Can we be able to live without

BREATHING???

CHAPTER 1: RESPIRATION

1.1 Human Breathing Mechanism

1) Human Respiratory System Living organisms must be able to take

oxygen from the air and get rid of carbon dioxide to the air.

Swapping oxygen for carbon dioxide in this way is called gas exchange.

Gas exchange takes place through a gas exchange surface also known as a respiratory surface.

For gas exchange we need a respiratory system.

Breathing is an external respiration. Breathing consist of two stage:

1. Inhalation: air is taken into the lungs

2. Exhalation: air is passes out of the lungs

The breathing system or the human respiratory system consists of the following structures:

1. The nasal cavity2. Trachea3. Bronchus 4. Bronchiole5. Lungs6. Rib cage7. Diaphragm 8. The intercostals muscles

Structure of the human respiratory system:

Nasal cavity

Trachea Nose

Mouth Heart

Alveoli

Diaphragm Bronchioles

Bronchus

Intercostals muscles

Lung

Structure of the lung The lungs are the respiratory organs. We have a pair of lungs in the thoracic

cavity. They are protected by the rib cage.

The lungs are connected to the trachea by two tubes. These tubes are right bronchus and left bronchus.

The bronchus divide into smaller tubes called bronchioles.

The bronchioles end in clusters of tiny air sacs known as alveoli, in the lungs.

Flow of air into the lungs:

Air is breathed in through the nose and enters the nostrils. The nostrils leads to the nasal cavity. While passing through

the nasal cavity the air is warmed up and moistened. Hairs and sticky mucus trap particles inside the nasal cavity.

The clean air then enters to the trachea. The trachea branches into two bronchi.Eachs bronchus

leads directly into a lung. The bronchus branches into bronchioles. Each bronchiole end in a cluster of air sacs called

alveoli/alveolus. The wall of the alveolus is only one-cell thick. It is thin, moist

and surrounded by a network of capillaries. The exchange of respiratory gases occurs between the

alveolus and capillaries.

The path of air into the lungs is summarized:

Nasal cavity Trachea

BronchioleAlveolus

Bronchus

The breathing mechanism Breathing mechanism involves:1. Inhalation (breathing in)2. Exhalation (breathing out) During inhalation:1. The intercostals muscles and the diaphragm contract.2. The diaphragm moves down wards, increasing the volume

of the thoracic cavity.3. The intercostals muscles pull the ribs up, expanding the ribs

and further increasing the volume of the thoracic cavity.4. These actions lower the air pressure in the alveoli.5. Air from the outside then rushes in through the nasal

cavities, trachea and lungs. The lungs expand.

During exhalation:1. The intercostals muscles relax causing the rib

cage to move downwards and inwards.2. At the same time, the muscles of the diaphragm

relax. The diaphragm curves upwards and returns to its original dome shape.

3. These action return the thoracic cavity to its original volume. The air pressure inside the lungs is now higher than the atmospheric pressure outside.

4. The lungs contract and the air is forced out through the respiratory tract.

Comparison between inhalation and exhalation:

Inhalation Aspect Exhalation

Diaphragm

Movement of rib cage and the wall of the thoracic cavity

Contract, flattens and is pushed downwards

Relaxes and is pushed upwards.

Move upwards and outwards.

Move downwards and inwards.

Inhalation Aspect Exhalation

Volume of thoracic cavity

Air pressure in the thoracic cavity

Movement of air

Increases Decreases

Decreases Increases

From the atmosphere to the lungs

From the lungs to the atmosphere

Exercise 1.1

1. Name all parts in the human respiratory system.

2. Trace the flow of inhaled air through the nostrils to the lungs

Nasal cavity,trachea,bronchus,lungs,rib cage,diaphragm and the intercostals muscles.

Nasal cavity Trachea

Bronchiole Alveolus

Bronchus

3. Explain how the diaphragm and the intercostals muscles force air out from the lungs.

The diaphragm muscles relax and move up and at the same time the intercostals muscles pull the ribs downwards and inwards. These actions cause the air to flow out of the lungs.

Transport of Oxygen in the Human Body

1. Diffusion of oxygen from the alveolus to the capillaries.

The exchange of gases occurs by diffusion in the alveoli.

The characteristics enable oxygen to diffuse through the walls of the alveoli easily and efficiently

1. Have very large surface areas

2. Thin walls (only one- cell thick).

3. The inner surfaces of the alveoli are always moist.

4. The outer surfaces of the alveoli are

surrounded by a network of blood capillaries.

Inhaled air is rich in oxygen. The oxygen concentration in

the alveolus higher than the oxygen concentration in the deoxygenated blood

in the capillaries. The difference in oxygen concentration

makes the oxygen diffuse easily into

the blood capillaries.

Oxygen in the alveolus diffuses through the walls into the blood.

