Lungs

Nasal Cavity

Nasal Cavity

Allows air to enter the respiratory system through the nose, filters air for pathogen and allergens, and warms the air. Most breathing happens through here.

Buccal Cavity

The mouth, works with the nasal cavity to allow the passage of air into the trachea.

Larynx

A hollow tube that lets air pass through the pharynx (throat) through to the trachea. Contains vocal cords.

Bronchi

Airways that lead from the trachea to the bronchioles.

Bronchioles

Branches of bronchi that lead to the alveoli.

Pharynx

Throat, air from the mouth & nose travels to the trachea. It is also a part of the digestive system where it carries food and water into the esophagus.

Epiglottis

A flap of cartilage that covers the trachea when we swallow so we don’t choke.

Trachea

Airway that carries air into the lungs from the nasal and buccal cavities.

• Contains C-shaped cartilage rings to provide structure and prevent it from collapsing while breathing

• Smooth muscle helps regulate airflow

• Mucus membrane lining traps dust, debris, and bacteria before entering the lungs.

Alveoli

Tiny sacs with a large surface area across which carbon dioxide and oxygen are exchanged between the air and blood.

Alveolar fluid/surfactant

Type II pneumocytes (cells in the alveoli) secrete alveolar fluid which moistens the surface of the alveoli, allowing gases to dissolve into the surfactant before diffusing across the wall of the alvoli.

Alveolar fluid contains surfactant (mixture of lipids and proteins) this..

reduces surface tension of the alveoli and thus helps prevent alveolar collapse.

Many alveoli

Create a large surface area, creating lots of area for carbon dioxide and oxygen to be exchanged across.

Highly branched network of bronchioles

Each bronchioles branches into many alveoli, the exchange surface of the blood thus increasing the surface area for gas exchange & the rate of gas exchange.

Extensive capillary beds surrounding alveoli

There is a very short distance for oxygen to diffuse from the air in the alveoli into the blood as well as a very short distance for carbon dioxide to diffuse from the blood into the alveoli.