RRB Group D Science Respiratory System, Important Concepts

RRB Group D Science Respiratory System is a crucial topic that every candidate must understand thoroughly for the exam. It deals with how the human body breathes, takes in oxygen, and removes carbon dioxide, ensuring that every cell gets the energy it needs to function.

 This system not only supports life but also plays a role in vocalization, protecting the body from harmful substances, and maintaining the acid-base balance in the blood. A clear understanding of its organs, mechanisms, and functions can help candidates answer questions confidently and accurately in the RRB Group D Science section.

RRB Group D Science Respiratory System

Respiratory System (श्वसन तंत्र) is one of the most important topics in RRB Group D Science. Understanding it is crucial for questions related to human biology, physiology, and basic science concepts. 

Introduction to Respiratory System

The respiratory system is responsible for taking in oxygen (O₂) from the environment and removing carbon dioxide (CO₂) produced as a waste product from the body. This system ensures that oxygen reaches every cell in the body and energy is produced for daily activities.

Key Functions:

• Supply oxygen to blood

• Remove carbon dioxide from the body

• Maintain acid-base balance

• Support vocalization and protective reflexes (coughing, sneezing)

Difference Between Breathing and Respiration

Many students confuse breathing with respiration, but they are different:

• Breathing is felt and observed; air enters and exits the lungs.

• Respiration occurs at the cellular level, producing energy (ATP), heat, and CO₂.

Also Read: Railway RRB Calendar 2026

Organs of the Respiratory System

The human respiratory system consists of the following parts:

1. Nasal cavity (Nares) – Entry point for air, filters dust.

2. Pharynx (Throat) – Common passage for air and food.

3. Larynx (Voice box) – Helps in sound production.

4. Trachea (Windpipe) – Tube that carries air to lungs.

5. Bronchi – Two main branches of trachea entering lungs.

6. Bronchioles – Smaller branches of bronchi within the lungs.

7. Alveoli – Tiny air sacs; the smallest functional unit of the lungs where gas exchange occurs.

8. Lungs – Primary organs; right lung has 3 lobes, left lung has 2 lobes (space for the heart).

9. Pleura membrane – Protective layer covering lungs.

Mechanism of Breathing

Breathing involves inhalation and exhalation:

• Inhalation: Diaphragm contracts → lungs expand → air enters

• Exhalation: Diaphragm relaxes → lungs shrink → air leave

The epiglottis plays a key role in protecting the windpipe while swallowing. It closes the airway to prevent food from entering the lungs.

Respiration: Aerobic vs Anaerobic

1. Aerobic Respiration (With Oxygen)

• Takes place in mitochondria

• Produces 38 ATP molecules per glucose

• Byproducts: CO₂ and water

• Essential for cellular energy

2. Anaerobic Respiration (Without Oxygen)

• Takes place in cytoplasm

• Produces lactic acid (in animals) or ethanol (in microbes)

• Produces less energy than aerobic respiration

Common Step: Glycolysis – Glucose is broken into pyruvate in the cytoplasm, occurs in both aerobic and anaerobic respiration.

Gas Exchange in Lungs

Composition of air:

• Oxygen is absorbed into the blood via hemoglobin in red blood cells.

• Carbon dioxide is removed from blood via alveoli during exhalation.

Control of Respiration

The medulla oblongata in the brain regulates involuntary breathing. It controls:

• Breathing rate

• Sneezing, coughing, swallowing

• Digestion, heartbeat, blinking, vomiting

This ensures continuous oxygen supply even during sleep or unconsciousness.

Protective Features

• Epiglottis: Prevents food from entering the windpipe.

• Pleura membrane: Covers lungs, reducing friction and protecting lungs during expansion.

Important Note: Swallowing while talking or laughing can cause food to enter the airway, leading to choking.

Occupational Hazards

Workers in industries with dust, silica, or chemicals are prone to respiratory diseases such as silicosis, which affects lung function over time.

Energy Production

Respiration produces ATP (Adenosine Triphosphate), the energy molecule used by cells to perform various functions like movement, growth, and repair.

• Aerobic: 38 ATP per glucose

• Anaerobic: 2 ATP per glucose