Lymphatic System

Jonathan Cash
Flashcards by Jonathan Cash, updated more than 1 year ago
Jonathan Cash
Created by Jonathan Cash over 5 years ago


5 HAP 1 Flashcards on Lymphatic System, created by Jonathan Cash on 10/16/2015.

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Question Answer
Lymphatic System Overview Consists of 2 part • lymphatic vessels • lymphoid tissue & organs
Lymphatic system functions • transports tissue fluid (lymph) back to the blood • Play essential roles in body defence & resistance to disease
Tissue Fluid Tissue Fluid Capillary beds – fluid forced out of blood Most reabsorbed Fluid left in tissues (approx 3L daily) = Tissue (Interstitial) Fluid (IF) IF plus leaked plasma protein enters lymph capillary Now called LYMPH – returned to blood Accumulated fluid = (O)EDEMA)
Lymph Capillaries Begin as blind ended tubes Easily opened flap like mini valves Throughout body Absent in bone and teeth, bone marrow and the entire CNS Inflamed tissue more permeable allows pathogens, cell debris and cancer cells enter lymphatic system
Collecting Vessels Structure and Function • Have the same three tunics as veins • Have thinner walls, with more internal valves • Collecting vessels in the skin travel with superficial veins • Deep vessels travel with arteries
Collecting vessels - continued • Lymphatic collecting vessels • Collects lymph from lymph capillaries • Carries lymph to and away from lymph nodes • Returns fluid to circulatory veins near the heart
Lymphatic Vessels 1. Lymphatic capillaries 2. Collective vessels 3. Lymphatic trunks – 5 major trunks 4. Collecting ducts – i) Right lymphatic duct ii) Thoracic duct 5. Subclavian vein
Function of Lymphatic Vessels • Return excess tissue fluid to blood • Return leaked protein to the blood • Carry absorbed fat from intestine to the blood • All returned to circulatory veins near the heart
Lymph Transport Properties of lymphatic vessels • One way system toward the heart • Valves • No pump • Lymph moves toward the heart
Mechanisms of Lymphatic Flow 1. Skeletal muscle pump 2. Respiratory pump 3. Smooth muscle in the walls of the larger lymphatic vessels 4. Squeezing of the lymphatic vessels by the expansion/recoil of arteries that are wrapped in the same connective tissue sheath
Structure of Lymph Nodes • Vary in size and shape - most bean shaped • More afferent vessels enter node than efferent vessel leaving at the hilus • Capsule – fibrous strands - called trabeculae -extend inwards & divide into compartment
Structure of Lymph Nodes Cortex (outer part of node) • Follicles = collection of lymphocytes (B & T) • Germinal centres = B cell replication to produce plasma cells and antibodies • Cells in transit – e.g. T cells. Medulla = cords and sinuses (central) • contains phagocytic macrophages 
Functions of Lymph Nodes • Filter lymph before it is returned to the blood • Slow flow through lymph node to allow time for antigen removal & protection • Defense cells within lymph nodes – macrophages – engulf and destroy foreign substances (antigens) – lymphocytes (B & T cells) – provide immune response to antigens
Spleen • Largest lymphoid organ • Destroys worn RBCs & sends break down products to liver • Site for lymphocyte proliferation, immune surveillance & response • Filters & cleanses blood of microbes • RBC production in fetus • Stores platelets • Blood reservoir
Thymus • Important in early life • Immunocompetence of T cells
Tonsils/Adenoids • Trap and remove antigens entering the pharynx in food or air.
Peyer’s Patches • Wall of the small intestine • Destroy bacteria – prevent entry into abdominal space
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