Physiology - Vessels Lecture 3

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Physiology - Vessels Lecture 3
2011-03-04 15:36:10

Distribution of bloodto the tissues, Exchange at the capillaries, and The lymphatic system
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  1. Distribution of blood to the tissues, Exchange at the capillaries, and The lymphatic system Learning Objectives:
    • 1. Explain how blood distributes in the body
    • 2. Describe the structure of the capillary system and how blood flow is regulated in the capillaries
    • 3. Describe the mechanisms for filtration and absorption in capillary network
    • 4. Describe the lymphatic system and how it interacts with the vasculature and what is its purpose
  2. Blood Flow:
    determined by a vessels resistance to flow, and when one vessel increases resistance then flow is diverted among lower resistance vessels (Flow 1/resistance)
  3. Capillary Exchange:
    • Capillary density is related to metabolic activity of cells
    • Bone marrow, liver and spleen do not have typical capillaries but sinusoids
    • continuous capillaries have leaky junctions to facilitate exchange.
    • Fenestrated capillaries have large pores or fenestrations to facilitate exchange
    • Exchange between plasma and interstitial fluid occurs by paracellular pathway or endothelial transport
    • Small dissolved solutes and gases move by diffusion
    • Larger solutes and proteins move by vesicular transport (In most capillaries, large proteins are transported by transcytosis)
  4. Bulk flow
    Bulk flow: Mass movement as a result of hydrostatic or osmotic pressure gradients
  5. Filtration
    • Filtration: fluid movement out of capillaries
    • • Caused by hydrostatic pressure
    • • Net filtration at arterial end
  6. Absorption
    • Absorption: fluid movement into capillaries
    • • Net absorption at venous end
  7. Lymphatic System:
    • returns fluid and proteins to circulatory system, picks up fat absorbed and transfers it to the cirulatory system
    • serves as a filter for pathogens
  8. Edema:
    • has 2 causes: inadequate drainage of lymph, or filtration is far greater than absorption
    • disruption of the balance between filtration and absorption causes: an increase in hydrostatic pressure, a Decrease in plasma protein concentration, and an Increase in interstitial proteins