3.2 Transport in Animals

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3.2 Transport in Animals
Transport ­ the movement of substances such as oxygen, nutrients, hormones, waste and heat
around the body
Three factors influence the need for transport systems:
1) Size
2) Surface area/volume ratio
3) Level of metabolic activity
Features of a good transport system:
A fluid or medium to carry substances around the body e.g. blood, lymph
A pump to create pressure to push fluid round the body
Exchange surfaces that enable substances to enter the fluid (blood) e.g. capillaries
Tubes or vessels to carry the fluid by mass flow
Two circuits, one for collection of oxygen and another for the delivery of oxygen
Single circulatory system ­ one in which the blood flows through the heart only once for each
circuit of the body e.g. heart gills body heart
Double circulatory system ­ one in which the blood flows through the heart twice for each circuit
in the body e.g. heart body heart lungs heart
The blood pressure
must not be too high in the
pulmonary circuit so as not
to damage the delicate
The heart can
increase the pressure after
it returns to the lungs so
that the blood circulates
through the body quickly
The systemic
circulation can carry higher
pressured blood than the pulmonary circulation
Blood Vessels
Artery Adaptions:
Artery walls are thick to withstand high
The lumen is small to maintain the high
The inner layer consists of a thin layer of
elastic tissue that allows the walls to stretch and
The middle layer consists of a thick layer of
smooth muscle
The outer layer is a thick layer of collagen and elastic tissue for strength and to support the
recoil for maintaining pressure.

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Small blood vessels that distribute the blood from arteries to the capillaries
They have a layer of smooth muscle which contracts to increase resistance to flow and
reduces the rate of blood flow
Constriction of arteriole walls is used to divert blood to regions of the body that are
demanding oxygen
Very thin walls consisting of a single layer of endothelium
Narrow lumen to squeeze red blood cells against the wall to aid in the transfer of oxygen
and reduce the diffusion distance…read more

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Oncotic pressure ­ the pressure created by the osmotic effects of the solutes and causes the
movement of tissue fluid into the blood (it has a negative figure and is also measured in kPa)
Structure of the Heart
Blood Pressure
Atria ­ These chambers have relatively thin walls as they do not need to create much pressure
Right ventricle ­ thicker walls than the atria but still not as thick as the left ventricle as the blood
only needs to be pumped as far as…read more

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The intercalated discs facilitate synchronised contraction
The Cardiac Cycle
What Happens
Diastole The muscular walls of all four chambers relax.…read more

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The pressure in the ventricles is now greater than that of the
arteries and so the semilunar valves open to allow blood to flow
into the arteries as the ventricles contract.
Blood enters the aorta and pulmonary artery in a rapid spurt but must be delivered in an even
flow to prevent damage so the structure of the artery walls come into play. The smooth muscle
and elastic fibre layers allow stretch and recoil with each beat of the heart which them lowers the
pressure.…read more

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This means that they contract from the apex upwards, forcing the blood in the correct direction.…read more

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After the first oxygen binds to the haemoglobin the haemoglobin undergoes a slight
conformational change which allows other oxygen molecules to more easily bond to its remaining
haem groups.
Fetal haemoglobin lies to the left of the normal haemoglobin dissociation curve as fetal
Haemoglobin has a higher oxygen affinity that normal haemoglobin as the fetal haemoglobin must
cause the dissociation of the mother's haemoglobin in the placenta and absorb oxygen from the
surrounding fluid as well.…read more

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Carbon dioxide concentration increases
The following increase in cell cytoplasm acidity causes changes in the tertiary structure of the
haemoglobin and reduced its affinity for oxygen
This causes the dissociation of the oxygen to the tissues in order to provide them with it for
This ensures that tissues that are respiring more such as contracting muscles get more oxygen in
comparison to those not respiring as quickly/actively
The Bohr shift refers to the change in the haemoglobin dissociation curve which moves down and
right…read more


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