1. Respiratory Tract
Nose
Pharynx & Larynx
Trachea
Bronchi
Bronchioles
Alveoli L U N G S
The respiratory tract starts from the external nostrils (the nose) and ends in the alveoli of the lungs.

2. Respiratory tract

3. Nose
Usually, air enters the respiratory system through the nostrils.  The nostrils lead to open spaces in the nose called the nasal passages.  
The nasal passages, lined with mucus, serve as a moistener and filter, and also warm up the air before it reaches the lungs.
The hairs within the nostrils filter out many foreign particles (dust, bacteria, etc.) from entering the lungs-but it can’t stop everything.  
The gooey mucus and cilia (little hair-like projections) in the lungs also collect foreign particles such as tar from cigarette smoke, but if too much gets collected, lung disease may begin.
The nose serves three purposes.  It warms, filters, and moistens the air before it reaches the lungs.  You will obviously lose these special advantages if you breath through your mouth.

4. Pharynx and Larynx
Air travels from the nasal passages to the pharynx, or the throat. When the air leaves the pharynx it passes into the larynx, or the voice box.  
The voice box is constructed mainly of cartilage, which is a flexible connective tissue. The vocal cords are two pairs of membranes stretched across the inside of the larynx.
Food and liquids are prevented from entering the larynx by the epiglottis, a thin, lid-like flap of cartilage attached to the base of the tongue- this helps you avoid choking while swallowing.
Larynx
Vocal
Cord
Humans can control the vibrations of the vocal chords, which enable us to make sounds

6. Trachea Click here to watch a movie on the trachea
The larynx feeds directly into the trachea or the windpipe.  
The trachea is a tube approximately 12 centimeters in length and 2.5 centimeters wide.  The trachea is kept open by rings of cartilage within its walls.  
Similar to the nasal passages, the trachea is covered with a ciliated mucous membrane.
Larynx
Trachea
Click here to watch a
movie on the trachea

7. Bronchi and Bronchioles
The trachea divides into two cartilage-ringed tubes called bronchi, near the center of the chest. This section of the respiratory system is lined with ciliated cells.  The bronchi enter the lungs and spread in a treelike fashion into smaller tubes called bronchial tubes.
The bronchial tubes divide and further subdivide, and their walls become thinner and have progressively less cartilage.  Eventually, they become a tiny group of tubes called bronchioles.

8. Alveoli
Smoking makes it difficult for oxygen to be taken through the alveoli.  When cigarette smoke is inhaled, about one-third of the particles remain within the alveoli.
Each bronchiole ends in a tiny air chamber that looks like a bunch of grapes.  Each chamber contains many cup-shaped cavities known as alveoli (air sacs).  
The walls of the alveoli, which are only about one cell thick, are the respiratory surface.  They are thin, moist, and are surrounded by several capillaries.
The exchange of oxygen and carbon dioxide between the blood and the air occurs through these walls.
Capillaries
Alveolus

9. Lungs
The lungs are large, lobed, paired organs in the chest (also known as the thoracic cavity).
Thin sheets of membranes separate the inside of the chest cavity from the outer surface of the lungs.

10. Ventilation Ventilation is the mechanics of breathing in and out.
It involves inhalation (taking in air) and exhalation (expelling air out) by using the diaphragm.

11. The bottom of the thoracic cavity is formed by the diaphragm (a thin muscular layer) that moves up and down, contracting when we inhale, and relaxing when we exhale.
Take a moment right now to feel the action of your diaphragm while inhaling and exhaling.

12. Inhalation/Inspiratin
When you inhale, muscles in the chest wall contract, lifting the ribs and pulling them, outward.
The diaphragm at this time moves downward enlarging the chest cavity.
Reduced air pressure in the lungs causes air to enter the lungs.

13. Exhalation/Expiration
When you exhale, muscles in the chest wall relax, lowering the ribs and pushing them, inward.
The diaphragm at this time moves back to its original position decreasing the volume of chest cavity.
Increased air pressure in the lungs causes air to rush out of the lungs.

14. Diseases of the Respiratory System
Asthma narrows the airways by causing allergy-induced spasms of surrounding muscles or by clogging the airways with mucus.
Bronchitis is an inflammation of the bronchi that reduces airflow and is caused by long-term exposure to irritants such as cigarette smoke, air pollutants, or allergens.
Cystic fibrosis is a genetic defect that causes excessive mucus production that clogs the airways.
Lung cancer is usually caused by smoking (90% of cancer patients) or breathing in second-hand smoke (over 5%).
Asthma
Bronchitis

15. Classroom Practice
Draw out the parts to the respiratory system and describe the function of each part.
Parts Needed:
Nose
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Diaphragm
Alveoli
Capilaries