Chapter 22: The Lymphatic System

Transcription

1 Slide 1 Chapter 22: The Lymphatic System Slide 2 What are the major components of the lymphatic system?

2 Slide 3 Components of the Lymphatic System 1. Lymph: a fluid similar to plasma does not have plasma proteins 2. Lymphatic vessels (lymphatics): network that carries lymph from peripheral tissues to the venous system 3. Lymphocytes, phagocytes, and other immune system cells 4. Lymphoid tissues and lymphoid organs: found throughout the body Slide 4 Organization of the Lymphatic System Figure 22 1

3 Slide 5 What are the major functions of the lymphatic system? Slide 6 Function of the Lymphatic System Collection of fluid and solutes lost by the capillaries 3.6L/day Distribution Hormones Nutrients Waste products Protects us against disease Production, maintenance and distribution of lymphocytes

4 Slide 7 1. Lymphatic Vessels Slide 8 Role of Lymphatic Vessels About 3.6L/day of fluid is lost from the capillaries each day This fluid is termed lymph fluid Similar to plasma but with little proteins This fluid is returned to the venous system by the lymphatic vessels Also transports hormones, nutrients, and waste products in the process

5 Slide 9 Lymphatic Vessels Formed from buds coming off the veins Lymphatic system begins with smallest vessels: lymphatic capillaries (terminal lymphatics) Slide 10 Distribution of Lymphatic Vessels Wide-spread originating from most capillary beds Absent from: Bone Teeth Bone marrow Nervous system Function is replaced by cerebral spinal fluid

6 Slide 11 Lymphatic Capillaries Differ from blood capillaries in 4 ways: start as pockets rather than tubes Originate in the capillary beds have larger diameters have thinner walls flat or irregular in section Slide 12 Lymphatic Capillaries Figure 22 2

7 Slide 13 Construction of Lymphatic Capillaries Endothelial cells loosely bound together with overlap Overlap acts as one-way valve: Called minivalves allows fluids, solutes, viruses, and bacteria to enter Can allow entry of cancer cells prevents return to intercellular space Slide 14 Lymphatic Vessels and Valves Figure 22 3

8 Slide 15 Lacteals Are special lymphatic capillaries in small intestine Very large diameter Transport lipids from digestive tract Slide 16 Lymph Flow From lymphatic capillaries have minivalves larger lymphatic vessels containing oneway valves like seen in veins Larger lymphatic vessels have smooth muscle that contracts rhythmically Movement also aided by respiratory and muscular pump

9 Slide 17 Lymphatic Ducts and the Venous System Figure 22 4 Slide 18 Superficial and Deep Lymphatics Join to form large lymphatic trunks Trunks empty into 2 major collecting vessels: thoracic duct right lymphatic duct

10 Slide 19 The lower portion of the Thoracic Duct Receives the lymph flow from structures inferior to the diaphragm Expands into cisterna chyli Cisterna chyli receives lymph from: right and left lumbar trunks intestinal trunk Slide 20 The upper portion of the Thoracic Duct Receives lymph flow from structures on the left side but superior to the diaphragm Collects lymph from: left bronchiomediastinal trunk left subclavian trunk left jugular trunk Thoracic duct empties into left subclavian vein

11 Slide 21 Lymphatic Ducts and the Venous System Figure 22 4 Slide 22 The Right Lymphatic Duct Receives lymph flow from structures on the right side but superior to the diaphragm Collects lymph from: right jugular trunk right subclavian trunk right bronchiomediastinal trunk Empties into right subclavian vein

12 Slide 23 Lymphatic Ducts and the Venous System Figure 22 4 Slide 24 Lymphedema Blockage of lymph drainage from a limb Causes severe swelling Interferes with immune system function

13 Slide Lymphocytes Slide 26 Lymphocytes Lymphatic system cells respond to: environmental pathogens toxins abnormal body cells, such as cancers

14 Slide 27 Lymphocytes Make up 20 30% of circulating leukocytes Most are stored, not circulating Slide 28 Lymphopoiesis Lymphocyte production involves: bone marrow thymus peripheral lymphoid tissues

15 Slide 29 Formation and Distribution of Lymphocytes Figure 22 5 Slide 30 Lymphoid Stem Cells Group 1: remain in bone marrow produce B cells and natural killer cells

16 Slide 31 Lymphoid Stem Cells Group 2: migrate to thymus produce T cells in environment isolated by blood-thymus barrier Slide 32 Differentiation B cells differentiate: with exposure to hormone interleukin-7 T cells differentiate: with exposure to several thymic hormones

17 Slide 33 3 Classes of Circulating Lymphocytes 1. T cells: thymus-dependent 2. B cells: bone marrow derived 3. NK cells: natural killer cells Slide 34 T Cells Make up 80% of circulating lymphocytes

18 Slide 35 3 Main Types of T Cells 1. Cytotoxic T cells 2. Helper T cells 3. Suppressor T cells Slide 36 Cytotoxic T Cells Attack cells infected by viruses Produce cell-mediated immunity

19 Slide 37 Helper T Cells Stimulate function of T cells and B cells Slide 38 Suppressor T Cells Inhibit function of T cells and B cells

