Lymphatic System Flashcards
(38 cards)
Three parts of the Lymphatic System
- Network of lymphatic vessels
- Lymph- fluid in vessels
- Lymph Nodes- which cleanses lymph
Function of Lymphoid Organs and Tissues
Provides structural basis of immune system
Houses phagocytic cells and lymphocytes
Its structure includes:
- spleen
- thymus
- tonsils
- lymph nodes
- other lymphoid tissues
Function of Lymphatic Vessels (lymphatics)
It returns interstital fluid and leaked plasma proteins back to blood
Only 3L/day
Once fluid enters lymphatic (they becomes lymph)
Distribution and Structure of Lymphatic Vessels
which way does lymph flows
Lymph flows toward the heart (it’s a one way system)
They includes:
- Lymphatic Capilliares
- Collecting Lymphatic Vessels
- Lymphatic trunks and ducts
Describe Lymphatic Capilliares(how is it different from blood capilliares)
Similar to blood capilliares
But:
-they are very permeable (takes up proteins, cell debris, pathogen, and cancer cells)
Structure of Lymphatic Capilliares
•Endothelial cells overlap loosely to form one-way minivalves
•Anchored by collagen filaments, preventing collapse of capillaries; increased ECF volume opens minivalves
–Pathogens travel throughout body via lymphatics
Structure continued
•Absent from bones, teeth, bone marrow, and CNS
•Lacteals: specialized lymph capillaries present in intestinal mucosa
–Absorb digested fat and deliver fatty lymph (chyle) to the blood
Describe Lymphatic Collecting Vessels
•Similar to veins, except
–Have thinner walls, with more internal valves
–Anastomose more frequently
•Collecting vessels in skin travel with superficial veins
•Deep vessels travel with arteries
•Nutrients supplied from branching vasa vasorum
Lymphatic Trunks
•Formed by union of largest collecting ducts
–Paired lumbar –Paired bronchomediastinal –Paired subclavian –Paired jugular trunks –Single intestinal trunk
Lymphatic Ducts(what two ducts that lymph is delivered into and what do they do)
•Lymph delivered into one of two large ducts
–Right lymphatic duct- drains right upper arm and right side of head and thorax
–Thoracic duct- arises as cisterna chyli; drains rest of body
•Each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body
Lymph is propelled by:
•Lymph propelled by
–Milking action of skeletal muscle
–Pressure changes in thorax during breathing
–Valves to prevent backflow
–Pulsations of nearby arteries
–Contractions of smooth muscle in walls of lymphatics
Describe Lymphoid Cells
•Lymphocytes main warriors of immune system –Arise in red bone marrow •Mature into one of two main varieties –T cells (T lymphocytes) –B cells (B lymphocytes)
Lymphacytes(what are the two cells and what do they do)
•T cells and B cells protect against antigens
–Anything body perceives as foreign
•Bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells
Function of T cells
–Manage immune response
–Attack and destroy infected cells
Function of B cells
–Produce plasma cells, which secrete antibodies
•Antibodies mark antigens for destruction by phagocytosis or other means
Other Lymphoid Tissues
•Macrophages phagocytize foreign substances; help activate T cells
•Dendritic cells capture antigens and deliver them to lymph nodes; activate
T cells
•Reticular cells produce reticular fiber stroma that supports other cells in lymphoid organs
Describe Lymphoid Tissues
•Houses, and provides proliferation site for, lymphocytes
•Surveillance vantage point for lymphocytes and macrophages
•Largely reticular connective tissue – type of loose connective tissue
•Two main types
–Diffuse lymphoid tissue; Lymphoid follicles
Lymphoid Tissues continued
•Diffuse lymphoid tissue of lymphoid cells and reticular fibers in ~ every body organ
–Larger collections in lamina propria of mucous membranes
Describe Lymphoid Follicles
•Lymphoid follicles (nodules) are solid, spherical bodies of tightly packed lymphoid cells and reticular fibers
–Germinal centers of proliferating B cells
–May form part of larger lymphoid organs
–Isolated aggregations of Peyer’s patches and in appendix
Describe Lymph Nodes
- Principal lymphoid organs of body
- Embedded in connective tissue, in clusters along lymphatic vessels
- Near body surface in inguinal, axillary, and cervical regions of body
Function of Lymph Nodes
•Functions
- Filter lymph—macrophages destroy microorganisms and debris
- Immune system activation—lymphocytes activated and mount attack against antigens
Structure of Lymph Nodes
•External fibrous capsule •Trabeculae extend inward and divide node into compartments •Two histologically distinct regions –Cortex –Medulla
Countined…
- Cortex contains follicles with germinal centers, heavy with dividing B cells
- Dendritic cells nearly encapsulate follicles
- Deep cortex houses T cells in transit
- T cells circulate continuously among blood, lymph nodes, and lymph
Countined…
- Medullary cords extend inward from cortex and contain B cells, T cells, and plasma cells
- Lymph sinuses contain macrophages
