Breathing and Exchange of Gases

Breathing and gaseous exchange is the most important life process which allows oxygen to enter the body and also remove carbon dioxide from the body. This is very important for cellular energy production and overall body function. Having the knowledge of how oxygen and carbon dioxide get in and out of the body helps students to understand the basics of human physiology.

This Story also Contains

1. What is Breathing and the Exchange of Gases?
2. Human Respiratory System
3. Respiratory Organs
4. Mechanism of Breathing
5. Respiratory Volumes and Capacities
6. Regulation of Respiration
7. Respiratory System Diseases
8. Transport of Gases
9. Recommended videos on Breathing and Exchange of Gases

This topic is frequently asked in competitive exams like NEET and AIIMS, making it an important part of the class 11 biology curriculum. It lays the foundation for more advanced studies in physiology and health sciences. Helping students build a strong base for medical and science-related courses. Hence, this chapter is highly important for any student studying biology.

What is Breathing and the Exchange of Gases?

Breathing is an important biological activity that allows organisms to take in oxygen and give out carbon dioxide. The structures that make up this process are the nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli. In class 11, these constituent parts are detailed by showing that air reaches different parts of the system and how gas exchanges occur in the alveoli.

Also Read:

• Respiration in plants

• Thorax

• Difference Between Breathing and Respiration

Human Respiratory System

The human respiratory system is responsible for the intake of oxygen and the removal of carbon dioxide from the body. It includes organs like the nose, trachea, lungs, and diaphragm, all working together to support breathing and gas exchange.

• The human respiratory system functions for the exchange of gases,i.e., carbon dioxide and oxygen, between the body and the environment.
• It includes the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
• Air enters through the nose where it is filtered, moistened, and warmed, then travels down the pharynx and larynx, passes through the trachea and enters the lungs via the bronchi inside the lungs.
• The bronchi are divided into smaller tubes called bronchioles that end in alveoli, which are tiny sac-like structures with thin walls surrounded by capillaries. This is where gaseous exchange occurs.
• Oxygen diffuses into the blood, and carbon dioxide diffuses out of the tissues. Breathing is important for respiration and also helps in vocalisation and regulating body pH.

Respiratory Organs

Respiratory organs like the lungs, trachea, bronchi and alveoli help in the exchange of gases in humans. Lungs are the primary organs where oxygen is absorbed and carbon dioxide is released. The organ and its related function are described below-

Mechanism of Breathing

Breathing is a rhythmic process involving inhalation and exhalation. It is regulated by the diaphragm and intercostal muscles, creating pressure changes that allow air to move in and out of the lungs. Breathing involves the following steps:

• The mechanism of breathing or pulmonary ventilation involves two phases, inspiration and expiration.
• During inspiration, the diaphragm contracts and moves downward, and the external intercostal muscles between the ribs contract to expand the chest cavity.
• This decreases the pressure inside the lungs compared to the outside atmosphere, causing air to rush in.
• During expiration, the diaphragm and intercostal muscles relax, reducing the volume of the thoracic cavity and increasing the pressure inside the lungs, which pushes the air out.
• Breathing is a rhythmic process controlled by the medulla oblongata and pons, and the brain stem, which regulates the rate and depth based on the levels of carbon dioxide in the blood.

Respiratory Volumes and Capacities

Respiratory volumes and capacities refer to the different measurements of air during various phases of breathing. These include tidal volume, vital capacity, and residual volume, and are important indicators of lung health and efficiency. The various lung volumes and capacities that are used to assess lung health are explained below-

Regulation of Respiration

Breathing is controlled by the respiratory centre in the medulla oblongata and pons of the brain, which responds to carbon dioxide levels and blood pH to adjust the breathing rate. The tabular form of the regulation of respiration is explained below-

Respiratory System Diseases

The diseases include asthma, bronchitis, pneumonia, and emphysema. These respiratory system disorders affect breathing efficiency and gas exchange, often as a result of infections, allergens, and long-term exposure to pollutants. Some of those diseases are explained below-

Transport of Gases

Gas transport in the body is important to supply oxygen to tissues and remove carbon dioxide produced during cellular respiration. The blood plays a central role in transporting both gases.

Transport of oxygen

• About 98.5% of oxygen is transported in the blood by binding to haemoglobin in red blood cells, forming oxyhaemoglobin. The remaining 1.5% is dissolved in the plasma.
• Oxygen binds to haemoglobin in the lungs, where oxygen concentration is high and is released in the tissues where oxygen concentration is low.

Transport of carbon dioxide

• 7% of carbon dioxide is transported dissolved in plasma.
• About 20 to 23% binds with haemoglobin to form carbamino haemoglobin.
• The majority, 70%, is transported as carbonic acid in the plasma.
• The enzyme carbonic anhydrase present in RBC helps convert carbon dioxide and water into carbonic acid, which then dissociates into bicarbonate and hydrogen ions. This reversible reaction helps maintain acid-base balance.

Oxygen Dissociation Curve

One molecule of haemoglobin binds with oxygen molecules. The binding of haemoglobin with oxygen relies upon:

1. The partial strain of oxygen.

2. The partial strain of carbon dioxide.

3. H+ ion concentration.

4. Temperature.

When the saturation of haemoglobin is plotted towards the partial oxygen, then it is known as the oxygen dissociation curve.

In low temperature, excessive partial oxygen, low partial carbon dioxide, much less H+ ion concentration (acidic pH), the curve in the direction of the proper suggests the formation of oxyhemoglobin, while in low partial oxygen, excessive carbon dioxide, primary pH, excessive-temperature the curve shifts in the direction of the left, which suggests the dissociation of oxygen with haemoglobin.

Also Read:

• Gases: Exchange And Regulation, Exchange of Gases in Human
• Respiration: Transport Of Oxygen and Carbon Dioxide
• Lung diseases
  

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