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Breathing and exchange of gases are interrelated to each other. It is part of the respiratory system activities that facilitate the exchange of gases. Animals breathe in oxygen and breathe out carbon dioxide.
- Breathing and exchange of gases require energy that is released by the decomposition of food.
- The process of moving air in and out of the lungs is called breathing.
- It will convert oxygen with carbon dioxide in the cells.
- The process of breathing is also known as respiration.
- The term respiration was first introduced by Dutrochet.
- Plants take in carbon dioxide to give out oxygen.
- Body cells require a steady supply of oxygen for metabolic reactions that keep them alive.
- The respiratory and circulatory systems work together to transport oxygen and remove metabolic waste.
- It also contributes to the regulation of blood pH.
Read More: Aerobic Anaerobic Respiration
Key Terms: Breathing and exchange of gases, Breathing, Exchange of Gases, Respiratory System, Lungs, Inspiration, Expiration, Carbon Dioxide, Oxygen, Trachea, Sinus, Chest
Human Respiratory System
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The process of the human respiratory system starts from the nostrils, which are opened into the nascal cavity. The nasal cavity is extended to the nasal passage, which includes the larynx, trachea, and bronchi.
- The exchange of oxygen and carbon dioxide between the atmosphere and the body's cells is called respiration.
- Nerve impulses trigger the breathing process, also known as ventilation.
- It pulls air into and out of the lungs every 3 to 5 seconds through a network of channels.
- Gases are then transferred between the lungs and the blood.
- The process of transfer of gases is called external respiration.
- The gases are transported to and from the tissue cells by the blood.
- The exchange of gases between the blood and tissue cells is referred to as internal respiration.
- Finally, cellular metabolism or cellular respiration is the process by which cells utilize oxygen to perform their specific functions.
- The sum of these processes is referred to as respiration.
Respiration in Human Beings
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Parts of Respiratory System
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The different parts of a respiratory system are given below.
Nose
The nose is the favoured entrance for outside air to enter the respiratory system. The air-cleaning system includes the hairs that line the inside of the nose.
Mouth
Air can also enter through the mouth, which is beneficial for those who have a mouth-breathing habit. Those whose nasal passages are temporarily closed by a cold, or those who engage in strenuous exercise.
Read More: Breathing in other animals
Throat
The throat gathers air from your nose and mouth and transports it to your windpipe (trachea).
Sinus
Sinuses are hollow chambers in the bones of your head that connect to your nose through small apertures above and below your eyes. The sinuses regulate the temperature and humidity of inhaled air.
Sinuses
Trachea
The trachea (windpipe) is the tube that connects your throat to your lungs. The windpipe is divided into two main bronchial tubes, one for each lung, which is further divided into each lung lobe. These are then divided into bronchioles.
Lobes
The lobes, or divisions of your right lung, are separated into three. Each lobe resembles a sponge-like bubble filled with tissue. Only one opening is a branch of the bronchial tube that allows air to enter and exit.
- The lobes in your left lung are separated into two parts.
Respiratory Tract
Read More: Difference between Pharynx and Larynx
Pleura
The pleura are the two membranes that encircle each lobe of the lungs and separate them from the chest wall. They are actually one continuous membrane folded on itself.
Pleura
Cilia
The cilia (like extremely minute hairs) that line your bronchial passages move in waves. Mucus (sticky phlegm or liquid) is carried upward and out into your throat by this motion, where it is coughed up or swallowed.
- Mucus traps and holds a lot of the dust, germs, and other undesirable particles.
- When you cough, sneeze, clear your throat or swallow, you get rid of this debris.
Cilia
Alveoli
The air sacs or alveoli are located at the end of the bronchial tubes' tiniest branches, known as bronchioles. Alveoli are tiny air sacs where oxygen and carbon dioxide are exchanged.
Capillaries in Lungs
Capillaries
Capillaries are blood veins that go through the alveolar walls. Blood flows through capillaries, entering through the pulmonary artery and exiting through the pulmonary vein.
