PSIO 202 EXAM 2.docx - LECTURE 11 OBJECTIVES 1 Describe the...

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LECTURE 11 OBJECTIVES: 1. Describe the structure and function of lymphatic capillaries and vessels, and explain how the lymph capillaries drain excess ISF and return it to the systemic circulation. Structure and Function of Lymphatic Capillaries: o slightly larger in diameter than blood capillaries o have a "one-way" structure that permits ISF to flow into them but not out o greater permeability than blood capillaries and can absorb larger molecules such as proteins and lipids Structure and Function of Lymphatic Vessels: o originate in "close-ended" lymph capillaries, which lie adjacent to blood capillaries in the tissue spaces o lymph nodes are found at irregular intervals along the lymph vessels o smaller than blood vessels Lymph Capillaries Draining ISF: o Lymph capillaries pick up excess interstitial fluid and other wastes from the blood capillaries, by being embedded within those capillaries in between cells. o Have the surface of one way valves to allow fluid in when the pressure is exceeded on the outside o Once they pick up that fluid it goes through the lymph node o passes through the valves, along the vessel, through the lymph duct, to the subclavian vein (systemic circulation) 2. List the body’s non-specific defenses and describe the components and mechanisms of each. Physical Barriers (first line of defense): o Skin: sebaceous glands, sudoriferous glands (sweat glands), and lysozyme o Mucus Membranes: mucus is secreted by specialized epithelial cells called goblet cells traps many microbes and foreign substances o Hairs and Cilia: mucus-coated hairs; cilia on specialized epithelial cells that line the trachea Hairs trap and filer microbes Cilia propels dust and microbes that have been trapped in mucus toward the throat = coughing and sneezing then accelerate the movement of mucus out of the body, swallowing the mucus sends pathogens to the stomach to be destroyed by gastric juices o Acid: the pH of the stomach is about 2.0 o Tears: also contain lysozyme capable of breaking down the walls of certain bacteria Fever: Abnormally high body temperature in response to invading microorganisms o The body’s thermostat is reset upwards in response to pyrogens (chemicals secreted by leukocytes and macrophages exposed to bacteria and other foreign substances) o High fever is dangerous because it can “denature” enzymes o Moderate fever can be beneficial, as it causes:
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The liver and spleen to sequester iron and zinc (needed by microorganisms). The combination of raised fever and lowered iron inhibits bacterial growth An increase in the metabolic rate, which speeds up the repair of tissues Triggers production of interferons Inflammation: Tissue response to injury o Nonspecific, defensive response of the body to tissue damage triggered whenever body tissues are injured o Prevents the spread of damaging agents to nearby tissues o Disposes of cell debris and pathogens o Sets the stage for repair processes o
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