the lymphatic system
DESCRIPTION
The Lymphatic System. Biology 2122 Chapter 20. Functions of the Lymphatic System. 1. Drain Excess ‘interstitial’ fluid 2-3 L of fluid lost from the blood stream/day 2. Transport dietary lipids From GI tract to the blood (lipids and lipid-soluble vitamins) 3. Immune Response - PowerPoint PPT PresentationTRANSCRIPT
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Biology 2122Chapter 20
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Functions of the Lymphatic System1. Drain Excess ‘interstitial’ fluid◦ 2-3 L of fluid lost from the blood stream/day
2. Transport dietary lipids◦ From GI tract to the blood (lipids and lipid-soluble vitamins)
3. Immune Response ◦ A. Cell-mediated response
T-cell response (cytotoxic cells destroy antigens)
◦ B. Humoral – response Antibody-mediated (B-Cells)
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Basic Structure 1. Lymph Fluid◦ Interstitial fluid ------ lymph
capillaries
2. Lymph Vessels◦ Capillaries, ducts, etc.
3. Lymph Tissue and Organs ◦ Specialized reticular tissue◦ Large numbers of lymphocytes ◦ Organs: Thymus gland;
Tonsils; Spleen
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Tissues to the Heart
Lost lymph fluid - returned to the heart. 1. Capillaries ◦ Endothelial Cells and mini-valves
Supported by collagen One way pressure from the capillaries
move lymph towards the capillaries
◦ Very permeable
2. Capillaries form vessels ◦ Skin follow veins; viscera follow path of
arteries ◦ Lymph flows into the nodes ◦ No lymph vessels (cartilage, epidermis,
cornea- all avacular); CNS and red bone marrow
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Chyle and Lacteals Lipids absorption take place in the small intestine
Lacteals◦ Small capillaries in the absorptive cells◦ Lipids transported from lacteals into the blood
Specialized lipid absorption
Chyle ◦ In small intestine lymph is white or creamy due to lipid presence
(lymph is normally clear)
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Flow and Structure
Capillaries ----- Collecting vessels ---- Nodes --- Trunks ------ Lymph ducts (thoracic and right lymphatic) ----- Internal jugular and Subclavian vein ---- Heart
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On the way to the heart 1. Trunks – lumbar, intestinal, bronchomediastinal, subclavian, jugular ◦ A. lumbar ◦ B. intestinal◦ C. bronchomediastinal ◦ D. subclavian ◦ E. Jugular
2. Thoracic (left lymphatic) duct ◦ Cisterna chyli ◦ Main duct for return of lymph to blood from left side of body◦ Drains into the L.internal jugular and L.subclavian vein
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On the way to the heart 3. Right lymphatic duct – Receives lymph from
right side of the body– Drains blood into
venous blood at junction of R. internal jugular and R. subclavian veins
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Flow of Lymph against Gravity Same problems as encountered by venous return
Pumps ◦ 1. Skeletal system pump ◦ 2. Respiratory pump
Organs and Tissues
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Organs and Tissues 1. Primary Organs – stem cell division produces mature cells – immunocompetent ◦ Red bone marrow
B – cells; pre-T cells ◦ Thymus
Pre-T cells migrate to thymus to become immunocompetent
2. Secondary Organs◦ Site of immune system response◦ Nodes, spleen, nodules
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Thymus Bi-lobed- surrounded by CT and separated by capsule
Trabeculae -separates tissue into lobes
Lobe ◦ Cortex -(T-cells and Dendritic
cells, Epithelial cells and Macrophages)
◦ Medulla – mature T-cells, dendritic cells and macrophoges
◦ Thymic (Hassal’s corpusles)
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Lymph Nodes Lymphatic Nodules ◦ B-cells (primary lymphatic nodule)◦ Plasma and memory B cells in outer
cortex (secondary lymphatic nodule)
B-cell in primary nodule recognizes antigen and transforms into a secondary nodule ◦ Germinal center ◦ B-cells, follicular dendritic cells,
macrophages
Antigen presented by APC (B-cell; dendritic , etc.) B- cells develop into plasma and memory cells
Inner cortex and medulla Covered by Dense CT capsule
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Spleen
Covered by Dense CT capsule Visceral peritoneum – serous membrane
Stroma ◦ Trabeculae, reticular fibers and fibroblasts
Parenchyma ◦ 1. White pulp – lymphocytes and macrophages around central
arteries (splenic artery branches)
◦ 2. Red pulp – venous sinuses, cords of splenic tissue or splenic cords (RBCs, macrophages, lymphocytes, plasma cells, granulocytes
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Nodules No capsuleFound in mucous membranes (near lamina propria) in GI
tract, urinary, reproductive, respiratory airways◦ “Mucosa-associated lymphatic tissue (MALT)
Can be small or larger tissue◦ Tonsils (5)-Pharyngeal area
Pharyngeal (adenoid- posterior nasopharynx) Palatine (2)-posterior region of oral cavity (tonsillectomy) Lingual (2)-base of tongue