The Human Respiratory System

1
The Human Respiratory System
2
Nasal Passage

• Function
• 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
• 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
• Voice box
• Houses the vocal cords
• Special Features
• 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
• 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
• 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
• 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
• Organ containing millions of alveoli
• Special Features
• 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