1. 37-3 The Respiratory System
Objectives:
Describe respiration.
Identify the function of the respiratory system.
Describe gas exchange and breathing.
Explain how smoking affects the respiratory system.

2. The Human Respiratory System
The basic function of the human respiratory system is the exchange of oxygen and carbon dioxide between the blood, the air, and tissues.

3. The respiratory system consists of the:
nose
pharynx
larynx
trachea
bronchi
lungs

4. Air entering the respiratory system must be warmed, moistened, and filtered.
Mucus moistens air and traps particles of dust or smoke.
Cilia sweep particles and mucus to the throat.
Mucus and particles are either swallowed or spit out.

5. Air enters the nose or mouth and moves to the pharynx, or throat.
The pharynx serves as a passageway for both air and food.
The respiratory system is responsible for the exchange of oxygen and carbon dioxide.

6. Air moves from the pharynx into the trachea, or windpipe.
The epiglottis covers the entrance to the trachea when you swallow.
Epiglottis
The respiratory system is responsible for the exchange of oxygen and carbon dioxide.

7. Larynx
At the top of the trachea is the larynx, which contains two elastic folds of tissue called vocal cords.
The respiratory system is responsible for the exchange of oxygen and carbon dioxide. Air moves through the nose, pharynx, larynx, trachea, and lungs.

8. Each bronchus leads into one of the lungs.
Air then passes through the trachea into two large passageways in the chest cavity called bronchi.
Each bronchus leads into one of the lungs.
Lungs
Bronchus
The respiratory system is responsible for the exchange of oxygen and carbon dioxide. Air moves through the nose, pharynx, larynx, trachea, and lungs. After reaching the lungs, the trachea branches into smaller and smaller tubes called bronchioles, which end in alveoli, or air sacs.

9. In each lung, the bronchus subdivides into smaller bronchi, and then into bronchioles.
The respiratory system is responsible for the exchange of oxygen and carbon dioxide. After reaching the lungs, the trachea branches into smaller and smaller tubes called bronchioles, which end in alveoli, or air sacs.

10. Bronchioles subdivide into millions of tiny air sacs called alveoli.
The respiratory system is responsible for the exchange of oxygen and carbon dioxide. After reaching the lungs, the trachea branches into smaller and smaller tubes called bronchioles, which end in alveoli, or air sacs.

11. Alveoli are grouped in clusters.
A network of capillaries surrounds each alveolus.
Pulmonary artery
Pulmonary vein
The respiratory system is responsible for the exchange of oxygen and carbon dioxide.
Capillaries

12. Gas Exchange Gas Exchange Gas exchange takes place in the alveoli.
Oxygen diffuses into the blood.
Gas exchange occurs by diffusion across the membrane of an alveolus and a capillary.
Capillary

13. Gas Exchange Carbon dioxide in the blood diffuses into the alveolus.
CO2
Gas exchange occurs by diffusion across the membrane of an alveolus and a capillary. 
Capillary

14. Breathing
Breathing
Breathing is the movement of air into and out of the lungs.
The force that drives air into the lungs comes from air pressure.

15. Breathing
Lungs are sealed in pleural membranes inside the chest cavity.
At the bottom of the cavity is a large, flat muscle known as the diaphragm.
During inhalation the rib cage rises and the diaphragm contracts, increasing the size of the chest cavity.

16. Breathing
During inhalation, the diaphragm contracts and the rib cage rises up.
This expands the volume of the chest cavity.
During inhalation the rib cage rises and the diaphragm contracts, increasing the size of the chest cavity.

17. Breathing
The chest cavity is sealed, so this creates a partial vacuum inside the cavity.
Atmospheric pressure fills the lungs as air rushes into the breathing passages.

18. Breathing Often exhaling is a passive event.
When the rib cage lowers and the diaphragm relaxes, pressure in the chest cavity is greater than atmospheric pressure.
Air is pushed out of the lungs.
Air Exhaled
Rib cage lowers
During inhalation the rib cage rises and the diaphragm contracts, increasing the size of the chest cavity.
Exhalation

19. 37-3 Section Assessment
Interpret the function of the respiratory system by stating what it does.
Explain the process of gas exchange in the lungs.
Describe how breathing is controlled.