Describe the structure and functioning of the human respiratory system.

Ans: The human respiratory system is responsible for the exchange of gases, primarily oxygen and carbon dioxide, between the body and the external environment. It consists of various structures and functions that allow for the process of respiration.:

Structure of the Human Respiratory System:

Nose and Mouth:

Air enters the respiratory system through the nose and mouth.
Hairs in the nose help filter out dust and particles, while mucus moistens and traps incoming air.

Pharynx (Throat):

The pharynx is a common passage for both air and food.
A flap called the epiglottis prevents food from entering the airway when swallowing.

Larynx (Voice Box):

The larynx contains vocal cords that vibrate to produce sound (voice).

Trachea (Windpipe):

The trachea is a tube that carries air from the pharynx to the lungs.
Rings of cartilage provide support and prevent the trachea from collapsing.

Bronchi and Bronchioles:

The trachea splits into two bronchi, one leading to each lung.
The bronchi further divide into smaller tubes called bronchioles.
Bronchioles are lined with tiny hairs called cilia that help trap particles, and they lead to air sacs called alveoli.


Alveoli are small, thin-walled sacs in the lungs where gas exchange takes place.
Oxygen from the air enters the bloodstream, and carbon dioxide is removed from the bloodstream and exhaled.

Functioning of the Human Respiratory System:


  • The act of inhaling and exhaling is called breathing.
  • When we inhale, the diaphragm contracts and moves downward, and the ribcage expands, creating more space in the chest cavity. This decreases air pressure inside the lungs, causing air to rush in.
  • When we exhale, the diaphragm relaxes, and the ribcage contracts, reducing the chest cavity’s size. This increases air pressure in the lungs, pushing air out.

Gas Exchange:

  • Oxygen from inhaled air diffuses across the walls of the alveoli into the bloodstream, where it binds to red blood cells and is transported throughout the body.
  • Carbon dioxide, a waste product of metabolism, is released from the blood into the alveoli and exhaled during exhalation.

Transport of Gases:

  • Oxygen-rich blood is pumped from the heart to body tissues, where it delivers oxygen.
  • Oxygen-poor blood returns to the heart, is pumped to the lungs, and releases carbon dioxide during exhalation.

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