HUMAN BREATHING MECHANISMThe chemical process whereby energy is released

from glucose or other simple substances is known as respiration.

In cellular respiration,Glucose + O2 Energy + CO2 + Water

Our body takes in O2 from atmosphere and releases CO2 .

This process which involves an exchange of gases is known as breathing.

The role of the respiratory system is to produce energy through three mechanism:Breathing to obtain energyTransport oxygen from blood to the body cellsCellular respiration to oxidize food using oxygen in the

body cells

The Structure of Human Respiratory System

PART FUNCTIONNasal cavity Moistens air that passes through

and traps dust particles in air.Trachea Help to trap dust particles and

microorganisms in air.Bronchi/bronchus Direct air to the lungs.

Lung Rich in blood vessels and alveoli.Ribs Protect lungs

Diaphragm Separate the thoracic cavity from the abdominal cavity.

Intercostal muscles

Move ribs during the breathing process.

The Structure of Human LungsLungs is the main respiratory organ of human.The lung is soft and spongy organ.Located in the thoracic cavity and protected by ribs.There are fine branches in the lung called bronchioles.Bronchioles branch out from the bronchi.There are many air sacs at the ends of the bronchioles

known as alveoli/alveolus.

Flow of Air from the Atmosphere to the Lungs

Alveoli surrounded by blood capillaries.Gaseous exchange takes place in the lungs by

diffusion.

An alveolus has the following adaptations to allow it to exchange gases effectively.has a very large surface areahas walls which are very thin and elasticis surrounded by a network of blood capillariesis moist

Breathing MechanismThe process of taking in air into the lungs is known as

inhalation.The air that enters the lungs is the inhaled air.The process of expelling carbon dioxide from the

lungs into the atmosphere is known as exhalation.The air expelled is known as exhaled air.

Model of the Human Respiratory System

Comparing Inhalation and Exhalation

TRANSPORT OF OXYGEN IN THE HUMAN BODY

During inhalation, the concentration of O2 in inhaled air is higher than O2 content in the blood capillaries.

Oxygenated air is drawn into the lungs through the nasal cavity, trachea, bronchi, bronchioles and finally into the alveoli.

Alveoli are tiny air sacs where the exchange of gases takes place.

During the exchange of gases, O2 will be transported from the alveoli to the body cells while CO2 will be transported from the body cells to the lungs.

Diffusion of O2 from the Alveoli into the Blood Capillaries

Alveoli have moist surfaces, thin walls and surrounded by blood capillaries.

O2 in the inhaled air will dissolve on the moist surface of alveoli.

This cause the concentration of O2 in alveoli to increase.

When concentration of O2 in the alveoli is higher than in the blood capillaries, O2 will be transported to the blood capillaries through diffusion.

Transport of Oxygen by Blood

Blood is a type of tissue fluid that flows in the blood capillaries.

Blood acts as a medium of transport of oxygen due to assistance from the haemoglobin.

Haemoglobin is the red pigment found in the red blood cells.

Haemoglobin is an important carrier of oxygen because it combines with oxygen easily.Haemoglobin + Oxygen Oxyhaemoglobin

Oxyhaemoglobin will be carried from the lungs to the other parts of the body cells that lack oxygen.

Diffusion of O2 from Blood Capillaries to Body Cells

When oxyhaemoglobin reaches the body cells that lack O2 , it breaks down into O2 and haemoglobin.

Oxyhaemoglobin Haemoglobin + OxygenThe released O2 will be absorbed by the body cells

while the haemoglobin will return to the lungs to combine with the O2.

At the same time, CO2 from the cells diffuses into the blood capillaries to be carried by haemoglobin back to the alveoli.

CO2 will be expelled out of the lungs during exhalation.

THE IMPORTANCE OF A HEALTHY RESPIRATION SYSTEM

Our respiratory system will be affected if it is exposed to the air pollutants.

Most pollutants are toxic and carcinogenic.Toxicity is a nature of substance that can harm living

cells.Carcinogenicity leads to the production of cancerous

cells.Toxic substances are known as toxins.Carcinogenic substances are known as carcinogens.

The Effects of Harmful Substances

We must avoid taking up smoking which can damage the respiratory system.

An activity to show the effects of cigarette smoke on white cotton wool can be conducted as follows:The white cotton is used as an analogy of the lung

tissues.

At the end of the activity, it is found that:Thermometer reading increases – cigarette smoke can

increase the temperature of lung.White cotton wool turns brownish and contains black

particles – cigarette smoke contains tar.Cotton wool has very strong nicotine smell – nicotine

from the cigarette smoke condense on the cotton wool.Hydrogen carbonate indicator turns yellow – nitrogen

oxide in cigarette smoke dissolves in it and makes it acidic.

Improving the Quality of the AirBanning open burning of rubbish.Using unleaded petrol in motor vehicles.Conducting campaigns for the preservation and

conservation of good air quality.