circulation Flashcards
circulation: explain the physical principles, structure and function of the circulation
purpose of circulation
transport blood (containing O2, nutrients, hormones, CO2, metabolites and immunity-related molecules) and regulate temperature
2 components of double circulation
pulmonary and systemic
what does the heart generate to produce circulation
pressure gradient that propels blood through blood vessels (circulation)
features of arteries
low SA, storing little blood but at a high, fluctuating pressure
features of arterioles
lead to capillaries, and site of drop in blood pressure; can be constricted to control flow of blood
features of capillaries
highest total SA, forming networks/beds for diffusion
feature of venules
connect veins to capillary beds
features of veins
hold most blood and at lowest pressure
why are capillaries necessary
tissues oxygenated by diffusion so require short diffusion distance (thin blood vessels) and highly branched structure
structure of walls in small arteries and arterioles
extensive smooth muscle in walls to regulate diameters and resistance to blood flow
structure of walls in venules and veins
highly compliant to act as reservoir for blood volume
2 reasons why pressure falls across circulation
viscous (frictional) pressure losses; small arteries and arterioles present more resistance to flow
what is microcirculation specific to
organs
describe microcirculation
1st order arterioles, covered in smooth muscle, branch off to capillaries via terminal arterioles → enter tissues → precapillary sphincters control blood flow to capillary bed → venules leave tissue to collect blood and deliver to heart
