) An induced inflammatory response is followed by apoptosis of target tissue
