Basic 9 · Science · Human Body Systems

The Circulatory System

In this topic you will explain the concept of the circulatory system, state the function of each part and discuss the health challenges associated with it.

By the end of these notes you should be able to:

Identify the parts of the circulatory system
Explain how blood circulates
Discuss health challenges of the circulatory system

What you already know

Blood cells

Copy everything that has a blue line on its left into your notebook. The other parts are for reading.

Lesson 1

Strand: Systems
Sub-strand: Human Body Systems
Indicator: B9.3.1.1.1 – Explain the concept of the circulatory system state the function of each part of the system and the health challenges associated with it

Introduction

Place your fingers on your wrist. Each beat is your heart sending blood on a journey that never stops.

1. The Circulatory System

Circulatory system: The system that transports blood around the body.

Your body's cells need a constant supply of oxygen and food, and they must get rid of waste. The circulatory system acts as the body's transport network. It has three parts: the heart, the blood vessels and the blood.

2. Blood Vessels

Blood vessels

Vessel	Function	Features
artery	carries blood away from the heart	thick walls, high pressure
vein	carries blood to the heart	thinner walls, valves
capillary	exchanges materials with cells	one-cell-thick walls

3. Blood

Components of blood

Component	Function
plasma	carries food, waste and hormones
red cells	carry oxygen
white cells	fight infection
platelets	help clotting

Plasma is the yellowish liquid part of blood. An adult has about 5 litres of blood. Blood also helps to spread heat around the body, and to protect it from disease.

A model of the human heart

Figure 1: Heart model Find your pulse and count the beats.

4. The Heart

Parts of the heart

Part	Function
right atrium	receives blood from the body
right ventricle	pumps blood to the lungs
left atrium	receives blood from the lungs
left ventricle	pumps blood to the body
valves	stop backflow
septum	separates left and right

The heart is a muscular pump about the size of your fist. It beats about 70 times a minute at rest, and more during exercise. The left ventricle has the thickest wall, as it must pump blood around the whole body. Valves make the "lub-dub" sound you can hear through a stethoscope.

5. Pulse

Finding pulse rate

A learner counts 18 beats in 15 seconds. Find the pulse rate per minute.

60 ÷ 15 = 4.
18 × 4.

Answer: 72 beats per minute

A pulse is the wave of pressure in an artery, felt at the wrist or the neck. Your pulse rate rises during exercise, because muscles need more oxygen. Regular exercise makes the heart stronger, and it lowers the resting pulse rate.

New words

artery: A vessel carrying blood from the heart.
vein: A vessel carrying blood to the heart.
capillary: A tiny blood vessel.
ventricle: A lower chamber of the heart.

Summary

The system has a heart, vessels and blood.
Arteries, veins and capillaries each have a role.
The heart is a four-chambered pump.

Class activity: Pulse Test

Measure your pulse at rest.
Exercise for one minute.
Measure it again and explain.

You need: Mammalian heart model, Stethoscope, Printed circulatory-system diagram

Exercises

Answer in your exercise book first, then check your answers.

1. Arteries carry blood…
- A. away from the heart
- B. to the heart
- C. to the lungs only
- D. to the stomach only
Show answer
Answer: away from the heartFunction.
2. The heart has how many chambers?
- A. four
- B. two
- C. three
- D. five
Show answer
Answer: fourStructure.
3. Veins have valves.
- A. True
- B. False
Show answer
Answer: TrueStructure.
4. The liquid part of blood is ______.
Show answer
Answer: plasmaTerm.
5. State the function of each blood component.
Show answer
Answer: Plasma carries substances, red cells carry oxygen, white cells fight germs and platelets clot blood.Function.
6. Why does the left ventricle have the thickest wall?
Show answer
Answer: It pumps blood around the whole body.Adaptation.

Lesson 2

Strand: Systems
Sub-strand: Human Body Systems
Indicator: B9.3.1.1.1 – Explain the concept of the circulatory system state the function of each part of the system and the health challenges associated with it

Introduction

Blood passes through the heart twice on each complete journey round the body.

1. Double Circulation

Two circuits

Circuit	Path	Purpose
pulmonary	heart → lungs → heart	picks up oxygen
systemic	heart → body → heart	delivers oxygen

2. The Path of Blood

Blood from the body enters the right atrium.
It passes to the right ventricle.
It is pumped to the lungs.
It takes in oxygen and gives out carbon dioxide.
It returns to the left atrium.
It passes to the left ventricle.
It is pumped to the body through the aorta.
Cells take oxygen and return waste.

Oxygen-rich blood is bright red, and oxygen-poor blood is dark red. In diagrams, oxygen-rich blood is often shown in red, and oxygen-poor blood in blue. Blood is never blue, however. Veins only look that way through the skin.

A doctor listening to a heartbeat

Figure 2: Doctor with stethoscope Draw the path of blood through the heart.

3. Exchange at the Capillaries

Capillaries are so thin that only one red cell can pass at a time. Their walls are only one cell thick. Oxygen and food pass through to the body cells, and carbon dioxide and waste pass back into the blood. Billions of capillaries give an enormous surface area. Every cell in your body is close to a capillary.

