1. The Respiratory System

2. The role of the respiratory system
The respiratory system helps the body obtain oxygen for respiration and remove the waste product carbon dioxide.
As we breathe, oxygen moves through the surface of the lungs into the body. It is then absorbed by the blood cells and transported around the body via the blood vessels.
The respiratory system is adapted for efficient exchange of gases between the lungs and the blood.
Photo: © Sebastian Kaulitzki, shutterstock.com

3. The respiratory system

4. The passage of air from nose/mouth to lungs
Click the mouse to follow the passage of air from the nose/mouth to the lungs

5. Nose Air enters the respiratory system through the nose and mouth.
It is here that the air is warmed, filtered (by tiny hairs), and moistened.
From the nose, the air passes through the throat (the pharynx).

6. Pharynx
The pharynx lies behind the nose and mouth and both cavities open into it.
Both food and air pass through the pharynx, the food is then directed to the oesophagus.

7. Larynx (Voice box)
The cavity of the larynx is separated from the pharynx by a flap known as the epiglottis.
This prevents food from entering the windpipe (trachea), into the lungs.

8. Trachea (Windpipe)
The trachea is approximately 10-12cm long and is kept open by a series of rings of cartilage.
It contains cells which remove foreign particles from the air.

9. Bronchi
The trachea divides into two bronchi, one leading to each lung.
Each bronchi then breaks up into smaller tubes known as bronchioles.

10. Bronchioles
The bronchial tubes further divide into smaller tubes called bronchioles before terminating in clusters of air sacs known as alveoli.

11. Alveoli Alveoli look like bunches of grapes.
There are millions of alveoli in each lung and it is here that gaseous exchange takes place.
They have large surface areas, thin walls and are surrounded by a network of pulmonary capillaries.

12. Gas exchange at the alveoli
The alveoli are bunches of tiny air sacks inside the lungs.
Each individual sack is called an alveolus.
When you breathe in, they fill with air.
The alveoli are covered in tiny capillaries (blood vessels).
Gases can pass through the thin walls of each alveolus and capillary, and into the bloodstream.
Gases can also pass from the bloodstream into the alveolus.

13. Gas exchange at the alveoli: describe in your own words what is happening

14. Gaseous exchange
Oxygen passes into the body and carbon dioxide leaves the body through the process called gaseous exchange.
For this process to work we must control the amount of each gas on each side of a semi-permeable membrane (a wall one cell thick that lets some things through but not others).
A gas will always move from an area of high concentration (or pressure) to an area of low concentration (or pressure).

15. Continued
When we breathe in there will be a high concentration of oxygen in the lungs and a low concentration in the blood. Therefore the oxygen will pass from the lungs into the blood capillaries surrounding the alveoli.
This highly oxygenated blood now transports the oxygen to the muscle capillaries, which have a low concentration of oxygen, thus allowing the oxygen to pass into the muscle where it will be used to release energy.
Carbon dioxide is diffused from the muscles into the bloodstream where it is transported to the lungs and diffused out into the alveoli.

16. The flow of air
1 .Air containing oxygen is inhaled and taken to the 2 alveoli in the lungs, where the oxygen diffuses into the 3 . blood and is taken to the heart to be pumped around the 4 . body to the muscles. At the same time 5 .carbon dioxide produced by the muscles is taken to the heart to be pumped to the lungs, where it diffuses out of the blood and into the alveoli to be exhaled.

17. Lungs
Situated in the thoracic cavity, there are 2 lungs. The Right lung is made up of 3 sections called lobes. Where the left only has 2. Why do you think this is? What organ do you know is situated towards the left side of the chest? The Heart

18. The lungs have 2 protective coverings called the PLEURAL MEMBRANES
The lungs have 2 protective coverings called the PLEURAL MEMBRANES. The visceral membrane is closest to the lungs and the parietal membrane is the one that’s furthest away from the lungs These are 2 layers that have a gap in between them. This gap is called the PLEURAL CAVITY. This gap is filled with pleural fluid. The membranes, cavity and fluid all work to protect the lungs and reduces friction between the lungs and the ribcage

19. Mechanisms of breathing – inspiration
Intercostal muscles pull ribs up and out
When you breathe in:
the intercostal muscles between the ribs contract, pulling the chest walls up and out.
the diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest.
the lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.
Diaphragm contracts and moves down

20. Mechanisms of breathing – inspiration

21. During Exercise (Inhalation)
During exercise the diaphragm and the intercostal muscles contract which makes the ribs moves upwards and outwards and results in more air being taken in

22. Mechanisms of breathing – expiration
Ribs move in and down
When you breathe out:
the intercostal muscles between the ribs relax so that the chest walls move in and down.
the diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.
the lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.
Diaphragm relaxes and bulges up

23. Mechanisms of breathing – expiration

24. During exercise (Exhalation)
During exercise the intercostal muscles relax to help decrease the size of the thoracic cavity, which means that more air can be forced out.