Anatomy Chapter 19:Blood vessels

What are the The three major types of blood vessels?

arteries, capillaries, and veins

What are arterioles?

smallest artery branches

What are venules?

smallest veins

arteries always carry __ blood

oxygenated

Veins carry ___blood

oxygen poor

Arteries and veins have special jobs where?

In pulmonary circulation and in the umbilical of a fetus.

What happens in pulmonary circulation?

Arteries carry oxygen poor blood to the lungs and veins carry oxygen rich blood from the lungs to the heart.

only the __ have intimate contact with tissue cells and directly serve cellular needs

capillaries

Tunic definition

Coverings or vessel layers.

What is the innermost tunic?

Tunica intima

Endothelium definition

Single layer of squamous cells that line the heart, blood vessels, and lymphatic vessels.

Vessels larger than 1mm, _______, consisting of a basement membrane and loose connective tissue, supports the endothelium.

Subendothelial layer

The middle tunic is called__

the tunica media

The ____, is mostly circularly arranged smooth muscle cells and sheets of elastin.

tunica media

The activity of the smooth muscle is regulated by _____of the autonomic nervous system and a whole battery of chemicals.

vasomotor nerve fibers

Vasoconstriction definition

Narrowing of blood vessels

Vasodilation definition

Relaxation of the smooth muscles of the blood vessels, producing dilation.

Which tunica bears the chief responsibility for maintaining blood pressure and circulation?

Tunica media

The outermost layer of a blood vessel all is________

tunica externa

What is the tunica externa composed of?

loosely woven collagen fibers that protect and reinforce the vessel, and anchor it to surrounding structures.

What is inside the tunica externa?

nerve fibers, lymphatic vessels, elastic fibers.

In larger vessels, the tunica externa contains___

the vasa vasorum

What are the vasa vasorum?

tiny blood vessels that nourish the more external tissues of the blood vessel wall.

arteries can be divided into three groups

elastic arteries, muscular arteries, and arterioles.

What are elastic arteries?

the thick-walled arteries near the heart.

elastic arteries are sometimes called__

conducting arteries

Elastic arteries are______ expanding and recoiling as the heart ejects blood.

pressure reservoirs

without the pressure-smoothing effect of the elastic arteries, the walls of arteries throughout the body experience______

higher pressures

____deliver blood to specific body organs

Muscular arteries

Minute-to-minute blood flow into the capillary beds is determined by________________

arteriolar diameter

arteriolar diameter varies in response to

changing neural, hormonal, and local chemical influences.

What are capillaries?

the smallest blood vessels

What are pericytes?

contractile stem cells that can generate new vessels or scar tissue, stabilize the capillary wall, and help control capillary permeability

_____ lack capillaries but receive nutrients from blood vessels in nearby connective tissues.

Cartilage and epithelia

the avascular cornea and lens of the eye receive nutrients from the

aqueous humor.

there are three types of capillaries

continuous, fenestrated, and sinusoid.

What are intercellular clefts?

unjoined membrane which allow limited passage of fluids and small solutes.

capillary beds are

interweaving networks

The flow of blood from an arteriole to a venule—that is, through a capillary bed is called ______

the microcirculation

What forms the capillary bed?

10 to 20 capillaries

As blood flows through the capillaries, it takes part in exchanges

of gases, nutrients, and wastes with the surrounding tissue cells.

Veins carry blood from the capillary beds toward

the heart

The smallest venules,_______ consist entirely of endothelium around which pericytes congregate.

the postcapillary venules

fluid and white blood cells move easily from the bloodstream through their walls

Postcapillary venules

Veins are called capacitance vessels and blood reservoirs because they can hold up to_____

65% of the body’s blood supply at any time

their large-diameter lumens, which offer relatively little resistance to blood flow

veins

___ prevent blood from flowing backward in veins

Venous valve

Venous valves are most abundant in

the veins of the limbs

Varicose veins are

veins that are tortuous and dilated because of incompetent (leaky) valves.

resulting varicosities in the anal veins are called

hemorrhoids

Venous sinuses are

highly specialized, flattened veins with extremely thin walls composed only of endothelium

