Passage of Oxygen in the Respiratory System

The correct representation of the passage of oxygen in the respiratory system is option 'D': Nose - Wind pipe - Lungs - Blood.

Explanation:

The respiratory system is responsible for the exchange of gases, particularly oxygen and carbon dioxide, between the body and the environment. Let's break down the passage of oxygen in the respiratory system step by step:

1. Nose:
- The process of respiration begins in the nose.
- When we inhale, air enters our body through the nostrils.
- The nose acts as the primary entrance for oxygen to enter the respiratory system.
- It filters, warms, and moistens the incoming air before it reaches the lungs.
- The oxygen passes through the nasal cavity and moves towards the next step.

2. Windpipe (Trachea):
- The windpipe, also known as the trachea, is a tube-like structure that connects the nose and mouth to the lungs.
- After passing through the nasal cavity, oxygen travels down the windpipe.
- The trachea is lined with tiny hair-like structures called cilia, which help in trapping dust particles and other foreign substances present in the air.
- The trachea then branches into two smaller tubes called bronchi.

3. Lungs:
- The bronchi further divide into smaller tubes called bronchioles, which lead to the lungs.
- The lungs are the main organs of the respiratory system and are responsible for the exchange of gases.
- Within the lungs, the bronchioles continue to divide into even smaller structures called alveoli.
- The alveoli are tiny air sacs surrounded by blood vessels called capillaries.
- It is in the alveoli that the actual exchange of oxygen and carbon dioxide takes place.
- Oxygen from the inhaled air diffuses through the thin walls of the alveoli and enters the capillaries.

4. Blood:
- Once oxygen enters the capillaries, it binds to red blood cells, which carry it throughout the body.
- The oxygen-rich blood is then pumped by the heart to various organs and tissues, where it is needed for cellular respiration.
- At the same time, carbon dioxide, a waste product of cellular respiration, is released from the cells into the bloodstream.
- The carbon dioxide is carried back to the lungs through the capillaries, where it is expelled from the body during exhalation.

Therefore, the correct representation of the passage of oxygen in the respiratory system is Nose - Windpipe - Lungs - Blood (option D).