blood vessels and haemodynamics Flashcards
what does a circulatory system consist of?
fluid for transporting materials
tubes for the fluid to go through
a force to drive the fluid
how can you workout how fast something diffuses?
divide the time of diffusion by the diffusion coefficient
functions of circulation
maintain an optimal environment for cells
transport of nutrients, waste, hormones
artery function
blood away fro the heart in high pressure
capillary functions
exchange of nutrietns and waste between vessels and cells, interstitial fluid exchange
vessesl structures
adventitia
media
intima
what is the adventitia?
fibroblasts and fibrous elements gradually merge with surronding connective tissues
anchors the vessel in place providing mechaninical strength
what is the media?
elastic fibres, collagen fibres, confumferentially arranged smooth muscle
can contract and relax
what is the intima?
endothelial cells
surrounded by sub-endothelium and elastic fibres
barrier to prevent substances moving
what layer is larger in arteries?
media
what are the types of arteries?
elastic
muscular
terminal
arteroiles
whats an elastic artery
convert pulsatile flow into smoother continuous flow
closer to the heart
whats a muscular artery
smooth muscle and less elastic fibres
smaller and give divergence off elastic arties
whats terminal artery
add resistance and regular downstream flow
whats an ateriole
also resistance vessels
control the release of blood into capillaries
key features of veins?
thinner walls
large blood volume
valves present
what are th valves conected to?
the intima
whats a small vein>
venules
endothelial layer surrounded by longitudinal smooth muscle and occasional pericyte
how does blood move in veins?
they are typically positioned next to muscle pumps that squeeze the vessels pushing up the blood
what happens to blood velocity moving away from the heart?
drops
at same time surface area increases
when at the capillaries the velocity is at its lowest
what regulate capillary perfusion?
terminal arteries regulate the number of perfused capillaries
what is vasomotion?
indivivual terminal arteries cycle in contraction and relaxation
this is the time between open and close that determines the amount of blood flow in them
what is a capillary sphincter?
ring of muscle around capillaries which can reduce blood fow by contracting and restricting the flow downstream
what happens to capillary sphinceters under high oxygen
constrict
reducing flow
what happens to capillary sphincters under high carbon doxide
high metabolic rate
needs more oxygen
vessels open
what happens to capillary sphincters under low pH
high metabolic activity
high carbon dioxide
open vessels
what happens to capillary sphincerts under high body temp
vessesl open to move blood to the surface and reduce the temp
three capillary types?
continuous
fenestrated
discontinuous
features of a continuous capillary
highly selective barrier
what is a caveola?
plasma membrane budds off into vesicle to move to inner lining to pass on substances
called caveola facilitated movement
where are continuous capillaries found?
fat, muscle, nervous system
features of a fenestrated capillary
thinner
porous membrane
permeable to small water soluble substrates
where are fenestrated capillaries found?
intestinal wall vili
endocrine system glands
kidney glomeruli
features of discontinuous capillaries
also called sinusoids
have large gaos in them
less selective as there are large gaps within
where are discontinuous capillaries/ sinusoids found?
liver
bone marrow
spleen
what is a pericyte?
cells like stem cells that are dormant around vesses
when there is damage they proliferate to help repair the vessel
how is the circulatory system regulated?
hydrostatic pressure
osmotic pressure
what is hydrostatic pressure?
the pressure the system exerts by the volume of blood when its confined within a vessel
it pushes fluid out of things
what is osmotic pressure
the pressure exerted by the flow of liquid through a semi-permeable membrane separating two solutions with different concentrations of solutes
what causes fluid to leak out?
higher hydrostatic pressure than osmotic
what causes fluid to seep in?
higher osmotic pressure than hydrostatic
where do hydrostatic and osmotic pressures need to be balanced?
at the arteriole end
what does darcy’s law say about blood flow?
flow is proportional to pressure difference
no pressure difference means no flow
flow occurs from high to low pressure
what is laminar flow?
The what’s condition for blood flow throughout most of the circulatory system.
how is laminar flow characterised?
It is characterized by concentric layers of blood moving in parallel down the length of a blood vessel. The highest velocity (Vmax) is found in the center of the vessel.
where is laminar flow found?
arteries
arteioles
veins
venules
what is turbulet flow?
pressure difference above a critical point flow transitions to turbulent flow:
blood does not flow linearly and smoothly in adjacent layers, but instead the flow can be described as being chaotic
the flow now increases as a square root of the pressure difference
where is turbulent flow found?
behind heart ventricles
what is single file blood flow?
the diameter of most capillaeires is less than that of RCB
all RBC line up in single file touching all walls
what reduced friction in single file blood flow
Friction between RBC and wall minimised by glycocalyx/thin film of plasma
why is single file blood flow used?
efficient transport to surrounding tissues as RBC touches all walls of the capillary
at rest which organ gets the most blood flow?
kidneys
at rest which organ gets the least blood flow
skin
at rest how much of cardiac output goes to the skeletal muscles?
20%
what does Poiseuille’s law describe?
the dependence of the vessel diameter
flow is proportional to area and increased area gives more force
what happens to resistance of blood vesles is series?
it adds up:
R1+R2=R
what happens to resistance of blood vessels in paralet?
1/R= 1/R1 + 1/R2
what controls blood flow?
arterioles
what does widespread contraction lead to
increase in peripheral resitance and blood pressure
what intrinsic factors control blood flow?
local factors such as temp myogenic response vasodilator metabolites endothelial factors local hormones
what extrinsic factors control blood flow?
hormones, nerve stimulation
vasoconstrctors
these can override intrinsic
what is metabolic hyperaemia?
s the increase of blood flow to different tissues in the body
what can cause metabolic hyperaemia?
Co2 lactic acid adenisine potassion phosphate osmolarity
what is intrinsic hyperaemia?
after exercise, blood flow to a muscle reamins elevated for a while
why does flow to muscles after exercise remain high for a while?
build up of vasodilator metabolites, protagladins and NO
what is nitric oxide?
diatomic free radical
lipid soluble and small, can pass through membranes
short lived
how is nitric oxide synthesised?
from L-argenine
how does NO cause smooth muscle relaxation?
- stress stimulated by endothelial NO production
- estrogens up regulate synthesis of NO
inflammatory mediators increase NO also
leading to relaxation
what causes smooth muscle contraction?
mechanical stretching
electrical depolarisation
hormones
how does smooth muscle contract?
- ixtracellular calcium increase, triggers release from sarcoplasmic reticulum
- Ca binds to calmodulin
- activated myosin light chain kinase ( MLCK)
- MLCK phosphorylatates heads of myosin increasing ATPase activity
- active myosin chrossbridges slide along actin creating muscel tension
how does smooth muscle relax?
- free Ca in ctosol decreases its pumped back out or into sarcoplasmic reticulum
- Ca unbinds from calmodulin, CaM
- myosin phophatase removes phosphate from moysin decreasing ATPase activity
- less myosin ATPase reseults in decreased muscle tension
