Module 5

• Tunica Intima:

  • endothelium
  • internal elastic membrane
• Tunica media:

  • Vasoconstriction - smooth muscles contract, decrease blood flow
  • Vasodilation - smooth muscles relax, increase blood flow
• Tunica externa (adventitia)

  • connective tissue
  • varies from dense near vessel to loose when merges with CT
• Elastic arteries (aorta + major branches)

  • elastic tissue
  • pressure reservoirs
  • conducting arteries
• Muscular arteries (medium size arteries)

  • thick walls
  • vasoconstriction + dilation
  • distributing arteries
• Arterioles (small muscular arteries)

  • decreasing in size with gradual loss of wall layers down to terminal arterioles
• Capillaries:

  • lipid-soluble and small water-soluble molecules through plasma membrane
  • larger water-soluble molecules pass through fenestrae/ gaps between endothelial cells
• Capillary beds:

  • blood flow controlled by opening + closing of pre-capillary sphincters

  Arteriovenous anastomoses:

  • connecting vessels through which blood bypasses capillaries + flow directly into post-capillary venules