A&P II QS 4

Under the microscope, a blood vessel is observed to have a relatively thin wall, a large lumen, is collapsed, and contains a thick tunica externa. This is probably a(n)

vein

T or F: If local blood flow in a tissue is inadequate, it may be due to a decrease in total blood flow.

TRUE

T or F: Vasodilator substances are produced in the extracellular fluid as the rate of metabolism increases.

TRUE

Blood flow ____________ according to metabolic needs. After a meal the ____________ receive priority and the skeletal muscles receive very little flow. During exercise the skeletal muscles receive ____________ blood flow. Most of the redirection will occur in the ____________ .

redirects intenstines more arterioles

Hyaline cartilage has a low degree of vascularization. This means that

blood delivery to the tissue is limited

The thyroid gland is highly perfused. Therefore, it has a ______ degree of vascularization.

high

Angiotensin II and ADH (in high doses) ____________ peripheral resistance and blood pressure; and angiotensin II, aldosterone, and ADH ____________ urine output to help maintain blood volume and blood pressure. ANP stimulates ____________ , which decreases ____________ and increases ____________ , which decreases blood ____________ . The net effect is a decrease in blood ____________ .

increase decrease vasodilation peripheral resistance urine output volume pressure

T or F: At rest, veins contain the largest percentage of blood in the body.

TRUE

total blood flow

- amount of blood throughout entire vasculature over time - L/min - equivalent to cardiac output - dependent upon the heart and blood vessels

true about veins...

- at rest, the contain the most blood in the body - during exercise, vasoconstriction of veins brings more blood into systemic circulation - after exercise, vasodilation of veins brings blood back into venous reservoirs

local blood flow

- blood delivered to capillaries of a specific tissue - mL/min - altered directly by tissue damage - dependent upon the degree of vascularization of a tissue

What causes a temporary increase in arterial blood pressure?

- increased blood volume - increased cardiac output - vasoconstriction

During period of exercise...

- the sympathetic nervous system can selectively reduce blood flow to the kidneys and digestive track - the sympathetic nervous system can increase perfusion of the skeletal muscles - metabolite accumulation in a tissue can stimulate local vasodilation

What could potentially result in an increase in arterial blood volume?

- vasoconstriction of arterioles - increase in cardiac rate - increase in stroke volume

How do veins return blood to the heart?

- veins have one-way valves that prevent backflow in the limbs - the constriction of skeletal muscles helps push the blood in veins back toward the heart

tissue autoregulation sequence

1. increased metabolic activity of tissue 2. perfusion of tissue temporarily inadequate 3. decreased levels of oxygen and nutrients 4. local vasodilation 5. increased blood to capillaries 6. decreased levels of CO2, H+, and K+ 7. local vasoconstriction

hormones that INCREASE bp

Angiotensin II ADH Aldosterone

hormones that affect bp

Angiotensin II ADH Atrial natriuretic peptide (ANP) Aldosterone

Imagine yourself sitting in an awkward position in an uncomfortable chair that is depriving part of your leg from normal blood flow. This deprivation of adequate perfusion will result in what sort of local changes in your leg?

Buildup of carbon dioxide and hydrogen ions will cause vasodilation.

T or F: Precapillary sphincters relax as the tissue concentration of nutrients, such as oxygen, glucose, amino acids, and fatty acids, increases.

FALSE

T or F: Tunica intima is the innermost tunic of a blood vessel, and contains predominantly smooth muscle cells supported by elastic fibers.

FALSE

T or F: If blood flow in the capillaries was too fast, there might not be sufficient time for exchange of nutrients and waste between tissues and blood.

TRUE

T or F: Local control of blood flow is achieved by the periodic relaxation and contraction of precapillary sphincters regulating blood flow through the tissues.

TRUE

T or F: When a person is still, blood accumulates in the limbs because venous pressure is not high enough to override the weight of the blood and drive it upward.

TRUE

structures from high bp to low

aorta arteries arterioles capillaries venules veins venae cavae

The ____________ is the first vessel blood enters upon exiting the heart. The ____________ expand and recoil with every heartbeat due to a histologically dominant network of elastic tissue in the tunica media. Just prior to entering capillary beds, ____________ have become extremely thin and present only a few layers of smooth muscle. The site of gaseous exchange, or ____________ , are characterized by extremely thin walls with only endothelium and basal lamina, which better suits diffusional requirements. After exiting the capillary, ____________ contain no muscle and are the first vessel that blood enters on its way back to the heart. The ____________ contain abundant but irregularly spaced smooth muscle with frequent valves present in the tunica interna. The superior vena cava is an example of a ____________ that includes smooth muscle circularly and longitudinally arranged in the tunica media and externa respectively.

aorta large (elastic) arteries arterioles capillaries venules medium veins large vein

- Most carry oxygenated blood from heart to the body - Have pulsatile flow of blood - Exhibit greater ability to alter vessel diameter

arteries

The vessels that are responsible for carrying blood away from the heart are

arteries

Blood pressure is highest in the ___________ and lowest in the _____________.

arteries closest to the heart veins

events of autonomic blood pressure regulation

bp increases blood vessel wall stretches baroreceptors in walls increase firing rates sensory input sent to cardiovascular center cardioacceleratory center decreases nerve signals along sympathetic pathways heart rate and stroke volume decrease blood flow returns to resting levels

In both pulmonary and systemic circulation, gas exchange occurs at the

capillaries

Under the microscope, the wall of a blood vessel is observed to contain only a tunica intima. This must be a(n)

capillary

order of factors that regulate blood pressure

cardiac output increases blood pressure rises baroreceptors in aortic arch and carotid sinuses are stimulated sensory impulses to cardiac center parasympathetic impulses to heart SA node inhibited heart rate decreases blood pressure returns toward normal

