vascular Flashcards
the right side of the heart delivers _____ of its blood to the _____
100%
lungs
the left side of the heart delivers oxygenated blood to other tissues in the body through systemic circulation. list the body parts in order of which recieves most to least;
digestive - 21%
kidneys - 20%
skeletal muscle - 15%
brain - 13%
skin - 9%
other - 8%
liver - 6%
bone - 5%
heart muscle - 3%
what is pressure a measure of?
force/area
what are modern units for pressure?
PSi (pounds per square inch), kPa (kilopascal), mmHg (milimeters of mercury)
what unit of pressure is used for measuring pressures in the cardiovascular system?
mmHG
what does mmHg represent?
the pressure exerted by a X mm column of liquid mercury
why drives the flow of blood through the vascular system?
pressure gradient established from the aorta to the right atrium
why does pressure decrease along the vascular tree?
due to conversion of energy into heat from friction
the rate of blood flow is ____ proportional to the pressure gradient and _____ proportional to vascular resistance
directly proportional
inversly proportional
how do you calculate rate of blood flow?
F = pressure gradient/resistance
what is pressure gradient?
the difference in pressure between the beginning and end of a vessel or organ
what is the direction of blood flow in terms of pressure?
blood flows from an area of high pressure to an area of lower pressure
______ provides the motive force to drive blood flow within conduit vessels and organs
blood pressure
what determines how much blood each organ will recieve?
vascular resistance
what is resistance?
the measure of the hindrance or opposition of blood flow through a vessel
how is resistance produced in the cardiac system?
by friction between the moving fluid and stationary walls
what are the 3 factors that resistance is dependent on?
- blood viscosity (n)
- vessel length (L)
- vessel radius (r)
a slight change in vessel radius produces a _____ change in blood flow
significant
what is the equation to which resistance is proportional to?
1/r^4
what are the assumptions for Poiseuille’s law?
- newtonian fluid - viscosity of blood remains constant
- laminar flow - blood travels smoothly without turbulence
- no slip condition - the speed of the blood that is in contact with the vessel wall is 0
- steady flow
- cylindrical vessels
- rigid vessel walls
flow is equivalent to what mathamatical equation?
r^4
flow is equivalent to what?
pressure gradient
what are arteries?
rapid transit ways that carry blood away from heart to tissues
what are arterioles?
smaller branches of arteries that control distribution of blood
what are capillaries?
smaller branches of arterioles optimized for excahnge with surrounding cells
what are venules?
after nutrient excahnge, blood goes into the venules for return back to heart
what are venules?
form when venules merge, return blood to heart
what is the structural features of arteries?
thick, highly elastic walls with a large radi
what are the structural features of arterioles?
highly muscular, well innervated walls with small radi
what are the structural features of capillaries?
very thin walled
what are the structural features of veins?
thin walled compared to arteries, highly distensible, with large radi
an artery has the following structure; (inner-outer)
endothelium
basement membrane
elastic fibers
smooth muscle
elastic fibers
connective tissue coat
an arteriole has the following structure; (inner-outer)
endothelium
basement membrane
smooth muscle
connective tissue coat
a capillary has the following structure; (inner-outer)
endothelium
basement membrane
a large vein has the following structure; (inner-outer)
venous valve + endothelium
basement membrane
smooth muscle
conncetive tissue
what are conduits?
rapid-transport passageways for blood from heart to organs. due to their large radius, these large arteries offer little resistance to blood flow
what is pressure reservoir?
provides driving force for blood when heart is relaxing and refilling
compliance of arteries is related to _________
connective tissue components including;
collagen fibers - tensile strength
elastin fibers - elasticity to arterial fibers
blood pressure on its own usually refers to the blood pressure within _________
large central arteries of the systemic circulation
why does mean BP fall across the systemic vasculature?
in proportion to the resistance it encounters
inadequate BP can lead to___
inadequate tissue blood flow
excessive BP can cause _______
immediate problems such as overload on the heart or excessive tissue blood flow
even modest increases in BP can increase the risk of _______
cardiovascular disease
pulse pressure can be determined by what mathamatical equation?