20 Slide 39 B Cells Make up 10 15% of circulating lymphocytes Differentiate into plasma cells Slide 40 Plasma Cells Produce and secrete antibodies (immunoglobin proteins)

21 Slide 41 Natural Killer (NK) Cells Also called large granular lymphocytes Make up 5 10% of circulating lymphocytes Responsible for immunological surveillance Attack: foreign cells virus-infected cells cancer cells Slide 42 T Cells and B Cells Migrate throughout the body: to defend peripheral tissues Retain their ability to divide: is essential to immune system function

22 Slide Lymphoid Tissues Slide 44 Characteristics of Lymphoid Tissues Connective tissues dominated by lymphocytes Strategically located to intercept and react with foreign material (antigens) Located where risk of infection is greatest

23 Slide 45 Types of Lymphoid Tissues Diffuse Lymphatic Tissue Lymphoid Nodules Lymphoid Organs Slide 46 Diffuse Lymphatic Tissue Simple in construction Loosely scattered lymphocytes located in areolar connective tissue Not enclosed by a capsule Location of lymphocytes is not static Located beneath the epithelia of most tissues Most common in GI, respiratory, genitourinary tracts

24 Slide 47 Lymphoid Nodule Areolar tissue with densely packed lymphocytes Germinal center contains dividing lymphocytes Slide 48 Lymphoid Nodules Figure 22 6

25 Slide 49 Distribution of Lymphoid Nodules Lymph nodes Spleen Respiratory tract (tonsils) Along digestive and urinary tracts Slide 50 Mucosa-Associated Lymphoid Tissue (MALT) Lymphoid tissues associated with the digestive system: aggregated lymphoid nodules: clustered deep to intestinal epithelial lining mass of fused lymphoid nodules Appendix: Peyer s patches

26 Slide 51 The 5 Tonsils In wall of pharynx: left and right palatine tonsils pharyngeal tonsil (adenoid) 2 lingual tonsils Contains crypts that trap infectious material Slide 52 Lymphoid Nodules Tonsils Figure 22 6

27 Slide 53 Lymph nodes Thymus Spleen Lymphoid Organs Slide 54 Lymphoid Organs Typically constructed of large collections of lymphatic nodules Are separated from surrounding tissues by a fibrous connective-tissue capsule Helps contain infectious material

28 Slide 55 Lymph Nodes Figure 22 7 Slide 56 Lymph Nodes Range from 1 25 mm diameter Function as a filter for the lymph fluid 600 bean-shaped lymph nodes scattered throughout the body Large numbers in the cervical, axillary, and inguinal regions Figure 22 7

29 Slide 57 Lymph Glands Large lymph nodes at groin and base of neck Swell in response to inflammation Slide 58 Function of Lymph Nodes A filter: purifies lymph before return to venous circulation Lymph fluid will pass through at least one node before returning to the circulation Removes: debris pathogens 99% of antigens

30 Slide 59 Flow of Lymph Fluid Enters the node through afferent lymphatic vessel Passes next to subcapsular sinus: Contains marophages Engulfs cellular debris and infectious material Contains dendritic cells Involved in initiation of immune response Antigen presentation Passes into the outer cortex: Contains lymphoid nodules housing B cells Germinal center contains dividing B cells and lymphatic dendritic cells Lymphatic Dendritic cells assist in maturation of B cells Slide 60 Flow of Lymph Fluid (cont.) Passes into the deep cortex: Dominated by T cells Involved in cell-mediated immunity Passes into the medulla: Contains B cells and Plasma cells Involved in antibody production (humoral immunity) Are arranged in elongated masses called medullary cords Exits the node by the efferent lymphatic vessel

31 Slide 61 Lymphadenopathy Chronic or excessive enlargement of lymph nodes may indicate infections, endocrine disorders, or cancer Slide 62 The Thymus Figure 22 8

32 Slide 63 The Thymus Located in mediastinum Deteriorates after puberty: diminishing effectiveness of immune system Slide 64 Divisions of the Thymus Thymus is divided into 2 thymic lobes Septa divide lobes into smaller lobules

33 Slide 65 A Thymic Lobule Contains a dense outer cortex And a pale central medulla Slide 66 Lymphocytes Divide in the cortex T cells migrate into medulla Mature T cells leave thymus by medullary blood vessels

34 Slide 67 Reticular Epithelial Cells in the Cortex Surround lymphocytes in cortex Maintain blood-thymus barrier Secrete thymic hormones (Thymosins) that stimulate: stem cell divisions T cell differentiation Slide 68 Reticular Epithelial Cells in the Medulla Form concentric layers (Hassall s corpuscles) The medulla has no blood thymus barrier: T cells can enter or leave bloodstream

35 Slide 69 The Spleen Figure 22 9 Slide 70 3 Functions of the Spleen 1. Removal of abnormal blood cells and other blood components by phagocytosis 2. Storage of iron recycled from red blood cells

36 Slide 71 3 Functions of the Spleen 3. Initiation of immune responses by B cells and T cells: in response to antigens in circulating blood Slide 72 Structure of the Spleen Inside fibrous capsule: red pulp: which contains many red blood cells white pulp: resembles lymphoid nodules

37 Slide 73 Trabecular Arteries Branch of the splenic artery that radiate toward capsule Finer branches surrounded by white pulp Capillaries discharge red blood cells into red pulp