Circulation and Gas

Exchange

Intermediate 2 Biology

Unit 3

ANIMAL PHYSIOLOGY

Learning Objectives Circulation

• Describe the structure of the heart in

relation to its function as a muscular

pump. (to include the four chambers,

valves, wall thickness and blood

supply)

• State that the heart receives its blood

supply from the coronary artery and

describe what affect a blockage in

this artery would have.

The Heart

• The function of the heart is to pump blood round the body.

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The Heart

• The heart consists of four chambers.

– Atria – two upper chambers

– Ventricles – two lower chambers

The Heart

Right atrium Left atrium

Left ventricle

Cardiac muscle

Right ventricle

The Heart

• The ventricles pump the blood

– Left Ventricle

• Round the body

– Right ventricle

• To the lungs

• The atria receive blood

• valves in the heart prevent the

backflow of blood

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The heart

semi-lunar valve semi-lunar valve

atrio-ventricular valve

atrio-ventricular valve

The Heart

Vena cava

Pulmonary artery Aorta

Pulmonary vein

The Heart

• All blood must pass through the heart

twice in each circulation.

• Deoxygenated blood from the body

enters the heart through the vena

cava into the right atrium.

• Complete the stages of circulation

until the blood is back in the vena

cava again.

The Heart

• Deoxygenated blood passes through

the right AV valve into the right

ventricle.

• Right ventricle contracts and blood is

pumped into the pulmonary arteries

through the semi-lunar valve

• In the lungs the blood loses its carbon

dioxide and gains fresh oxygen before

entering the pulmonary veins.

The Heart

• This oxygenated blood now returns to

the heart and enters the left atrium.

• Oxygenated blood moves through the

left AV valve into the left ventricle.

• The left ventricle then pumps the

blood through the SL valve into the

aorta which takes it around the body.

The Heart

• The wall of the left ventricle is very thick since it has to pump blood all round the body.

• The wall of the right ventricle is less thick since it pumps blood only to the lungs.

The Heart

• The heart wall is made of cardiac

muscle and also requires its own blood

supply.

• The blood vessels which do this are

called the coronary arteries.

Coronary Arteries

Coronary artery

Coronary arteries

• Coronary arteries supply oxygen and

glucose to the cardiac muscle

• Coronary veins return the blood to the

vena cava.

• If the coronary arteries narrow or

become blocked in any way, this can

result in angina, a heart attack or in

severe cases heart failure.

Learning Objectives Circulation

• Give the names and positions of;

pulmonary artery and vein, aorta and

vena cava, hepatic artery, hepatic

vein, mesenteric artery, hepatic portal

vein, renal artery and renal vein.

• Colour in the key and the diagram using

– Blue

• deoxygenated blood

– Red

• Oxygenated blood

Circulatory System Pulmonary artery

Pulmonary vein

Aorta

Hepatic artery

Mesenteric artery

Hepatic vein

Hepatic portal vein

Renal artery Renal vein

Vena cava

Pulmonary artery Pulmonary vein

Aorta

Hepatic artery

Mesenteric artery

Hepatic vein

Hepatic portal vein

Renal artery

Renal vein

Vena cava

Learning Objectives Circulation

• Describe the path of blood flow

through the heart and its associated

vessels.

• Describe the functions of arteries,

capillaries and veins; give structural

adaptations of these blood vessels in

relation to their function.

Blood Vessels

• There are three main types of blood

vessel – arteries, veins and capillaries.

• Arteries carry blood away from the

heart.

• Veins carry blood back to the heart.

• Capillaries connect arteries to veins

and this is where the exchange of

essential materials takes place.

Arteries • Arteries have thick muscular walls.

• This allows them to withstand the

pressure created by the heart.

Arteries

• Pulse

– Each time the heart beats, blood is forced along the arteries

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Veins • Veins have thinner walls than arteries

but a wider cavity.

• This is because the blood is now at a

much lower pressure.

Veins

• Veins contain valves

– prevent the backflow of blood.

Capillaries

• Capillaries are microscopic blood

vessels

Capillaries

• Walls are only one cell thick.

– allows for the exchange of materials between the blood and body cells

– Examples - glucose, oxygen, carbon dioxide

In Summary – the bare minimum

• Blood leaves heart in arteries, flows through

capillaries and returns to heart in veins

• The pulse indicates that blood is pumped through arteries;

• Structural adaptations of arteries, veins and capillaries related to function.

• The heart obtains its blood supply from the coronary arteries.

Learning Objectives Gas Exchange

• Describe the internal structure of the lungs (to include trachea, bronchi, bronchioles, and alveoli).

• Describe the features of the alveoli which allow efficient gas exchange

• Describe the role of diffusion in the exchange of oxygen and carbon dioxide.

• Describe the features of the capillary network which allow efficient gas exchange in tissues.

Gas Exchange

• Gas exchange occurs in the lungs.

• Stages

– Inhalation

– Gas Exchange

• oxygen from the air passes from the lungs into

the blood and carbon dioxide passes from the

blood into the lungs.

– Exhalation

Structure of the Lungs

• Air passes down the – trachea (windpipe) which splits into 2 bronchi

– Bronchi split into smaller tubes called bronchioles.

– bronchioles terminate in tiny air sacs called alveoli.

• The trachea and bronchi are kept open by rings of cartilage – The cartilage stops the airways from

collapsing when the pressure changes

Alveoli

Bronchiole

Alveolus

Blood Capillary

Gas Exchange

• Alveoli provide a large surface area for

the gas exchange

• The lining of each alveolus

– very thin

– Moist

– Surrounded by a capillary network

Gas Exchange

• Blood arriving in the lungs from the body is deoxygenated.

• Oxygen diffuses through the thin lining of the alveolus into the blood capillary

– Diffusion takes place because the concentration

of oxygen in the alveolus is higher than the

oxygen concentration in the blood.

Gas exchange

• Carbon dioxide diffuses in the opposite

direction.

– the concentration of CO2 in the blood from the body is higher than the concentration of CO2 in the alveoli.

• The blood now leaving the lungs is

oxygenated.

Features which make gas exchange more efficient.

Feature Function

Thin lining To allow rapid diffusion

Lining moist Allows oxygen to

dissolve

Large surface area To absorb oxygen

Dense network of capillaries

To absorb and transport oxygen