Mass Transport Systems in the Human Body

Mass Transport Systems in the Human Body

Living cells require regular supplies of oxygen and nutrients for

metabolic reactions such as respiration. These important materials

such as glucose need to get to living cells and the waste products

such as ammonia and urea need to be removed. This diffusion of

materials into cells and waste products out of cells (which may need

to happen via active transport if it is against the concentration

gradient) can easily happen in small, single cellular organisms as

they have a large surface area : volume ratio and also have a short

diffusion path to all cells so enough material can get to cells

sufficiently quickly.

But as the organism gets larger the surface area : volume ratio

decreases and also the diffusion path increases making it difficult to

get substances to cells in the centre of the organisms and so there is

a need to adapt and so have internal transport systems to keep large

diffusion gradients an adequately supply nutrients to cells and take

away waste products. It is important to have specialised transport

systems so that there is rapid an efficient transport and diffusion of

substances. The more active an organism is the greater the need for a

more efficient transport system to continually supply materials and

take away waste. Hence there is a need for mass transport systems

especially in large organism for efficient diffusion, providing

materials for all cells.

A transport systems allows flow of material ie in humans flow of

blood, and hence as there is a flow there can continue to be a

difference in concentration in materials between cells and the

substance in which the materials are contained/dissolved in, (ie the

cell and its environment) and so allows efficient diffusion of

materials.

It also allows a path to all cells so all cells can take up vital

materials and carry out vital metabolic reactions, for example this

can be seen in blood capillaries, arteries break into arterioles an

the smallest tubes are capillaries which pass directly next to cells,