Anatomy & Physiology Bio 2402 Lab Lecture. Instructor: Daryl Beatty Lab 4 A&P 2 Lymphatic System

Transcription

1 Anatomy & Physiology Bio 2402 Lab Lecture Instructor: Daryl Beatty Lab 4 A&P 2 Lymphatic System

2 20 The Lymphatic System

3 Lymphatic System: Overview Consists of two semi-independent parts: A network of lymphatic vessels Lymphoid tissues and organs scattered throughout the body And of course: Lymph

4 Lymphatic System: Overview Functions: Returns interstitial fluid and leaked plasma proteins back to the blood Lymph is: interstitial fluid once it has entered lymphatic vessels Critical in the function of immune system.

5 Lymphatic System: Overview Figure 20.2a

6 Lymphatic System: Overview Figure 20.1a

7 Lymphatic System: Overview Lymphatic Capillaries Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Figure 20.1a

8 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

9 Lymphatic Vessels One-way system, lymph flows toward the heart Lymph vessels include: Microscopic, permeable, blind-ended capillaries Lymphatic collecting vessels Trunks and ducts

10 Function of Lymphatics? Must return this leakage ISF to the venous system. Return plasma proteins to the blood also.

11 How is Lymph formed? How is it different from plasma?

12 Estimating Lymphatic Flow About 125 ml/hour Blood flow is how many times greater?

13 Circulatory Shock Circulatory shock any condition in which blood vessels are inadequately filled and blood cannot circulate normally Results in inadequate blood flow to meet tissue needs

14 Circulatory Shock Three types include: Hypovolemic shock results from large-scale blood loss Vascular shock poor circulation resulting from extreme vasodilation Cardiogenic shock the heart cannot sustain adequate circulation

15 Circulatory Shock Three types include: shock results from large-scale blood loss shock poor circulation resulting from extreme vasodilation shock the heart cannot sustain adequate circulation

16 Why does lymph flow? 3 Mechanisms Contraction of smooth muscle surrounding vessels Contraction of skeletal muscles Respiratory pump May be hindered by elevation or restrictions

17 Restriction of lymphatic flow Elephantiasis Filaria worm

18 Lymphatic Capillaries Similar to blood capillaries, with modifications: Very permeable Loosely joined endothelial minivalves Withstand interstitial pressure and remain open The minivalves function as one-way gates that: Allow interstitial fluid to enter lymph capillaries Do not allow lymph to escape from the capillaries

19 Lymphatic Capillaries Figure 20.1b

20 Lymphatic Capillaries During inflammation, lymph capillaries can absorb: Cell debris Pathogens Cancer cells Cells in the lymph nodes cleanse and examine this debris Lacteals specialized lymph capillaries present in intestinal mucosa Absorb digested fat and deliver chyle to the blood

21 Lymphatic Capillaries

22 Lymphatic Capillaries Called lacteals - Absorption of lipids from lumen of the small intestine

23 Lymphatic Collecting Vessels Have the same three tunics as veins Have thinner walls, with more internal valves Anastomose more frequently Collecting vessels in the skin travel with superficial veins Deep vessels travel with arteries

24 Lymphatic Trunks Lymphatic trunks are formed by the union of the largest collecting ducts (Note valves)

25 Lymphatic Trunks Lymph is delivered into one of two large trunks Right lymphatic duct drains the right upper arm and the right side of the head and thorax Thoracic duct drains the rest of the body

26 Lymphatic Trunks Figure 20.2b

27 Lymph Transport The lymphatic system lacks a pumping organ Vessels are low-pressure conduits Uses the same methods as veins to propel lymph: Pulsations of nearby arteries Contractions of smooth muscle in the walls of the lymphatics

28 Lymphoid Cells Lymphocytes are the main cells involved in the immune response Two main varieties: T cells B cells

29 Lymphocytes T cells and B cells protect the body against antigens Antigen anything the body perceives as foreign Bacteria and their toxins; viruses Mismatched RBCs or cancer cells

30 Lymphocytes T cells Manage the immune response Attack and destroy foreign cells B cells Produce plasma cells, which secrete antibodies Antibodies immobilize antigens

31 Lymph Nodes Principal lymphoid organs of the body Embedded in connective tissue and clustered along lymphatic vessels Aggregations of these nodes occur near the body surface in inguinal, axillary, and cervical regions of the body Figure 20.4a

32 Lymph Nodes Two basic functions: Filtration macrophages destroy microorganisms and debris Immune system activation monitor for antigens and mount an attack against them

33 Structure of a Lymph Node Nodes are bean shaped and surrounded by a fibrous capsule Trabeculae extended inward from the capsule and divide the node into compartments Nodes have two histologically distinct regions: a cortex and a medulla Figure 20.4a

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35 Structure of a Lymph Node Figure 20.4a, b

36 Lymphoid Organs Figure 20.5

37 Other Lymphoid Organs The spleen, thymus gland, and tonsils Peyer s patches and bits of lymphatic tissue scattered in connective tissue All are composed of reticular connective tissue All help protect the body Only lymph nodes filter lymph

38 Spleen Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm It is served by the splenic artery and vein, which enter and exit at the hilus Functions: Site of lymphocyte proliferation Immune surveillance and response Cleanses the blood

39 Additional Spleen Functions Stores breakdown products of RBCs for later reuse Spleen macrophages salvage and store iron for later use by bone marrow Site of fetal erythrocyte production (normally ceases after birth) Stores blood platelets

40 Structure of the Spleen Figure 20.6a, b

41 Thymus A bilobed organ that secretes hormones (thymosin and thymopoietin) that cause T lymphocytes to become immunocompetent Size of the thymus varies with age: In infants, it is found in the inferior neck and extends into the mediastinum where it partially overlies the heart It increases in size and is most active during childhood It stops growing during adolescence and then gradually atrophies

42 Thymus The thymus differs from other lymphoid organs in important ways It functions strictly in T lymphocyte maturation It does not directly fight antigens

43 Thymus Changes with age Young person on left

44 Tonsils Simplest lymphoid organs; form a ring of lymphatic tissue around the pharynx Location 3 main types: Palatine tonsils either side of the posterior end of the oral cavity Lingual tonsils lie at the base of the tongue Pharyngeal tonsil posterior wall of the nasopharynx (ALSO) Tubal tonsils surround the openings of the auditory tubes into the pharynx

45 Tonsils - Locations

46 Palatine Tonsils Most common problem

47 Pharyngeal (Adenoids)

48 Lingual Tonsils

49 Tonsils Lymphoid tissue of tonsils contains follicles with germinal centers Tonsil masses are not fully encapsulated Epithelial tissue overlying tonsil masses invaginates, forming blind-ended crypts Crypts trap and destroy bacteria and particulate matter

50 Aggregates of Lymphoid Follicles Peyer s patches isolated clusters of lymphoid tissue, similar to tonsils Found in the wall of the distal portion of the small intestine Similar structures are found in the appendix Peyer s patches and the appendix: Destroy bacteria, preventing them from breaching the intestinal wall Generate memory lymphocytes for long-term immunity

51 Peyer s Patches

52 MALT MALT mucosa-associated lymphatic tissue: Peyer s patches, tonsils, and the appendix (digestive tract) Lymphoid nodules in the walls of the bronchi (respiratory tract) MALT protects the digestive and respiratory systems from foreign matter

53 Appendix Lymphatic follicles May have immune monitoring function.