Vascular System

Structure

veins

Functions

carry blood through the body

deliver oxygen and nutrients to the body tissues

remove waste products

(with heart & lungs) ensure there is adequate supply of oxygen during exercise

capillaries

arteries

smaller lumen

thick smooth muscle layer

elastic outer layer

smooth inner layer

less elastic outer layer

wider lumen

thin smooth muscle walls

valves

thin

dense network

semi-permeable membrane

one cell thick

pre-capillary sphincters

venous return

return of blood to right side of the heart via the vena cava

mechanisms

pocket valves

gravity

skeletal muscle pump

smooth muscles

respiratory pump

suction pump of heart (diastole)

  • pressure changes in thoracic cavity
  • muscles contract and relax when breathing
  • muscles contract
  • veins between muscles are compressed
  • blood squeezed back to heart
  • changes in pressure compress veins
  • assisting blood return
  • prevent backflow of blood

transportation and storage of blood gases

oxygen

carbon dioxide

attaches to haemoglobin

oxyhaemoglobin

dissolves in blood plasma

dissolves in blood plasma

form bicarbonate ions

attaches to haemoglobin

carbominahaemoglobin

attaches to myoglobin in muscle

myoglobin has higher affinity for oxygen than haemoglobin

stores oxygen and transports to mitochondria

A-VO2 Diff (Arterio-Venous Oxygen difference)

difference in oxygen concentration in arteries to veins

vascular shunt (redistribution of blood)

vasodilation

pre-capillary sphincters

vasoconstriction

vascular shunt

contraction of vessels that narrows lumen

relaxation of vessels that widens lumen

ring of muscle wrapped around outside of start of capillaries

squeezing/directing blood flow to where it is needed

control of blood flow (vascular shunt)

  • impulse sent to vasomotor control centre
  • receptors (chemoreceptors, baroreceptors, proprioceptors)

sympathetic nervous system

sympathetic nervous system

  • increase impulse firing
  • decrease impulse firing
  • vasodilation of arterioles
  • relax and open pre-capillary sphincters
  • vasoconstriction of arterioles
  • contract and close pre-capillary sphincters

Oxy-haemoglobin dissociation curve

dissociate

'to leave'

when oxygen leaves haemoglobin, enters muscle (myoglobin)

blue line

when PPO2 is high, Hb will be fully saturated

when PPO2 is low, Hb will be less saturated

green line

during exercise

BOHR SHIFT

line shifts to the right

causes:

increase concentration of CO2

increase in blood acidity, more hydrogen ions

increase in temperature