Chap 3: Breathing and Respiration -

Breathing and respiration are two terms that people often mix up. However, they are two completely different things.

Breathing

Breathing is simply the process of moving air.
It describes the physical movement of air as it enters and leaves the lungs.
This process can also be called ventilation.

Respiration

Respiration is a series of chemical reactions.
These chemical reactions happen inside a living thing’s cells.
The main purpose of these reactions is to release energy.
These chemical reactions can be described using a word equation.
In a word equation, the reactants are the starting materials. They are listed on the left side of the arrow.
The products are the materials that are produced. They are listed on the right side of the arrow.

Word Equation for Respiration: Glucose + Oxygen → Carbon Dioxide + Water

Aerobic and Anaerobic Respiration

The process of respiration can be split into two main types. Both of these types of respiration are explained in detail below.

Aerobic Respiration

In the summary of respiration, oxygen is a reactant. This means that it is a starting material.
The type of respiration that uses oxygen is called aerobic respiration.
This type of respiration happens in the mitochondria. Mitochondria are parts of cells.
All plants and animals, including human cells, use aerobic respiration.
The energy released during this process is released in a controlled way.
This energy is then used by the cells to keep themselves and the body alive.

Anaerobic Respiration

Anaerobic respiration happens when the body does not have enough oxygen for aerobic respiration.
An example is when you are sprinting. You can’t breathe fast enough to get the oxygen your muscles need.
To get the energy your muscles need, your body releases it through a different process. This process is called anaerobic respiration.
This process also creates other substances.
These other substances need to be broken down by aerobic respiration.
This is why after a sprint, you breathe in large amounts of air. This provides the oxygen that is needed.

Parts of the Respiratory System

The respiratory system is made up of several key parts.
These include the nose, windpipe (trachea), voice box (larynx), bronchus, and bronchiole.
The lungs are the main organs, which are protected by the ribs and the chest wall.
The diaphragm is a muscle located below the lungs.

The Nose

Air usually enters the body through the nose.
The nose has hairs that trap some of the dust particles in the air.
The lining of the nose makes a watery liquid called mucus.
This mucus makes the air moist as it passes through. It also helps trap bacteria in the air.
There are small blood vessels underneath the lining of the nose.
These blood vessels release heat to warm up the air before it goes into the lungs.

The Windpipe (Trachea)

The windpipe is a tube that is about 10 cm long and 1.5 cm wide.
It is made of rings of a stiff substance called cartilage.
The rings of cartilage have a C-shape.
The inner lining of the windpipe has cells with tiny hairs called microscopic hairs.
These hairs move back and forth to get rid of mucus that has trapped dust and bacteria.
The mucus moves up to the top of the windpipe. From there, it goes to the back of the mouth and is swallowed.

The Bronchi and Bronchioles

The windpipe (trachea) divides into two smaller tubes called bronchi.
The two bronchi are also made of rings of cartilage and have the same lining as the windpipe.
The bronchi divide up into many even smaller tubes called bronchioles.
These bronchioles have a diameter of about 1 mm.

The Respiratory System: Supporting Structures and a Common Condition

The chest wall and the diaphragm are two key structures that surround the space inside the chest, where the lungs are located.

The Chest Wall

The chest wall is made up of ribs and their attached muscles.
Each rib is connected to the backbone by a joint. This allows for a small amount of movement.
The muscles between the ribs are called the internal and external intercostal muscles.
The movement of these muscles helps to move the ribs.

The Diaphragm

The diaphragm is a large, thin sheet of muscle.
It is attached to the edges of the tenth pair of ribs and the backbone.
The diaphragm separates the chest cavity from the lower body cavity.
The lower body cavity contains the stomach, intestines, liver, kidneys, and female reproductive organs.

– Asthma

The bronchioles, unlike other tubes in the respiratory system, have walls made of muscle instead of cartilage.
These muscle walls can change the diameter of the bronchioles, making them either narrower or wider.
Asthma is a disease that affects people all over the world, including children and adults.
If a person has asthma, their body reacts to certain substances by making the bronchioles narrower.
This makes breathing very difficult, and the person is said to be having an asthma attack.
An asthma attack can be triggered by substances such as dust mites (found in bedding and carpets), animal fur and bird feathers, pollen, mold spores, and air pollution.
When a person reacts to these substances, they are said to be allergic to them.
There are many different treatments available to reduce or prevent asthma attacks.
A common treatment for an asthma attack is the use of an inhaler.
An inhaler contains medicine that makes the muscles in the bronchioles relax. This widens the bronchioles so that breathing becomes easier.

– Asthma Monitoring and Research

People with asthma can use a peak flow meter to check how open their bronchioles are.
You blow hard into the meter.
If the score is high, it means the bronchioles are wide.
If the score is low, the bronchioles are narrow.
Research into lung diseases like asthma is happening all over the world.
Sometimes people get involved in this research because a family member has the disease.

Breathing Movements

There are two main types of breathing movements: inspiration and expiration.
Inspiration is the act of breathing in.
During inspiration, the external intercostal muscles contract and pull the rib cage up and out.
The diaphragm also contracts and pulls down.
This makes the chest space bigger, and the lungs expand.
Air then rushes in to fill the extra space in the lungs.
Expiration is the act of breathing out.
The diaphragm and rib cage muscles relax.
This causes the diaphragm and rib cage to return to their original shape.
The lungs then deflate, and the air is pushed out.

