CHAPTER 20

Vasculature

The entire network of blood vessels in the body.

Tunica intima

The innermost layer of blood vessels that provides a smooth inner surface for blood to flow over.

Tunica media

The middle layer of blood vessels, primarily composed of smooth muscle, which controls the diameter of the blood vessel.

Tunica externa

The outermost layer of blood vessels, also known as adventitia, made of connective tissue that protects and anchors the vessel.

Arteries

Blood vessels that carry blood away from the heart.

Veins

Blood vessels that carry blood toward the heart.

Capillaries

The smallest blood vessels, where exchange of materials between blood and tissues occurs.

Arterioles

Small branches of arteries that control blood flow into capillary beds.

Hydrostatic pressure

The pressure exerted by fluid, which pushes fluid out of the capillaries.

Colloid osmotic pressure

The pressure exerted by plasma proteins that pulls fluid into the capillaries.

Systolic pressure

The pressure in the arteries during ventricular contraction; the top number in a blood pressure reading.

Diastolic pressure

The pressure in the arteries during ventricular relaxation; the bottom number in a blood pressure reading.

Pulse pressure

The difference between systolic and diastolic pressure.

Mean arterial pressure (MAP)

The average pressure driving blood through systemic circulation; approximated as diastolic pressure + 1/3(pulse pressure).

Erythropoietin (EPO)

A hormone produced by the kidneys that stimulates red blood cell production.

Hepatic portal system

The blood vessel system that carries blood from the digestive organs to the liver before it returns to the heart.

Baroreceptors

Sensory receptors that detect changes in blood pressure by sensing the stretch of arterial walls.

Transcytosis

The movement of substances across endothelial cells by endocytosis and exocytosis.

Venous return

The amount of blood returning to the heart through the veins.

Resistance vessels

Arterioles, which are crucial in regulating blood flow and blood pressure.

Capillary exchange

The process of movement of substances between blood, interstitial fluid, and cells.

Continuous capillaries

Capillaries with the least permeability, allowing only small substances to pass through.

Fenestrated capillaries

Capillaries with tiny pores that allow for greater permeability, typically found in organs involved in absorption and filtration.

Sinusoidal capillaries

Capillaries with larger openings, allowing large molecules and sometimes cells to pass; found in the liver and spleen.

Cardiac output

The amount of blood the heart pumps per minute, influencing blood pressure.

Peripheral resistance

The resistance that blood encounters as it flows through the blood vessels.

Mean arterial pressure formula

MAP is approximated as diastolic pressure + 1/3(pulse pressure).

Epinephrine

A hormone that increases heart rate, contractility, and vasoconstriction, ultimately raising blood pressure.

ADH

Antidiuretic hormone that increases water reabsorption by the kidneys and promotes vasoconstriction.

RAAS

Renin-Angiotensin-Aldosterone System, a hormone system that regulates blood pressure and fluid balance.

ANP

Atrial natriuretic peptide released by the atria, which decreases blood pressure by promoting sodium and water excretion.