Lymphatic System Flashcards
2 semi independent parts of the lymphatic system
- Lymphatic vessels
2. Lymphoid tissues and organs
Functions of the lymphatic system
▪ Transports escaped fluids from the cardiovascular system back to the blood
▪ Plays essential roles in body defence and resistance to disease
What is lymph
excess tissue fluid and plasma proteins carried by lymphatic vessels
What happens if excess fluid is not picked up
edema (inflammation) occurs as fluid accumulates in tissues. Edema impairs the ability of tissues to make exchanges with blood
Lymphatic vessels duty
▪ Lymphatic vessels (lymphatics) pick up excess fluid (lymph) and return it to the blood
▪ Form a one-way system ▪ Lymph flows only toward the heart
Describe the lymph capillaries
▪ Weave between tissue cells and blood capillaries
▪ Walls overlap to form flaplike minivalves
▪ Fluid leaks into lymph capillaries
▪ Capillaries are anchored to connective tissue by filaments
▪ Higher pressure on the inside closes minivalves
▪ Fluid is forced along the vessel
What are lymphatic collecting vessels
▪ Collect lymph from lymph capillaries
▪ Carry lymph to and away from lymph nodes
▪ Return fluid to circulatory veins near the heart
▪ Right lymphatic duct drains the lymph from the right arm and the right side of the head and thorax
▪ Thoracic duct drains lymph from rest of body
Features of lymphatic vessels
- Thin Walled
- Larger vessels have valves
- Low pressure, pumpless system
What is lymph action aided by
- Milking action of skeletal muscles
- Pressure changes in thorax during breathing
- Smooth muscle in walls of lymphatics
Duties of the lymph nodes
▪ Lymph nodes filter lymph before it is returned to the blood
▪ Harmful materials that are filtered ▪ Bacteria ▪ Viruses ▪ Cancer cells ▪ Cell debris
Defence cells of the lymph nodes
▪ Macrophages—engulf and destroy bacteria, viruses, and other foreign substances in lymph
▪ Lymphocytes—respond to foreign substances in lymph
Anatomic features of lymph nodes:
▪ Most lymph nodes are kidney-shaped, less than 1 inch long, and buried in connective tissue
▪ Surrounded by a capsule
▪ Divided into compartments by trabeculae
▪ Cortex (outer part) ▪ Contains follicles—collections of lymphocytes
▪ Germinal centers enlarge when antibodies are released by plasma cells
▪ Medulla (inner part) ▪ Contains phagocytic macrophages
Flow of lymph through nodes
- Lymph enters the convex side through afferent lymphatic vessels
- Lymph flows through a number of sinuses inside the node
- Lymph exits through efferent lymphatic vessels
- Because there are fewer efferent than afferent vessels, flow is slowed
Describe the spleen
▪ Located on the left side of the abdomen
▪ Filters and cleans blood of bacteria, viruses, debris
▪ Provides a site for lymphocyte proliferation and immune surveillance
▪ Destroys worn-out blood cells
▪ Forms blood cells in the fetus
▪ Acts as a blood reservoir
Describe the thymus
▪ Found overlying the heart
▪ Functions at peak levels only during youth
Some lymphocytes mature here turning into t cells
