lecture 16: hemodynamics (blood vessels and flow) Flashcards
hemodynamics
describes flow of blood through circulatory system
blood vessels and flow
blood composition
8% of our body weight
plasma
buffy coat —> leucocytes
erythrocytes
plasma
55% of blood composition
90% water
electrolytes (salts)
small organic molecules
has proteins (7%)
—-albumin (55%): made in liver, help to maintain capillary osmotic pressure
—-immunoglobulins: antibodies
—–fibrinogen: made by the liver, clotting factors
buffy coat of blood
leucocytes —> white blood cells
platelets
both made in the bone marrow
erythrocytes
red blood cells
carry oxygen, make hemoglobin (protein) it binds to
made in the bone marrow
make sure your tissues get enough oxygen
anemia
low RBC count
not enough O2 carried to the tissues
low hematocrit
can be caused by low hemoglobin concentration even with normal RBC count
fatigued
hematocrit
look at this to assess O2 carrying capacity of the blood
[RBC volume/ total volume] x 100
total volume is 10
normal —-> women: 38-46%, men: 42-54%
almost 1/2 of blood made out of RBCs
put blood in graduated capillary tube, goes in centrifuge, denser part moved to bottom (RBC) and less dense fluid on top (plasma), buffer coat (WBC) in middle
polycythemia
high hematocrit
having 100% is not good
blood very dense, very viscous
heart will have to work very hard to move blood
creates resistance
artery
carries blood away from the heart
vein
carries blood towards the heart
pulmonary circulation
blood from pulmonary artery goes to —-> lungs to have blood exchange oxygen with air in alveoli —–> get arterial blood —–> pulmonary veins —-> L. atrium —-> L. ventricle —> aorta —-> tissues
systemic circulation
blood from aorta —-> all tissues —-> back to vena cava
coronary circulation
carries oxygenated blood to the heart
gives nutrients/O2 to the heart
venous blood moves through coronary veins into venous circulation
blood flow pressure changes
goes from areas of high to low pressure
pressure created by contracting muscles/ventricles that is transferred to blood
driving pressure created by ventricles
flow from a tube is directly proportional to the pressure gradient (change in P = P1 - P2)
the higher the pressure gradient = the greater the fluid flow
ex: 100 mmHg —–> 10 mmHg is larger blood flow than 100 mmHg —-> 50 mmHg
Ohm’s law
describes the flow of blood
Q = change in P/R
flow rate = pressure gradient/resistance to flow
larger pressure gradient —-> larger flow rate
larger resistance —-> lower flow rate
resistance
tendency of the cardiovascular system to oppose blood flow
inversely proportional to blood flow
aorta
largest BP, coming straight from the heart
vena cavae
lower BP, almost 0, no pressure
driving force decreases
furthest from the heart
highest resistance
blood has fiction against walls of blood vessels
what causes blood flow from vena cavae
blood that comes after pushes blood in front back into R. atrium to be pushed again
vein vasoconstriction by sympathetic NS
skeletal pump
help with venous return too
Poiseuille’s Law
R = [8(viscosity)(length)]/[(pi)(radius^4)] or proportional to R = [(viscosity)(length)]/[(pi)(radius^4)]
resistance increases as length increases (doesnt really change over time)
resistance increases as viscosity increases (can change but not immediately, longer process, can change with hematocrit)
resistance decreases as radius increases (most important determinant of resistance, can change within seconds)
——-vasoconstriction and vasodilation
——-smooth muscle relaxation and contraction
vasoconstriction
decrease in blood vessel diameter/radius
decrease in blood flow
vasodilation
increase in blood vessel diameter/radius
increase in blood flow
blood vessel structure
tunica intima
tunica media
tunica externa
tunica intima
innermost part of blood vessel, in contact with lumen/blood
endothelial cells
basement membrane (anchors endothelial cells)
glues cells together
tunica media
circular smooth muscle
affects resistance
vasoconstriction and vasodilation
tunica externa
elastic fibers and connective tissue
aorta and arteries
ensure continuous flow of blood through circulatory system
pretty hard to expand as potential energy is stored in aorta during contraction
L ventricle relaxes —> no more pressure pushing blood in aorta
lots of elastic fibers, elastic recoil
aorta as biggest blood vessel
elastic recoil
characteristic of aorta and arteries
goes back to normal shape, cause blood to go forward, prevents back and forth
SL valve closed
arteriole
less elastic, not as much elastic fibers in tunica externa
several layers of smooth muscle
resistance blood vessels —-> significantly able to vasoconstrict and vasodilate
capillaries
one cell thick endothelial cells
due to diffusion, exchange blood vessels
no smooth muscle
lowest velocity of flow
WBCs too big to go through
venules
convergent pattern
smooth muscle in larger ones
veins
relatively thin walled
easy to stretch
metarterioles
not completely surrounded by smooth muscle like arterioles
WBCs too big to go through capillaries so they go through these instead
have continuous blood flow even though capillary bed is closed sometimes
precapillary sphincters
rings of smooth muscle
between arterioles and veins
precapillary sphincters open
blood flow from arteriole through capillary bed, through capillaries to the venules
precapillary sphincters closed
blood bypasses capillaries
no pathway for them
blood goes straight from arterial to the venal through metarterioles which has continuous flow
some blood flows through even with closure
continuous capillaries
most common type of capillary
connective, neural, muscle tissues, etc.