Psystolic - Pdiastolic
BP refers to the pressure generated as a consequence of _______
ventricular ejection
how do you determine mean arterial pressure?
MAP = diastolic pressure + 1/3 pulse pressure
pressure ahead of resistance is also known as?
arterial pressure
pressure after resistance is also known as?
venous pressure
ohms law determines;
Parterial - Pvenous = CO x TPR (total peripheral vascular resistance)
which pressure is normally very small and can be considered neglible in ohms law?
Pvenous
a decrease in CO will have what effect of BP?
decrease
an increase in TPR will have what effect on BP?
increase
an increase in CO and decrease in TPR will have what effect on BP?
stabilized
can the normal distribution of blood from the left side of the heart at rest be changed?
yes. it is changed according to metabolic demands of the tissues
veins carry deoxygenated blood, arteries carry oxygenated blood… but there is 1 exception to this rule, what is it?
the pulmonary arteries that carry deoxygenated blood from the heart to the lungs
what is the tunica adventitia or externa?
the external layer of blood vessel tissues
what is the tunica media?
the middle layer of blood vessel tissues
what is the tunica intima?
the inner layer of blood vessel tissues
all types of blood vessels have a single layer of _______ cells that makw up most of the tunica intima
endothelial cells
where is the highest proportion of collagen fibers found?
in large veins
what is the windkessel effect?
when the heart contracts it ejects blood into the aorta which will stretch the arteries aas it rapidly flows. this energy will be stored as elastic energy and when the heart finishes contracting there will be elastic recoil.
what type of pressure is covered under hydrodynamics?
blood pressure produced by the contraction of the ventricular muscle which drives blood flow through circulation
what is hydrostatic pressure?
- pressures of fluid that are somehow confined and not able to move and for which ohms law does not apply
- the pressure resulting from the height of the fluid column
what is the equation that is representative of hydrostatic pressure?
P = height of fluid coolumn x fluid density
mercury is ________ times denser than water
13.6
what type of system was used to make the ffirstt measurement of BP?
a vertical glass column of water
why would a coulmn of water have to be taller than a column of mercury to accurately depict the same BP?
beacuse of the difference in density
can gravity affect BP?
yes because blood is a clumn of fluid
would regions above the heart have increased or decreased arterial pressure?
decreased
would regions below the heart have increased or decreased arterial pressure?
increased
blood is ______ times denser than water
1.06
each meter of elevation of a verticle column of blood corresponds to __________ mmHg
78
to minimize the effect of gravity on BP, what is used as a referance point?
the heart (brachial artery)
can BP measurements be taken from places other than the brachial artery
yes they would just have to corrected to the pressure expected at the heart level
when standing, what effect does gravity have on blood?
promote the pooling of blood in the veins of the lower limbs and impede venous return to the heart
what does a sphygmomanometer combine?
a cuff to occlude an artery
something to generate cuff pressure
something to measure cuff pressure
hg column
how does a blood pressure cuff work?
- the BP cuff is inflated well above systolic pressure and then slowly deflated
- when it is above systolic pressure the artery is collapsed and no arterial blood flow will occur and a korotkoff sound will not be heard
- when it is below systolic pressure but above diastoli cpressure thge artery is partially collapsed so some aarterial flow will occur and a korotkoff sound will be heard
- when cuff pressure is less that diastolic the aretery will be open and blood flow can occur quietly so korotkoff sounds wont be heard
what is the method for noninvasive BP measurement?
korotkoff sounds with a stethoscope
inflating the BP cuff causes;
when it is above systolic pressure the artery is collapsed and no arterial blood flow will occur and a korotkoff sound will not be heard
as the cuff begins to deflate what happens?
