THE RESPIRATORY

SYSTEM

Learning Objectives

To state the function of the Respiratory

System.

To describe the structure and workings of

the Respiratory system.

To name the major parts of the

Respiratory System.

To describe the effects of physical activity

on the Respiratory System.

What are the functions of the

Respiratory System?

Inspiration or breathing of air into the

lungs.

Exchanging oxygen for Carbon Dioxide

with the Circulatory system in the lungs.

Expiration or breathing out of air from the

lungs.

What makes up the Respiratory

System?

The nasal Cavity

Air passages

The lungs

The diaphragm.

Structure of the Human

Respiratory System The respiratory system in human beings can

be divided into the upper respiratory tract

that consists of the nasal passages, pharynx

and the larynx and the lower respiratory tract

that is composed of the trachea, the primary

bronchi and the lungs.

The Upper Respiratory Tract

Nose (nostrils) - It is the entrance of the

respiratory tract.

Pharynx - It is situated behind the mouth and is

the passage to the stomach and the lungs.

Larynx - It is present at the top of trachea and

contains vocal cords. It is also known as the

voice box.

Trachea (windpipe) - It is a tube like structure

that helps in passage of air from larynx to the

bronchi.

The Lower Respiratory Tract

Bronchi (bronchioles) - These are the

branches of the bronchi that conduct air

into the lungs.

Alveoli (air sacs) - The sacs in the lungs

where gas exchange occurs.

Lungs - The two inverted-cone shaped

organs present in the chest of human

beings.

How do you breathe?

The diaphragm is a sheet of muscle under

the lungs which controls breathing.

When the diaphragm contracts, the lungs

expand and air flows into the lungs.

When the diaphragm relaxes, the lungs

relax and air is forced out of the lungs

Inhalation and Exhalation

How does the Respiratory System

work?

When you breathe in, air enters through the nose or mouth and goes down the trachea.

At the end of the trachea are 2 branches called bronchi, which carry air into each lung.

Inside the lungs the air passes from the bronchi to the bronchioles and then to air sacs. (Alveoli)

Each alveolus is surrounded by capillaries. These are very small blood vessels.

How does the Respiratory

System work? Cont’d The walls of the air sacs and capillaries

are very thin and they are close together.

Oxygen passes through the walls to the blood in the capillaries and carbon dioxide passes to the air sacs.

When you breath out carbon dioxide is removed from the body.

Gas exchange

We need to get oxygen from the air into

the blood, and we need to remove waste

carbon dioxide from the blood into the air.

Moving gases like this is called gas

exchange. The alveoli are adapted to

make gas exchange in lungs happen

easily and efficiently.

Here are some features of the alveoli that allow

this:

• They give the lungs a really big surface area

• They have moist, thin walls (just one cell thick)

• They have a lot of tiny blood vessels called capillaries.

The gases move by diffusion from where they have a

high concentration to where they have a low

concentration:

Oxygen diffuses from the air in the alveoli into the blood.

Carbon dioxide diffuses from the blood into the air in the

alveoli.

Some water vapour is also lost from the surface of the

alveoli into the lungs - we can see this condensing when

we breathe out on cold days.

The effects of Physical Activity on

the Respiratory System.

Increasing the amount of air taken in with

each breath.

Reducing the rate of breathing

Reducing the time it takes to recover your

normal breathing rate after strenuous

exercise.

Strengthening the muscles that are

involved in the breathing process.