The Human Respiratory System

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

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)

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

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

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.

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.

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)

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