Chapter 19 - The Cardiovascular System: Blood Vessels
what are the three major types of blood vessels?
arteries, veins, capillaries
In the systemic circulation, arteries always carry ___________ blood and veins always carry __________ blood.
oxygenated, oxygen poor
In the pulmonary circulation, arteries always carry ___________ blood and veins always carry __________ blood
oxygen poor, oxygenated
which blood vessel type has intimate contact with tissue cells and directly serve cellular needs?
capillaries
tunics
"coverings" layers of the blood vessels, the walls of blood vessels have 3 tunics
lumen
cavity inside blood vessel, blood containing space
what are the three tunics of the blood vessels?
tunica intima
tunica media
tunica externa
innermost tunic
tunica intima, contains endothelium
endothelium
single layer of simple squamous cells that line the lumen of all vessels, minimizes friction as blood moves through the lumen
subendothelial layer
in vessels larger than 1mm diameter, layer consisting of basement membrane and loose connective tissue that supports the endothelium
middle tunic layer
tunica media
describe the tunica media
circularly arranged smooth muscle cells and sheets of elastin, activity of the smooth muscle is regulated by sympathetic vasomotor nerve fibers of the autonomic nervous system
vasoconstriction
narrowing of blood vessel, lumen diameter decreases as the smooth muscle of the tunica media contracts
vasodilation
relaxation of the smooth muscle of the blood vessel, producing dilation, lumen diameter decreases as smooth muscle relaxes
bulkiest layer of the arteries
tunica media
which layer of the blood vessels has the chief responsibility of maintaining blood pressure and circulation?
tunica media
outermost layer of the blood vessel wall
tunica externa (tunica adventitia)
describe the tunica externa
loosely woven collagen fibers that protect and reinforce the vessel, and anchor it to its surrounding structures
function of each layer of the blood vessel walls
tunica intima- forms a slick surface that minimizes friction as blood passes through the lumen
tunica media- maintains blood pressure and circulation by controlling the constriction and dilation of the blood vessel
tunica externa- protects the blood vessel, anchors it to its surroundings
vasa vasorum
nourish the most external tissues of the blood vessel wall, system of tiny blood vessels in the tunica externa of larger vessels
three types of arteries
elastic arteries, muscular arteries, and arterioles
elastic arteries
thick walled arteries near the heart (aorta and major branches) largest in diameter, conducting arteries (conduct blood from heart to medium-sized arteries), contain elastin (mostly in tunica media), inactive in vasoconstriction
muscular arteries
deliver blood to specific organs, distributing arteries, thickets tunica media
what type of artery has the thickest tunica media?
muscular arteries
arterioles
smallest type of artery, blood flow into capillaries determines by arteriole diameter, constriction=less blood flow, dilation=more blood flow
smallest type of artery
arterioles
capillaries
smallest type of blood vessel, contain pericytes, rbc's slip through in single file, 3 different types
smallest type of blood vessel
capillaries
pericytes
smooth muscle-like cells that stabilize the capillary wall and help control capillary permeability
3 different types of capillaries
continuous
fenestrated
sinusoid
most common type of capillary
continuous
fenestrated capillaries
endothelial cells pierced with small pores, much more permeable to fluids and small solutes than continuous capillaries,
intercellular clefts
gaps of unjoined membrane
sinusoid capillaries
sinusoids, highly modified, leaky capillaries found only in the liver, bone marrow, spleen, and adrenal medulla, irregular shaped lumen and are fenestrated, allow large molecules to pass between blood and surrounding tissue, incomplete basement membrane
stellate macrophages
found in sinusoids, remove and destroy bacteria
least permeable capillary
continuous
capillaries found in areas of active absorption and filtration (kidney, small intestine)
fenestrated
most permeable capillary, found in specific locations such as the liver, bone marrow, spleen, etc.
sinusoids
capillary beds
interweaving network, connect arterioles to venules, enable exchange of nutrients
venule
allows blood to return from capillary beds to veins
mircocirculation
flow of blood from arterioles to venules
how many types of vessels does a capillary bed consist of?
2
vascular shunt- short vessel that directly connects the arterioles to venules at opposite ends of the bed
true capillaries- the actual exchange vessels
terminal arteriole
feeds capillary beds
capacitance vessels or blood reservoirs: veins or arteries?
veins
venous valves
folds of tunica intima, most abundant in the limbs, usually absent in veins of the thoracic and abdominal cavities
varicose veins
twisted and dilated vein because of leaky valves
venous sinuses
highly specialized flattened veins with extremely thin walls composed of only endothelium, coronary sinus is an example
vascular anastomoses
joining of blood vessels
collateral channels
alternative pathways for blood
blood flow
volume of blood flowing through a vessel, organ, or entire circulation in a given period
blood pressure
the force per unit area exerted on a vessel wall by the contained blood, systemic arterial blood pressure in the largest arteries near the heart
pressure gradient
the different in BP within the vascular system, provides the driving force to keep blood moving from an area of high pressure to an area of low pressure
resistance
opposition to flow, measure of the amount of friction blood encounters as it passes through the vessels
peripheral resistance
most friction occurs in the peripheral (systemic) circulation, well away from the heart, so this term is commonly used
blood viscosity
thickness of blood
true of false: the longer the blood vessel, the greater the resistance
true
true or false: when BP increases, blood flow speeds up, and when it decreases it declines
true
true or false: if resistance increases, so does blood flow
false
F = BP/R
-
true or false: blood moves from higher pressure to lower pressure areas
true
systemic blood pressure is highest in the____
aorta
BP reaches 0mm Hg in the _____
right atrium
The steepest drop of blood pressure occurs in the ___
arterioles which offer the greatest resistance to blood flow
Arterial BP depends on what two factors?
