Respiratory System

Introduction

The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation).

• The respiratory system of animals is crucial for the life as it allows the exchange of gases between an organism and the environment.
• This exchange of oxygen and carbon dioxide is called respiration.

Parts of the Respiratory System

The human respiratory system comprises of

• the Nose and Mouth: Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils, the air is warmed and humidified. Cilia (tiny hairs) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.
• Pharynx (throat): The nasal cavity and the mouth openings meet at the pharynx at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air. At the bottom of the pharynx, this pathway divides in two, the esophagus, which leads to the stomach and the other for air. The epiglottis, a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs.
• The larynx (voice box): Top part of Trachea. This short tube contains a pair of vocal cords, which vibrate to make sounds.
• Trachea:  The walls of the trachea are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs.
• Bronchi: At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles.
• Alveoli: Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each person has hundreds of millions of alveoli in their lungs.
• This network of alveoli, bronchioles, and bronchi is known as the bronchial tree.

The chest cavity, or thorax, houses the bronchial tree, lungs, heart, and other structures.

• The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by the diaphragm.
• The chest walls form a protective cage around the lungs and other contents of the chest cavity.

Classification of Respiratory Function

The respiratory system is divided based on the structure into two distinct parts:

• Upper Respiratory Sytem
• Lower Respiratory System

Based on function the system is divided into two zones:

• Conducting Zone
• Respiratory Zone