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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)
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
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
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)
Flow and Structure
Capillaries ----- Collecting vessels ---- Nodes --- Trunks ------ Lymph ducts (thoracic and right lymphatic) ----- Internal jugular and Subclavian vein ---- Heart
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
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
Flow of Lymph against Gravity Same problems as encountered by venous return
Pumps ◦ 1. Skeletal system pump ◦ 2. Respiratory pump
Organs and Tissues
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
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)
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
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
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