When the cuff pressure is high enough to keep the brachial artery ____________ , no blood flows through it and no sound is heard. When cuff pressure ____________ and is no longer able to keep the artery closed, blood is pushed through, producing turbulent blood flow and a sound. ____________ pressure is the pressure at which the first Korotkoff sound is heard. At first, the artery is closed during ____________ but as cuff pressure continues to decrease, the artery partially opens. Turbulent blood flow during systole produces ____________ sounds, although the pitch of the sounds changes as the artery becomes more open. Nonturbulent flow is reestablished and ____________ sounds are heard. ____________ pressure is the pressure at which the sound disappears.

closed decreases Systolic diastole Korotkoff no Diastolic

As the cross-sectional area of blood vessels increases, velocity of blood flow

decreases

Within systemic capillaries, substances such as oxygen, hormones, and nutrients move by ____________ from their relatively ____________ concentration in the blood into the interstitial fluid and then into the tissue cells, where the concentration of these materials is ____________ . Very small solutes and fluids may pass via the ____________ , while larger solutes, must pass through the fenestrations in ____________ or gaps in ____________ . Endothelial cells may use ____________ to fuse fluid-filled vesicles with the plasma membrane. This type of ____________ can move contents either from the blood to the interstitial fluid or from the interstitial fluid into the blood. Solutes such as certain ____________ and fatty acids are transported across the endothelial cells by this method.

diffusion high low endothelial cells capillaries sinusoids pinocytosis vesicular transport hormones

When carbon dioxide accumulates in a tissue, local arterioles will _________, increasing perfusion and decreasing carbon dioxide levels

dilate

Blood flow is ____________ related to the pressure gradient. Thus, as the blood pressure gradient increases, total blood flow ____________ , and as the blood pressure gradient decreases, total blood flow ____________ (assuming ____________ remains the same). An increase in ____________ will increase the pressure gradient, and a decrease in cardiac output will decrease the ____________ .

directly increases lessens resistance cardiac output pressure gradient

Blood delivered to the capillaries of a specific tissue is ____________ blood flow and is measured in ____________ per minute. The specific amount of blood entering capillaries per unit time per gram of tissue is called ____________ . The ultimate goal of the cardiovascular system is adequate perfusion of all tissues. The amount of blood transported throughout the entire vasculature in a given period of time is ____________ blood flow and is usually expressed in ____________ per minute. This type of blood flow equals ____________ . If this increases, the amount of blood available to body tissues ____________ .

local mL perfusion total L cardiac output increases

Relatively small amounts of blood are within the ____________ circulation (about 18%) and the ____________ (about 12%). The largest percentage of blood is within the ____________ circulation (about 70%), with the greatest amount (about 55%) within the body's ____________ . The relatively large amount of blood within these vessels allows them to function as blood reservoirs. Blood may be shifted from these reservoirs in times of ____________ physical exertion with ____________ . When less blood is needed at rest, it will be shifted back through by ____________ .

pulmonary heart systemic systemic veins increased vasoconstriction vasodilation

Capillary beds have precapillary ____________ at the junction of capillaries and the metarteriole. Constriction of these sphincters ____________ the blood flow through their respective capillaries. When this occurs, blood is ____________ to tissue or organs elsewhere. When the sphincters are open, blood will ____________ the capillary bed.

sphincters reduces diverted fill

The cardiovascular system is really two separate circuits of blood flow. The ____________ circuit delivers blood to all the cells of the body. The other circuit will involve the same structures you named but functions to deliver oxygen-poor and carbon dioxide-rich blood to the lungs and is the ____________ circuit. In these circuits, exchange takes place at the ____________ . These become larger vessels known as ____________ , which converge into even larger vessels known as ____________ before they return to the heart.

systemic pulmonary capillaries venules veins

A major function of the cardiovascular system is to ____________ . To fulfill this purpose, you have the following structures: The ____________ , provides pressure to pump the fluids into the large and elastic ____________ , which will carry the blood to the body. The vessels leaving the heart will branch and become smaller in diameter, these are the ____________ . The vessels will continue to branch and get smaller into ____________ . Eventually, they will become the ____________ , which are the sites of gas, nutrient, and waste exchange.

transport fluids heart aorta arteries arterioles capillaries

Capillaries have only a

tunica interna

A relatively small blood pressure gradient is generally insufficient to move blood through the veins under given conditions, thus venous return must be facilitated by ____________ within veins and two "pumps." The skeletal muscle pump assists the movement of blood primarily within the ____________ . As skeletal muscles contract, veins are squeezed to help propel the blood ____________ the heart. The respiratory pump assists the movement of blood within the ____________ . The ____________ contracts and flattens as we inspire. Intra-abdominal pressure ____________ and places pressure on the vessels within the ____________ . Concomitantly, thoracic cavity volume increases and intrathoracic pressure ____________ . Blood is propelled from the abdominopelvic cavity into the thoracic cavity.

valves limbs toward thoracic cavity diaphragm increases abdominal cavity decreases

In a working tissue like skeletal muscle, carbon dioxide may accumulate along with an increase in lactic acid. In this example, carbon dioxide and lactic acid will act as

vasodilators

- Contain majority of the blood at any one time - Usually denoted in blue systemically - Collapsed when empty - Rely on muscular pumps to propel blood

veins

Resistance in the blood vessels is primarily controlled by altering

vessel radius