The lymphatic system Flashcards
Structure of lymphatic system
-consists of lymph, lymphatic vessels, red bone marrow, lymphatic tissue
3 functions of lymphatic system
-drain excess interstitial fluid to maintain fluid balance
-absorbs fat (lacteals) from digestive tract that are too large to enter capillaries
-carry our immune responses (lymphocytes, lymphoid tissue)
Lymph
-clear watery fluid, similar to plasma, but less protein
-contains lymphocytes
-carries away particles, cell debris, damaged tissues etc
4 characteristics of lymphatic capillaries
-closed at one end
-permeable- permits interstitial fluid in but not out
-larger diameter than blood capillaries
-unique one way structure
Lymphatic vessels
-capillaries unite forming large lymphatic vessels
-resemble veins, but thinner walls and more valves
-valves allow flow toward the thorax only
Lymph trunks
-lymphatic vessels unite to form trunks
-Trunks: lumbar, intestinal, broncho mediastinal, subclavian and jugular
-passes from trunks into 2 main channels (thoracic/ right lymphatic ducts) before draining into subclavian veins
Formation and flow of lymph
-more fluid filters out capillaries than fluid reabsorbed
-excess filtered fluid drains into lymphatic vessels and become lymph
-uses same pumps as venous return: skeletal muscle pump and respiratory pump
2 types lymphatic organs
-primary lymphatic organs- site where stem cells divide, red bone marrow, thymus
-secondary lymphatic organs- sites where most immune response occurs eg. lymph nodes, spleen, lymph nodules
Thymus gland
-centre of chest
-outer cortex composed of large number of T cells
-T cells mature from red bone marrow
-macrophages clear dead and dying cells
Function lymph nodes
-filter
-trap foreign substances which are then destroyed by macrophages, lymphocytes (phagocytosis)
Lymph nodes
-located along lymphatic vessels
-scattered throughout body
-stroma- supporting connective tissue
-parenchyma- functional part
3 layers
-outer cortex- B cells called lymphatic nodules
-inner cortex- T cells and dendritic cells
-medulla- B cells, antibodies, plasma cells
Axillary lymph nodes
-armpits
-enlarge on infection in upper extremities and breasts
Tracheobronchial lymph nodes
-smoking, polluted areas
-become filled with airborne contaminants
Mesenteric lymph nodes
-between layers peritoneum
-100-150 nodes, peyer patches and appendix
Inguinal lymph nodes
-groin
-enlarge with infection from lower extremities and external reproductive organs
