Chapter 19 Flashcards

Central blood-containing space in the vessel

innermost tunic, contains the endothelium (the simple squamous epithelium that lines the lumen of all vessels)

middle tunic, mostly circularly arranged smooth muscle cells and sheets of elastin

lumen diameter decreases as the smooth muscle contracts- allows more blood flow

lumen diameter increases as the smooth muscle relaxes - decreases blood flow

outermost layer of a blood vessel wall, composed largely of loosley woven collagen fibers that protect and reinforce the vessel, and achor it to surrounding structure

In larger vessels, the tunica externa contains a system of these tiny blood vessels

Thick-walled arteries near the heart (the aorta and its major branches) They are also known as pressure reservoirs aka: conducting arteries

deliver blood to specific body organs (sometimes called distributing arteries)

smallest of the arteries-lumen diameter ranging from 0.3mm down to 10 Um

smallest blood vessels

smooth muscle-like cells that stabilize the capillary wall and help control capillary permeability

abudant in skin and muscles, these are the most common and have intercellular clefts (least permeable capillary)

gaps of unjoined membrane that are large enough to allow limited passage of fluids and small solutes

riddled with oval pores, or fenestrations and increase permeability (fenestra=window)

highly modified, leaky capillaries found only in the liver, bone marrow, spleen, and adrenal medulla.most permeable capillary

remove and destroy any bacteria (can be found in sinusoid capillaries)

interweaving networks that connect arteriole and venule

flow of blood from an arteriole to a venule (through a capillary bed)

1. Vascular Shunt
2 True capillaries

short vessel that directly connects the arteriole and venule at opposite ends of the bed

actual exchange vessels; number 10-100 per capillary bed

an arteriole that divides into capillaries.

vessel structurally intermediate between an ateriole and a capillary (continuous with the thoroughfare channel)

intermediate between a capillary and a venule (connects with the metarteriole)

joins with the thoroughfar channel and then drains the capillary bed

surrounds the root of each true capillary at the metarteriole and acts as a valve to regulate blood flow into the capillary

Capillaries unite to form venules; extremely porous (like capillaries)

venules join to form veins; walls are always thinner and their lumens larger than those of corresponding arteries, however, veins are usually collapsed and their lumens appear slitlike

AKA VEINS; with their large lumens,&thin walls, veins can accomodate a fairly large blood volume.

up to 65% of the body's blood supply at any time (although they are usually only partially filled)

formed from fold sof the tunica intima, prevent blood from flowing backward

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

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

coming together

blood vessels that form special interconnections

most organs receive blood from more than one arterial branch, and arteries supplying the same territory often merge, forming arterial anastomoses

altenbate pathways, called collateral channels (helps blood to reach a given body region)

meterteriole-thoroughfare channel shunts of capillary beds that connect arterioles and venules

veins that interconnect much more freely than arteries, and are very common

the volume of blood flowing through a vessel, or an organ

the force per unit area exerted on a vessel wall by the contained blood (exptressed in mm Hg)

opposition to flow and is a measure o the amt of friction blood encounters as it passes through vessels

most friction is encountered in the peripheral (systemic) circulation, well away from the heart, this is the term we use

related to the thickness or "stickiness" of the blood

relationship betwn total blood vessel length and resistance is straightforward: the longer the vessel, the greater the resistance

Blood vessel diameter changes frequently and significantly alters peripheral resistance (think of a river: water runs rapidy in the center, but slower on the sides)

F=∆P/R

F=blood flow
∆P= difference in blood pressure betwn two points in circulation
R=peripheral resistance

The pressure peak generated by ventricular contraction

averages 120 mm Hg

aortic valves close, preventing blood from flowing back into the heart. during this time aortic pressure drops to its lowest level

70 to 80 mm Hg

difference between the systolic and diastolic pressures

the pressure that propels the blood to the tissues.
MAP=diastolic pressure+ pulse pressure/3

1. The muscular Pump
2. The respiratory pump
3. Sympathetic Venoconstriction

arterioles

consists of skeletal muscle activity: as skeletal muscles surrounding the deep veins contract and relax, they "mil" blood toward the heart