4. Transport in the Blood

What blood carries

Substance	From	To
oxygen	lungs	cells
carbon dioxide	cells	lungs
glucose	gut	cells
urea	liver	kidneys
hormones	glands	target organs
heat	muscles	skin

5. Blood Groups

Human blood can be grouped into A, B, AB and O. There is also a Rhesus factor, which is positive or negative. Transfusions must match, because the wrong blood can be dangerous. Blood is tested in a laboratory before transfusion, and it is screened for diseases such as HIV and hepatitis. Knowing your blood group can be useful in an emergency.

New words

pulmonary: Relating to the lungs.
aorta: The main artery of the body.
double circulation: Blood passing through the heart twice.
transfusion: Giving blood to a patient.

Summary

Blood follows two circuits.
Capillaries exchange materials with cells.
Blood transports oxygen, food and waste.

Class activity: Heart Walk

Draw a large heart on the ground.
Walk the path of blood.
Name each part.

You need: Mammalian heart model, Stethoscope, Printed circulatory-system diagram

Exercises

Answer in your exercise book first, then check your answers.

1. The main artery of the body is the…
- A. aorta
- B. vein
- C. capillary
- D. septum
Show answer
Answer: aortaTerm.
2. Blood goes to the lungs from the…
- A. right ventricle
- B. left ventricle
- C. left atrium
- D. aorta
Show answer
Answer: right ventriclePath.
3. Capillary walls are one cell thick.
- A. True
- B. False
Show answer
Answer: TrueStructure.
4. Giving blood to a patient is a ______.
Show answer
Answer: transfusionTerm.
5. Name the two circuits of circulation.
Show answer
Answer: Pulmonary and systemic.Term.
6. Why is double circulation efficient?
Show answer
Answer: Blood is pumped twice, so it reaches the body at high pressure with plenty of oxygen.Function.

Lesson 3

Strand: Systems
Sub-strand: Human Body Systems
Indicator: B9.3.1.1.1 – Explain the concept of the circulatory system state the function of each part of the system and the health challenges associated with it

Introduction

Heart disease and stroke often give no warning. Understanding them can help to save lives.

1. Common Conditions

Circulatory conditions

Condition	Meaning	Causes or risks
hypertension	high blood pressure	salt, stress, obesity, age
heart attack	blocked blood to heart muscle	fatty deposits, smoking
stroke	blocked or burst vessel in the brain	hypertension
anaemia	too little haemoglobin	lack of iron, malaria
sickle cell disease	inherited blood disorder	genes
leukaemia	cancer of blood cells	various causes

2. High Blood Pressure

Blood pressure is measured in millimetres of mercury (mmHg). A normal reading is around 120/80. Hypertension is often called a "silent killer", as many people feel nothing. Over time, it damages the heart, kidneys and brain. Doctors in Ghana report that many adults have high blood pressure, but do not know it. Adults should have it checked regularly, at a clinic or a pharmacy.

3. Risk Factors

Risk factors

Can be changed	Cannot be changed
too much salt and fat	age
smoking	family history
lack of exercise	inherited conditions
too much alcohol
obesity
stress

A nurse checking blood pressure

Figure 3: Checking blood pressure List foods that are good for the heart.

4. Prevention

Eat more fruit, vegetables and beans.
Reduce salt, sugar and fat.
Exercise for at least 30 minutes on most days.
Avoid tobacco.
Limit alcohol.
Keep a healthy weight.
Have regular check-ups.

Many Ghanaian meals can be very healthy, especially those rich in vegetables and fish. However, a large amount of salt, fried food and sugary drinks raises the risk. Good habits start young. Fatty deposits in the arteries can begin to form in childhood.

5. Recognising a Stroke

FAST signs of a stroke

Letter	Sign
F	face drooping
A	arm weakness
S	speech difficulty
T	time to get help

A stroke needs urgent medical care, as brain cells die within minutes. Call for help, and take the person to hospital quickly. Do not give them food or drink. Teach these signs to your family. They could save a life.

New words

hypertension: High blood pressure.
stroke: Sudden loss of blood to the brain.
risk factor: Something that raises the chance of disease.
obesity: Being seriously overweight.

Summary

Hypertension, stroke and anaemia are common challenges.
Many risks can be reduced by lifestyle.
Know the FAST signs of stroke.

Class activity: Heart Health Poster

Make a poster on protecting the heart.
Include FAST.
Display it at school.

You need: Mammalian heart model, Stethoscope, Printed circulatory-system diagram

Exercises

Answer in your exercise book first, then check your answers.

1. Hypertension means…
- A. high blood pressure
- B. low sugar
- C. a broken bone
- D. a skin rash
Show answer
Answer: high blood pressureTerm.
2. Which is a changeable risk factor?
- A. smoking
- B. age
- C. family history
- D. height
Show answer
Answer: smokingRisk.
3. High blood pressure may have no symptoms.
- A. True
- B. False
Show answer
Answer: TrueSilent.
4. In FAST, S stands for ______.
Show answer
Answer: speechStroke.
5. State three ways of preventing heart disease.
Show answer
Answer: Reducing salt, exercising and avoiding tobacco.Any three.
6. Why is hypertension called a "silent killer"?
Show answer
Answer: It often has no symptoms, but it damages organs.Reason.

Homework

Teach your family the FAST signs of stroke.