Circulatory Systems

Mammals have a closed system, with;

a double pump3 types of tubes

a liquid moving one way

Functions of the Circulatory System

• Transports oxygen and nutrients from where it enters blood to all body cells

• Transports carbon dioxide and other wastes from body to where they are removed

• Transports hormones and antibodies around body• Prevents blood loss by clotting• Kills germs• Controls the amount of fluid in tissues• Helps control body temperature

The Heart• A double pump to move blood through blood

vessels• Left side stronger than right• Made from Cardiac Muscle• 4 chambers: 2 atriums ( auricles) above and 2

ventricles below• 4 valves, to stop backflow• Cardiac muscles contract due to electric impulses

that pressurize the blood.

Blood flow in summary

Left ventricle – aortic valve - aorta – body – vena cava – right atrium (auricle) – tricuspid valve – right ventricle – mitral (bicuspid) valve - pulmonary artery – lungs – pulmonary vein – left atrium (auricle) – pulmonary valve - left ventricle … and so on…

Heart beat (pulse rate) control• The heart beat and pulse rate is controlled by an electrical

signal from the sinus node, located in the upper right atrium. • From the sinus node, the electrical signal spreads across the

2 atria, causing them to contract, and to push their load of blood into the ventricles. The signal then causes the 2 ventricles to contract and push the blood out of the heart towards the lungs and body tissue.

• This signal controls the number and sequence of heart contractions and assures the heart works as efficiently as possible.

Blood vessels3 main types:

• Arteries: carry blood away from the heart, thick walled, under high pressure (arterioles link to capillaries).

• Veins: carry blood back to the heart, thinner walls than arteries, larger internal diameter, valves stop back flow (venules link to capillaries).

• Capillaries: smallest vessels, fluid leaks out of capillary walls to bathe the surrounding tissue cells to exchange gases, nutrients, wastes and kill germs

Blood

Blood Components• Red Blood Cells (RBC) – full of haemoglobin (an iron based

molecule) which carries oxygen, disc shaped cells with no nucleus so cannot self-repair, made in bone marrow.

• White Blood Cells (WBC) – protects body against disease, cells with a nucleus, no haemoglobin, can move through capillary walls into tissues, made in bone marrow.

• Plasma – 90% water, part of blood that RBC, WBC, platelets, nutrients and wastes travel in, carbon dioxide dissolves in as bicarbonate.

• Platelets – involved in blood clotting, also made in bone marrow