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

reduces the volume of blood in the veins-the capacitance vessels

consists of the cardiac centers and the vasomotor center that controls the diameter of blood vessels

controls diameter of blood vessels

vasomotor center transmits impulses at the fairly steady rate along sympathetic efferents

arterioles are almost always in a state of moderate constriction

when arterial blood pressure rises, it activates baroreceptors. These inhibit (or bar) to the vasomotor and cardioacceleratory centers

1. Arteriolar Vasodilation
2. Venodilation
3. Decreased Cardiac Output

decreased output from the vasomotor centers allows arterioles to dialte

decreased output from the vasomotor center also allows veins to dilate, which shifts blood to venous reservoirs. This decreases venous return and CO (cardiac output)

impulses to the cardiac centers inhibit sympathetic activity and stimulate parasympathetic activity, reducing heart rate and contractile force.

protects the blood supply to your brain (these are from baroreceptors)

helps maintain adequate blood pressure in your systemic circuit as a whole

epinephrine, and norepinephrine goes to the blood; causing an increase in cardiac output and promoting generalized vasoconstriction

When blood pressure or blood volume are low the kidneys release renin. Renin generates Angiotensin II which stimulates intense vasoconstriction, promoting a rise in systemic blood pressure. It stimulates release of aldosterone and ADH

this leads to a reduction in blood volume and blood pressure (vasodilation)

stimulates kidneys to conserve water.

alters blood volume independently of hormones

through this the kidneys can also regulate blood pressure indirectly.Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II.

a hormone that enhances renal reabsorption of sodium

this is how clinicians assess the efficiency of a person's circulation by measuring pule and blood pressure

alternating expansion and recoil of arteries during each cardiac cycle allow us to feel a pressure wave

the pulse points on the body that are compressed to stop blood flow into distal tissues during hemorrhage

measure systemic arterial blood pressure indirectly in the brachial artery of the arm

Sphygmomanometer

chronically elevated blood pressure

low blood pressure (below 90/60 mm Hg)

90% are Primary and only 10% are secondary. Primary hypertension is when there has been no underlying cause identified. Secondary Hypertension is when there is an identifiable condition.

addison's disease, hypothyroidism, sever malnutirition

Blood flow through body tissues

1. delivering oxygen and nutrients to tissue cells & removing wastes
2. exchanging gases in the lungs
3. absorbing nutrients from digestive tract
4. forming urin in kidneys

this is how each organ or tissue manage to get the blood flow it needs. The automatic adjustment of blood flow to each tissue in proportion to the tissue's requirements at any instant.

powerful vasodilator which acts via a cyclic GMP second-messenger system.

the endothelium also releases potent vasoconstrictors, called endothelins, which are among the most potent vasoconstrictors known.

fluctuations in systemic blood pressure would cause problems for individual organs were it not for the myogenic responses of vascular smooth muscle.

refers to the dramatically increased blood flow into a tissue that occurs after the blood supply to the area has been temporarily blocked

when muscles become active, blood flow increases (hyperemia) in direct proportion to their greater metabolic activity

the on/off opening and closing precapillary sphincters in response to l local auto-regulatory controls

tends to force fluids through capillary walls (a process called filteration) leaving behind cells and most proteins.

blood pressure-which forces fluid out of the capillaries is opposed by the HPif acting outside the capillaries and pushing fluid in.

abundant plasma proteins in capillary blood (primarily albumin molecules) develop this.

this considers all the forces acting at the capillary bed.

any condition in which blood vessels are inadequately filled and blood cannot circulate normally.

the most common form of circulatory shock:which result from large-scale blood or fluid loss.

blood volume is normal, but circulation is poor as a result of extreme vasodilation.

pump failure, occurs when the heart is so inefficient that it cannot sustain adequate circulation. (could be caused by heart attacks)

The endothelial lining of blood vessels is formed by mesodermal cells which collect in little masses

Elastic Arteries are sometimes called this.

muscular arteries

alters blood volume independently of hormones

1. stimulates adrenal cortex to secrete aldosterone; also stimulates sodium reabsorption by kidneys
2.prods posterior pituitary to release ADH; promotes more water reabsorption by kidneys
3. triggers sensation of thirst, by activating hypothalamic thirst center
4. potent vasoconstrictor, increasing blood pressure by increasing PR

NO (Nitric Oxide), often this overrides sympathetic vasoconstriction when tissues need more blood flow

true

red (slow oxidative) fibers

external jugular

cavernous sinus

median cubital vein

femoral