Breathing and Exchange of Gases
Breathing and gaseous exchange are among the most important life processes that allow oxygen to enter the body and remove carbon dioxide from the body. This oxygen is required for cellular respiration and energy production, while the carbon dioxide is removed as a waste product. Understanding how the gases move between the body and the environment allows the students to learn the basic principles of human physiology and respiratory function.
This Story also Contains
- What is Breathing and the Exchange of Gases?
- Difference Between Breathing and Respiration
- Human Respiratory System
- Respiratory Organs
- Mechanism of Breathing
- Exchange of Gases
- Respiratory Volumes and Capacities
- Regulation of Respiration
- Respiratory System Diseases
- Transport of Gases
- Breathing and Exchange of Gases Quick Revision Notes
- Recommended videos on Breathing and Exchange of Gases
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Every year, multiple questions from this chapter are asked in exams like NEET and others, which makes it an important topic from an examination perspective. This chapter forms the foundation for understanding advanced concepts related to human health and physiology. Hence, it 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:
Difference Between Breathing and Respiration
Breathing is the physical process of inhaling oxygen and exhaling carbon dioxide, whereas respiration is the biochemical process in which food is broken down to release energy.
Feature | Breathing | Respiration |
Definition | Exchange of gases between the body and the environment | Oxidation of food to release energy |
Site | Respiratory organs | Cells, mainly mitochondria |
Nature | Physical process | Biochemical process |
Energy Release | No energy is released | Energy is released in the form of ATP |
Purpose | Supplies oxygen and removes carbon dioxide | Produces energy for cellular activities |
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-
Component | Function |
Nostrils | The entry point for air filters dust with hair follicles. |
Pharynx | It serves as the common passage for air and food, and prevents food from entering the larynx. |
Larynx | It is also known as the soundbox, and contains the vocal cords and is protected by the epiglottis. |
Trachea | The primary bronchi is divided by the windpipe, and are supported by the C-shaped cartilaginous rings. |
Bronchi & Bronchioles | These are the branching tubes that lead to alveoli and is responsible for air circulation. |
Alveoli | These are the microscopic air sacs where the gaseous exchange takes place and are surrounded by capillaries. |
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.
Exchange of Gases
The exchange of gases occurs mainly in the alveoli of the lungs and between the blood and body tissues. It takes place due to differences in the partial pressures of oxygen and carbon dioxide.
Site of Gas Exchange | Oxygen Movement | Carbon Dioxide Movement |
Alveoli (Lungs) | Oxygen moves from the air in the alveoli into the blood. | Carbon dioxide moves from the blood into the alveoli and is removed during exhalation. |
Body Tissues | Oxygen moves from the blood into the body cells. | Carbon dioxide produced by the cells moves into the blood for transport to the lungs. |
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-
Volume/Capacity | Measurement (ml) | Description |
Tidal Volume (TV) | 500 ml | Normal inhalation/exhalation |
Inspiratory Reserve Volume (IRV) | 2500-3000 ml | Extra air inhaled |
Expiratory Reserve Volume (ERV) | 1000-1100 ml | Extra air exhaled |
Residual Volume (RV) | 1100-1200 ml | Air remaining after forced expiration |
Vital Capacity (VC) | TV + IRV + ERV | Maximum air breathed in/out |
Total Lung Capacity (TLC) | VC + RV | Total lung capacity |
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-
Aspect | Description |
Primary Control Centres | The medulla oblongata and pons regulate respiration based on oxygen requirements. |
Respiratory Rhythm Centre | Located in the medulla, it generates the basic rhythm of breathing. |
Pneumotaxic Center | Found in the upper pons, it modulates the rhythm by reducing the duration of inspiration. |
Chemosensitive Area | Sensitive to levels of carbon dioxide (CO₂) and hydrogen ions (H⁺), signalling changes in expiration rates. |
Receptors | Chemoreceptors in the carotid artery and aorta detect blood levels of CO₂ and H⁺ ions. |
Feedback Mechanism | Elevated CO₂ levels trigger increased respiratory activity to maintain oxygen supply and remove CO₂. |
Voluntary Control | Respiration can be voluntarily controlled through higher brain centres for activities like speaking or breath-holding. |
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-
Disorder | Description |
Asthma | Narrow and inflamed airways leading to difficulty in breathing. |
Bronchitis | Inflamed bronchioles, caused by smoking, lead to cough and mucus. |
Emphysema | Damaged alveoli leading to reduced surface area, seen in smokers |
Pneumonia | Lung infection causes inflammation and fluid buildup in the alveoli. Symptoms are cough, fever, and chest pain. |
Tuberculosis | Bacterial infection caused by Mycobacterium tuberculosis affects the lungs. |
Occupational Lung Diseases | Exposure to harmful substances like coal, dust or asbestos causes the disease. Leads to breathing problems and lung damage |
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.
