Lymphatic System Flashcards
What is the function of the lymphatic system?
- To return fluid and plasma proteins to blood
- To return lymphocytes of the circulating pool
- To add antibodies formed in lymph nodules
The ultrafiltrate of blood plasma, lymph, is formed by?
Seepage of blood fluid across capillary walls
What lymphatic structure is this?
- less well structured than blood capillaries
- thin-walled vessels lined with endothelium
- variable in size and calibre
- endothelium often very thin, clefts between endothelial cells
- incomplete basement membrane
- end blindly in extracellular spaces, retrieve lymph
Lymph capillary
What does the flow of lymphatic vessels depend on?
The pressure from neighboring structures
What lymphatic structure is characterized by these:
- relatively larger lumen than blood vessels of comparable size
- thicker wall than lymph capillaries, - intima, media, adventitia present
- valves conspicuous - insure unidirectional flow
- flow depends on pressure from neighbouring structures
Lymphatic vessels
Name some lymphatic ducts (trunks)
Right lymphatic duct and thoracic duct
What lymphatic structure is similar to veins? Why?
Lymphatic duct
-they posses valves and they have more smooth muscle in media than veins
Where do lymphatic ducts drain?
Empty into great veins at the base of the neck
What lymphoid tissue is not sharply delineated from the surrounding connective tissue?
Diffuse lymphoid tissue
Where can you find diffuse lymphoid tissue underling the epithelial lining?
The digestive and respiratory systems
Also in lymph nodes, spleen and tonsils
What lymphoid tissue consist of a network of reticular fibers and reticular cells?
Diffuse lymphoid tissue
In diffuse lymphoid tissue, ___ of lymphoid tissue fill the spaces
Free cells
What are dense aggregations of lymphoid tissue?
Lymphoid nodules
Where are lymphoid nodules found?
In the cortex of lymph nodes and in white pulp in the spleen
(And in tonsils, appendix, under epithelium if digestive and respiratory tract)
What is a primary nodule?
A round collection of tightly packed small lymphocytes
What is a secondary nodule?
A spherical cluster of larger pale staining cells (germinal centre) surrounded by a cap of small lymphocytes
What are small organs that occur along the course of lymphatic vessels?
Lymph nodes
What is the function of lymph nodes?
Filter lymph (2k-20k cells cu. mm)
Remove undesirable cells, invading microorganisms, particulate matter
Function in immune system (lymphocyte production)
Where are lymph nodes consistently found?
Mesentery, axilla, groin
Malt
Balt
Galt
What are these?
Mucosal associated lymphoid tissue
Bronchial associated lymphoid tissue
Gut associated lymphoid tissue
What does the cortex of lymph nodes contain?
(Outer) Primary and secondary nodules
Deep: diffuse lymphoid tissue
Where is the thymus dependent zone in the lymphoid node?
Mid and deep cortex of lymph node
The lymphocyte of the cortex of the lymph node are ____ that are seeded from the thymus.
Chiefly T-lymphocytes
Where do the blood vessels of the lymph nodes enter and leave?
At the hilus and run in the trabeculae
What are the characteristics of postcapillary venues in the lymph node? (High endothelial venules)
course radially in the deep cortex (i.e. the thymus-dependent zone),
- tall endothelial cells form their wall - no muscular coat is present
- HEV’s are traversed by small lymphocytes from the blood
- they represent the portal of entry from blood into the lymphatic circulation
The spleen contains large amount of _____ tissue
Lymphoid
What structure is a complex filter of blood which clears the blood of particulate matter and worn out cells
Spleen
Note: it participates in immune defense against blood-borne antigens
What are the functions of the spleen?
Storage/destruction of blood cells and platelets
Hemopoiesis- production of lymphocytes
Production of myeloid elements in embryos
Hemoglobin degradation and iron metabolism. Iron is stored in the macrophages
Immune response. Production of antibodies
Describe the capsule of the lymph nodes.
A connective tissue covering that thickens at the hilus. It extends into the node as trabeculae
