Blood Vessels and Circulation Flashcards

Flashcards covering the anatomy and physiology of blood vessels, including vessel wall structure, capillary exchange, and mechanisms of cardiovascular regulation.

Arteries

Blood vessels that carry blood away from the heart.

Arterioles

The smallest branches of arteries.

Capillaries

The smallest blood vessels and the location of exchange between blood and interstitial fluid.

Venules

Small veins that collect blood from capillaries.

Veins

Blood vessels that return blood to the heart.

Tunica intima

The inner layer of a blood vessel, including the inner endothelial lining and surrounding connective tissue.

Tunica media

The middle layer of a blood vessel, consisting of concentric sheets of smooth muscle.

Tunica externa

The outer layer of a blood vessel, composed of a connective tissue sheath that stabilizes and anchors the vessel to adjacent tissues.

Internal elastic membrane

An outer layer of elastic fibers found in the tunica intima of arteries.

Vasa vasorum

Small arteries and veins in the walls of large arteries and veins that supply the cells of the tunica media and tunica externa with blood; literally "vessels of vessels."

Vasoconstriction

The contraction of arterial smooth muscle that causes a decrease in vessel diameter.

Vasodilation

The relaxation of arterial smooth muscle that causes an increase in vessel diameter.

Elastic Arteries

Conducting arteries with the largest diameters, such as the pulmonary trunk and aorta, characterized by many elastic fibers and fewer muscle cells in the tunica media.

Muscular Arteries

Medium-sized distribution arteries that branch off elastic arteries and have a tunica media containing many muscle cells.

Resistance vessels

A term for arterioles, which function to regulate blood flow by changing diameter in response to local conditions or sympathetic/endocrine stimulation.

Aneurysm

A bulge in an arterial wall caused by a weak spot in elastic fibers, which may rupture and lead to hemorrhage.

Continuous Capillaries

Capillaries with a complete endothelial lining, found in most active tissues except epithelia and cartilage, permitting the diffusion of water and small solutes.

Fenestrated Capillaries

Capillaries containing pores in the endothelial lining that permit rapid exchange of water and large solutes between blood and interstitial fluid.

Sinusoids

Capillaries with gaps between adjacent endothelial cells and a thin or absent basement membrane, permitting free exchange of water and large plasma proteins.

Precapillary Sphincter

A circular band of muscle that guards the entrance to each capillary and constricts to slow or stop blood flow.

Collaterals

Multiple arteries that contribute to one capillary bed, allowing circulation even if one artery is blocked.

Arterial anastomosis

The fusion of two collateral arteries as they form an arteriole.

Arteriovenous anastomosis

Direct connections between arterioles and venules that bypass the capillary bed when dilated.

Vasomotion

The contraction and relaxation cycle of capillary sphincters that causes blood flow in capillary beds to constantly change routes.

Venous Valves

Folds of the tunica intima in veins that prevent blood from flowing backward.

Capacitance

The relationship between blood volume and blood pressure, representing the tendency of a vessel (like a vein) to stretch and shrink without great changes in pressure.

Pressure Gradient ($\Delta P$)

The difference in pressure between two points generated by the heart to overcome resistance.

Total Peripheral Resistance (TPR)

The resistance of the entire cardiovascular system, determined by vascular resistance, blood viscosity, and turbulence.

Vascular Resistance

Resistance due to friction between blood and vessel walls, depending on vessel length and vessel diameter.

Viscosity

Resistance to flow caused by molecules and suspended materials in a liquid; whole blood viscosity is about five times that of water.

Turbulence

Swirling action that disturbs the smooth flow of liquid, occurring in heart chambers and great vessels.

Systolic pressure

The peak arterial pressure measured during ventricular systole.

Diastolic pressure

The minimum arterial pressure measured during ventricular diastole.

Pulse pressure

The difference between systolic pressure and diastolic pressure.

Mean arterial pressure (MAP)

A single blood pressure value calculated using the formula: $\text{MAP} = \text{diastolic pressure} + 1/3 \, \text{pulse pressure}$.

Hypertension

Abnormally high blood pressure defined as a value greater than $130/80\,mmHg$.

Venous Return

The amount of blood arriving at the right atrium each minute.

Respiratory pump

A mechanism assisting venous return where inhalation decreases thoracic pressure to push blood toward the thoracic cavity and exhalation pushes blood into the right atrium.

Blood colloid osmotic pressure (BCOP)

Pressure required to prevent osmosis in the blood, caused by suspended blood proteins that are too large to cross capillary walls.

Net Filtration Pressure (NFP)

The difference between net hydrostatic pressure and net osmotic pressure, calculated as $\text{NFP} = (\text{CHP} – \text{IHP}) – (\text{BCOP} – \text{ICOP})$.

Edema

Abnormal accumulation of interstitial fluid or swelling caused by a disruption in the balance between hydrostatic and osmotic pressure.

Autoregulation

Adjustment of blood flow where local factors cause immediate, localized changes in the dilation or constriction of precapillary sphincters.

Baroreceptor reflex

Reflexes involving stretch receptors in the carotid and aortic sinuses that respond to changes in blood pressure.

Chemoreceptor reflex

Reflexes that respond to changes in chemical composition, particularly $pH$ and dissolved gases like $O_2$ and $CO_2$.

Natriuretic Peptides

Hormones like ANP and BNP produced by heart muscle cells in response to excessive stretching that function to lower blood volume and blood pressure.