Biology 2.3 Transport Systems in Animals

Single circulatory systems

blood passes through the heart once during one circuit of the body

double circulatory system

blood passes through the heart twice during one circuit

Circulation in a fish

The heart pumps deoxygenated blood to the gills. Oxygenated blood is then carried to the tissues before returning to the heart

Circulation in mammals

double

pulmonary to lungs

systemtic to body

right side of the heart

pumps deoxygenated blood to the lungs

left side of the heart

pumps oxygenated blood to the body tissues

advantages of a double circulatory system

separate circulation to the body and the lungs.

oxygenated and deoxygenated blood is separated

High blood pressure is maintained to the body tissues which leads to greater oxygenation

artery

Transport blood from the heart to the body tissues

vein

Transport blood from the body tissues

back to the heart

capillary

Facilitates the exchange of substances between the blood and body tissues

semi lunar valves

prevent backflow of blood in veins

where is the highest blood pressure

aorta and arteries

a rhythmical rise and fall in pressure is found here which corresponds to the contraction and relaxation of the ventricles

Arterioles

adjust their diameter to control blood flow. Pressure depends on whether the arterioles are dilated or contracted

reason for low pressure in capillaries

allows time for the exchange of substances

pressure in veins

low

valves

forced open due to an increase in blood pressure as the atria or ventricles contract

tendons are attached to the valves to prevent the valve turning inside out

cardiac cycle

sequence of events which makes up one heartbeat

Atrial systole

Atria contract
Blood flows through the atrio-ventricular valves into the ventricles

the pressure developed during this contraction is not very great due to the thin atrial walls

backflow is prevented by the valves closing

Ventricular systole

Ventricles contract

Atrio-ventricular valves close

Semi-lunar valves in the aorta and pulmonary artery open
Blood flows into the arteries
Thick muscular walls generate greater pressures in the ventricles

The left ventricular wall is particularly thick and strong as it has to pump blood around the entire body

ventricular diastole

The heart muscle relaxes and pressure in the ventricles drops.
Semi-lunar valves snap shut to prevent backflow of blood from the arteries

diastole

The whole of the heart muscle relaxes

Blood from the veins flows into the atria

SA node

a wave of electrical activity spreads out over the atrial walls

This causes contraction of the atrial wall at the same rhythm as the SAN

AV node

causes a delay between contraction

How do the ventricles contract

the AVN passes the impulse down the bundle of His

the bundle of His branches, forming Purkinje tissue

The electrical impulse is transmitted to the apex

The electrical impulse spreads outwards and upwards from the apex, through the ventricle walls causing the ventricles to contract

ECG

electrocardiogram

tissue fluid

bathes the cells, supplying them with glucose, amino acids, fatty acids, salts and oxygen. Tissue fluid also removes waste materials such as carbon dioxide and urea from the cells