Lymphatics PDF - Phty140

LYMPHATICS PHTY140 Anna Rees  INTENDED LEARNING OUTCOMES 1. Describe the structure of a capillary and how this relates to their function. 2. Describe what tissue fluid (interstitial fluid) is and how it is formed. 3. Describe how lymph is formed and what it contai...

LYMPHATICS PHTY140 Anna Rees  INTENDED LEARNING OUTCOMES 1. Describe the structure of a capillary and how this relates to their function. 2. Describe what tissue fluid (interstitial fluid) is and how it is formed. 3. Describe how lymph is formed and what it contains. 4. Describe the organization of the lymphatic system with reference to the conducting system and the lymphoid tissue, briefly describe the roles of each. 5. Briefly describe the different roles of the primary and secondary lymphatic organs, stating the names of the primary and secondary lymphatic organs. 6. Describe the structure of a lymphatic capillary and how this relates to its function. 7. Define oedema and describe two physiological situations which may lead to oedema.  Thin walls – decreases diffusion distance CAPILLARY Numerous and highly branched – large surface area for STRUCTURELoading… exchange Lumen is narrow – RBC squashed against side of AND capillary, reducing diffusion distance FUNCTION white blood cells can pass through Spaces between the lining (endothelium), therefore LYMPHATIC SYSTEM – CONDUCTING SYSTEM AND LYMPHOID TISSUE Loading… LYMPHATIC CAPILLARIES Blind-ended bulbous tubes Endothelial cells in walls Allow entry of fluids proteins and bacteria but prevent exit Merge into collecting lymphatics Lymphatic vessels contain smooth muscle and unidirectional valves  Conducting system Carries the lymph and consists of tubular vessels that include the lymph capillaries, the lymph vessels and the right and left thoracic ducts LYMPHATIC Lymphoid Tissue SYSTEM Primarily involved in immune responses and consists of lymphocytes and other white blood cells enmeshed in connective tissue through which the lymph passes. Can be primary, secondary or tertiary LYMPHOID TISSUE  PRIMARY 1. Thymus and bone marrow – production and early LYMPHOID selection of lymphocytes 2. Generate lymphocytes from immature cells ORGANS SECONDARY 1. Maintain mature naïve lymphocytes and initiate an acquired immune response LYMPHOIDLoading… 2. Sites of lymphocyte activation ORGANS adenoids, tonsils 3. Include lymph nodes, spleen, Peyer’s patches,  Swelling in the tissues due to the excess fluid in the interstitial space OEDEMA Caused when filtration is increased to the extent that the lymphatics are unable to remove fluid fast enough or caused by dysfunctional lymphatic drainage Elephantiasis Nematode worm in EXAMPLE OF lymphatic DYSFUNCT vessels IONAL LYMPHATI C DRAINAGE - ELEPHANT IASIS WHY MIGHTThe net flow of water across the capillary wall is determined by the balance between the osmotic FILTRATION pressure (related to the protein content of the capillary) and the capillary hydrostatic pressure (determined by BE the arterial and venous pressures) INCREASED? EXAMPLE OF LOW PLASMA PROTEIN - KWASHIORKOR BRIEF RECAP….. Filtration at the capillary Formation of tissue/interstitial fluid Formation of lymph Lymphatic capillary Lymph transported through the conducting system Lymphoid tissue Primary and secondary lymphatic organs Oedema