Inspiration and Expiration

This table explains what happens to the different parts of the respiratory system when you breathe in and breathe out.

Part of Respiratory System: The Internal Intercostal Muscles

Inspiration (breathing in): The muscles relax.
Expiration (breathing out): The muscles contract.

Part of Respiratory System: The External Intercostal Muscles

Inspiration (breathing in): The muscles contract.
Expiration (breathing out): The muscles relax.

Part of Respiratory System: Ribs

Inspiration (breathing in): The ribs move up.
Expiration (breathing out): The ribs move down.

Part of Respiratory System: Diaphragm Muscles

Inspiration (breathing in): The muscles contract.
Expiration (breathing out): The muscles relax.

Part of Respiratory System: Diaphragm

Inspiration (breathing in): The diaphragm moves down and becomes flatter.
Expiration (breathing out): The diaphragm moves up and becomes dome-shaped.

Part of Respiratory System: Chest Volume

Inspiration (breathing in): The chest volume increases.
Expiration (breathing out): The chest volume decreases.

Part of Respiratory System: Air

Inspiration (breathing in): The air moves in.
Expiration (breathing out): The air moves out.

Exchanging Gases

The Process of Gas Exchange

At the very end of each bronchiole, there is a small tube called an alveolus that has a balloon-like structure.
These structures are called air sacs.
Each air sac has a thin, moist lining and is covered by tiny blood vessels called capillaries.
The air sacs and capillaries form the respiratory surface.
The process that happens here, where gases are exchanged, is called gaseous exchange.

How Gases Move

Diffusion is the process where a substance, like oxygen, moves from a place where it is in a large amount to a place where it is in a small amount.
In the lungs, oxygen dissolves in the moist lining of the air sacs. It then moves into the capillaries through diffusion.
The oxygen that enters the blood is carried by red blood cells. Blood containing oxygen is called oxygenated blood.
This oxygenated blood is then pumped out of the lungs by the heart.
We have also learned that carbon dioxide is dissolved in the blood plasma.
Carbon dioxide travels to the lungs. It moves by diffusion through the capillary walls, the air sac walls, and into the air sacs.
From there, the carbon dioxide is ready to be breathed out.
Blood moves through the capillaries very quickly, so a large amount of oxygen and carbon dioxide can be exchanged in a short time.

An Analogy for Understanding

An analogy is a comparison that helps you understand something.
The following analogy is used to help students understand the lungs and their surface area.
The lungs have a very large surface area because they are made up of 300 million tiny air sacs.
A large surface area allows for a lot of oxygen and carbon dioxide to be exchanged.
The combined surface area of the air sacs in your lungs is about the same size as a tennis court.

QUESTIONS & ANSWERS

1. What would happen if the energy was released in an uncontrolled way?

If energy was released in an uncontrolled way, it would likely be released suddenly as a large burst of heat, which would damage and destroy the cell. The body wouldn’t be able to use the energy efficiently for its normal life processes.

2. What are the life processes that take place to show that an organism is alive?

An organism is considered alive when it carries out certain life processes that help it maintain itself and survive. These processes include:

Reproduction: producing new individuals to continue the species.
Respiration: releasing energy in a controlled way from food to power other activities of the cell and body.
Nutrition: taking in and using food or nutrients for growth, repair, and energy.
Excretion: removing waste products that could be harmful if they build up.
Growth: increasing in size or number of cells.
Movement: the ability to move parts of the body

3. What structures hold the air passages open in the windpipe (trachea) and bronchi?

The windpipe (trachea) and bronchi are held open by rings of cartilage.

4. Why is it more difficult to breathe during an asthma attack?

It is harder to breathe during an asthma attack because the small air tubes in the lungs (bronchioles) tighten and become narrow, making it difficult for air to pass through. An inhaler helps by relaxing these tubes and opening them up so breathing becomes easier.

5. What is the movement of air in and out of the lungs called?

The movement of air in and out of the lungs is called breathing or ventilation.

6. What is the name of the process which is summarised in the following word equation?

The process shown by the equation glucose + oxygen → carbon dioxide + water is called respiration, which is how living things release energy from food. Since it uses oxygen, it is a type of respiration known as aerobic respiration.

7. Where do you find mitochondria?

You find mitochondria inside the cells of all plants and animals, including our own body cells.

8. What happens in the mitochondria?

Aerobic respiration takes place in the mitochondria. This is where energy is released in a controlled way to keep the cell and the body alive.

9. Describe the changes that take place in your chest when you:

a) Breathing in (inspiration):
The muscles between the ribs and the diaphragm tighten. This makes the ribs move up and out, and the diaphragm flatten downwards. The chest space gets bigger, so air is pulled into the lungs.

b) Breathing out (expiration):
The muscles relax. The diaphragm moves back up into a dome shape, and the ribs move down. The chest space gets smaller, so air is pushed out of the lungs.

10. Describe what happens in the lungs to the oxygen in the air and the carbon dioxide in the blood.

In the lungs, oxygen from the air moves into the blood, and carbon dioxide from the blood moves out. Oxygen passes through the thin walls of the air sacs into tiny blood vessels, while carbon dioxide moves from the blood into the air sacs so it can be breathed out.