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Capillary Beds

Capillary Beds. Capillary Beds : network of capillaries in tissues. Microcirculation : flow of blood from arteriole to venule through the capillary bed Oxygen and nutrients cross to cells Carbon dioxide and metabolic waste products cross into blood. Figure 11.10. Capillary Beds.

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Capillary Beds

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  1. Capillary Beds • Capillary Beds: network of capillaries in tissues. • Microcirculation : flow of blood from arteriole to venule through the capillary bed • Oxygen and nutrients cross to cells • Carbon dioxide and metabolic waste products cross into blood Figure 11.10

  2. Capillary Beds • Consists of 2 types vessels • Vascular shunt: vessel that directly connects the arteriole and venule • True capillaries: actual exchange vessels • Pre-capillary sphincter: surrounds root of each capillary, regulating flow of blood into the capillary • Open: blood thru true capillary • Closed: blood through shunt

  3. Capillary Exchange • Substances exchanged due to concentration gradient • Substances entering or leaving the bloodstream may take one of four routes across the plasma membrane of the single layer capillary wall • Diffusion directly through cell membranes if lipid-soluble • Enter or leave blood by endo or exocytosis if lipid-insoluble

  4. Movement Into or Out of Bloodstream • Clefts in plasma membrane of capillaries • Limited passage of fluid and small solutes thru clefts • Fenestrated Capillaries • Pore covered by a delicate membrane • Found where filtration/absorption: priority • Kidneys/intestinal linings • Allows for free passage of small solutes and fluids

  5. Pressure at Capillary • Blood pressure: high at arterial end • Tends to force fluids/solutes outward • Osmotic pressure: high at venous end • Draws fluid back in • Fluid: • Leaves capillary through clefts at the arterial end • Returns to blood at venous end

  6. Diffusion at Capillary Beds Figure 11.20

  7. Major Arteries of Systemic Circulation Figure 11.11

  8. Major Veins of Systemic Circulation Figure 11.12

  9. Fetal Circulation • 3 vessels • 1 umbilical vein: carries nutrient/Oxygen rich blood to fetus from placenta • 2 umbilical arteries: carries C02 and wastes from fetus to placenta • Shunt that bypasses nonfunctional liver • Ductus venosus: blood moving superiorly to the heart, by passes the liver through the ductus venosus, which connects to the inferior vena cava

  10. Fetal Circulation • Foramen ovale: some of blood entering right atrium passes through this shunt and into the left atrium • Shunt that bypasses the immature lungs • Blood entering into right ventricle and moving into pulmonary trunk, is met by a second shunt, ductus arteriosus. • Ductus arteriosus: connects the aorta and the pulmonary trunk

  11. Circulation to the Fetus Figure 11.15

  12. Developmental Aspects of Cardiovascular System • Heart begins: tube-like structure • Beating/Pumping blood by 4th week of embryonic development • Atherosclerosis: Change of the arterial wall • Arteriosclerosis: results from aging • End stage of atherosclerosis • Gradual loss of elasticity in arteries • Results in hypertension, heart disease, coronary artery disease, stroke • Cardiovascular disturbances • Venous valves weaken

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