Physiology - Vessels Lecture 3

• 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

determined by a vessels resistance to flow, and when one vessel increases resistance then flow is diverted among lower resistance vessels (Flow 1/resistance)

• 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)

Bulk flow: Mass movement as a result of hydrostatic or osmotic pressure gradients

• Filtration: fluid movement out of capillaries
• • Caused by hydrostatic pressure
• • Net filtration at arterial end

• Absorption: fluid movement into capillaries
• • Net absorption at venous end

• returns fluid and proteins to circulatory system, picks up fat absorbed and transfers it to the cirulatory system
• serves as a filter for pathogens

• 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