1. The Human Respiratory System

2. Nasal Passage Function: Special Features:
To pass air into the upper respiratory tract
The oral cavity also serves this function
Special Features:
Turbinates (thin bones) increase surface area
Mucus moistens the air
Capillaries warm the air
Cilia (small hairs) filter dirt and bacteria

3. Pharynx Function: Special Features:
Connects the mouth and nasal cavity to the larynx and esophagus
The “crossroads” for food and air
Special Features:
The air pathway in the pharynx is always open, except when you swallow
At that point it is covered by the epiglottis (small flap of cartilage that prevents food from entering the trachea)

4. Larynx Function: Special Features: Voice box Houses the vocal cords
When you breathe normally, there is a large gap between the 2 cords
When you speak, muscles around the larynx contract, bringing the cords closer together.
The vibration of the cords causes different sounds

5. Trachea Function: Special Features: Windpipe
Carries air to the bronchi
Special Features:
Supported by C-shaped cartilage rings
Lined with mucus and cilia which trap dirt and sweep it up to the pharynx where it can be expelled or swallowed

6. Bronchi/Bronchioles Function: Special Features:
Two bronchi (singular bronchus) carry air from the trachea into the lungs
Special Features:
In the lungs, the bronchi branch into smaller bronchioles (which connect to the alveoli)
Bronchi and bronchioles are lined with mucus and smooth muscles which control the size of the airways.

7. Alveoli Function: Special Features:
A cluster of tiny sacs surrounded by a network of capillaries
Site of gas exchange between respiratory and circulatory system (diffusion and facilitated diffusion)
Special Features:
HUGE surface area (size of a tennis court)
Bronchi and bronchioles are lined with mucus and smooth muscles which control the size of the airways.

8. Lungs Function: Special Features: Organ containing millions of alveoli
Right lung has 3 lobes
Left lung has 2 lobes (to make room for the heart)
The lungs are contained within the pleural membrane (thin layers of tissue)

9. Diaphragm
Function:
Muscle layer between the thoracic cavity (heart and lungs) and the abdominal cavity (stomach etc.)
Facilitates breathing