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A&P 2 Chapter 19
Terms in this set (221)
What is the sequence of how the heart pumps blood?
through the arteries, capillaries and the veins of the pulmonary and systemic circuits
what are blood vessels?
conduct blood between the heart and peripheral tissues
what are arteries?
carry blood away from the heart
what are arteries also called?
what are veins?
carry blood to the heart
what are veins also called?
what are capillaries
they exchange substances between blood and tissues
what do capillaries interconnect?
smallest arteries and smallest veins
what are the two circuits?
pulmonary and systemic circuit
what is the pulmonary circuit?
to and from gas exchange surfaces in the lungs
what is the systemic circuit?
to and from the rest of the body
what is the start of circulation pathway?
start with the right atrium (entry way), which collects blood from the systemic circuits and pumps it to the right ventricle to the pulmonary circuit
what chamber is known as the entry way for blood circulation?
what is the following step in the circulation pathway of blood after right atrium receives blood from the systemic system?
the pulmonary circuit, which starts with the pulmonary arteries then to the pulmonary capillaries and then to the pulmonary veins
what happens in the circulation pathway of blood after it gets to the pulmonary veins ?
gets to the left atrium that receives the blood from the pulmonary circuit and then get it to the left ventricle which is then pump to the systemic circuit (the whole body)
what happens once the blood circulation gets to the systemic circuit?
it then goes to the systemic arteries to the systemic capillaries and then to the systemic veins
which chamber of the heart receives blood from the systemic circuit?
what are efferent vessels?
what are afferent vessels?
what are exchanged vessels?
how do arteries and veins differ?
in the structure and thickness of their walls
what are the layers of the arteries and veins?
tunica intima (or tunica interna), tunica media, and tunica externa
what is the innermost layer and the thinnest layer of the arteries and veins?
tunica interna (or tunica intima)
what type of cells are within the tunica intima layer?
simple squamous ENDOthelial cells that have connective tissue with elastic fibers
what do the outer layer margin in arteries have?
elastic fivers (internal elastic membrane)
what does the outer layer margin in arteries provide?
smooth surface for blood flow
what is the middle layer of arteries and veins?
what layer of veins and arteries are regulated by the sympathetic nervous system?
what kind of muscle tissue does the tunica media contain?
concentric sheets of smooth muscle
what do contractions of the tunica media cause?
decreases in vessel diameter or vasoconstriction
what are vasodilators?
local chemicals that increase blood flow
what does relaxation cause in the tunica media?
increase in vessel diameter or vasodilation
how are the tunica media and the tunica externa separated?
by the external elastic membrane
what is considered to be the bulkiest layer in arteries to maintain blood pressure and circulation?
what is the outmost layer of the arteries and veins?
tunica externa or tunica adventitia
what kind of tissue does tunica externa contain?
connective tissue sheath
in arteries, what does the tunica externa contain?
collagen and scattered elastic fibers
what do the collagen fibers do in the tunica externa?
protect and reinforce vessels
in the veins, which is thicker the tunica media or the tunica externa?
what does the tunica externa contain in the veins?
networks of nerve fibers, elastic fibers, and bundles of smooth muscle cells
what does the tunica externa do?
anchors vessels to surrounding tissues
what are the fiver general blood vessel classes?
arteries, arterioles, capillaries, venules, and veins
what are elastic arteries?
large vessels close to the heart that stretch and recoil when heart beats
what are muscular arteries?
medium-sized arteries that are distal to the elastic arteries and distribute blood to skeletal muscles and internal organs
what type of artery accounts for the most named arteries?
what are arterioles?
the smallest arteries and lead to capillary beds
what are capillaries?
only blood vessels to allow exchange between blood and interstitial fluid
what do capillaries have and what do they allow?
very thin walls and allows for easy diffusion
what are venules and what do they do?
the smallest veins and they collect blood from capillaries
when do medium-sized veins form ?
when venules converge
what do large veins contain?
all three vessel wall layers
tunica intima, tunica media, and tunica externa
what is a feature of medium-sized arteries?
usually round with relatively thick wall and small lumen
what is a feature of medium-sized veins?
usually flattened or collapsed, with relatively thin wall and large lumen
what is a feature of the tunica intima in medium-sized arteries?
