Chapter 20: Cardiovascular System: Blood Vessels

Vocabulary flashcards covering major blood vessel anatomy, physiology, and regulation concepts from the lecture notes.

Arteries

Blood vessels that carry blood away from the heart; usually oxygenated; thick walls and high pressure; no valves.

Veins

Blood vessels that carry blood toward the heart; thinner walls, larger lumen, valves; low pressure; act as blood reservoirs.

Capillaries

Microscopic exchange vessels; one cell thick; endothelium + basement membrane; site of gas, nutrient, and waste exchange.

Arterioles

Small arteries that connect arteries to capillaries; major regulators of blood flow and blood pressure; can constrict or dilate.

Venules

Small veins that receive blood from capillaries; transition from capillary exchange to venous return; site of WBC migration.

Companion vessels

Artery and vein supplying the same body region that lie next to each other; can remain patent even if the other is occluded.

Tunica intima

Innermost vessel tunic; endothelium with a smooth lining.

Tunica media

Middle tunic; smooth muscle and elastic fibers; thicker in arteries.

Tunica externa (adventitia)

Outer tunic; connective tissue that protects and anchors vessels.

Capillaries: endothelium + basement membrane

Capillary walls composed of endothelial cells supported by a basement membrane; essential for exchange.

Elastic arteries

Largest arteries with many elastic fibers; stretch to accommodate stroke volume; examples include the aorta and pulmonary trunk.

Muscular arteries

Medium arteries with more smooth muscle and less elastin; distribute blood to specific organs; can constrict/dilate.

Capillary bed

Network of 10–100 capillaries supplying a tissue region; perfusion regulated by precapillary sphincters and metarterioles.

Continuous capillaries

Most common capillaries with continuous endothelium and tight junctions; least permeable.

Fenestrated capillaries

Capillaries with pores that allow more exchange; found in kidneys, small intestine, endocrine glands.

Sinusoidal capillaries

Capillaries with large gaps and discontinuous basement membrane; most permeable; allow cells and proteins through.

Precapillary sphincters

Rings of smooth muscle at capillary entrances that regulate capillary perfusion.

Metarterioles

Vessels that bypass capillaries as shunts to regulate tissue perfusion.

Diffusion

Capillary exchange mechanism where gases, nutrients, and wastes move across capillary walls.

Vesicular transport

Capillary exchange via vesicles (pinocytosis); transports large molecules like proteins and hormones.

Filtration

Bulk flow where fluid exits capillaries at the arterial end due to higher hydrostatic pressure.

Reabsorption

Bulk flow where fluid enters capillaries at the venous end due to higher osmotic pressure.

Net filtration pressure (NFP)

Net pressure driving filtration vs. reabsorption across a capillary; positive = filtration, negative = reabsorption.

Capillary hydrostatic pressure

Blood hydrostatic pressure that pushes fluid out of capillaries (arterial end higher than venous end).

Capillary osmotic pressure

Osmotic pressure due to plasma proteins that pulls water back into capillaries.

Veins as blood reservoirs

Veins hold about 60–65% of blood at rest due to their high compliance and low pressure.

Skeletal muscle pump

Contractions of skeletal muscles squeeze veins, pushing blood toward the heart.

Respiratory pump

During inspiration, changes in thoracic and abdominal pressures aid venous return toward the heart.

Venous valves

Valves in veins that prevent backflow and help blood return from the limbs.

Venoconstriction

Sympathetic constriction of veins to mobilize blood during stress or exercise.

Blood Pressure

Force exerted by blood against vessel walls; measured in mmHg; generated by the heart and maintained by elasticity and peripheral resistance.

Systolic pressure

Peak pressure during ventricular contraction (systole).

Diastolic pressure

Lowest pressure during ventricular relaxation (diastole).

Pulse pressure

Difference between systolic and diastolic pressures; reflects arterial elasticity (example: 120–80 = 40 mm Hg).

Mean arterial pressure (MAP)

Average effective pressure driving blood into tissues; MAP ≈ diastolic + 1/3 pulse pressure.

Baroreceptors

Stretch receptors in carotid sinuses and aortic arch that regulate BP by adjusting heart rate and vessel tone.

Vasomotor center

Medullary center that maintains baseline sympathetic tone and regulates vasoconstriction/dilation.

Chemoreceptors

Receptors in carotid and aortic bodies that detect changes in O2, CO2, and pH to modulate BP and respiration.

Alpha-1 receptors

Receptors on smooth muscle that mediate vasoconstriction when bound by norepinephrine.

Beta-2 receptors

Receptors that mediate vasodilation in skeletal muscle and coronary vessels when bound by epinephrine (at low concentrations).