when it is below systolic pressure but above diastoli cpressure thge artery is partially collapsed so some aarterial flow will occur and a korotkoff sound will be heard
when the cuff is almost fully deflated what happens?
when cuff pressure is less that diastolic the aretery will be open and blood flow can occur quietly so korotkoff sounds wont be heard
when are korotkoff sounds heard?
when the BP cuff is less than systolic pressure but higher than diastolic pressure
using the korotkoff method, how do you determin systolic and diastolic BP?
systolic - when korotkoff sound first appears
diastolic - when the last korotkoff sound is heard
what are considered as major resistance vessels?
arterioles
how does adjusting the radius of arteriooles beneficial?
- help distribute cardiac output ammong systemic organs depending on bod’s momentary needs
- help regulate arterial blood pressure
what are the methods involvedd in adjusting arteriole resistance?
vasoconstriction and vasodialation
what is vasoconstriction?
- descrbes the process of narrowing a vessel
- results from contraction of smooth muscle layer
- leads to increased resistance and decreased flow through that vessel
what is vasodialation?
- the enlargement in internal circumference and internal radius if vessel
- results from relaxation of smooth muscle layer
- leads to decreased resistance and increased flow through that vessel
vascular smooth muscle cells sustain a level of partial contraction which is referred to as __________
vascular tone
what are the 2 factors responsible for vascular tone?
myogenic activity of smooth muscle
sympathetic fibers continually release norepi
vasoconstriction can be caused by;
- increased myogenic activity
- increased oxygen
- decreased carbon dioxide
- increased endothelian
- increassed sympathetic stimulation
- vasopression
- angiotensin 2
- cold
vasodialation can be caused by;
- decreased myogenic activity
- decreased oxygen
- increased carbon dioxide
- increased nitic oxide
- decreased sympathetic stimulation
- histamine release
- cold
if an arteriole changes radius within a certain organ, does that affect other vessels in another\?
yes
what are chemical influences on arteriolar radius?
local metabolic change
histamine release
what are physical influences on arteriolar radius?
local application of heat or cold
chemical response to shear stress
myogenic response to stretch
during exercise, cardiac output changes, what organ/body part would have the highest percent change in flow?
skeletal muscle
what are vasoactive mediators?
- decreased oxygen - hypoxia and initiate vasodialation
- increase carbon dioxide - hypercapnia and initiated vasodialation
- increased acid - acidosis and iinitiate vasodialation
- increased potassium - hyperkalemia and initiate vasodialation
- increased osmolarity - initiate vasoconstriction
- adenosine release - initiate vasodialation
- prostaglandi release - different protsglandins will initiate different responses
venous pressures are low at the heart level.
true or false
true - approximately 10 mmHg
which has higher venous pressure, the foot or the vena cava?
the foot
does the cross section of blood vessels maintain its form even in an absence of pressure? why?
yes because the coat of collagen on the outside limits the maximum diameter changes
at rest, skeletal muscle recieves about 15% of cardiac out put but goes to _____- during exercise
64%
why does the blood supply to the heart and skin increase during exercise?
for increasing the cardiac output and for radiating the heat generated during exercise
why does blood supply to the digestive system and kidneys decrease suring exercise?
to send more blood to skeletal muscle
what is a decrease in oxygen content referred to as?
hypoxia
what is an increase in carbon dioxide content referred to as?
hypercapnia
what is an increase in acid referred to as?
acidosis
what is an increase in potassium concentration referred to as?
hyperkalemia
endothelial cells play an essential role in regulating ________
arteriolar diameter
how do endothelial cells regulater arterolar diameter?
- release chemical mediators
- release locally activating chemical messengers in response to chemical changes in the environment
- Endothelian-1 type A causes vasoconstriction in
- endothelian-1 type B causes no release
NO is one of the most studied ___-
local vasoactive mediators
what are the functions of endothelial cells?
