33.2b Anatomy of the Peripheral Circulation

peripheral circulation

The (?) transports oxygenated blood from the heart to the tissues and subsequently transports deoxygenated blood back to the heart.

arterial system, venous system

Oxygenated blood leaves the heart via the (?) whereas deoxygenated blood returns via the (?).

a single layer

A capillary wall consists of (? ) of cells.

several layers

The walls of arteries and veins are composed of (?).

tunica intima

The arteries’ and veins’ innermost lining, the (?), is only a single cell thick.

tunica media

The middle layer, the (?), consists of elastic fibers and muscle.

strength and recoil

The tunica media gives blood vessels their (?), which results from the difference in pressure inside and outside the vessel.

much thicker in arteries than in veins

The tunica media is (?).

tunica adventitia

The outermost lining is the (?), a fibrous tissue covering.

strength to withstand the pressures generated by the heart’s contractions

The tunica adventitia gives the vessel (?).

lumen

The cavity inside a vessel is the (?).

the amount of blood they can transport

Vessels’ diameters vary significantly and are directly related to (?).

the greater the blood flow

The larger the diameter, (?).

the fourth power of the vessel’s radius

In fact, according to Poiseuille’s law, the blood flow through a vessel is directly proportional to (?).

1 mL of blood per minute at a pressure difference of 100 mmHg

A vessel with a relative radius of 1 would transport (?).

256 mL

If the vessel’s radius were increased to 4, keeping the pressure difference constant, the flow would increase to (?) (44) per minute.

high pressure

The arterial system, which carries oxygenated blood from the heart, functions under (?).

arteries

The larger arterial vessels are the (?).

arterioles

The arteries branch into smaller structures called (?), which use their degree of resistance to control blood flow to various organs.

capillaries

The arterioles continue to divide into smaller structures until they become (?), which are the vessels that connect the arterial and venous systems.

gases, fluids, and nutrients

The vascular system and the tissues are able to exchange (?) through the very thin capillary walls.

from the peripheral tissues back to the heart

The venous system transports blood (?).

surrounding muscles and one-way valves within the veins

The venous system functions under low pressure with the aid of (?).

capillaries

Blood enters the venous system from the arterial system through the (?), which drain into the small venules.

veins, venae cavae, right atrium

The venules, in turn, drain into the larger (?), the veins into the (?), the two large veins that drain blood from the upper body and from the lower body, and the venae cavae drain into the (?) of the heart.