Chapter 31 Flashcards
Lymphatic system functions (3)
Maintain fluid balance in the body
Plays a role in immunity
Fat absorption and transport
Structures of the lymphatic system
Lymph, lymphatic vessels, lymph nodes, thymus, tonsils, spleen
Intersitial fluid (IF)
Plasma that has already filtereed out of the capillaries and is in tiny spaces between cells of tissue
Lymph is
Excess Intersitial fluid that isnt absorbed by tissue cells or reabsorbed by the blood before it flows out of the tissue
Lymphatic vessels
Permit one-way movement of lymph towards heart
Collect excess IF (as lymph) and returns it to the blood stream via veins
Two types:
Lymphatic capillaries
Lymphatic ducts
Lymphatic capillaries
Microscopic, blind-ended (open at one end) tubes found in tissue spaces wherever blood capillaries are (except bone, teeth, bone marrow and CNS)
Walls are simple squamous epithelium and are very porous/permeable due to structure
Called ‘lacteals’ in the intestinal wall (Digestive System)
Lymphatic Capillaries
Similar to veins but have thinner walls, more valves, and contain lymph nodes
Edges of cells loosely overlap each other = one-way ‘swinging doors’ (e.g. valves)
Fluid pressure in interstitial fluid determines if fluid will move into our out of lymphatic capillaries:
When fluid pressure is greater in interstitial spaces than in lymphatic capillaries, ‘doors’ are pushed open & fluid moves in
When fluid pressure is greater inside the lymphatic capillary than in interstitial spaces, doors are pushed shut, preventing lymph from leaking backwards
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Right lymphatic ducts
Drains lymph from right upper extremity, right side of head, neck, and upper torso right subclavian vein
Thoracic duct
Thoracic Duct
Largest lymphatic vessel
Drains lymph from the rest of the body left subclavian vein
A structure called cisterna chyli found along its course (storage area for lymph moving towards entering the venous system)
Function of lymphatic vessels
Remove high–molecular-weight substances and even particulate matter from interstitial spaces
Lacteals absorb fats and other nutrients from the small intestine
Circulation of lymph
No pump
Relies on breathing and skeletal muscle contractions
Lymph nodes or glands
Filter lymph
Located in clusters along the pathway of lymphatic vessels where they converge to form larger trunks (see Figures in Textbook)
Functions include defense and WBC formation
Structure of lymphatic nodes
Oval shaped
Fibrous capsule
Biological filters
Flow of lymph
In to node via several afferent lymph vessels
Drained away from node by a one or more efferent lymph vessels
2 functions of lymph nodes
Defense functions
Hematopoesisis
Denfense function
Mechanical filtration (physcial trapping of particles) Biological filtration (cells destroy and remove particles)
Hematopoeisis
Maturation of some lymphocytes and monocytes
Closer look at defense functions
If any antigens/pathogens are detected in the lymph entering the lymph node, various WBCs in the lymph node will get to work to eliminate them (e.g. phagocytosis)
Other immune system cells are called into action and ‘sent’ to the lymph nodes. The increased numbers of immune system cells fighting the infection will make the node expand and become ‘swollen’
Lymphatic drainage of the breast
Clinically important as cancer cell infections can spread along lymphatic pathways to lymph nodes and other organs in the body
Drained by 2 sets of lymphatic vessels
Drains skin over the breast (minus the skin of the areola and nipple)
Drains underlying substances of breast, plus the skin of the areola and nipple
___% of lymph from the breast goes to the axillary lymph nodes
85%
TONSILS COMPOSED OF WHAT 3 MASSES
Palatine tonsils (“the tonsils”) are the largest, and most often infected. On each side of throat Pharyngeal tonsils (adenoids) Lingual tonsils
FUNCTION OF TONSILS
To gather and remove pathogens entering pharynx
Thymus
Primary organ of lymphatic system
Vital role in immunity – its hormones (thymosin) enable lymphocytes T cells
Lymphoid tissue organ located in mediastinum
Completes most of its work in childhood. In adults, lymphoid tissue is largely replaced by fat and connective tissue in a process called involution
Spleen
Largest lymphoid organ in body; ovoid shape
Located in upper left quadrant of abdomen
Often injured by trauma to abdomen
Surgical removal called splenectomy
Spleen function
Defense: filtration & phagocytosis of bacteria and other pathogens
Tissue repair: spleen has a reservoir of monocytes that can migrate to sites of injury to promote healing & repair
Hematopoiesis – monocytes & lymphocytes complete their development in the spleen
Destroys & Recycles: Destroys old RBCs & platelets; stores breakdown products of RBCs (e.g. iron & hemoglobin) which can be ‘reused’
Blood reservoir