how much the elastic arteries close to the heart can stretch, and the volume of blood forced into them at any time
True or false: if the amount of blood entering and leaving the elastic arteries in a given period were equal, arterial pressure would be constant
true
pulsatile
rises and falls in a regular fashion
systolic pressure
pressure exerted by blood on blood vessel wall during ventricular contraction
average systolic pressure
120 mm Hg
diastolic pressure
lowest level of any given cardiac cycle, arterial blood pressure reached during or as a result of diastole
average diastolic pressure
70-80 mm Hg
pulse pressure
the difference between the systolic and diastolic pressure
why does atherosclerosis chronically increase pulse pressure?
elastic arteries become less stretchy
MAP (mean arterial pressure)
the pressure that propels the blood into the tissues
which last longer, diastole or systole?
diastole
true or false: the MAP is equal to the diastolic pressure plus one third pulse pressure?
true
MAP = diastolic pressure + pulse pressure/3
true or false: MAP and pulse pressure increase with increasing distance from the heart
false, MAP and pulse pressure decrease with increasing distance from the heart
blood pressure when first reaches capillaries and when leaving capillary beds
35 mm Hg - 17 mm Hg
why are low capillary pressures desirable?
they are fragile and extremely permeable
true or false: venous blood pressure is relatively stable and unchanging
true
three functional adaptions critical to venous return
muscular pump
respiratory pump
sympathetic venoconstriction
three factors that maintain blood pressure
CO, PR, BV
how to BP, CO, and PR relate to each other in formulas
F = BP/PR
BP= F x PR
CO = ?
CO = SV x HR
vasomotor fibers
sympathetic nerve fibers that cause the contraction of smooth muscle in the walls of blood vessels, therefore regulation blood vessel diameter
vasomotor tone
state of moderate constriction
baroreceptors
a sensory nerve ending in the wall of the carotid sinus or the aortic arch sensitive to vessel stretching
when stretched, baroreceptors _____
send a stream of impulses to the cardiovascular center, decreasing blood pressure
three mechanisms that bring about a decrease in blood pressure
arteriol vasodilation
venodilation
decreased CO
rapidly responding baroreceptors protect the circulation against_____
short term changes in BP
chemoreceptors
sensitive to various chemicals in a solution, most prominent are carotid and aortic bodies, play a larger role in regulating respiratory rate
reflexes that regulate BP are located in the ____
medulla oblongata
two adrenal medulla hormones
epinephrine and norepinephrine
effect of epinephrine and norepinephrine on BP
increase BP, increase CO and promote vasoconstriction
When blood pressure of volume is low, kidneys release _____
renin
Angiotensin II affect on BP
increases BP, stimulates vasoconstriction, promoting a rise in systemic BP, also stimulates release of aldosterone and ADH, which act in long term regulation of BP by enhancing BV
Atrial Natriuretic peptide (ANP) affect on BP
decreases BP, reduces BV and causes vasodilation
Antidiuretic hormone (ADH) affect on BP
increases BP, stimulates kidneys to preserve water, not usually important in short term regulation, vasoconstriction
Aldosterone affect on BP
increases BP
long term regulation mechanisms alter ___
BV
true of false: increase BV = increased BP
true
direct renal mechanisms
alter blood volume independently of hormones
when BP or BV rises, speed of fluid filtering from the blood stream to the kidney speeds up so more of it leaves in urine therefore BV and BP fall. and BP or BV is low, water is conserved to the bloodstream so BP and BV rise
hormones that increase BP
epinephrine and NE, ADH, & angiotensin
hormones that decease BP
ANP
indirect renal regulation of blood volume involves what hormonal mechanism
renin-antiotensin-aldosterone mechanism
explain indirect renal mechanism
when BP falls, the kidneys release renin, which triggers the formation of angiotensin II. angiotensin II causes:
1) release of aldosterone, stimulation salt and water retention
2) vasoconstriction
3) release of ADH
4) thirst
hypertension
high BP
what BP would be considered hypertension?
140/90
prehypertension
blood levels elevated but not in hypertension range
prolonged hypertension is the major cause of ___
heart failure, vascular disease, renal failure, and stroke
what enlarges as a result of hypertension
myocardium because it has to work harder to pump
primary hypertension
no underlying cause, cant be cured, 90% cases
suspected causes:
heredity
diet
obesity
age
diabetes
stress
smoking
secondary hypertension
10% cases, due to identifiable conditions, cured by curing problem that caused it
hypotension
low blood pressure 90/60
true or false: low blood pressure is associated with long life and an old age free of cardiovascular disease
true
when is low blood pressure a concern?
if it leads to inadequate blood flow to tissue
orthostatic hypotension
temporary drop in BP from rising suddenly
tissue perfusion
blood flow through tissue
blood flow is involved in _____
delivering oxygen and nutrients to tissue cells
exchanges gases in the lungs
absorb nutrients from digestive tract
form urine in the kidneys
autoregulation
the local adjustment of blood flow to individual organs based on their immediate requirement