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Home , Capillary, Cisterna chyli, Lymph

3/28/2016

Lymphatic System

• system: outflow of fluid slightly exceeds return Cardiovascular System • Fluid is returned to the bloodstream via AND LYMPHATIC VESSELS

Venous system Arterial system Large HeartHeartHeart (capacitance Regional Internal jugular vessels) Elastic lymph nodes: LargeLargeLarge (conducting Cervical nodes lymphatic vessels) Entrance of right vesselsvesselsvessels lymphatic duct into vein LymphLymphLymph nodenodenode Muscular arteries Entrance of thoracic (distributing duct into vein Axillary nodes Lymphatic vessels) systemsystemsystem Small veins Thoracic duct (capacitance Arteriovenous vessels) Lymphatic Lymphatic Inguinal nodes Sinusoid capillary Lymphatic collecting vessels Drained by the right (resistance vessels) lymphatic duct Postcapillary Terminal Drained by the venulevenulevenule thoracic duct Thoroughfare Precapillary (a) General distribution of lymphatic collecting vessels channel (exchange vessels) and regional lymph nodes.

Figure 19.2Figure19.2 Figure 20.2a

Lymphatic System Lymphatic System

• Consists of three parts • Functions – A network of lymphatic vessels carrying lymph 1. Returns interstitial fluid and leaked plasma proteins • Transports fluid back to CV system back to the – Lymph nodes 2. Disease surveillance • Filter the fluid within the vessels 3. Lipid transport from intestine via – Lymphoid organs • Participate in disease prevention

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Venous system Arterial system Lymphatic system: Lymph Lymph trunk Lymphatic collecting vessels, with valves • Interstitial fluid which enters lymph capillaries fluid Blood Lymphatic capillaries Tissue cell capillary Blood Lymphatic – Lower concentration of proteins than blood capillaries capillaries (a) Structural relationship between a capillary bed of the blood vascular – Electrolyte differences system and lymphatic capillaries. • Hydrostatic and colloid osmotic pressure Filaments anchored to regulate exchange

Endothelial cell

Flaplike minivalve

Fibroblast in loose connective tissue

(b) Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Figure 20.1

Lymphatic Vessels Lymphatic Capillaries

• One-way system, lymph flows toward the heart • Similar to blood capillaries, except… • Lymph vessels (lymphatics) include – Dead end vessels – Lymphatic capillaries – No = very permeable – Lymphatic collecting vessels • Take up cell debris, pathogens and cells – – Lymphatic trunks and ducts Endothelial cells overlap to form one-way mini- valves

Filaments anchored to connective tissue

Endothelial cell

Flaplike minivalve

Fibroblast in loose connective tissue

(b) Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves.

Figure 20.1b

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Lymphatics Lymphatic Ducts

• Collecting vessels • Lymph is delivered into one of two large ducts • Capillaries join to form larger vessels = – lymphatics • Drains the right upper & the right side of the head & – Empty into thoracic duct or right lymphatic duct • Similar to veins, except – Thoracic duct – Have thinner walls • Arises from the cisterna chyli & drains the rest of the body – Anastomose more frequently • – More valves Connect with subclavian veins – Occasionally modified to form nodes

Lymphatics Regional Lymph Transport Internal jugular vein lymph nodes: Cervical nodes Entrance of right • No pump lymphatic duct into vein • Entrance of thoracic Lymph movement similar to venous return duct into vein Axillary nodes – Valves Thoracic duct – contraction – Thoracic pump Cisterna chyli Aorta – Pressure gradients Inguinal nodes Lymphatic – Contraction of nearby arteries & collecting vessels Drained by the right lymphatic duct within vessels Drained by the thoracic duct – Movement is slow and sporadic (a) General distribution of lymphatic collecting vessels and regional lymph nodes.

Figure 20.2a

Edema Lymphatic Tissues

• • Tissues house and provide a proliferation site – Prevention of return of lymph to blood for • May be due to: – Furnish a surveillance vantage point – Osmotic changes • Mucosa-associated lymphatic (MALT) – Blockage of lymph vessels – Respiratory, digestive, urinary, reproductive systems • Parasites – Peyer’s patches – • Junction of large and – Surgery

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Lymph Nodes Lymph Nodes

• Solid, spherical, well-defined organs • Functions – Distributed along course of lymphatic vessels 1. Filter lymph – Concentrated • destroy microorganisms and debris • Cervical region 2. – Behind the ear, inferior mandible and lateral neck • Lymphocytes are activated and mount an attack against • Axillary region antigens • Abdomen – Along and mesenteric arteries • Inguinal region

Lymph Nodes Lymphatic System Components

• Structure PLymph – Outer cortex PLymphatic vessels • Follicles with germinal centers, heavy with dividing B cells PLymph nodes – Inner medulla Lymphatic tissues • Medullary sinuses P – Macrophages • Lymphatic organs

Spleen

• Largest lymphoid Capsule Trabecula – Macrophages remove old RBC’s, platelets and Splenic cords bacteria Venous sinuses Arterioles and Splenic capillaries – Production of RBC’s • In fetus and severely anemic patients Splenic vein Hilum White pulp Central artery – Splenic contraction (a) Diagram of the , anterior view Splenic artery • May return 200-300 mls of blood to circulation from Splenic vein sinuses (b) Diagram of spleen

Figure 20.6a,b

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Thymus Tonsils

• Involution • Simplest lymphoid organs – – Stops growing during adolescence and then gradually 3 pairs • Palatine tonsils atrophies – Posterior end oral cavity • Replaced by adipose and connective tissue – “Sore throat” • • Lingual tonsils – Grouped at the base of – Thymopoetin and thymosin the • Assist in differentiation • Pharyngeal tonsils – – Posterior wall of the nasopharynx

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