Chapter 21 Lymphatic and Immune Systems 21 1

Chapter 21 Lymphatic and Immune Systems 21 -1

Ch. 21 Study Guide 1. Critically read Chapter 21 pp. 816 -829 right before 21. 2 (Nonspecific Resistance) section. 2. Comprehend Terminology (those in bold) 3. Study-- Figure questions, Think About It questions, and Before You Go On (sectionending) questions 4. Do end-of-chapter questions: – Testing Your Recall— 1 -4, 11 -13 – True or False– 1, 2, 5 – Testing Your Comprehension-- #2 2

§ The Lymphatic System 1. What is the lymphatic system? a network of vessels that penetrate nearly every tissue of the body and a collection of tissues and organs that produce immune cells. Fig. 21. 3, 21. 1 2. Components of the system: – Lacking a contractile “heart”; “pumpless” – Lymph: * Blood is to blood vessels as _______ is to lymphatic vessels. – Lymphatic vessels: – Lymphatic tissue & lymphatic organs: 21 -3

Capillary bed Lymphatic capillary Where are lymphatic capillaries? 21 -4

• Lymphatic vessels? • 5 lymphatic organs– (A-E) A-Tonsils E-Lymph nodes (7 locations): 1. Cervical B-Thymus C-Spleen 2. Axillary 3. Thoracic 4. Abdominal MUST MEMORIZE this information. D-Red bone marrow 5. Intestinal & mesenteric 6. Inguinal 7. Popliteal 21 -5 “Swollen glands”

§ Functions of Lymphatic System (1) 1. Fluid recovery: – absorbs ECF proteins and fluid (2 to 4 L/day) from tissues and returns it to the bloodstream • interference with lymphatic drainage leads to severe edema (Fig. 21. 2) 21 -6

Elephantiasis— Cause- mosquitoborne roundworms infect the lymph nodes and block the flow of lymph Symptoms– chronic edema, especially extremities; Thickening of the skin 21 -7

§ Functions of Lymphatic System (2) 2. Immunity: – fluids from all capillary beds are filtered – immune cells (where are they? ) stand ready to respond to foreign cells or chemicals encountered 3. Lipid absorption: – Lacteals (what are they? ) in small intestine absorb dietary lipids 21 -8

§ Lymph and Lymphatic Vessels (1) 1. Lymph – clear, colorless fluid, similar to plasma but much ____ protein; others include. . . 2. Lymphatic capillaries (structures) A. -- Closed at one end B. -- Tethered to surrounding tissue by protein filaments C. -- Endothelial cells loosely overlapped; tight junctions? Basement membrane? D. -- Valvelike flaps at the edges of endothelial cells Fig. 21. 3 b 21 -9

Fig. 21. 3 b– uptake of tissue fluid by a lymphatic capillary 21 -10

§ Lymph and Lymphatic Vessels (2) 1. Larger lymphatic vessels composed of 3 layers: – tunica interna: endothelium and valves – tunica media: elastic fibers, smooth muscle – tunica externa: thin outer layer 2. Compared to veins, lymphatic vessels: – Their walls: thinner / thicker – Their valves: (intervals) closer together/ farther apart; therefore; ____ (more/less) valves in lymphatics compared to veins 21 -11 Fig. 21. 4 b

Fig. 21. 4 b: valves ensure a one-way flow of lymph 21 -12 Lymph flows forward through open valves Closed valves

§ Fluid exchange between the circulatory and lymphatic systems (A) – Principle: the lymphatic system picks up excess tissue fluid and returns it to the bloodstream – Routes: Continual recycling of fluid from blood (blood capillaries) to the tissue, to the lymph, and back to the blood stream – Through what specific veins does the lymph draining back to the bloodstream? – Answer: ____ Fig. 21. 5 _______ veins 21 -13

Lymphatic, one-way, system 4. Two Collecting duct 3. Six lymphatic trunks Cardiovascular system Pulmonary circuit Subclavian vein Superior vena cava Lymph node Blood flow 2. Collecting vessels 1. Lymphatic capillaries Systemic circuit 21 -14

§ Fluid exchange between the circulatory and lymphatic systems (B) The sequence of fluid flow: 1. blood capillaries (blood) 2. interstitial spaces (interstitial fluid) 3. ________(lymph) 4. lymphatic vessels (lymph) 5. lymphatic trunks (lymph) 6. ________(lymph) 7. subclavian veins (blood) 21 -15

§ Route of Lymph Flow-A 1. Lymphatic capillaries 2. Collecting vessels: course through many lymph nodes; 3. (Six) larger Lymphatic trunks: drain major portions of body; 4. (Two) Collecting ducts: A. right lymphatic duct – receives lymph from R arm, R side of head and thorax; empties into R subclavian vein (Fig. 21. 6 b -c) 21 -16

Areas drained by right lymphatic duct. Areas drained by thoracic duct (left lymphatic duct). 21 -17