- The blood releases carbon dioxide into the alveoli through the capillary wall.
- It absorbs oxygen from the air in the alveoli.
Read More: Pharynx and Larynx
Respiratory Organs
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The process of breathing and exchange of gases is vary from organisms to organisms. In unicellular organisms, exchange of gases take place by the process of diffusion.
- In the process of diffusion entire body of organisms come in contact with air.
- Aquatic animals carry out the process of breathing with the help of gills.
- They use vascularised bags called lungs for exchange of gases.
- The process is different for mammals.
- They have fully developed respiratory system for exchange of gases.
The table below summarizes the respiratory organs for various animals.
| Respiratory Organs | Examples |
|---|---|
| Moist Skin | Earthworms, Frogs |
| General Body Surface | Sponges, Coelenterates, Flatworms |
| Lungs | Reptiles, Birds, Mammals |
| Tracheal Tubes | Insects |
| Gills | Aquatic Arthropods, Molluscs, Fishes |
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Process of Respiration
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The process of respiration is as follows:
- Firstly, breathing is initiated, by which oxygen from the surroundings is drawn in, and carbon dioxide is released.
- The second step involves the diffusion of oxygen and carbon dioxide into the alveolar membrane.
- It transports gases by the blood vessels.
- Next, diffusion of oxygen and tissues takes place between blood vessels and tissues.
- Lastly, the utilisation of oxygen takes place by the cells for catabolic reactions.
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Respiratory Volumes and Capacities
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Various respiratory volumes and capacities are as follows:
Tidal Volume (TV)
Tidal Volume is defined as the volume of air inspired and expired during the process of respiration. A healthy and fit man can inspire approximately 6000 to 8000 mL per minute. It is denoted by TV.
Inspiratory Reserve Volume (IRV)
Inspiratory Reserve Volume is a type of volume where a man can inspire additional air by for forcible inspiration. The average inspiratory reserve volume (IRV) is 2500 to 3000 mL.
Expiratory Reserve Volume (ERV)
Expiratory Reserve Volume is defined as the additional volume of air that is expired by man forcefully. The average expiratory reserve volume is 1000 mL to 1100 mL.
Residual Volume (RV)
The amount of air left in the lungs after the process of forcible respiration is called residual volume. The average residual volume is 1100 mL to 1200 mL.
Inspiratory Capacity (IC)
Inspiratory Capacity is defined as the total amount of air that a person can inspire after the process of expiration. The average inspiratory capacity is 9700 mL. It is the sum of TV + IRV.
Vital Capacity (VC)
Vital Capacity is defined as the maximum amount of air that a person can breathe inside the lungs after forcible expiration is called vital capacity. The average vital capacity is 10000 mL.
Total Lung Capacity (TLC)
Total lung capacity is the defined as the amount of air that is found in the lungs after the process of forcible inspiration. The average total lung capacity is 11000 mL.
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Breathing Mechanism
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The air we breathe in and out of our lungs has a different pressure. As a result, when the air pressure drops, the alveolar gaps widen, allowing air to enter the lungs (inhalation).
- When the pressure of the alveoli within the lungs exceeds the atmospheric pressure, the air is exhaled.
- The amount of the pressure difference determines the airflow rate.
Two processes are involved in the breathing mechanism which are as follows:
Inspiration
During inspiration, muscles connected to the ribs on the outer side contract, pulling the ribs out and expanding the chest cavity. Later, the diaphragm contracts and slides downwards which widens the chest cavity, causing the abdominal muscles to contract.
- The chest cavity expands, creating a partial vacuum that draws air into the lungs and fills the expanded alveoli.
- Inspiration is the process of taking in atmospheric air.
- It is a dynamic process.
- When the thoracic cavity expands and the air pressure drops, this is referred to as inspiration.
- The volume of the thoracic cavity is increased by contracting the external intercostal muscles.
- The diaphragm's contraction raises the size of the thoracic activity even further.
