Flashcards in Mammalian Cardiovascular Deck (102)
at the most basic level, what is circulation responsible for?
delivering vital life substances to body tissues. Including oxygen ,hormones and nutrients and removing waste.
other uses for circulation than delivering and removing substances
immune response, regulation of body temperature and pH, homeostatic functions
which ventricles and atrium of the heart are used for systemic circulation?
left ventricle, right atrium
which ventricles and atrium of the heart are used for pulmonary circulation?
right ventricle - left atrium - left ventricle. (completing double circuit)
features of blood pressures as it passes along systemic circulation
decreases, pulsatile (especially in arteries)
Why is flow continuous despite pulsatile pressure in vessels?
always a forward pressure gradient
what is Poisseullie's law used for?
how resistance to laminar flow changes along circulation
what is the role of arteries?
Distribution vessels (relatively low resistance)
Why do we use Arterial Blood pressure? (ABP)
little loss of pressure as blood passes through arteries, pressure is essentially the same in all large arteries
Diameter of an artery
Why is arteriole total resistance much higher than that of arteries or capillaries?
arteries - much larger diameter, capillaries - much larger number in parallel series.
Uses of arterioles (due to highest resistance)
primary site of control of blood flow in circulation
Why does Poisseuille's law break down for capillaries?
diameter is similar to a red blood cell (-7μm ), allowing for bolus flow.
what is Bolus flow?
erythrocytes travel singularly, separated by segments of plasma. Reduces resistance to flow of blood through capillaries (Fahreus-Linndquist effect)
what is the function of capillaries?
site of exchange between circulation and tissues.
why are all cells close to capillaries?
exchange of substances is primarily by diffusion (X = t2/2D)
why does exchange slow along capillary?
as exchange occurs, between capillaries and interstitial fluid, becomes more similar.
roughly how many capillaries are present per gram of skeletal muscle?
roughly how many capillaries are pursued at rest ?
20-25% (empty and collapsed)
single layer of endothelial cells connected by inter endothelial junctions, surrounded basement membranes.
where do the structure of capillaries differ
in different organs, gives regional differences in permeabilities to different substances. [e.g. in liver allow passage of newly synthesised plasma proteins, in lungs primarily exhange CO2 and O2]
3 types of capillaries
Continuos, Fenestrated and Sinusoidal (discontinues)
why are water movements across a capillary important?
influence both circulating volume and local interstitial fluid volume
driving forces for water movement across a membrane
convective movements (rather than purely diffusive). Hydrostatic pressure difference and effective osmotic pressure difference.
how does capillary pressure (Pc) change along the length of the capillary?
decreases, due to resistance and outward movement of water, is somewhat pulsatile.
when can Pif be negative?
non-encapsulated organs (WRT atmospheric pressure)
what is interstitial fluid?
complex gel of proteoglycans and water within a network of collagen fibres.