The Lymphatic System Flashcards
What is the function of the lymphatic system
Carries excess ecf back to venous system
Fluid is a result of filtration from capillaries and include large particles such as pathogens, cells of lymphatic system, cell products and cell debris
Color of lymph
Colorless
Opaque and milky in intestine due to presence of chylomicrons (called chyle)
Places where lymphatic vessels dont exist
Brain
Bone marrow
Avascular tissues such as (epithelia and cartilage)
What does the lymphatic system consist of
Lymph nodes
Lymphatic vessels
Lymphatic ducts
Spleen
What are the lymphatic vessels
Form extensive and complex interconnected network of channels which begin as porous blind ended lymphatic capillaries
What are the 2 lymphatic ducts
Thoracic and right lymphatic duct
Where does the thoracic duct begin and end
What does it drain
Begins: in cisterna chili in abdomen
Ascends through posterior abdominal and thoracic walls deviating to the left
Terminates: at junction of left subclavian vein and left internal jugular vein
Drains lymph from all body except upper right quadrant
Where does the right lymphatic duct end and what does it drain
Upper right quadrant
Terminates at the junction of right subclavian and right internal jugular vein
What are the 2 parts forming the lymphoid organs
Stroma: CT supportive framework of organ
2 parts: covering dense CT capsule and CT trabeculae that extend from capsule for structural organization of organ
Fine stroma: fine reticular fibers forming a supportive network for the cells of the organ
Parenchyma: functional cellular part
Divided in to outer cortex and inner medulla
Describe the thymus
Primary lymphoid organ
Site of maturation of t lymphocytes
Originates early in embryo and continues to grow until puberty
35-40g
Involute and turns to adipose cells in old age
Describe the histological structure of the thymus
Capsule of thymus is composed of dense irregular collagenous CT
Sends septa in to the lobes subdividing them in to lobules
Lobule is composed of a cortex and medulla
What is the function of the thymus
Immunological competency of t cells
Elimination of self intolerant t cells
MHC recognition occur in the thymic cortex
What are the cells in the cortex on thymus
T lymphocytes
Macrophages
Epithelial reticular cells
Function of epithelial reticular cells
Interconnected branches forming a cellular network that supports developing t cells
Type1 shares in formation of blood thymic barrier
What is the function of the blood thymic barrier and what are its components
Components:
▪️Cont endothelium of blood cap and their basal lamina
▪️Epithelial reticular fibers that are attached to each other by tight junctions and their basal lamina
Prevents developing t cells from having contact with any foreign ag in blood
Cells attached by tight junctions and allows only contact of t cells with self ag to educate t cells to tolerate self ag
If not they will undergo apoptosis
What happens to the educated t cells
Enter the medulla of the thymus as naïve t lymphocytes and then distributed to secondary lymphoid organs via the vascular system
Describe the medulla
Characterized by hasall’s corpuscles
All t cells in medulla are immunocompetent
How are hasall’s corpuscle’s formed
Epithelial reticular cells:
Whorl shaped thymic corpuscles whose numbers inc with a person’s age
Type 4 cells mat become highly cornfield and even calcified
What are the lymph nodes
▪️Small oval encapsulated structures along the course of the lymphatic vessels
▪️Convex outer surface and concave one which contain hilum
▪️divided in to outer and inner cortex
Describe the stroma of the lymph nodes
▪️Dense CT capsule that is thickened at the hilum(portal of exit or entry of blood vessels)
▪️incomplete trabeculae arise from the capsule of the cortex and medulla subdividing them in to small compartments
Describe the cortex of the lymph node
Subdivided in to compartments that house b cell rich primary and secondary lymphoid
2 types: primary and secondary
Secondary have germinal centers
Describe whats in the primary and secondary lymphoid nodes
Primary: small b cells
Secondary: small germinal center formed of large lymphocytes that represent proliferating b cells in response to exposure of ag
Lymphoblasts differentiate in to plasma cells and memory b cells
Describe the paracortex
▪️Houses mostly t cells(thymus dependent zone of lymph node)
▪️High endothelial venules
Describe the medulla
▪️Composed of large tortuous lymph sinuses surrounded by lymphoid cells that are organized in clusters known as medullary cords
▪️cells: lymphocytes plasma cells and macrophages (emeshed in network of reticular fibers and reticular cells)
What are the functions of the lymph node
▪️act as sites for ag recognition
▪️flow rate is reduced as lymph enters lymph node which gives macrophages time to phagocytose matter
▪️b memory and plasma cells leave cortex and form medullary cords
Where do remaining of plasma cells go
Sinuses and go to bone marrow where they continue to manufacture ab until they die
Describe lymphangitis and lymphadenitis
Secondary inflammations of lymphatic vessels and lymph nodes
May occur when lymphatic system is involved in chemical or bacterial transport after severe injury or infection
May become apparent as red streaks in skin and nodes become enlarged
May lead to septicemia
Describe lymphedema
Localized edema
Occurs when lymph doesn’t drain from an area in body
How does lymphogenous spread occur
Solid cell growths may permeate lymphatic vessels and form minute cellular emboli which may break free and pass to regional lymph nodes
How do lymphocytes leave the vascular supply
Lymphocytes leave the vascular supply by migrating between cuboidal cells of unusual epithelium and enter substance of lymph node
B cells migrate to outer cortex while t cells remain in paracortex
