Mammalian circulatory system : Mammals animals and therefore have small surface area to volume ratios
are large .
This means mammals cannot rely on direct exchange with the environment across their surface to supply the need
for metabolites by the internal tissues .
Circulatory system is
necessary
to transport materials :
Double circulation : blood travels through the heart twice for each complete circuit of the body .
There are two circuits: Pulmonary supplies the lungs
systemic supplies the other intestines and kidneys
organs of the body including ; brain, liver , .
Pulmonary
lungs vein
Pulmonary Arteries transport blood
away from the heart .
artery Blood under high pressure
RA LA elastic fibres allow for stretch and recoil since
they are subject to pressure surges from the heart
inferior
vena ta A thick layer of smooth muscles in their walls to
cava py µ
control distribution and facilitate vasoconstriction and
vasodilation .
A lumen to maintain high blood pressure
narrow
and to cope with high blood pressure .
Fibrous outer layer for protection
Hepatic
.
Hepatic vein
liver
artery
Veins Return blood to the heart
~ Hepatic
portal Blood under lower pressure
vein
wider lumens to facilitate return of blood to the
intestines memetic heart .
vein
Pocket values which close by backward flowing
renal veins
kidneys
artery
blood
being trapped against them to ensure unidirectional
flow of blood .
Fibrous outer layer for protection .
legs - Muscular contraction of surrounding muscles helps
transport blood back toward heart .
Capillaries Walls composed of a single layer of Veins
carry larger volumes of blood due to their wider
squamos endothelium to reduce diffusion distance lumen .
and maintains permeability to enable diffusion .
promote single file passage of red blood cells thereby reducing diffusion distance
' '
Narrow lumen to -
.
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