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Capillaries definitions

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  • Capillaries
    Smallest blood vessels, 5-10 micrometers in diameter, facilitating nutrient and gas exchange between blood and tissues.
  • Tunica intima
    The only layer in capillary walls, consisting of endothelium and a basement membrane, allowing for efficient exchange.
  • Erythrocytes
    Red blood cells, about 7.5 micrometers in diameter, often travel single file through capillaries.
  • Capillary beds
    Networks of branched capillaries facilitating microcirculation, fed by arterioles and drained by venules.
  • Continuous capillaries
    Most common type, least permeable, with tight junctions and small intercellular clefts.
  • Fenestrated capillaries
    Capillaries with small pores, moderate permeability, found in kidneys and endocrine glands.
  • Sinusoid capillaries
    Most permeable capillaries with large holes, found in liver and bone marrow, allowing large molecules to pass.
  • Microcirculation
    Blood flow through capillary beds from terminal arterioles to postcapillary venules.
  • Vascular shunt
    Structure in mesenteric capillary beds allowing blood to bypass capillaries, consisting of metarteriole and thoroughfare channel.
  • Metarteriole
    Transitional vessel with precapillary sphincters, part of the vascular shunt controlling blood flow.
  • Thoroughfare channel
    Continuation of metarteriole without smooth muscle, connecting to postcapillary venule.
  • Precapillary sphincters
    Smooth muscle rings controlling blood flow into capillary beds, part of metarterioles.
  • Arterioles
    Small arteries regulating blood flow to capillary beds through vasoconstriction.
  • Postcapillary venules
    Smallest venules receiving blood from capillary beds, beginning the return to the heart.
  • Endothelium
    Inner lining of capillaries, forming a barrier for exchange of substances between blood and tissues.