7.3: Circulatory system of a mammal Flashcards
What type of system?
a mass transport system
Multicellular organisms
SA:V ratio
low SA:V ratio
Circulatory system
specialised transport system that carries raw materials from specialised exchange organs to their body cells
Circulatory system made up of
heart and blood vessels
Blood transports
respiratory gases, products of digestion, metabolic wastes and hormones
Coronary arteries
supply the heart with blood
Double circulatory system
blood passes through the heart twice in one circuit
Arteries
characteristics in relation to functions
2
thick and muscular walls with elastic tissue to stretch and recoil = maintain high pressure
endothelium is folded = allows it to stretch and helps maintain high pressure
Arterioles
A network of smaller vessels throughout the body.
Arterioles
function
Muscles inside the arterioles direct blood to areas of high demand by contracting or relaxing.
Veins
characteristics in relation to functions
wider lumen, little elastic and muscle tissue = lower pressure
contain valves = prevents back flow of blood
body muscles around veins contract = to help blood flow
Arterioles branch into
capillaries
Capillaries
info.
one cell thick
adapted for efficient diffusion
found near cells in exchange tissues = short diffusion pathway
large number of capillaries = increase SA for exchange
Networks of capillaries in tissue
capillary beds
Tissue fluid is formed from
the blood
Tissue fluid
the fluid that surrounds cells which is made from small molecules that leave the blood plasma
Pressure filtration
substances move out of capillaries into the tissue fluid in the capillary bed
Pressure filtration
overview
at start of capillary bed = hydrostatic pressure inside capillaries is greater than in tf.
difference in hydrostatic pressure = fluid forced out into spaces around cells forming tf.
this reduces hydrostatic pressure in capillaries = hydrostatic pressure lower at venule end
water potential lower at venule end too
water re-enters capillaries from tf. by osmosis
Excess fluid from tissue fluid
drained into the lymphatic system
Lymphatic system
a network of tubes which transports the excess tf. and drains it back into the circulatory system