About 70% of carbon dioxide is transported as bicarbonate ions 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 can bind with four molecules of oxygen to form oxyhaemoglobin.
The partial pressure of oxygen.
The partial pressure of carbon dioxide.
Hydrogen ion concentration (pH)
Temperature.
When the saturation of haemoglobin is plotted towards the partial oxygen, then it is known as the oxygen dissociation curve.
High partial pressure of oxygen, low carbon dioxide concentration, low hydrogen ion concentration, and low temperature are the conditions which favour the formation of oxyhemoglobin. On the other hand, low partial pressure of oxygen, high carbon dioxide concentration, high hydrogen ion concentration, and high temperature help the release of oxygen from haemoglobin in the tissue.
Breathing and Exchange of Gases Quick Revision Notes
Breathing is the process of taking in oxygen and giving out carbon dioxide.
The human respiratory system consists of the nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.
During inspiration, the diaphragm contracts and the chest cavity expands, allowing air to enter the lungs.
During expiration, the diaphragm relaxes, and the chest cavity becomes smaller, pushing air out of the lungs.
Oxygen is transported in the blood mainly by haemoglobin in the form of oxyhaemoglobin.
Most carbon dioxide is carried in the blood as bicarbonate ions.
The medulla oblongata and pons help regulate the rate and depth of breathing.
The tidal volume of a healthy adult is about 500 mL of air per breath.
Oxygen and carbon dioxide are exchanged between the lungs, blood, and tissues by simple diffusion
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Frequently Asked Questions (FAQs)
The middle of the respiratory rhythm, positioned withinside the vicinity of the medulla of the brain, is frequently chargeable for regulating the respiratory. The pneumatic middle can alternate the feature of the respiration rhythm middle with the aid of sending alerts to lessen the inspiratory fee. The chemosensitive location is close to the respiration middle. It is touchy to carbon dioxide and hydrogen ions. This vicinity sends alerts to alternate the expiratory fee to do away with connections.
Receptors withinside the carotid artery and aorta file the concentrations of carbon dioxide and hydrogen ions withinside the blood. As the carbon dioxide degree rises, the respiration middle sends nerve impulses for the important changes.
Insects have a trachea machine that contains a community of tubes. The change of gases happens via the trachea machine. Spiracles are the small openings at the aspect of the insect’s frame that are chargeable for soaking up oxygen-wealthy air in the frame. The spiracles are related to the trachea. The oxygen is then transported to the trachea through spiracles. The oxygen begins off evolved defusing withinside the frame. Whereas, carbon dioxide takes the opposite path. From the molecule of the frame, it travels to the tracheas and exits from the spiracles.
1. Breathing or pulmonary airflow with the aid of oxygen from the atmospheric air is drawn internal and carbon dioxide-wealthy alveolar air is launched out.
2. Diffusion of each oxygen and carbon dioxide throughout the alveolar membrane.
3. Gases are transported at some stage in the frame cells with the aid of using the blood.
4. Diffusion of oxygen and carbon dioxide among blood and tissues of the frame.
5. The cells make use of oxygen for catabolic reactions, ensuing withinside the launch of carbon dioxide.
The most quantity of air a person breathes in after a pressured expiration is known as critical ability. Vital ability is better for athletes and singers. Vital ability indicates the power of our idea and expiration.
This process of exchange of O2 from the atmosphere with CO2 produced by the cells is called breathing, commonly known as respiration. Place your hands on your chest; you can feel the chest moving up and down. You know that it is due to breathing.
