Concept 30.5

Biology
Concept 30.5
Rodrigo Duarte
Juan José Granai
Jose Juan Uclés

Vocabulary
Pharynx
Epiglottis
Larynx
Trachea
Bronchus
Lung
Bronchiole
Alveolus
Diaphragm

Definitions
Pharynx: The junction in the throat of the alimentary canal and the trachea.
Epiglottis: Flap of tissue that covers the trachea during swallowing, preventing food from entering the lungs.
Larynx: Voicebox; contains the vocal cords.
Trachea: Tube between the larynx and bronchi through which air travels to the lungs; also called the windpipe.
Bronchus: One of two tubes connecting the trachea to each lung.
Lung: Organ consisting of sponge-like tissue that exchanges oxygen and carbon dioxide with the blood.
Bronchiole: Thin tube that branches from a bronchus within a lung.
Alveolus: One of millions of tiny sacs within the lungs where gas exchange occurs.
Diaphragm: Sheet of muscle that forms the bottom wall of the chest cavity; contracts during inhaling and relaxes during exhaling.

Anatomy of the Respiratory System
The structures of the respiratory system include the mouth, nose, pharynx, larynx, trachea, and lungs. As you inhale, air enters the respiratory system through the nose or mouth. Many of the impurities in air, such as dirt and bacteria, are filtered by hair and mucus in the nose.
As air enters the body through the nose or mouth, it is warmed and moisture is added. Next, air passes into the pharynx where the passageways for air and food cross. The air pathway in the pharynx is always open, except when you swallow.
Then a flap of tissue called the epiglottis momentarily covers the air pathway and prevents water or food from entering.

Within each lung, the bronchus branches repeatedly into finer and finer tubes called bronchioles. This branching pattern looks somewhat like an upside-down tree, and in fact the system of tubes is sometimes called "the respiratory tree." Each bronchiole ends in grapelike clusters of tiny air sacs called alveoli.
Lungs contain millions of these tiny air sacs. The inner surface of each alveolus is lined with a layer of moist epithelial cells. Oxygen in the air you inhale dissolves in the film of moisture on these epithelial cells. Oxygen then diffuses into a web of capillaries surrounding each alveolus and enters red blood cells, binding to hemoglobin.

Breathing
The process of moving air into and out of your lungs is called breathing. Although you were most likely unaware of it, you probably took a breath of air and released it while you were reading this sentence. On average, you breathe about 15 times per minute, or more than 21,000 breaths each day.
A sheet of muscle called the diaphragm, which forms the bottom wall of the chest cavity, plays a key role in breathing.
This action increases the volume of your lungs, resulting in reduced air pressure within the alveoli. Since air tends to move from an area of higher pressure to an area of lower pressure, air rushes in through the nose or mouth and fills the alveoli.

Regulation of Breathing

QUESTIONS?

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Concept 30.5

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