Circulation

Body In action

SG Biology

What you need to know!

• Substances are transported around

the body, for example from where

they are taken into the body to cells;

or from cells to where they are

removed from the body, by the

circulation system, the heart, the blood

vessels and the blood.

Learning Outcomes

Lesson 1

• To be able to explain the circulation system are a double circulation.

• To label a diagram of the body showing the major blood vessels, saying in each case if the blood is oxygenated of deoxygenated.

• To understand the main features of arteries, veins and capillaries

Why do we need a circulatory

system?

• Transport over short distances is achieved by diffusion, osmosis or active transport.

• Situation in larger organisms is different

• Giant redwoods need to transport water to a height of 100m without the expenditure of energy

Why do we need a circulatory

system? • Cell Metabolism – What do cells need?

– Amino acids, glucose, oxygen

– Removal of waste products

• What is important in determining whether an organism has a transport system? – Size

– Surface area to volume ratio

– Level of activity

Features of transport systems

• Suitable medium to carry materials

• Closed system of tubular vessels

• Mechanism to maintain flow in one

direction

• A mean of controlling the flow of the

transport medium to suit the changing

needs

Types of circulation

• Open circulation

– E.g. insects

• Closed circulation

– Single circulation

– e.g. fish

– Double circulation

– e.g mammals

Circulation System Double Circulation

• The heart is divided into two halves, the left and the right. The blood on the right side does not mix with the blood on the left. So the circulation is in two parts.

• The blood passes through the heart twice in one circuit, this is called a double circulation.

• Blood picks up oxygen in the lungs (oxygenated), and gives up its oxygen to the body cells (deoxygenated).

Double Circulation

Blood Vessels

• The blood flows from the heart to organs through arteries and returns through veins.

• Arteries have thick walls containing muscle and elastic fibres, they carry blood to the organs. – Arteries contract and bounce back to force

the blood along, this bouncing back can be felt as a “pulse” as the blood flows through.

• Veins have thinner walls and often have valves to prevent the back-flow of blood.

Blood Vessels

• In the organs the blood flows

through capillaries.

– These are very narrow, thin-walled

blood vessels, they are only one cell

thick.

– Substances needed by the cells in

body tissues pass out of the blood,

and substances produced by cells

pass into the blood through the walls

of the capillaries.

Learning Outcomes

Lesson 2

• To be able to label a diagram of the

heart

• To take part in a heart dissection,

demonstrating the main parts of the

heart.

• To be able to describe the events in

the cardiac cycle.

The Structure of the heart

Structure of heart aorta

pulmonary vein

left atrium semi-lunar valve

bicuspid valve

tendon supporting valve

left ventricle

muscle

right ventricle

tricuspid valve

right atrium

vena cava

pulmonary artery

The Heart • The heart pumps blood through the

circulatory system all round the body.

• The heart is a double pump.

– The right side collects blood from the body and

pumps it to the lungs.

– The left side collects blood from the lungs and

pumps it to the rest of the body.

Heart Dissection

Valves in the heart • There are three main types of valves in the

heart. These are:

– Semi-lunar valves

• aorta and pulmonary artery

– Tricuspid valves

– Bicuspid valves

• The valves are attached to the wall of the

heart by tendons (heart strings), which

prevent the valves being turned inside out.

What do these valves do?

• Each valve has a particular function – Semi-lunar valves – these prevent

blood sucking back into the ventricles when they stop contracting.

– Tricuspid valve (between the right atrium and ventricle) and bicuspid valve (between the left atrium and ventricle) these prevent blood passing up into the atria when the ventricles contract.

The Cardiac Cycle • Draw a flow chart to demonstrate the

blood flow through the heart.

– Mention which muscles are contracted

– Which valves are open

– Which valves are closed