- Simultaneously, the lungs expand.
- The air pressure inside the lungs reduces when the lungs expand.
- When the pressure equalises, atmospheric air rushes into the lungs.
Inspiration and Expiration
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Expiration
Expiration is the second stage of breathing mechanisms. The expiration process happens after the gaseous exchange happens in the lungs and the air is evacuated.
- The act of exhaling is known as expiration.
- The muscles linked to the ribs contract while the diaphragm and abdominal muscles relax.
- It results in a reduction in the volume of the chest cavity.
- It will increase in the pressure in the lungs, causing the air in the lungs to be forced out via the nose.
- Expiration is the process of exhaling carbon dioxide. It's a non-active procedure.
- It happens when the size of the thoracic action shrinks, and the outside air pressure rises.
- The external intercostal muscles are now relaxed, whereas the internal intercostal muscles are contracting.
- The ribs are forced inwards as a result, and the thoracic cavity's size is diminished.
- The lungs become squeezed as the diaphragm relaxes.
- As a result, the pressure rises, forcing the air outside.
Changes during Inspiration and Expiration
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Exchange of Gases
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The exchange of gases takes place in the following way:
Oxygen Transport
Oxyhaemoglobin, the chemical composition of oxygen and haemoglobin, and oxygen solution in blood plasma are two forms of oxygen transported to tissue by the blood.
- When the concentration of oxygen in the blood is high, it mixes with haemoglobin to form haemoglobin.
- Oxyhemoglobin dissociates to release oxygen because it is unstable.
- The dissociation process is accelerated by low oxygen, low pH, and high temperatures.
Oxygen Transport Cycle
Carbon Dioxide Transport
Carbonic acid is formed when carbon dioxide dissolves with plasma water. Bicarbonate ions are formed when carbonic acid ionizes. The enzyme carbonic anhydrase catalyzes the formation of hydrogen ions.
- Sodium bicarbonate and potassium bicarbonate are formed when bicarbonate ions mix with sodium and potassium.
- Carbaminohemoglobin is formed when carbon dioxide reacts with haemoglobin.
- Finally, it reaches the lungs and is expelled from the body during expiration.
Carbon dioxide transport cycle
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Disorders of Respiratory System
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The various disorders of respiratory system are as follows:
Asthma
Asthma is a form of chronic disease that affects the airways in the lungs. The airways are in the form of tubes that are used to carry air in and out of the lungs.
Emphysema
Emphysema is a form of respiratory disorder that damages the alveolar walls. It will result in shortness of breath as air sacs are damaged.
Occupational Respiratory Disorder
Occupational Respiratory Disorder is a chronic disease commonly found in industrial workers engaged in grinding or stone-breaking. They are exposed to dust particles, which lead to inflammation.
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Things to Remember
- Breathing and exchange of gases involves inhaling oxygen and expelling carbon dioxide.
- Inhalation and exhalation are the two basic processes involved in breathing.
- The diaphragm and intercostal muscles relax during exhalation.
- Diaphragm and external intercostal muscles contract in case of inspiration.
- Overall volume of air inside the lungs changes as muscles around the lungs contract or relax.
- The air rushes out when the pressure inside the lungs is greater than the pressure outside.
- The lungs have increased compliance due to the high flexibility of lung tissue and low surface tension of fluids in the lungs.
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Sample Questions
Ques. What is the definition of inspiration? (2 marks)
Ans. Inhaling oxygen is the process of inspiration. The diaphragm contracts and slides downward when we breathe in. This increases the amount of room available in the chest cavity for our lungs to expand. As a result, the chest cavity is enlarged by the intercostal muscles between the ribs.
Ques. What is the mechanism of expiration and how does it work? (2 marks)
Ans. Expiration is the process of the body releasing carbon dioxide. The diaphragm relaxes during expiration, reducing the volume of the thoracic cavity while increasing the pressure inside. As a result, the lungs constrict and the air escapes.