- line the blood vessels and heart chambers like a physical barrier between blood and vessel wall
- secrete vasoactive substances for relaxation or contraction
- secrete substances to stimulate new vessel growth and proliferation of smooth muscle cells
- participate in material exchange between blood and surrounding tissue
- influence formation of platelet plus, clotting, and clot dissolution
- participate in the determination of capillary permeability by contracting to vary the size of the pores between adjacent endothelial cells
ACh stimulation of ________ cells causes an influx of _______- into fluo-4 loaded ______- cells which result in flourescence.
the decrease in _________ in the surrounding smooth muscle causes _________
endothelial
Ca2+
endothelial
CA2+
vasodialation
what are the functions of NO?
- causes relaxation of arteriolar smooth musclr - control of blood flow through tissues and maintaining mean arterial BP
- dilates the arterioles of the penis and clitoris
- acts as chemical warfare against bacteria and cancer cells via release from macrophages, large phagocyte cells of the immune system
- interferes with platelet function and clotting at vessel damage sites
- serves as a neurotransmitter
- plays a role in the changes underlying memory
- helps regulate peristalsis by promoting relaxation of digestive tract smooth muscle
- helps keep airways open to facilitate movement of air in and out of lungs by relaxing thr smooth muscle cells
- modulates the filtering process involved in urine formation
- directs blood flow to oxygen-starved tissues
- relaxation of skeletal muscle
heat leads to ____
vasodialation
it is used in the skin to shed heat from the body core
flushing/reddening
cold leads to ____
vasoconstriction
preserves core heat
frost bite
people with raynaud’s syndrome experience more sensitivity to the cold which in turn leads to greater degrees of ____
vasoconstriction
what does shear stress refer to?
the forces exerted on the endothelial cells as blood passes over it
increasing sheer stress causes _______
vasodialation - partially through NO
in a blood vessel wall, sudden increase in aarterial pressure ___________ the cells and as a result, cell contractions will reduce the radius of the vessels
stretches
what is reactive hyperanemia?
an increase in blood flow that occurs after the occlusion of a blood vessel.
the degree of vasodialation is proportionate to the oxygen debt created during the stopped flow
what is pressure autoregulation?
- intrinsic mechanisms that maintain a constant level of blood flow over a specific range of pressures
- blood flow is kept constant by mechanisms that adjust the radius in order to alter resistance in response to a change in pressure
what is autoregulation critical for?
functions of the kidneys, brain and heart
what are the influences of norepi on smooth muscle?
- brain arterioles do not constrict with norepi
- smally coronary vessels do not constrict with norepi
- no parasympathetic innervation to arterioles
norepi and epi can influence the ____________- control center in the medulla
cardiovascular
sympathetic stimulation of the adrenal medulla influences…
vasopressin and angotensin 2 to maintain body’s fluid balance
what do vasopressin and angiotensin 2 do?
maintain body’s fluid balance
vasopressin and angiotensin 2 are potent ___________
vasoconstrictiors
receptor alpha1 is located __________ and recieves _________ from sympathetic fibers and adrenal medula and results in the ___________ response
in all arteriolar smooth muscle except the brain
norepi
vasoconstriction
receptor beta2 is located ______ and recieves _______ from the adrenal medulla and results in the __________ response
arteriolar smooth muscle in the heart and skeletal muscles
epi
vasodialation
capillaries maximize what factor to be the site of exchange between blood and surrounding tissue cells?
surface area
there are ________ in capillary walls to passs water soluble substances
pore
plasma proteins ___ cross the capillary wall
cannot
lipid soluble substances pass through the capillary wall via ____
endothelial cells
how are exchangeable proteins moved across the capillary wall?
vesicualr transport
to support increased metabolic demands capillaries are _____ to support RBC flux
recruited
endothelial cells produce NO using an enzyme called __________
NO synthase
there are 3 types of NO synthases, what are they?
endothelial NO synthase (eNOS)
neuronal NO synthase (nNOS)
inducible NO synthase (iNOS)
eNOS oxidises what amino acid into NO?