___are supported by the tissues that surround them, rather than by any additional tunics

Venous sinuses

vascular anastomoses are

Blood vessels form special interconnections

arteries supplying the same territory often merge, forming____

arterial anastomoses

Most organs receive blood from______arterial branch

more than one

anastomoses provide alternate pathways__________for blood to reach a given body region

called collateral channels

Arterial anastomoses occur________, where active movement may hinder blood flow through one channel.

around joints

thoroughfare channel shunts of some capillary beds that connect arterioles and venules are examples of

arteriovenous anastomoses

Because ____ are abundant, an occluded vein rarely blocks blood flow or leads to tissue death.

venous anastomoses

Blood flow is

the volume of blood flowing through a vessel, organ, or the entire circulation in a given period.

Blood pressure is

the force per unit area exerted on a vessel wall by the contained blood.

Resistance is

opposition flow and is a measure of the amount of friction blood encounters as it passes through vessels.

Why do we generally use the term total peripheral resistance(TPR)?

most friction is in the peripheral (systemic) circulation.

What are the three important sources of resistance?

blood viscosity, vessel length, and vessel diameter.

what is viscosity?

the internal resistance that exists in all fluids.

Polycythemia is

excessive numbers of red blood cells

the longer the vessel, the _____ the resistance

greater

the smaller the diameter, the _____ the resistance

greater

Blood vessel diameter _____________and _________ total peripheral resistance.

changes frequently, significantly alters

Blood viscosity and vessel length are normally _________ and so the influence is ______.

unchanging, constant

What is laminar flow or streamlining?

the relative speed and position of fluid in different regions of the tube’s cross section remain constant in a tube of a given size.

What are the major determinants of total peripheral resistance?

small-diameter arterioles

turbulent flow is

irregular fluid motion where blood from the different laminae mixes.

When blood encounters an abrupt change or a protruding area of the tube wall the smooth laminar blood flow is replaced by

turbulent flow

Turbulence dramatically ________ resistance

increases

Blood flow is directly proportional to the difference in

blood pressure

When blood pressure (P) ______, blood flow _______

increases

Blood flow is inversely proportional to

the peripheral resisitance.

TPR is far more important than ______ in influencing local blood flow.

blood pressure

______ can easily be changed by altering blood vessel diameter.

TPR

systemic blood pressure is ____ in the aorta

highest

systemic blood pressure declines throughout the pathway

The steepest drop in blood pressure occurs in
_______, which offer the greatest resistance to blood flow.

the arterioles

As long as______ exists blood continues to flow until it completes the circuit back to the heart.

a pressure gradient

Arterial blood pressure reflects two factors:

(1) how much the elastic arteries close to the heart can stretch(2) the volume of blood forced into them at any time.

blood pressure is pulsatile in the elastic arteries near the heart.

it rises and falls in a regular fashion

pressure peak generated by ventricular contraction is called

systolic pressure

During diastole, the aortic valve closes, preventing blood from flowing back into the heart.

diastolic pressure

The difference between the systolic and diastolic pressures is called the

pulse pressure.

mean arterial pressure (MAP)

the pressure that propels the blood to the tissues.

low capillary pressures are desirable because:

Capillaries are fragile and high pressures would rupture them.

even the low capillary pressure can force solute-containing fluids (filtrate) out of the bloodstream into the interstitial space.

venous blood pressure is ___ and changes ____ during the cardiac cycle.

steady, very little

three functional adaptations are critically important to venous return:

The muscular pump, respiratory pump, and sympathetic venoconstriction

As the skeletal muscles surrounding the deep veins contract and relax, they squeeze or “milk” blood toward the heart, and once blood passes each successive valve, it cannot flow back

The muscular pump

moves blood up toward the heart as pressure changes in the ventral body cavity during breathing.

The respiratory pump

reduces the volume of blood in the veins—the capacitance vessels (Venous volume is reduced and blood is pushed toward the heart.)

Sympathetic venoconstriction

Cardiovascular system homeostasis regulation involves three key variables:

Cardiac output, Total peripheral resistance,Blood volume

blood pressure varies directly with ____ and __

CO, TP

Anything that increases cardiac output or total peripheral resistance increases _____

blood pressure

Blood pressure also varies directly with blood volume because ____ depends on blood volume

CO