blood vessels Flashcards
anatomy of arteries
adventitia- structural strength and holds vessels in place (has small vessels called vasavorum in large vessels)
elastin- mechanical strength, stretch and recoil
endothelium- blood, body interface that filyters and secretes vasoactive products
smooth muscle- contractile power and regulates lumen diameter
pre capillary sphincter- controls blood flow to capillary beds
role of arterioles with MAP
alter levels of resistance to blood flow to distribute blood to where its needed without disturbing MAP
active hyperaemia
- what is it
- process
- chmical changes when metabolic rate increases
- increased blood flow to satisfy the metabolic needs of a tissue
- increased metabolic activity - less o2 and more metabolites present - arterioles dilate - increased blood flow
- less o2, increased co2, la (pH falls), k, atp, bradykinin, nitric oxide
flow autoregulation
- what is it
- process
-maintenance of blood flow
-arterial pressure in organ falls, therfore blood flow - so arteriole dilates and blood flow is restored
- vice versa!
how is arterial diameter regulated in a myogenic manner
pressure increases eg. heart beat, muscles stretch, then constrict allowing flow to remain constant
regulation of arterial diameter
- how is arterial smooth muscle in its normal state
- how do arteries relax
- how do sympathetic post ganglionic neurones cause vasoconstriction
- how does the adrenal medulla affect diameter
- examples of local control, vasodilators and constrictors
- in a tonic state (partially contracted)
- withdrawal of sympathetic stimulation (little parasympathetic involvement)
- release norepinephrine which causes vasoconstriction
- secrete epinephrine to blood which causes vasodilation/constriction depending on what receptors it binds to.
- con- internal blood pressure
- dil- less o2, increased co2, k+, h+, bradykinin, nitric oxide, LA
capillary basics
- 2 important things about them
- ficks law of diffusion
- thin so can facilitate diffusion
- have a slow velocity of blood due to largest CSA of all vessels (very numerous and reach all of body) allowing enough time for diffusion to reach equilibrium
- flow of gas= area/thickness x D x (P2-P1)
capillary endothelial cell and basement membrane arrangement (3)
- why important
- continous (no gaps), fenestrated (small gaps), discontinous (larger gaps)
- means exchange can be very selective or flow freely where needed
types of transport (3)
diffusion- o2 + co2
vesicle transport- larger molecules, eg. proteins
bulk flow- water + solutes
fluid balance at capillary level
- filtration and absorption
- what happens when filtration exceeds absorption
-fluid from caps to interstitial fluid when hydrostatic exceeds osmotic pressure.
- fluid from interstitial fluid to caps ehen colloid osmotic exceeds hydrostatic pressure
- tissue fluid accumulates and in dealt with by lymphatic system
veins differences to arteries (9)
- larger volume
- closer to skin
- larger diameter
- have valves
- less elastic tissue and smooth muscle
- thinner walls
- over 60% of blood volume
- pressure about 10mmHg
- veins affected by hydrostatic pressure which opposes flow to heart
pressure and flow
- what is pressure like
- what is the driving pressure for venous return
- what is CVP determined by
- how to change compliance
- low and non pulsatile
- diff between central venous pressure and right atrial pressure
- blood volume and compliance
- sympathetic stimulation releasing norepinephrine to vein smooth muscle causing vasoconstriction, circulating epinephrine and paracrine vasoconstrictors and vasodilators can affect diameter
2 main mechanisms of venous return
- skeletal muscle pump- blood squeezed to heart by surrounding muscles, also ensures CVP increases during exercise.
- respiratory pump- inspiration- diaphragm contracts and moves down increasing volume in thoracic cavity reducing intrathoracic pressure and reducing volume of abdominal cavity increasing intra abdominal pressure, which both increase flow to heart
- expiration- when diaphragm relaxes intrathoracic pressure increases reducing flow to heart.
the lymphatic system
- what does it do
- composition of lymph
- what do lymph nodes do
- collects tissue fluid from interstitial space and returns it to blood at the subclavian veins which join the superior vena cava.
- similar to plasma minus the protein which stays in blood
- filter and trap viruses, bacteria and causes of illness
oedema
- what is it
2 things that cause it
- accumulation of excess fluid in interstitial space when filtration exceeds lymphatic drainage.
- high capillary hydrostatic pressure
- low plasma osmotic pressure