Ques. What distinguishes breathing from respiration? (5 marks)
Ans. The difference between breathing and respiration are as follows:
| Breathing | Respiration |
|---|---|
| Breathing is a process of inhaling oxygen from surrounding and exhaling out carbon dioxide. | Respiration is the process of breaking of glucose and oxugen molecules into energy molecules. |
| It is a extracellular process. | It is an intra cellular process. |
| Breathing does not produce any energy. | Respiration produce large amount of energy. |
| It does not make use of enzymes. | It does make use of enzymes. |
| The process is initiated in lungs. | The process is initiated in cells. |
Ques. What are the lungs' primary functions? (2 marks)
Ans. Breathing is a vital process that involves the lungs. The carbon dioxide exits the blood and the oxygen inhaled from the outside environment enters. The lungs assist in this inhaling and exhaling.
Ques. What causes you to breathe? (2 marks)
Ans. Carbon dioxide stimulates breathing. Our bodies must expel the carbon dioxide that has accumulated in them. As a result, carbon dioxide is the primary cause of breathing. Low oxygen levels, on the other hand, are a considerably weaker trigger for breathing than carbon dioxide.
Ques. Is it better to breathe from your chest or your stomach? (2 marks)
Ans. We take a deep breath in via our nose. With the diaphragm contracting, air travels to our stomach. Our stomachs expand and our lungs fill up with air. This kind of breathing is the most efficient since it pulls the lungs down.
Ques. Explain the process of the exchange of gases? (4 marks)
Ans. The chemical component oxyhaemoglobin is generated during the transfer of oxygen. Oxyhaemoglobin is just haemoglobin combined with oxygen, as the name suggests. When the blood oxygen level is higher, this happens. The second type is the same oxyhaemoglobin solution that forms inside the blood plasma.
- Carbon dioxide is now delivered into the lungs by three mechanisms:
- In the process of CO2 dissolving in plasma water, carbonic acid (CH2O3) is generated.
- Carbonic acid produces bicarbonate ions by dissociating atoms via a chemical process known as ionization.
- These H2 ions are catalyzed by carbonic anhydrase.
- Carbaminohemoglobin is created when CO2 interacts with haemoglobin.
Ques. Explain the process of expiration? (4 marks)
Ans. Expiration Processes
- Expiration is the act of breathing out carbon dioxide. It's a process that takes place in the background.
- It happens when the size of the thoracic action shrinks while the outside air pressure rises.
- Internal intercostal muscles contract while external intercostal muscles relax.
- The ribs are pressed inwards as a result, and the thoracic cavity shrinks.
- The lungs are squeezed while the diaphragm relaxes.
- As a result, the air is driven outside as the pressure rises.
Ques. What are the features of respiratory system? (3 marks)
Ans. Respiratory system is a biological system that is made of organs and tissues.It consists of lungs, airways and blood vessels that is used for exchange of gases. It will exhale out carbon dioxide from the body.
- It is used for inhalation of oxygen.
- The oxygen is transported to different part of the body through cellular respiration.
- The respiratory system consists of nose, larynx, pharynx, trachea and bronchi.
- The whole body of an individual is divided into upper and lower airway systems.
Ques. What is the difference between inspiratory and expiratory capacity? (3 marks)
Ans. The difference between inspiratory and expiratory capacity are as follows:
| Inspiratory Capacity | Expiratory Capacity |
|---|---|
| Inspiratory capacity is defined as the total volume of air that can inhaled after normal expiration. | Expiratory Capacity is defined as the total volume of air that can be exhaled after normal inspiration. |
| It includes inspiratory reserve volume. | It includes expiratory reserve volume. |
| Its range is 9700 mL. | Its range is 8700 mL. |
Ques. Name three diffusion membrane? (3 marks)
Ans. The three diffusion membrane are as follows:
- A thin layer of squamous epithelium that is situated in the alveoli.
- The second layer includes endothelium, which consists of alveolar capillaries.
- The third layer includes substances that are found at the basement between the epithelium and endothelium.
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