Download The circulatory system

The circulatory system
The circulatory system can be greatly affected by the type and amount
of training a person does and therefore has to be considered very closely
compared to other body systems.
The main functions of the circulatory system are:
●
TranspOrt- carrying blood, water, oxygen and nutrients
throughout the body, and transport the removal of waste.
●
BOdy temperature cOntrOl- the blOOd absOrbs the bOdy heat then
carries it tO the lungs and tO the skin, where it is then released.
●
PrOtectiOn- it helps tO fight disease, e.g. antibOdies, which fight
infectiOn, are carried in the blOOd and the clOtting Of seals cuts and
wOunds.
The circulatOry system has fOur main parts:
The heart
● The blood vessels
● The blood
● The pulmonary and systemic circuits.
●
The heart
l.
The blood enters the right-hand atrium. The blood is
deoxygenated.
2. The right atrium pumps this blood into the right ventricle.
3. The right ventricle pumps the blood through the pulmonary
artery to the lungs where oxygen is picked up.
4. The blood then returns to the left atrium through the pulmonary vein.
5. The left atrium pumps the blood into the left ventricle. The
blood leaves here through the aorta to be distributed to the
rest of the body.
From here the blood looses its oxygen because it is used for other bodily
functions. The cycle then takes place all over again.
Blood vessels
Arteries- These carry blood at high pressure away from the heart; these
are the thickest blood vessels. The artery has an inner lining called the
endothelium, then a layer of involuntary muscle and elastic fibres so
the artery can expand and contract. There is an outer layer of tough
fibrous tissue. The aorta is the largest artery in the body this divides into
arterioles then into capillaries.
Capillaries- These are so small they are only one cell thick, because of
this they are semi- permeable and allow things to pass through the
wall. Capillaries are found in clusters and feed the muscles and organs.
At the end of the capillaries the blood flows into veins.
Veins- The structures of veins are the same as arteries but they are
smaller; the fibrous tissue and involuntary muscle is smaller. The veins
pump blood back up to the heart; they have valves to stop the blood
from flowing backwards. The skeletal pump also helps the
blood in veins. Arteries near the veins push against them when a surge
of blood goes through them, gravity assists veins above the heart, the
action of breathing causes pressure changes and as the heart pumps, it
also causes a sucking action that affects veins close to the heart.
The blood
Cells make up 45 percent of blood and are it `solid section'. There are
three types:
Red blood cells (erythrocytes)- there are many of these and give the
blood its red colour. These are produced in the bone marrow and
contain haemoglobin. Red blood cells transport oxygen and carbon
dioxide. Up to 2million red blood cells are produced and destroyed every
second.
White blood cells (leukocytes)- there are less of these than red blood
cells but are also produced in the bone marrow in the lymph tissue. Their
main function is to fight against infection. Pus in wounds is formed by
dead white blood cells.
Platelets- these help to clot the blood and seal the skin. These are
fragments of larger cells. Platelets do the same on small blood vessels.
Plasma forms the remaining 55 per cent of the blood. This is the
`liquid section' and is mainly composed of water. It contains fibrinogen
protein (which helps to clot), nutrients such as glucose and amino acids,
waste products such as urea and some carbon dioxide and oxygen.
The pulmonary and systemic circuits
The pulmonary circuit carries deoxygenated blood through the heart to
the lungs where it exchanges carbon dioxide for oxygen to become reoxygenated. The pulmonary vein transports oxygenated blood to the
left atrium of the heart.
The systemic circuit carries oxygenated blood through the aorta from
the left ventricle of the heart to all over the body, through capillaries.
Having deposited most of the oxygen the blood flows back through
the veins, into the right atrium through the vena cava. In this circuit
the blood visits the cardiac muscle of the heart, the stomach, the
intestines and liver, the muscles and skin. Oxygen transported through
this system is vital for physical activity.