Regions of the body drained by the right lymphatic duct 21 -18

§ Route of Lymph Flow-B 4. (Two) Collecting ducts (continued): B. thoracic duct - larger and longer; begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, L arm, L side of head, neck, and thorax; empties into L subclavian vein Fig. X 21 -19

R 1 L 1+2 R 2 L 3 R 3 Intercostal trunks 4 L 5 R 5 6 21 -20

§ Route of Lymph Flow-C Six principal lymphatic trunks: Jugular (R + L) What Subclavian (R + L) vein do Bronchomediastinal (R+L) they drain Intercostal trunks into? Cisterna chyli The intestinal trunk Lumbar trunks (R + L) 21 -21

§ Mechanisms of Lymph Flow • Lymph flows at low pressure and speed Primary ones: 1. Moved along by rhythmic contractions of ______. 2. _____ prevent backward flow Others mechanisms: 3. Flow aided by skeletal muscle pump 4. Arterial pulsation-5. Thoracic pump aids flow from abdominal to thoracic cavity 6. Rapidly flowing blood in subclavian veins, draws lymph into it 21 -22

§ Lymphatic Cells/lymphocytes 1. Natural killer (NK) cells-- Large lymphocytes; destroy bacteria & certain host cells Fig. 21. 17, 18. 18 2. T lymphocytes (T cells) Fig. 21. 20 – Lymphocytes mature in thymus Lymphocytes 3. B lymphocytes (B cells)– lymphocytes mature in bone marrow; They differentiate into plasma cells that produce antibodies 4. Antigen Presenting Cells: present to T cells – macrophages (from monocytes); very large; phagocytosis (Fig. 21. 7; 21. 21) – dendritic cells (in epidermis, mucous membranes and lymphatic organs); perform endocytosis (similar to phagocytosis) – reticular cells stationary, in the thymus Fig. 21. 10 21 -23

White blood cells production Pluripotent stem cell Colony-forming units (CFUs) Mature cells Precursor cells leaves Eosinophilic CFU Eosinophilic myeloblast Eosinophilic promyelocyte Eosinophilic myelocyte Eosinophil Basophilic CFU Basophilic myeloblast Basophilic promyelocyte Basophilic myelocyte Basophil Neutrophilic CFU Neutrophilic myeloblast Neutrophilic promyelocyte Neutrophilic myelocyte Neutrophil Monocytic CFU Monoblast Promonocyte B prolymphocyte Lymphocytic CFU Lymphoblast Monocyte B lymphocyte T prolymphocyte T lymphocyte NK prolymphocyte NK cell

The actions of a natural killer cell 21 -25

The life history and migration of B and T cells 21 -26

Phagocytosis by macrophages 21 -27

1 --The action of antigenpresenting cells (macrophages); 2 --Then T-cells initiate an attack 21 -28

Figure 21. 10 Thymus Reticular epi. cells of cortex Capsule Reticular epi. cells of medulla Trabecula 21 -29

§ Lymphatic Tissue– aggregation of lymphocytes-- two forms: 1. Diffuse lymphatic tissue – lymphocytes in mucous membranes and CT of many organs – prevalent in 4 body systems open to exterior– Respiratory, digestive, etc. systems • It is called Mucosa-Associated Lymphatic Tissue (MALT) (Fig. 21. 8) 21 -30

Lymphatic nodule in the mucosa of the small intestine Intestinal villus Lymphatic nodule 21 -31

§ Lymphatic Tissue– aggregation of lymphocytes-- two forms: 2. Lymphatic nodules A. come and go-- dense oval masses of lymphocytes and macrophages, congregate in response to pathogens B. permanent feature-– in some organs– lymph nodes (Fig. 21. 12), tonsils, and appendix – In the ileum– called Peyer patches: clusters found at junction of small to large intestine 21 -32

Lymphatic nodules A lymph node Fig. 21. 12 a and b Afferent lymphatic vessels Efferent lymphatic vessel 21 -33

§ Lymphatic Organs In contrast to the diffuse lymphatic tissue, these organs have: well defined anatomical sites; have CT capsules 1. Primary lymphatic organs – site where B and T cells become immunocompetent – ________ and _______ 2. Secondary lymphatic organs – immunocompetent cells populate these tissues – lymph nodes, _____, and tonsils 21 -34

§ A. Red Bone Marrow 1. Functions– hemopoiesis and immunity (supply of lymphocytes) 2. Structure– Fig. 21. 9 – Highly vascularized, numerous arteries enter the bone surface, and empty into large sinusoids capillaries – The sinusoids drain into a central longitudinal vein that exit the bone – Reticular cells; location? (1) induce formation of WBCs; (2) aging reticular cells become adipose cells 21 -35

