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