1. 33.3 The Respiratory System
Lesson Overview
33.3 The Respiratory System

2. Structures of the Respiratory System
What is the function of the respiratory system?

3. Structures of the Respiratory System
What is the function of the respiratory system?
The human respiratory system picks up oxygen from the air we inhale and releases carbon dioxide into the air we exhale.

4. Structures of the Respiratory System
For organisms, respiration means the process of gas exchange between a body and the environment.
The human respiratory system picks up oxygen from the air we inhale and releases carbon dioxide into the air we exhale.
The circulatory system links the exchange of gases in the lungs with our body tissues.
The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs.

5. Pharynx, Larynx, and Trachea
Air moves through the nose to a cavity at the back of the mouth called the pharynx, or throat, which serves as a passageway for both air and food.
Air moves from the pharynx into the trachea, or windpipe.
When you swallow food or liquid, a flap of tissue called the epiglottis covers the entrance to the trachea, ensuring that the food or liquid goes into the esophagus.

6. Lungs
From the trachea, air moves into two large tubes in the chest cavity called bronchi. Each bronchus leads to one lung.
Within each lung, the large bronchus divides into smaller bronchi, which lead to even smaller passageways called bronchioles.
Bronchi and bronchioles are surrounded by smooth muscles, controlled by the autonomic nervous system, that regulate the size of air passageways.

7. Lungs
The bronchioles continue to divide until they end at a series of tiny air sacs called alveoli.
Alveoli are grouped in clusters, like bunches of grapes. A network of capillaries surrounds each alveolus.

8. Gas Exchange and Transport
How are oxygen and carbon dioxide exchanged and transported throughout the body?

9. Gas Exchange and Transport
How are oxygen and carbon dioxide exchanged and transported throughout the body?
Oxygen and carbon dioxide are exchanged across the walls of alveoli and capillaries. Chemical properties of blood and red blood cells allow for efficient transport of gases throughout the body.

10. Gas Exchange
When air enters alveoli, oxygen dissolves in the moisture on their inner surface and then diffuses across thin capillary walls into the blood.
Oxygen diffuses in this direction because the oxygen concentration is greater in the alveoli than it is in the blood.
Carbon dioxide diffuses from blood into the alveoli because its concentration is greater in the blood than it is in the air in the alveoli.

11. Gas Exchange
The air you inhale usually contains 21 percent oxygen and 0.04 percent carbon dioxide.
Exhaled air usually contains less than 15 percent oxygen and 4 percent carbon dioxide.
Your lungs remove about a fourth of the oxygen in the air you inhale and increase the carbon dioxide content of that air by a factor of 100.

12. GILLS
Most fish breathe by means of gills. They consist of many tiny filaments supplied with blood vessels.
Water enters the open mouth. Then the fish closes its mouth and the water is forced over the filaments and out through the opercula.
Oxygen dissolved in the water is absorbed into the bloodstream through the delicate membrane of the filaments.
Inside the mouth are straining devices called gill rakers. They prevent food and debris from passing over and injuring the gills.

13. LUNGS
Lung Details Lung View

14. VERTEBRATE RESPIRATORY SYSTEMS: FISH
Why are gills different from lungs?
In what ways are gills like lungs?

15. VERTEBRATE RESPIRATORY SYSTEMS : FROG
A frog can breathe through his skin as well as his lungs. What
would you predict that a cross-section of skin would be
like?
What happens to a frog when you handle it?

16. VERTEBRATE RESPIRATORY SYSTEMS: TURTLE
A turtle does not breathe through his skin. How would you predict that the relative size of frog and turtle lungs would compare?

17. VERTEBRATE RESPIRATORY SYSTEMS: BIRD
A bird’s lungs are enormous compared to his body size.Why
would a bird have bigger lungs?

18. BIRD RESPIRATION
Birds never get out of breath, because they have very strong hearts and a breathing system that works very well. The movement of a bird's wings pushes in on the lungs and air sacs, causing old, stale air to move out of them. Then fresh air can move in.
The faster a bird flies, the more the wings push on the lungs, and the more the oxygen moves into the lungs and air sacs. This gives the bird all of the oxygen it needs for the hard work of flying.

19. VERTEBRATE RESPIRATORY SYSTEMS: HUMAN
Why are there blue and red lines drawn through these lungs?
Lungs and gills have a high “surface to volume ratio.” What does that mean? Why do they all have it?
Why must lung and gill surfaces remain moist?