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BIO A221 - Blood Vessels Reading Guide Notes

Blood Vessel Types

  • Three major types: arteries, veins, capillaries.
  • Arteries: carry blood away from the heart (except pulmonary).
  • Veins: carry blood to the heart (except pulmonary).

Vessel Structure

  • Lumen: Hollow central space for blood flow.
  • Tunica Intima: Innermost layer, endothelium reduces friction.
  • Endothelium: Epithelial cells lining the lumen, act as a barrier.
  • Tunica Media: Middle layer, smooth muscle controls vessel diameter and blood pressure.
  • Tunica Externa: Outermost layer, connective tissue protects and anchors the vessel.

Arteries vs. Veins

  • Arteries have thicker walls and smaller lumens than veins.

Elastic vs. Muscular Arteries

  • Elastic arteries: Stretchy, closer to the heart.
  • Muscular arteries: Control blood flow to organs, farther from the heart.

Microcirculation

  • Perfusion: Blood carries oxygen/nutrients to tissues/organs and transports waste.
  • Consists of arterioles, capillaries, venules.
  • Metarteriole: Links arterioles to capillaries.
  • Terminal Arteriole: Supplies blood to capillary beds.
  • Precapillary sphincter: Regulates blood flow into capillaries.
  • Vascular Shunt: Blood flows through when precapillary sphincters are closed.
  • True Capillaries: Blood flows through when precapillary sphincters are open.

Valves in Veins

  • Function: Prevent backflow, aid in venous return, located in veins.

Blood Pressure

  • Blood pressure: Force exerted by blood against vessel walls.
  • Systolic pressure: Pressure during heart contraction.
  • Diastolic pressure: Pressure during heart relaxation.
  • Pulse points: Areas where pulse can be felt.

Blood Pressure Measurement

  • Auscultatory method: Using a stethoscope to listen for Korotkoff sounds.
  • Sphygmomanometer: Instrument used to measure blood pressure.

Factors Influencing Blood Flow and Pressure

  • Stroke volume, heart rate, vasoconstriction, blood volume, etc.

Capillary Exchange

  • Fluid movement: At arterial end, fluid exits; at venule end, fluid enters due to pressure differences.

Vasoconstriction and Vasodilation

  • Vasoconstriction: Decrease in vessel diameter.
  • Vasodilation: Increase in vessel diameter.
  • Regulated by the Sympathetic Nervous System; increased sympathetic innervation leads to vasoconstriction, increasing BP

Venous Return

  • Muscular pump and respiratory pump aid blood return to the heart.

Hypertension

  • High blood pressure.

Atherosclerosis

  • Plaque buildup in blood vessel walls.

Fetal Circulation

  • Placenta: Source of oxygen in fetus.
  • Foramen ovale: Shunts blood from right atrium to left atrium; becomes fossa ovalis after birth.
  • Ductus arteriosus: Shunts blood from pulmonary trunk to aorta; becomes ligamentum arteriosum after birth.

Key Equations

  • BP = SV \times HR \times PR