Circulatory system Flashcards
what’s the function of the circulatory system?
maintain a steep intracellular to extracellular concentration gradient - to deliver nutrients / remove waste from central located cells
primary- distribution of gases and molecules
secondary- fast chemical signalling, loss of heat, mediates inflammatory and host defence
what are the 3 functional parts of the human cardiovascular system?
Pump (heart)
Fluid (Blood)
Set of containers (blood vessles) arteries –> capillaries –> veins
The % of blood supplied to organs can change depending on certain conditions. what are the conditions?
-sleep/awake
-rest/exercise, acceleration/deceleration HR
digestion
-emotional stress, thermal stress
-body position/intrathoracic pressure
Why does the % of blood supply tightly maintained in the cerebral?
Because the brain is sensitive to oxygen deficit
what are the 2 serial circuits in the heart?
Left heart - Systemic circulation
parallel pathways from left to right
usually flows through a single capillary bed
two capillary beds in series e.g. kidneys
capillary beds in parallel and series e.g spleen, intestines and liver
Right heart - Pulmonary circulation
single pathway from right to left side of the heart
functions for different Vasculature
Arteries - the distribution system, under HIGH pressure (major arteries –> minor arteries –> arterioles)
Microcirculation - diffusion and filtration system (capillaries - site of exchange)
Veins - collection system, returns to the heart under LOW pressure (reservoir) - (venules –> minor veins –> major veins)
What are the 3 layers of Blood vessel walls?
intima (tunica interna)
media (tunica media)
adventitia (tunica externa)
What are the 4 building blocks in vascular wall?
Endothelial cells
Elastic fibres
Collagen fibres
Smooth-muscle cells (VSMC - V=vascular)
what happens to vessel radius with branching?
decreases
what properties vary with vessels branching?
Vessel radius decrease with branching
Combined cross-sectional area (CSA) of daughter vessels are larger than parent vessels
Sharpest CSA increase in microcirculation - no change in volume - so velocity decreases
function of vessel relates to structure
What’s the benefit of Collagen and elastic fibres in blood vessels?
varying elastic and collagen fibres determine he distensibility and compliance of vessels
Arteries have low volume capacity, but can withstand large transmural pressure differences
Veins have a large volume capacity, but can only withstand a small transmural pressure difference
What are the properties of Arterioles?
Smooth muscle enables blood flow regualtion to capillary networks
they have terminal regions called metarterioles - the blood can be diverted through them (like a netword shortcut sort of thing)
Precapillary sphincters monitor blood flow to capillary
What are the properties of Venules?
Postcapillary venules - they are porous - act as exchange sites for nutrients and waste
Muscular venues - have thin smooth muscle layer (less muscular that arterioles)
This walls allow expansion - excellent reservoirs for blood
What are the properties of Veins?
Less muscular and elastic - but distensible - adapt to variations in blood volumes and pressure
store blood
What exactly are valves?
they are extensions (flods) of the Tunica Intima inside the vein
what are the properties of LARGE veins?
They have more muscle lining than venules
valves prevent backflow
defective, leaky valves allow backflow and can lead to varicose veins
What do capillaries exchange?
Gases
water
nutrients
waste products
What are the 3 types of capillaries?
Continuous capillary
Fenestrated capillary - contains many more holes that 1
Discontinuous capillary - even more porous
What are the factors that drive Fluid transfer in capillaries?
Hydrostatic pressure - pressure exerted by the blood pushing against the blood vessle wall
Osmotic pressure –> specifically Colloid osmotic pressure = oncotic pressure, due to serum proteins
What is hydraulic conductance (Kf)? what’s the formula?
*Starlings Forces
water permeability of capillary wall
Jv= Kf [(Pc - Pi) - (πc - πi)]
