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Home , Capillary, Cisterna chyli, Lymph, Lymph duct, Metarteriole, Precapillary sphincter

Cardiovascular System

LYMPH AND LYMPHATIC VESSELS Venous system Arterial system Large (capacitance vessels) Elastic Large (conducting lymphatic vessels) vessels node Muscular arteries (distributing Lymphatic vessels) system Small veins (capacitance Arteriovenous vessels)

Lymphatic Sinusoid (resistance vessels) Postcapillary Terminal Thoroughfare Precapillary channel (exchange vessels)

Copyright © 2010 Pearson Education, Inc. Figure 19.2 Regional Internal jugular lymph nodes: Cervical nodes Entrance of into vein

Entrance of thoracic duct into vein Axillary nodes Thoracic duct

Cisterna chyli

Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes.

Figure 20.2a

 Outflow of fluid slightly exceeds return  Consists of three parts 1. A network of lymphatic vessels carrying lymph 1. Transports fluid back to CV system 2. Lymph nodes 1. Filter the fluid within the vessels 3. Lymphoid organs 1. Participate in disease prevention

Lymphatic System

 Functions 1. Returns interstitial fluid and leaked plasma proteins back to the 2. Disease surveillance 3. Lipid transport from intestine via Venous system Arterial system Heart Lymphatic system: Lymph trunk Lymphatic collecting vessels, with valves fluid Blood Lymphatic capillaries Tissue cell capillary Blood Lymphatic capillaries capillaries (a) Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries.

Filaments anchored to

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 Lymph

 Interstitial fluid which enters lymph capillaries  Lower concentration of proteins than blood  Electrolyte differences  Hydrostatic and colloid osmotic pressure regulate exchange HP = hydrostatic pressure • Due to fluid pressing against a wall • “Pushes” • Arteriole Venule In capillary (HPc) • Pushes fluid out of capillary Interstitial fluid • 35 mm Hg at arterial end and 17 mm Hg at venous end of capillary in this example Capillary • In interstitial fluid (HPif) Net HP—Net OP Net HP—Net OP • Pushes fluid into capillary (35—0)—(26—1) (17—0)—(26—1) • 0 mm Hg in this example

Net Net OP = osmotic pressure • Due to presence of nondiffusible HP OP Net Net 35 25 solutes (e.g., plasma proteins) HP OP • “Sucks” mm mm 17 25 • In capillary (OPc) mm mm • Pulls fluid into capillary • 26 mm Hg in this example • In interstitial fluid (OPif) • Pulls fluid out of capillary NFP (net filtration pressure) NFP is ~8 mm Hg; • 1 mm Hg in this example is 10 mm Hg; fluid moves out fluid moves in

Figure 19.17 Venous system Arterial system Large veins Heart (capacitance vessels) Elastic arteries Large (conducting lymphatic vessels) vessels Lymph node Muscular arteries (distributing Lymphatic vessels) system Small veins (capacitance Arteriovenous vessels) anastomosis

Lymphatic Sinusoid capillary Arterioles (resistance vessels) Postcapillary Terminal arteriole venule Metarteriole Thoroughfare Capillaries channel (exchange vessels)

Figure 19.2 Lymphatic Vessels

 One-way system, lymph flows toward the heart  Lymph vessels (lymphatics) include:  Lymphatic capillaries  Lymphatic collecting vessels  Lymphatic trunks and ducts Lymphatic Capillaries

 Similar to blood capillaries, except…  Not continuous  No = very permeable  Take up cell debris, pathogens, and cells  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 Lymphatics

 Collecting vessels  Capillaries join to form larger vessels = lymphatics  Empty into thoracic duct or right lymphatic duct  Similar to veins, except  Have thinner walls, with more internal valves  Anastomose more frequently  More valves  Occasionally modified to form nodes

Lymphatic Ducts

 Lymph is delivered into one of two large ducts  Right lymphatic duct  Drains the right upper and the right side of the head and  Thoracic duct  Arises from the and drains the rest of the body  Connect with subclavian veins Right jugular trunk Internal jugular veins Right lymphatic duct Right subclavian trunk Right Left subclavian trunk Right broncho- Left jugular trunk mediastinal trunk Left subclavian vein Brachiocephalic veins Entrance of thoracic duct into vein Left bronchomediastinal Azygos vein trunk Thoracic duct Cisterna chyli

Right lumbar trunk Left lumbar trunk Inferior vena cava Intestinal trunk (b) Major lymphatic trunks and ducts in relation to veins and surrounding structures. Anterior view of thoracic and abdominal wall.

