Respiratory System

Nasal cavity Oral cavity

Trachea Left main (primary) Right main (primary) bronchus

Right Left lung Inhalation & Exhalation • A key component of inhalation ( in) is taking up into the body. • A key component of exhalation (breathing out) is releasing out of the body.

• Note that the air in the atmosphere has both oxygen and carbon dioxide (as well as nitrogen and other gasses). When one inhales, we take in a mixture of all of these gasses found in the atmosphere into the . When we exhale, we exhale a mixture of all of these gasses. • The main function for breathing is to take in oxygen and remove excess carbon dioxide from our bodies.

• Oxygen (O2) is needed by every cell in the body (brain, , muscles, etc.) to generate energy.

• Carbon dioxide (CO2) is a biproduct of producing energy. Having excess carbon dioxide can be toxic to the body, therefore, it is necessary to remove excess carbon dioxide from the body. Oxygen Flow • Oxygen enters the body through the nasal cavity or oral cavity during inhalation (breathing in). Oxygen then passes through the pharynx (posterior to nasal and oral cavities), down the larynx, and into the .

• The trachea branches into the left Nasal cavity Oral cavity and right bronchi Pharynx (singular bronchus) Larynx leading oxygen to Trachea Left main the lungs. (primary) Right main bronchus (primary) bronchus

Right lung Left lung Oxygen Flow Trachea Bronchi • In the lungs, the left (branch smaller and right bronchi and smaller) branch into smaller and smaller bronchi (see image), like branches on a tree.

• Oxygen flows through these smaller and smaller branches. Oxygen Flow • The smallest of these branches are called respiratory , and these lead to many alveoli (alveolus singular).

• The alveolus is a round structure that is part of the lungs, and is where occurs. Alveolus = 1 Alveoli = more than 1 Alveolar sac = bundle/bunch of Alveoli

Alveoli

Respiratory Alveolar duct bronchioles Terminal Alveolar sac Oxygen Flow • The alveolus is where gas exchange occurs between the lungs (alveolus) and blood. • Alveoli are covered in to allow gas exchange. • Reminder: capillaries are the smallest of blood vessels. • At the alveolus, oxygen passes from the alveolus through the respiratory membrane and into the blood.

Respiratory bronchiole

O2

Alveolus CO2

Capillaries Alveolus Respiratory Membrane Carbon Dioxide Flow • As oxygen passes from the alveolus and into the blood, carbon dioxide exits the blood by passing from the blood (in capillaries), though the respiratory membrane, and into the alveolus. • Carbon dioxide then passes from the alveolus to respiratory bronchioles.

Respiratory bronchiole

O2

CO2 Alveolus Capillary

Capillaries Alveolus Respiratory Membrane Carbon Dioxide Flow • Carbon dioxide continues to pass through the bronchi in the lungs, to the trachea, into the larynx, then pharynx, until it reaches the oral or nasal cavity and then is released into the atmosphere when exhaling (breathing out).

Trachea Bronchi Nasal cavity Oral cavity Pharynx Larynx

Trachea Left main (primary) Right main bronchus (primary) bronchus Left lung Right lung