The ENDOthelium is usually ripped because of vessel constriction and an internal elastic membrane is present
what is a feature of the tunica intima in medium-sized veins?
often smooth ENDOthelium with no internal elastic membrane
what is a feature of the tunica media in medium-sized arteries?
thick and dominated by smooth muscle cells and elastic fibers and have external elastic membrane present
what is a feature of the tunica media in medium-sized veins?
thin, dominated by smooth muscle cells and collagen fibers and no external elastic membrane
what is a feature of the tunica externa in medium-sized arteries?
collagen and elastic fibers
what is a feature of the tunica externa in medium-sized veins?
collagen, elastic fivers and smooth muscle cells
what affect the rates of exchange between the blood and interstitial fluid?
capillary structure and capillary blood flow
what are two major types of capillaries?
continuous and fenestrated capillaries
what does a typical capillary consist of ?
a tube of endothelial cells with delicate basement membrane and lacking both tunica media and tunica externa
what is the most common capillary?
where are fenestrated capillaries found?
wherever active capillary absorption or filtrate formation occurs
what is a capillary bed?
interconnected network of capillaries working together and may be supplied by more than one artery
what are multiple arteries called?
what is anastomosis
joining of blood vessels
what does a capillary bed allow?
continuous delivery of blood to capillary bed even if one artery is blocked or compressed
what is a metarteriole capillary?
contains smooth muscle that can change the vessel's diameter and adjust flow rate
at what sites in the body are fenestrated capillaries located?
kidney filtratration sites
what does the venous system have and what does it contain?
low pressures and contains almost 2/3rd of the body's blood volume
what contains almost 2/3rd of the body's blood volume?
what is the largest artery?
what are valves?
folds of tunica intima projecting from vessel wall and pointing in the direction of blood flow
what do valves ensure?
one-way blood flow towards the heart
what is involved in the process of maintaining blood flow in veins?
valves and contraction of skeletal muscles
what does the contraction of skeletal muscles do?
squeezes veins and the blood within them
what do valves permit?
blood flow in one direction and prevent back flow of blood toward capillaries
what could happen in valves do not work properly?
blood can pool in veins causing distention and a range of effects
what are varicose veins?
veins in the thighs and legs
what are hemorrhoids?
form in the venous networks of the anal canal
what do valves superior to the contracting muscle do?
open, allowing blood to move toward the heart
what do valves inferior to the contracting muscle do?
close, preventing back flow of blood to the capillaries
what is venoconstriction?
contraction of smooth muscle fibers in veins
what does vasoconstriction do?
reduces diameter of the veins and the amount of blood in the venous system
what affects cardiac output?
pressure, resistance and venous return
what is cardiovascular regulation accomplished?
adjusting cardiac output
what is cardiac output?
it must generate enough pressure to force blood through miles of peripheral capillaries
what is cardiac output determined by
venous return and hormonal controls
what is central regulation?
makes coordinated adjustments to the heart rate, stroke volume, peripheral resistance and venous pressure so cardiac output is sufficient
involves neural and endocrine mechanisms
what is blood pressure?
pressure within the cardiovascular system as a whole
what pressure is higher...venous or arterial pressure?
why is arterial pressure higher than venous pressure?
must push blood a greater distance through smaller vessels
what is the flow through blood vessels influenced by?
what is peripheral resistance?
resistance of the arterial system as a whole and increases as vessels get smaller
is blood flow in capillaries fast or slow?
is capillary pressure low or high?
what does capillary regulation allow?
plenty of time for capillary exchange
what is capillary exchange?
diffusion between blood and interstitial fluid
how is blood pressure in veins maintained?
by valves and muscular compression of peripheral veins
what happens as blood moves toward the heart?
vessels get larger and the resistance decreases
what is venous return?
amount of blood arriving at the right atrium each minute
where does autoregulation act
what is the main source of resistance within the cardiovascular system?
vessel luminal diameter
what three factors do peripheral resistance depend on?
vascular resistance, viscosity and turbulence
what is total peripheral resistance?
resistance of entire cardiovascular system
must overcome by sufficient pressure from the heart in order for circulation to occur
what is vascular resistance?
opposition to blood flow in vessels
what is the largest component of total peripheral resistance?
what is the primary result of total peripheral resistance?
friction between blood and vessel walls
what does the amount of friction in total peripheral resistance depend on?
vessel length and diameter
what is blood flow determined by?
the interplay between arterial pressure and peripheral resistance
what is blood flow?
volume of blood flowing per unit of time through a vessel or group of vessels
what is blood flow directly proportional to?
true or false - low-viscosity fluids have lower resistance, so they flow at lower pressures?
what an an example of a low-viscosity fluid
viscosity of 1.0
true or false - high-viscosity fluids have higher resistance, so flow only at high pressures
example - molasses (viscosity 300)
what is viscosity?
resistance to flow caused by interactions among molecules and suspended materials in a liquid
why is blood viscosity fives times the amount of water?
due to cells and plasma proteins and viscosity is normally stable
what is blood flow inversely proportional to?
