Ch 13: Blood Vessels And Circulation

Arteries carry blood ____ from the heart

away

Microcirculation

Process where nutrient and gas exchange occurs.

Arterioles

Small blood vessels supplying capillaries.

Capillaries

Tiny vessels facilitating exchange with tissues.

Venules

Small vessels collecting blood from capillaries.

Veins

Blood vessels returning blood to the heart.

The vital functions of the cardiovascular system take place at the ______

capillary level

Chemical and gaseous exchange between the blood and interstitial fluid takes place across_____

capillary walls

Why does tissue cells rely on capillary diffusion?

It obtains nutrients and oxygen to be able to remove metabolic waste such as carbon dioxide and urea.

Blood flowing out of a capillary bed first enters structures called ________.

Venules, the smallest vessels of the venous system

Venules, slender vessels merge to form small___

veins

Tunica interna

Innermost layer, directly contacts blood.

Tunica media

Middle layer, composed of smooth muscle.

Vasoconstrict

Narrowing of blood vessels, increases pressure.

Vasodilate

Widening of blood vessels, decreases pressure.

Tunica externa

Outer layer, made of loose connective tissue.

Largest arteries, closest to the heart.

Systole

Phase when heart contracts, arteries stretch.

Diastole

Phase when heart relaxes, arteries recoil.

Muscular arteries

Medium-sized arteries, regulate blood flow.

Arterioles

Tiny branches of arteries, lead to capillaries.

Capillary networks

Microcirculation sites for nutrient exchange.

Elastic arteries during ventricular systole do what?

stretch

Elastic arteries during ventricular diastole do what?

Recoil

Muscular arteries distribute blood to?

Skeletal muscles and internal organs

Large vein

superior and inferior vena cava and their branches within the abdominopelvic and thoracic cavities

Medium-sized vein

The tunica media in these veins is thin, and contains few smooth muscle fibers

Venule

small vein, collect blood from capillaries, lack a tunica media

What kind of arteries are the pulmonary trunk and aorta?

elastic arteries

The tunica media of elastic artery contain few______compared to____

smooth muscle fibers, elastic fibers

Muscluar arteries have a thick___

tunica media

What does the muscular artery contain more percentage than elastic fibers?

smooth muscle fibers

Arteriole vessels are much____than muscular arteries

thinner

What does the arteriole poorly have defined?

Tunica externa

What does the arteriole vessel tunica media consist of?

scattered smooth muscle fibers that may not form a complete layer

Capillaries are the only blood vessels whose walls permit?

exchange between blood and the surrounding interstitial fluid.

Most substances enter or leave the capillary by______across endothelial cells or through gaps between them.

Diffuse

What material can easily diffuse into the surrounding interstitial fluid?

Water, small solutes, and lipid-soluble

Capillaries do not function as individual units. Instead, they function as part of an interconnected network called a

Capillary bed

Capillaries collect into several_____, the smallest venous vessels

venules

What are the smallest venous vessels?

venules

What band of smooth muscle, guards the entrance to each capillary?

Precapillary sphincter

Each precapillary sphincter undergoes________of______, alternately contracting and relaxing perhaps a dozen times each time.

Cycles, activity

What is vasomotion?

The cyclical contraction and relaxation of precapillary sphincters, causing intermittent blood flow in capillaries.

How does blood reach venules in different ways over time?

Due to vasomotion, blood flow is not constant but varies based on the contraction and relaxation of precapillary sphincters.

what triggers changes in blood flow at the tissue level?

Local changes in the concentration of chemicals and dissolved gases on the interstitial fluid

What is the process of local blood flow control at tissue level called?

Autoregulation

What are the five general classes of blood vessels?

Arteries, arterioles, capillaries, venules, and veins.

What typeof vessel are small, thin-walled, and have very little smooth muscle in the Tunica media

Capillaries

Why are valves found in veins but not in arteries?

Valves are found in the veins because the very low blood pressure in the venous circulation makes the movement of blood against the force of gravity difficult. Blood flow within peripheral veins depends on the contractions of skeletal muscles to propel the blood, and on valves to prevent blood from backing up.

What is the function of venous valves?

Prevent backflow of blood back down the venules and help maintain venous return to the heart

What helps push blood through veins against gravity?

The contraction of adjacent skeletal muscles compresses veins and pushes blood upward

What is an arteriovenous anastomosis?

A vessel that directly connects an artery to a vein, bypassing capillary beds

The pressure of blood within a capillary bed is called

capillary pressure

Capillary exchange between the plasma and interstitial fluid plays a key role in

homeostasis

What is diffusion?

The net movement of ions or molecules from an area where their concentration is higher to an area where there concentration is lower.

What kind of molecules like plasma proteins cannot normally leave the bloodstream?

Larger water-soluble

Lipid-soluble materials-including steriods, fatty acids, and dissolved gases______across the endothelium, passing through the membrane lipids.

diffuse

What is filtration?

the removal of solutes as a solution flows across a porous membrane

Reabsorption takes place as the result of

Osmosis

Osmosis refers to

the diffusion of water across a selectively permeable barrier

Homeostatic processes regulate cardiovascular activity to ensure that tissue blood flow, and meets the demand for oxygen and nutrients also called?

Tissue perfusion

What factors affect tissue blood flow?

Cardiac output, peripheral resistance, and blood pressure

What are the 3 goals of cardiovascular regulation to ensure blow flow changes take place?

At an appropriate time, in the right area, and without drastically altering blood pressure and blood flow to vital organs.

If autoregulation fails to normalize tissue conditions, what is activated as backup?

Neural and endocrine processes are activated

The nervous system responds to changes in

arterial pressure or blood gas levels sensed at specific sites

What nervous system adjusts cardiac output and peripheral resistance to maintain adequate blood flow

Autonomic nervous system

The endocrine system releases hormones that enhance

short-term adjustments and long-term adjustments in cardiovascular performance

Short-term responses adjust

cardiac output and peripheral resistance to stabilize blood pressure and blood flow to tissues

Long-term adjustments involve

alterations in blood volume that affect cardiac output and the transport of oxygen and carbon dioxide to and from active tissues.

Factors that promote the dilation of precapillary sphincters are called

Vasodilators

Those that stimulate the constriction of precapillary sphincters are called

vasoconstrictors