Figure 20.2b Lymphatics Regional Internal lymph nodes: Cervical nodes Entrance of right lymphatic duct into vein

Entrance of thoracic duct into vein Axillary nodes Thoracic duct

Cisterna chyli Aorta

Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes.

Figure 20.2a Lymph Transport

 No pump  Lymph movement similar to venous return  Valves  contraction  Thoracic pump  Pressure gradients  Also contraction of nearby arteries and within vessels  Movement is slow and sporadic

 Prevention of return of lymph to blood  May be due to:  Osmotic changes  Blockage of lymph vessels  Parasites   Surgery Elephantiasis Lymphatic Tissues

 Tissues house and provide a proliferation site for  Furnish a surveillance vantage point  Mucosa-associated lymphatic (MALT)  Respiratory, digestive, urinary, reproductive systems  Peyer’s patches  Junction of large and Lymphoid nodules (follicles) of Peyer’s patch

Smooth muscle in the intestinal wall

Figure 20.9 Lymph Nodes

 Solid, spherical, well-defined organs  Distributed along course of lymphatic vessels  Concentrated  Cervical region  Behind the , inferior and lateral  Axillary region   Along and mesenteric arteries  Inguinal region Lymph Nodes

 Functions 1. Filter lymph  destroy microorganisms and debris 2.  Lymphocytes are activated and mount an attack against antigens Lymph Nodes

 Structure  Outer parenchyma  Inner medulla  Medullary sinuses  Macrophages  Cortex contains follicles with germinal centers, heavy with dividing B cells

Macrophage

Reticular cells on reticular fibers Lymphocytes

Medullary sinus Reticular fiber

Copyright © 2010 Pearson Education, Inc. Figure 20.3 Regional lymph nodes: Cervical nodes Entrance of right lymphatic duct into vein

Entrance of thoracic duct into vein Axillary nodes Thoracic duct Abdominal Cisterna chyli Aorta

Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes.

Figure 20.2a Afferent Cortex lymphatic • Lymphoid follicle vessels • Germinal center • Subcapsular sinus

Efferent lymphatic Follicles vessels Trabecula

Subcapsular sinus

Hilum Capsule Medulla: • Medullary cord • Medullary sinus Medullary cords

Trabeculae Medullary sinuses Capsule (b) Photomicrograph of part of a (a) Longitudinal view of the internal structure lymph node (72x) of a lymph node and associated lymphatics

Figure 20.4

 Largest lymphoid  Macrophages remove old RBC’s, platelets and bacteria  Production of RBC’s  In fetus and severely anemic patients  Splenic contraction  May return 200-300 mls of blood to circulation from sinuses Regional Internal jugular vein lymph nodes: Cervical nodes Entrance of right lymphatic duct into vein

Entrance of thoracic duct into vein Axillary nodes Thoracic duct Spleen Cisterna chyli Aorta

Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes.

Figure 20.2a Capsule Trabecula Splenic cords Venous sinuses Arterioles and Splenic capillaries Splenic vein Hilum Central artery (a) Diagram of the spleen, anterior view Splenic artery Splenic vein (b) Diagram of spleen

Figure 20.6a,b Big spleen!

 Involution  Stops growing during adolescence and then gradually atrophies  Replaced by adipose and connective tissue Thymus

Thymic (Hassall’s) corpuscle Medulla Cortex

Figure 20.7 Thymus

 Thymopoetin and thymosin  Assist in differentiation Tonsils

 Simplest lymphoid organs  3 pairs  Palatine tonsils  Posterior end oral cavity  “Sore throat”  Lingual tonsils  Grouped at the base of the  Pharyngeal tonsils   Posterior wall of the nasopharynx

Pharyngeal tonsil Palatine tonsil Lingual tonsil

Tonsil

Tonsillar crypt

Germinal centers in lymphoid follicles

Figure 20.8 Tonsillitis Questions?

Remember HW due on Tuesday and in Lab! Quiz Study Guide is in the “Exams” Section