21 -36

§ B. Thymus (1) Thymus 21 -37

Thymus (2) • Large in fetus; after age 14 begins involution • Capsule gives off trabeculae, divides thymus into lobules • Reticular epithelial cells (Fig. 21. 10 a-c) – Form BTB__________; Where? – secretes hormones (thymopoietin, thymulin and thymosins etc. ); Function? • T Cells– develop in the cortex, migrate to the medulla, and enter blood or lymphatic vessels 21 -38

Figure 21. 10 a See next slide 21 -39

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Figure 21. 10 c Reticular epi. cells of cortex Reticular epi. cells of medulla Medulla Cortex 21 -41

§ C. Lymph Nodes (1) • Lymph nodes - only organs that filter lymph; only organs have afferent lymphatic vessels • Bean-shaped, less than 3 cm long, hilum present; most numerous lymphatic organs 1. Two main functions– A. Cleanse the ______ B. A site for T and B cell activation 2. 7 major locations— Fig. 21. 1, Fig. 21. 11 – Cervical lymph nodes etc. 21 -42

• 5 lymphatic organs– (A-E) • Locations of lymph nodes-- A-Tonsils E-Lymph nodes (7 locations): 1. Cervical B-Thymus C-Spleen 2. Axillary 3. Thoracic 4. Abdominal MUST MEMORIZE this information. D-Red bone marrow 5. Intestinal & mesenteric 6. Inguinal 7. Popliteal 21 -43

Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Colon Superior mesenteric lymph nodes Transverse mesocolic lymph nodes Superior mesenteric artery Inferior mesenteric artery Ileocolic lymph nodes Small intestine Appendicular lymph nodes Appendix (a) Inferior mesenteric lymph nodes

§ C. Lymph Nodes (2) 3. Structure: (Fig. 21. 12) A. Stroma– capsule with trabeculae, subcapsular sinus (reticular fibers, macrophages etc. ) B. Parenchyma– C-shaped cortex and medulla (they perform functions of the lymph nodes) 4. Outer cortex: (outer 4/5) • lymphatic nodules- shapes? • When fighting a pathogen, germinal centers develop where B cells become plasma cells • Cortical sinuses subcapsular s. medullary s. 21 -45

Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. A--Stroma: Capsule Trabecula B 1 --Cortex Medulla cord Lymphatic nodule Germinal center B 2 --Medulla Afferent lymphatic vessels (a) Efferent lymphatic vessel

§ C. Lymph Node (3) 5. Inner medulla: – Branching network of medullary cords, composed of lymphocytes, plasma cells, macrophages, reticular cells – Medullary sinuses 6. Routes of lymphatic flow: Afferent lymphatic v. (Network of sinuses) Subcapsular space Outer cortex and then deep cortex Sinuses of the Medulla (the core) Efferent lymphatic v. (at the hilum) 21 -47

Disorders on lymph nodes • Lymphadenopathy – Collective term for all lymph node diseases • Lymphadenitis – swollen, painful node responding to foreign antigen • Lymph nodes are common sites (called lymphoma) for metastatic cancer – swollen, firm and usually painless 21 -48

§ D. Tonsils • Def. Patches of lymphatic tissue located at the entrance to the pharynx and vicinity • Each tonsil: – Covered by epithelium – Having deep pits called tonsillar crypts – Tonsillar crypts lined by lymphatic nodules Fig. 21. 13 21 -49

Histology of pharyngeal tonsil 21 -50

Three Locations of Tonsils 1. Pharyngeal tonsil (adenoid) – single tonsil on wall of pharynx 2. Palatine tonsils – A pair; at posterior margin of oral cavity – Largest and most often infected called tonsillitis (treatments-- tonsillectomy or with antibiotics) 3. Lingual tonsils (many) – at root of tongue Fig. 21. 13, 25. 5 21 -51

Regions of pharynx Lingual tonsils Pharyngeal tonsil Hyoid bone Cricoid cartilage 22 -52

Figure 21. 13 a Only 1 2; a pair many 21 -53

Figure 25. 5 a 21 -54

§ E. Spleen (1) • Largest lymphatic organ • Location of the spleen: – Protected by ribs 10 -12 – Left hypochondriac region – Dorsolateral to the stomach – Fits between the diaphragm, stomach, and kidney; – The spleen has gastric area, renal area, and colic area Fig. 21. 14 a, b, x 21 -55

21 -56

ID these five organs —A-E E D C A B 21 -57

21 -58

§ E. Spleen (2) • Two types of tissue in fresh specimens as: – red pulp: sinuses filled with erythrocytes – white pulp: lymphocytes, macrophages; surrounds small branches of splenic artery • Functions of the spleen: – ________ in fetus – RBC disposal (graveyard) – Monitor the blood foreign antigens; stabilize blood volume by transferring excess plasma from the blood into the lymphatic system Fig. 21. 14 c, Fig. Y 21 -59

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Fig. 21. 14 c What cells account for the colors of the red pulp and white pulp, respectively? 21 -61