Carbon dioxide and water vapour diffuse from the blood into the alveolus.

Diffusion of oxygen from the alveolus to the capillaries

2. Oxygen transport Haemoglobin in the red blood cell

needs to carry oxygen from the lungs

to all parts of the body.

Haemoglobin is a blood pigment.

As the oxygen concentration

is high in the alveolus, oxygen

diffuses into the capillaries.

Oxygen then combines with

haemoglobin in the red blood

cells and forms oxyhaemoglobin.

3. Diffusion of oxygen from the capillaries to the body cells

When blood reaches the body cells, oxyhaemoglobin is broken down into haemoglobin and oxygen.

The oxygen then diffuses through the walls of the capillaries into the cells.

Oxygen is then used to oxidise food to release carbon dioxide during cell respiration.

At the same time,carbon dioxide from the cells diffuses into the capillaries to be carried back to the lungs.

Exercise 1.2

1. What process is involved in the exchange of gases in the alveolus?

2. Which gases are exchanged in the alveolus?

The movement of gases through the wall of the alveolus is known as diffusion

Oxygen and carbon dioxide

3. What are the two characteristics of the alveolus which enable it to function efficiently?

4. Why are the alveoli in the lungs surrounded by blood capillaries?

i. Has a very large surface area.

ii. Has a thin wall which is one-cell thick.

This is to allow oxygen in the alveolus to enter the blood in the capillaries and carbon dioxide from the blood in the capillaries to diffuse into the alveolus.

Activity: Gathering Information

1

4

3

2

The importance of a healthy respiratory system

1. Effects of harmful substances:

i. Nicotine in cigarettes cause

the following effects:

a) Stimulates the production of cells

in the trachea and lungs

and leads to lung cancer.

a) Narrows and hardens the

blood vessels. This affects blood flow

and causes heart attacks.

ii. Tar in tobacco is carcinogenic and can cause lung cancer.iii. Nitrogen dioxide in cigarette smoke forms an acid which can

destroy lung tissues.iv. Sulphur dioxide is very soluble in the alveoli and it forms an

acid which destroys the lungs.v. Carbon monoxide is a toxic gas, combines with haemoglobin in the red blood cells and prevents oxygen from combining with haemoglobin.ii. Dust and dirt can hinders the exchange of gases.

2. Diseases of the respiratory system: Air pollution, the presence of harmful

microbes in air, smoking and crowded cities cause respiratory diseases. Examples include asthma, influenza, pneumonia, tuberculosis, bronchitis, emphysema and lung cancer.

Asthma: condition in which the tubes of the lungs become inflamed. This is because the air tubes are narrower and partially blocked.

Diseases of the respiratory system

Asthma Influenza Pneumonia Tuberculosis Bronchitis Emphysema Lung cancer

Influenza: cause by viruses which attack the mucus membranes in the respiratory system. Symptoms: Blocked nose, teary eyes, headache, aches in the limbs, cough and fever.

Pneumonia: caused by bacteria, viruses and chemical substances in polluted air. The lungs are filled with pus and fluid.

Symptoms: chest pain, fever and cough.

Tuberculosis: caused by bacterial infection which are carried by water droplets and dust in the air.

Symptoms: prolonged cough and spit out blood in the end stages.

Bronchitis: caused by viral infections. Symptoms: cough, produce a lot of mucus, colds and phlegm. Makes respiration and gaseous exchange difficult.

Emphysema: This disease is linked to smokers and people who work in dust areas. The patient experiences breathing difficulties.

Lung cancer: Cause by smoking cigarettes. Air polluted with carcinogen from factories and vehicle emissions, dust and asbestos also cause lung cancer.

3. Improving Air Quality Pollution is mainly caused by irresponsible

human behavior and improperly planned activities.

We must be responsible for preserving and conserving air quality.

Air pollution interferes with the respiratory process.

It can cause respiratory diseases which can be fatal.

To preserve and conserve the quality

of air we must:

1. Support and campaign against open burning

of rubbish.

2. Give up the habit of smoking.

3. Reduce the number of vehicles

on the road.

4. Avoid the burning of forest

for agriculture, housing and industries.

Exercise 1.31. Name 4 respiratory diseases caused by

pollutants in the air.

2. Why does a person feel sick and dizzy after inhaling carbon monoxide?

Asthma, bronchitis, emphysema and lung cancer.

Carbon monoxide combines with haemoglobin in the blood.This prevent oxygen from combining with haemoglobin.Oxygen cannot be transported to the body cells that need it.This makes a person feels sick and dizzy.

3. Name four dangerous chemical substances in cigarette.

4. State two human activities which can help to reduce air pollution.

Nicotine,tar,carbon monoxide and hydrogen cyanide.

Stop open burning of rubbish and use public transport to help reduce pollutants and keep the air clean.