L-arginine
the ________ artery has the lowest innervation of sympathetic fibers
gracilis feed artery
there are 3 different types of capillaries, what are they?
continuous
fenestrated
sinusoidal
what is a continuous capillary?
has very little gaps between adjacent endothelial cells which leads to limited exchange through the pores
what is a fenestrated capillary?
the endothelial cells have large pores which facilitae the movement of large molecuels from the vasculature to the extracellular spce
what is a sinusoidal capillary?
endothelial cells feature large gaps between cells which requires the movement of even bigger molecules out of the vasculature
- usually liver and lymph node tissue
froms most to least, how is the volume of blood is the circulatory system distributed?
- systemic veins
- systemic arteries
- pulmonary vessels
- heart
- systemic capillaries
- systemic arterioles
what factors effect venous return?
- driving pressure from cardiac return
- sympathetically induced venous vasoconstriction
- skeletal muscle activity
- effect of venous valves
- respiratory activity
- effect of cardiac suction
what are the most common sites of varicose veins?
lower limbs
esophagus
anal canal
what happens to varicose veins? (symptom)
affected vein and surrounding tissue become inflamed and painful
what causes varicose veins?
leaky venous valves
describe inhalation;
- increased abdominal pressure pushes on the inferior vena cava
- the venous valves ensure unidirectional flow towards thorax
- reduced pressure in the thorax creates suction
describe exhalation;
- reduced pressure in the abdomin, it is easier for blood to go up the vena cava
- increased pressure in the thorax compresses thoracic vena cava to push blood to the right atrium
ISF resembles __________ in composition
plasma
80% of ECF is _________
20% of ECF is _________
ISF
plasma
the walls of capillaries are ________
highly permeable
capillary BP is denoated by?
Pc
what does capillary bP refer to?
fluid or hydrostatic pressure exerted on the inside of the capillary walls by blood
- 37 mmHg arteriolar end
- 17 mmHg venular end
how is Plasma-colloid osmotic pressure denoted?
(pi)p
what is plasma-colloid osmotic pressure?
forces caused by the colloid dispersion of the plasma proteins. protein concentration tends to be higher in the plasma so this force directs fluid into the capillaries
- 25 mmHg
how is interstitial fluid hydrostatic pressure denoted?
PiF
what is interstitial hydrostatic pressure?
the pressure exerted on the outside of the capillary wall by ISF. tends to push fluid into the capillaries
what is interstitial fluid-colloid osmotic pressure deonted by?
(pi)iF
what is interstitial fluid-colloid osmotic pressure?
colloid dispersion of plasma proteins inn the ISF, tends to pull fluid out of the capillaries
bulk flow of ISF occurs any time there is _________
a net + or - exchange pressure
bulk flow is critical is ___________
regulating the distribution of extracellular fluids between plasma and interstitum
- maintains normal balance of plasma and ISF
following a hemorrhage, a fall in Pc promotes ________
reabsorption of ISF
bulk flow can lead it excess ISF volume in _________
edema
what is the lymphatic system?
the network of vessels that start with blind-ends and end with a single connecction to the venous circulation
an accessory route for returning fluid from interstitial to blood
what is lymph
interstitial fluid that has entered the lymphatic system
how does lymph enter the vessel?
fluid pressure on the outside of the vessel pushes the endothelial cells free edge inward permitting its entrance
why cant lymp escape?
fluid pressure on the inside of the vessel forces the overlapping edges together
what is edema?
swelling of tissues that occurs when there is too much ISF
what are the possible causes of edema?
- reduced concentration of plasma proteins (loss of proteins from urine in kidney disease, reduced synthesis from liver disease, diet, large burn)
- increased capillary wall permeability (histamine release from injury or allergy)
- increased venous pressure (congestive heart failure, pregnancy)
- blockage of lymph vessels (lymph node removal)
