Arteries carry oxygenated blood away from the heart to all parts of the body.
Veins return deoxygenated blood back to the heart.
Capillaries are tiny vessels where exchange between cells and blood occurs.
Blood pressure is maintained by the contraction of elastic fibres in artery walls.
Exchange surfaces are adapted for their role by:
high SA:V
thin - small diffusion distance
large surface area - larger area for diffusion to occur over
some adaptations that are not directly affecting the membrane itself
counter current flow - maintains a steepconcentration gradient
Process of fish breathing
Mouth opens, operculum closes and buccal cavity expands increasing the volume of the mouth which brings in water
mouth closes and buccal cavity constricts decreasing the volume and increasing the pressure which forces the oxygen rich water to pass through gills over the lamellae where gas exchange takes place and out the now open operculum
The ways the gills of a fish are adapted for gas exchange?
the gill arch has many gill filaments and lamallae that are wide and thin to maxmise the rate of diffusion, by decreasing diffusion distance, and increasing the area that it can occur over.
Counter current flow: the blood flows opposite to the direction the oxygenated water enters which ensures a steep concentration gradient and allowing to reach a blood oxygen saturation rate upto 100%
Blood is pumped straight from the heart to the open body cavity and comes into direct contact with cells where exchange takes place and returns to the heart through an open vessel
Found mostly in insects where their blood is called haemolymph and transports food and waste
Substances dissolved in plasma diffuse out through the capillary walls except red blood cells and proteins as they are too large and the fluid between the capillary and cells is the tissue fluid
Blood is under pressure from being pumped out near the arteries
This is called hydrostatic pressure which is greater than the oncotic pressure and causes fluid to leave the plasma to form tissue fluid and exchange takes place between the fluid and cells
Tissue fluid that does not return to the vessel is known as lymph fluid and drains into lymph capillaries, they also pick up fatty acids from the vili of the intestines, they eventually are transported through one way valves and the squeezing of body muscles back into the blood. along the way there are lymph nodes that contains lymphocytes that produce antibodies that are needed and can intercept and pathogens that happen to be in the lymph.