what is more important than absolute pressure?
what is pressure gradient?
difference in pressure from one end of vessel to other
where is the highest blood pressure?
at the aorta
what is turbulence in total peripheral resistance?
type of fluid flow with eddies and swirls
what is turbulence in total peripheral resistance caused by?
high flow rates, irregular surfaces and sudden changes in vessel diameter
what is turbulence in total peripheral resistance responsible for?
production of third and fourth heart sounds
what happens with increased turbulence?
increased resistance and slow blood flow
what does decreasing diameter do in blood flow ?
increases resistance which = decreased pressure which = decreased flow
when does pressure drop?
at each branching in arterial system
what produces more resistance and reducing pressure?
smaller, more numerous vessels
where are the highest blood pressure, largest diameter, and highest blood flow?
where is blood flow slowest?
in the capillaries
what has the smallest diameter in blood flow ... aorta or capillaries?
why is it important for capillaries to have slow blood flow?
to allow exchange between blood and interstitial fluid
where does blood flow accelerate?
why does blood flow accelerate in the venous system?
because of larger diameter vessels causing a lower resistance
when does arterial pressure change?
rises during ventricular systole (ventricular contraction)
what is systolic pressure?
when peal pressure is measured during systole
when does pressure decline?
during ventricular diastole (ventricular relaxation)
what is diastolic pressure?
minimum pressure measured during diastole
what number is on top when taking someone's blood pressure?
the systolic number
what number is on the bottom when taking someone's blood pressure?
what is considered to be a normal blood pressure?
if someone has a blood pressure of 120/80, which number is the systolic number and which is the diastolic number?
120 = systolic number
80 = diastolic number
what is pulse pressure?
the difference between systolic and diastolic pressure
example - 120-80 = 40 mm Hg
why is mean arterial pressure (MAP) important?
because it measures pressure that propels blood to the tissues
how do you get the mean arterial pressure (MAP)?
adding 1/3rd of pule pressure to diastolic pressure
example = 90 + (120-90)/3 = 100 mm Hg
what affects blood flow?
what does capillary exchange involve?
combination of diffusion, osmosis, and filtration
what is capillary hydrostatic pressure (CHP)?
blood pressure within capillary beds
what does capillary hydrostatic pressure provide and do (CHP)?
provides the driving force for filtration and pushes water and small molecules out of the bloodstream into the interstitial fluid
what remains in the blood incapillary hydrostatic pressure (CHP)?
larger molecules such as plasma proteins
what type of process is capillary exchange?
dynamic process that includes diffusion, and reabsorption
what is diffusion?
net movement of substances from an area of higher concentration to lower concentration
when does diffusion most rapidly occur?
when distances are short
when concentration gradient is large
when ions or molecules involved are small
where does diffusion occur continuously across and how does the transport mechanism vary?
capillary walls and varies for different substances
what do cardiovascular regulatory mechanisms do?
respond to changes in blood pressure or blood chemistry
what is homeostatic mechanisms?
ensure adequate tissue perfusion (blood flow through tissues)
what does blow flow must match?
changes in demand for oxygen and nutrients
what are two regulatory pathways?
autoregulation and central regulation
what is autoregulation?
involves local changes in blood flow within capillary beds
occurs at a local level
what is central regulation?
neural and endocrine control and activated if autoregulation is ineffective
how is homeostasis restored?
increasing blood flow
what is homeostasis disturbed by?
chemical changes (decreased O2 or pH, increased CO2 or prostaglandins)
increased tissue activity
physical stress (trauma, high local temperature)
what are endocrine mechanisms?
involve long-term increases in blood volume and blood pressure
what are neural mechanisms?
increase cardiac output and decrease blood flow to nonessential or inactive tissues
what are autoregulation regulated by?
precapillary sphincters in response to chemical changes in the interstitial fluid
what are baroreceptor reflexes?
respond to changes in blood pressure
where are baroreceptor reflexes located?
in walls of the carotid sinuses, aortic sinuses, and right atrium
what do endocrine responses respond to?
low blood pressure and low blood volume
what do endocrine responses provide?
short-term and long-term regulation of cardiovascular function
what utilizes endocrine functions?
the heart, kidneys, pituitary gland (antidiuretic hormone, or ADH)
what are hormonal responses are important to low blood pressure and volume?
immediate response of epinephrine (E) and norepinephrine (NE),
what are other hormones important to the long-term response of low pressure and volume?
antidiuretic hormone (ADH), angiotensin II, erythropoietin (EPO) and aldosterone
where does the immediate response of Epinephrine and norepinephrine come from?