endothelial cell tight junctions at capillary wall have some material that will leak out/into the capillaries
allow water and some small dissolved solutes to pass
fenestrated capillaries
in liver and kidney —> need bulk movement in and out of them
endothelial cell tight junctions
capillary wall has bigger gaps or pores to allow for more material to move in/out of capillaries
more permeable
capillary exchange
bulk flow
filtration
absorption
bulk flow
mass movement of fluid and materials as a result of hydrostatic or osmotic pressure gradients
filtration
fluid movement out of capillaries, some solute too
1. capillary blood pressure (Pc)
2. oncotic interstitial pressure (pi i)
net filtration at arterial/beginning end
capillary blood pressure
Pc
correlated to BP —-> increase in BP = increase in flow rate to capillary bed = increase Pc
hydrostatic pressure —> blood against walls of capillaries
hydrostatic pressure
pressure exerted by fluid against walls of a compartment
oncotic interstitial pressure
pi i
other force causing filtration in capillaries
solutes in interstitial compartment generating pressure and “sucking” up fluid to capillary
absorption
fluid movement into capillaries
1. oncotic capillary pressure (pi c) —> albumin
2. interstitial tissue pressure (Pi)
net absorption at venous/end of capillary
oncotic capillary pressure
pi c
albumin is main solute causing this (protein made in liver)
due to solutes inside capillary
cant move because theyre too big —> suck fluid into capillary to cause absorption
interstitial tissue pressure
Pi
pressure generated by interstitial fluid
pushing against walls of capillary and pushing fluid back in
Kwashiorkor
severe malnutrition cause by lack of protein intake
liver doesnt have the proteins to make albumin
symptoms —> edema/swelling in abdominal area, ankles, feet, underneath jaw, poor wound healing, poor growth
filtration > absorption
low oncotic capillary pressure (pi c) moving fluid back into capillaries
marasmus
inadequate energy intake in all forms (no food intake)
symptoms —-> reduced muscle mass, skinny, no edema, lethargy
edema
filtration/absorption not balanced OR lymphatic system not working properly
normal exchange between circulatory system and the lymphatic system is disrupted
fluid pushing against walls and not being absorbed correctly
accumulation of fluid in tissues —-> swelling
increasing hydrostatic/capillary pressure
two main causes of edema
- inadequate drainage of lymph: obstruction of the lymphatic system (parasites, cancer)
- filtration greater than absorption
three ways filtration > absorption
- increase in hydrostatic pressure (elevated venous pressure, caused by heart failure)
—–Pc
—–ex: heart failure, R. ventricle not pumping blood properly, even when L. ventricle is working
——backup of pressure, excessive blood in venous circulation, higher BP and capillary pressure
—–increase in filtration - increase in interstitial proteins (pi i)
—–affects sucking things out - decrease in plasma protein concentration (severe malnutrition or liver failure)
—–absorption decrease, cant keep up with filtration (stays the same)
—–cant produce albumin
—— pi c affected
lymphatic system
blind end lymph capillaries
return fluid and proteins to the circulatory system
serve as filter for pathogens (immune function)
lymph vessels pick up whatever filtration doesnt
—-filters pathogens, preventing accumulation of fluid in interstitial compartment
Starling equation
ultrafiltration
flux = K[(Pc + pi i) - (Pi + pi c)]
flux = filtration coefficient [(capillary pressure + oncotic interstitial pressure) - (interstitial pressure + oncotic capillary pressure)]
flux = K ( what is forced out - what is forced in)
flux = amount of fluid moving out of capillaries
K = filtration coefficient, constant for each tissue, how easy it is for fluid to move out of capillary (ex: brain has small K)
Pc is only value that changes, HIGHER at arterial end
flux is positive
fluid leaves the capillary
net filtration
forces out > forces in
flux is negative
influx of fluid into the capillary
net absorption
forces out < forces in
ex of flux calculations
arterial flux = [(30 + 8) - (0+25)] —> 13 mmHg = net filtration (more moving out than in at beginning of capillary)
venous flux = [(15+8) - (0+25)] —-> - 2 mmHg = net absorption (mainly fluid moving in, bringing back into circulation, dont want fluid in interstitial compartment)
