1. The Respiratory System

2. Blood transports oxygen from the lungs to cells and carries carbon dioxide from the cells to the lungs. It is the function of the respiratory system to transport gases to and from the circulatory system. The respiratory system involves both external respiration and internal respiration. External Respiration is the exchange of gases between the atmosphere and the blood. Internal respiration is the exchange of gases between the blood and the cells of the body.

3. The Lungs
a. Site of gas exchange between the atmosphere and the blood.
b. Located inside the thoracic cavity, bounded by the rib cage and the diaphragm.

4. Passage of Air
1. External respiration begins at the mouth and nose and moves into the
pharynx.
2. The pharynx allows passage of both food and air.
3. The epiglottis covers the opening to the air passage when food is
swallowed.
4. Air passes from the pharynx to the trachea.
5. The upper end of the trachea is the larynx where sounds are produced.
6. The trachea branches off into two bronchi which lead to the lungs.
7. The bronchi branch into smaller tubes called bronchioles which cluster
into tiny air sacs called alveoli.
8. All gas exchange in the lungs occurs in the alveoli.

5. Nasal Passage
Pharynx (throat)
Larynx (voice box)
Trachea (windpipe)
Bronchial Tube
Pleura
Bronchiole
Alveoli
Diaphragm

8. Mechanism of Breathing
a. Breathing is the process of moving air into and out of the lungs.
b. Inspiration is taking air into the lungs.
1. Ribs move outward.
2. The diaphragm pushes down on the abdomen.
c. Expiration is expelling air from the lungs.
1. Rib muscles relax.
2. Elastic tissues of the lungs recoil, deflating the lungs.
d. The rate of breathing is controlled by the brain, which monitors the
amount of CO2 in the blood.

9. Expiration
Inspiration

10. Supports the skeletal system Absorbs nutrients from food
Which of the following describes the primary function of this body system?
Supports the skeletal system
Absorbs nutrients from food
Responds to stimuli in the environment
Exchanges gases with the environment

11. Supports the skeletal system Absorbs nutrients from food
Which of the following describes the primary function of this body system?
Supports the skeletal system
Absorbs nutrients from food
Responds to stimuli in the environment
Exchanges gases with the environment