are endocrine responses to decreased low pressure and volume different or the same as to endocrine responses to high blood pressure and volume?
how do hormonal responses respond to low blood pressure and blood volume?
high blood volume stretches the heart wall during diastole, which triggers a release of natriuretic peptides
what triggers release of natriuretic peptides?
when high blood volume stretches the heart wall during diastole
what are two types of natriuretic peptides?
atrial and brain natriuretic peptide (ANP & BNP)
what is atrial natriuretic peptide and where is it released?
natrium, sodium + ouresis, urination) or ANP
released from the right atrial walls
where is brain natriuretic peptide or BNP released from?
ventricular muscle cells
what happens when there is a decrease in blood volume and pressure?
decreased stress on heart walls, which decreases production of natriuretic peptides
what do chemoreceptors monitor?
the chemical composition of the blood and cerebrospinal fluid
what do chemoreceptor reflexes respond to?
blood and CSF changes in CO2, oxygen and pH
what are chemoreceptors located?
carotid bodies, aortic bodies and ventrolateral surface of medulla oblongata
how is homeostasis in blood and CSF restored?
decreasing CO2 levels and increasing pH and O2 levels
how is homeostasis in blood and CSF disturbed?
increasing CO2 levels and decreasing pH and O2 levels
what is the cardiac output when someone is at rest?
what does the cardiovascular center do during exercise?
makes extensive adjustments to cardiac output and blood distribution
During light exercise, what are the three changes to take place?
vasodilation occurs, peripheral resistance drops, and capillary blood flow increases
venous return increases with skeletal muscle contraction; increased respiration creates negative pressure in thoracic cavity, drawing blood back (respiratory pump)
cardiac output increases to 9500 mL/min
what cardiovascular adjustments occur during heavy exercise?
cardiac output approaches maximal levels (about 17,500 mL/min)
major changes in peripheral blood distribution allow large increase in flow to skeletal muscles without overall decrease in systemic blood pressure
what occurs during heavy exercise?
increased flow to skeletal muscles
increased flow to skin (promotes heat loss)
reduced flow to digestive viscera and kidneys
brain blood flow remains unchanged
true or false trained athletes have bigger hearts and stroke volumes?
what can trained athletes maintain during exercise?
normal blood flow with lower heart rate (as low as 32 bpm)
what do short-term and long-term mechanisms compensate for?
a reduction in blood volume
what are compensation mechanisms when there is a reduction in blood volume?
when homeostasis fails to prevent significant blood loss, entire cardiovascular system adjusts to compensate
what is a response to blood loss?
what does it mean if someone goes into shock due to blood loss?
it is known as acute cardiovascular crisis which is marked by low blood pressure (HYPOtension), inadequate peripheral blood flow
what are the two processes involved in blood vessel formation?
vasculogenesis and angiogenesis
what is angiogenesis?
growth of new blood vessels from preexisting vessels
what does the pulmonary circuit carry?
deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium
what is the pulmonary circuit composed of?
arteries and veins that transport blood between the heart and lungs
where does the pulmonary circuit begin and end?
at the right ventricle and left atrium
what does the systemic circuit do?
transports oxygenated blood to all organs and tissues
where does the systemic circuit begin and end?
the left ventricle and right atrium
what is the pulmonary trunk?
large artery coming out of the right ventricle and branches into the right and left pulmonary arteries
where does the pulmonary trunk branch into?
right and left pulmonary arteries
what do the right and left pulmonary arteries branch into?
smaller arteries and pulmonary arterioles
what do the smaller arteries and the pulmonary arterioles supply
alveolar capillaries around the alveoli (air pockets) where gas exchange occurs
where do pulmonary veins drain into?
the left atrium
what forms pulmonary veins?
oxygenated blood that returns along small venules that join together
how do the arteries and veins in the systemic circuit operate?
in parallel and the major vessels often have similar names
where do arterial system vessels orginiate?
all vessels originate from the aorta (the largest elastic artery) extending from the left ventricle
true or false- most arteries are paired?
true (right and left)
where do the venous system vessels drain into?
superior vena cava anf inferior vena cava
where doe the superior vena cava supply to?
from the head, neck, check and upper limbs
where does the inferior vena cava supply to?
all structures inferior to the diaphragm (trunk and lower limbs)
what is one significant difference between arteries and veins
is the distribution in the neck and limbs
where are arteries located and how are they protected?
deep in the skin, protected by bones and soft tissues
where are veins typically located and what do they control?
generally two sets, one deep and one superficial and control body temperature
where does venous blood flow when there is hot weather?
blood flows superficially to radiate heat
where does venous blood flow when there is cold weather?
blood flows deep to conserve heat
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