Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Topic: Transport in Mammals( Part 1)

At the end of lesson, you should be able to:

Identify the main blood vessels to and from the heart, lungs, liver and kidney.

Describe the structure & function of the heart in terms of muscular contraction and the working of valves.

Outline the cardiac cycle in terms what happens during systole and diastole.

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Double Circulation

Pulmonary Circulation

Systemic Circulation

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Type of Circulation:

PulmonaryCirculation

SystemicCirculation

(i) Pressure Low High

(ii) Destination of blood flow from heart to

Lung The rest of the body

(iii) Walls of the ventricle

Walls of the right ventricle are thinner and less muscular.

Walls of the left ventricle are thicker and more muscular.

(iv) Blood Deoxygenated Oxygenated

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

How does the heart pumps blood?

• When both atrium contract, the oxygenated blood in left atrium is pumped into the left ventricle while the deoxygenated blood in right atrium is pumped into right ventricle.

• When the left ventricle contracts, the aorta carrries oxygenated blood to the rest of the body.

• Simultaneously, the deoxygenated blood flows out of right ventricle to the lungs through the pulmonary artery when the right ventricle contracts.

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Deoxygenated blood from vena cava.

Right atrium Left atrium

Left ventricleRight ventricle

Pulmonary artery Aorta

Lung

enters

The rest of the body

Oxygenated blood from pulmonary vein.

enters

When both atrium contract,blood is pumped into

ventricles.

When both ventricles contract,blood is pumped out of the

heart.

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Events of a Cardiac Cycle

• A cardiac cycle is a complete heartbeat.• It contains 2 main phases: • systole and diastole, which are defined by

whether the ventricles are contracted or relaxed.

• During the cycle, valves open and close, producing the familiar “lub-dub” sound.

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

3

• After a short pause, the ventricles contract. This is called ventricular systole.

• The increase in blood pressure forces the bicuspid and tricuspid valves to close, preventing backflow of blood into the atria. This produces a loud ‘lub’ sound.

• When the pressure in the left ventricle becomes higher than the pressure in the aorta, the semilunar valves are forced open.

• Oxygenated blood flows from the left ventricle into the aorta. As the ventricles contract, the atria relax.

right ventricle

2

left ventricle

right ventricle

1pulmonary vein

left ventricle

left atrium

vena cava

right atrium

aortic arch

3

pulmonary arch

bicuspid valve

tricuspid valve

The Cardiac Cycle

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

• The pressure in the ventricles changes during the cardiac cycle.

• When the pressure of blood in the ventricles is high, it forces the semilunar valves to open. It also forces the tricuspid and bicuspid valves to close.

semilunar valves

tricuspid & bicuspid valves

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

• The pressure in the aorta changes during the cardiac cycle.

• When the left ventricle contracts, the semilunar opens and the blood rushes into the aorta. The pressure of the aorta increases.

semilunar valves

aorta

Prepared By, Mrs Yap-Wong Fui Yen (HKSS)

Parts of the Circulatory System

4

artery

blood flowing from the heart

Veins• The blood vessels that carry blood

back to the heart are called veins.

heart

arteriesarteriolescapillaries

venulesveins

blood flowing back to the heart

vein

a capillary network links arteries and veins

3 Blood capillaries• The microscopic thin-walled (one cell

thick) blood vessels that carry blood from a small artery (arteriole) to a small vein (venule) are called capillaries.

• The thin walls of the capillaries also allow certain substances to diffuse rapidly through the capillary walls.

2 Arteries• The blood vessels that carry blood

away from the heart are called arteries.

1The heart• The heart is a muscular organ which

drives the blood around the body.