Animal Transport Systems
Circulatory System
The circulatory system consists of the heart and blood vessels. Nutrients, oxygen, carbon
dioxide and hormones are all transported around the body in the blood.
Heart
The heart is made of cardiac muscle and is divided into two separate sides, each containing
two hollow chambers as shown in the diagram:
Right atrium
Left atrium
Right ventricle
Left ventricle
The muscular wall is thicker on the left hand side of the heart as blood must be pumped
from the left ventricle all around the body.
Blood which is pumped out of the right ventricle is transported to the lungs.
There are 4 valves situated within the heart which ensure the blood flows in one direction and
that there is no backflow.
Blood vessels to and from the heart
Pulmonary artery (blood from the
right atrium to the lungs)
Aorta (blood from the left
atrium to the body)
Vena cava (blood from the
body to the right atrium
Pulmonary vein (blood
from lungs to left atrium)
Blood Flow through the heart
The flow of blood through the heart is summarised as follows:
1. Blood enters the right atrium from the vena cava.
2. Atrium contracts pumping blood into the right ventricle.
3. Right ventricle contracts pushing blood into the pulmonary
artery.
4. Blood is carried to the lungs for gaseous exchange.
5. Pulmonary vein returns blood to the left atrium.
6. Atrium contracts pumping blood into left ventricle.
7. Left ventricle contracts pushing blood around the body via the
aorta
Vena cava
Body
Right atrium
Aorta
Right ventricle
Left ventricle
Pulmonary artery
Lungs
Left atrium
Pulmonary veins
Blood vessels
Arteries
Arteries carry blood away from the heart.
They have thick muscular walls which enables them to withstand the high pressure of
blood being pumped by the heart.
As blood is pumped into the arteries when the heart contracts, the walls stretch and they
recoil when the heart relaxes – this change in the arteries is felt as pulse. Since it happens
with every heartbeat, the pulse rate is the same as the rate of heartbeat.
Veins
A vein is a vessel which carries blood back to the heart.
It has a thinner muscular wall than an artery as the blood flows at a lower pressure.
Veins have valves to prevent backflow of blood.
Artery
Vein
Arteries
Veins
Have thick muscular walls and narrow
channels
Have thin muscular walls and wide channels
Carry blood away from the heart
Carry blood to the heart
Blood is at high pressure
Blood is at low pressure
No valves
Have valves to prevent backflow of blood
Contain oxygenated blood (except the
pulmonary artery)
Contain deoxygenated blood (except the
pulmonary vein)
Capillaries
Capillaries are the smallest and most numerous blood vessels in the body. Groups of
capillaries, called capillary beds are close to all body cells.
Capillary bed
Body cells
Tissue fluid surrounding body cells
Capillaries
In capillary beds, substances are exchanged between the blood and the body cells – oxygen and
glucose pass out of the blood and into the cells and carbon dioxide and other wastes pass out of the
cells and into the blood.
Direction of blood
flow
Oxygen and glucose diffuse from blood to cells
CAPILLARY
Carbon dioxide and wastes diffuse from cells to
blood
BODY CELLS
Capillaries have thin walls and a large surface area to allow efficient exchange of these
materials
Transport of oxygen
Oxygen is transported by red blood cells.
Red blood cells contain a substance called haemoglobin.
In the lung capillaries, where the oxygen concentration is high, haemoglobin binds to oxygen
to make oxyhaemoglobin. Oxygen is carried to the body cells as oxyhaemoglobin.
In other body tissues where oxygen concentration is low, oxyhaemoglobin breaks down into
oxygen and haemoglobin. The oxygen then diffuses into the body cells to be used for
respiration.
Lung capillaries
Oxygen + Haemoglobin
Oxyhaemoglobin
Body capillaries
Respiratory system
The diagram shows the respiratory or breathing system
Rings of cartilage
Cartilage rings around the trachea and
bronchi keep the airways open
Rings of cartilage
Trachea
Bronchi
Bronchioles
Alveoli (air sacs)
Alveoli (air sacs)
The smallest tubes inside the lungs, the bronchioles, end in structures called alveoli or air
sacs. It is in the alveoli that gases are exchanged between the air and the blood.
Features of alveoli that make them efficient for gas exchange
bronchiole
alveoli
capillaries
These features of the alveoli allow efficient
gas exchange:
1. They have a large surface area
2. They have thin walls so gases can pass
through quickly
3. They have a good blood supply (they
are surrounded by capillaries)
Gas exchange in the alveoli
Air sac
capillary
Oxygen from the air in the alveoli dissolves in
liquid lining the alveoli and diffuses into the
blood.
Carbon dioxide diffuses from the blood into the
alveoli and is breathed out.
Mucus and cilia
The trachea is lined with ciliated
epithelium and goblet cells.
cilia
ciliated
epithelium
cells
goblet cell
Goblet cells produce a sticky substance
called mucus that traps dust and germs to
prevent them getting into the lungs.
The cilia beat to sweep the mucus and
trapped dust and germs out of the
windpipe.
Digestive system
The diagram shows the digestive system
Salivary glands
Oesophagus
Liver
Gall bladder
Stomach
Pancreas
Small intestine
Large intestine
Movement of food through the digestive system
Food is moved through the digestive system by a process called peristalsis.
Muscles behind the food contract
Muscles in front of the food relax
Food is pushed through
the digestive system in
this direction
in the
wall of the digestive system behind the food contract to push it through,
ntMuscles
of the food
relax
while the muscles in the wall of the digestive system in front of the food relax.
Absorption of digested food
Digestion of food changes starch to glucose, proteins to amino acids and fats to glycerol and
fatty acids. The digested food is absorbed into the blood in the small intestine.
The small intestine has a large
surface area for absorbing food
because its inner surface has folds
that contain extensions called villi.
Structure of a single villus
The villus is efficient at absorbing food because:
Single layer of
cells lining the
villus
Capillary
Lacteal
1. It has a thin lining (just one cell thick) that
food passes through quickly
2. Its lining cells have microvilli that increase
the surface for absorbing food
3. It has capillaries that absorb glucose and
amino acids
4. It has a lacteal – this is a vessel of the
lymphatic system – that absorbs glycerol
and fatty acids.