Why We Cannot Breath Underwater?
When we go underwater, we automatically stop breathing, yet water actually carries oxygen. How can fish breathe oxygen while we have to bring our own cylinders down to sea level? Also, if oxygen is found in the air, then why can't fish do the same?
The answer is the difference between terrestrial and marine respiration. When a human breathes, air containing oxygen and carbon dioxide travels from the nose, down the trachea, and into the lungs. In the lungs, air travels through the bronchi until they become so thin that oxygen can pass through the lung membranes and into the blood. A few seconds after ingesting glucose, blood cells release carbon dioxide into the exhaled air.
The Science Behind Breathing Underwater
Covalently bound hydrogen and oxygen atoms in water molecules require more energy to break apart and release oxygen. The human lung lining isn't meant for such a process, and a person would die before getting enough oxygen to resume breathing. Also, oxygen in its atomic state is not good for the lungs. Air has 20 times more oxygen than water, thus extracting dissolved oxygen from water is difficult. Fish are cold-blooded; therefore, they need less oxygen to breathe underwater.
Warm-blooded marine creatures, such as whales and dolphins, have trouble obtaining adequate oxygen through gills. Fish need oxygen to survive, but they don't breathe H2O; their gills collect dissolved oxygen from water. Several gasses can dissolve in liquids, as shown in carbonated soft drinks, which generate bubbles when opened. Some amphibians, including tadpoles, use their nostrils for breathing, like fish gills. Because amphibian tadpoles grow in water.
Liquid Breathing
Liquid breathing or water breathing is a type of respiration in which an organism that normally breathes air instead breathes an oxygen-rich liquid, like a perfluorocarbon. To facilitate gas exchange, a liquid suitable for maintaining substantial volumes of oxygen and carbon dioxide must be chosen.
Some perfluorochemicals (PFCs) have the right physical properties, such as the ability to dissolve gasses in the lungs, density, viscosity, vapor pressure, and the ability to dissolve lipids. So, it is very important to choose the right PFC for a specific biomedical application, such as liquid ventilation, drug delivery, or blood substitutes. PFC liquids have a wide range of physical properties, but they all have one thing in common: they dissolve respiratory gasses very well. These liquids carry more carbon dioxide and oxygen than blood does.
In theory, liquid breathing could help treat people who have severe damage to their lungs or hearts, especially children. Some people have also thought that liquid breathing could be used for deep diving and space travel. Even though liquid ventilation has made some progress recently, there is still no standard way to use it.
Duration of Breath Holding
The normal breath holding time of a person to hold their breath, while doing so deliberately, spans anywhere from 30 to 90 seconds. Breath-holding is a skill that can be trained to help an individual expand their lung capacity, and there are training recommendations available to assist with this goal. The training process typically takes a few months. These training methods could be utilized for advanced military training, free diving, swimming, or other recreational pursuits.
Importance of Breath Holding Time
Patients can try to hold their breath for longer periods of time by practicing once every hour.
The breath holding time normal values are 25 seconds and are safe.
A person needs to be careful not to overexert themselves.
Holding your breath has been shown in some early animal studies to aid in repairing brain injury.
In some cases, inflammation can be reduced by practicing specific breathing techniques, one of which is holding one's breath.
Regular relaxation practice can include certain breathing techniques in which you hold your breath for many seconds. It has the potential to boost cardiovascular health as well.
Why is It Advisable to Breathe Through Nose?
The structure of your nose is optimized for healthy, effective breathing. This is possible because:
Your nasal hair acts as a filter, trapping dust, allergies, and pollen before they may enter your lungs.
When you breathe through your nose, it warms the air and adds moisture to it. This makes the air we breathe in more comfortable for the lungs because it is closer to your body temperature.
- Inhaling through the nose releases nitric oxide, which has various health benefits. As a vasodilator, nitric oxide (NO) aids in the dilation of blood vessels. This can boost oxygen flow throughout your body.
How to Breath Underwater?
Inhale through your mouth and exhale through your nose until it seems natural.
Many swimmers shake their heads to breathe out of the side of their mouths.
However, you should only tilt your head to one side while breathing in through your mouth, and then turn your head back and exhale slowly through your nose.
Take time to practise lap swimming before venturing out.
How to Increase Breath Holding Capacity?
Diaphragmatic breathing, or "stomach breathing," uses the diaphragm to conduct most of the breathing work.
Pursed-lips breathing slows breathing and keeps airways open longer, minimizing work. This enhances lung function and oxygen-carbon dioxide exchange.
Yoga is a workout routine that mixes motion and relaxation techniques.
Learning these breathing exercises and practicing them regularly may help control asthma symptoms. Patients may also need less asthma medication.
Interesting Facts
Insects breathe through tracheae as they do not have lungs.
The maximum breathing capacity is 6 liters.
Our lungs get slightly older at the age of 20-25.
Key Features
In water breathing, the organism breathes oxygen-rich liquid.
The normal breath-holding time is 25 seconds.
Nitric oxide acts as a vasodilator.
FAQs on Breathing - A Detailed Summary
1. What is breathing and why is it essential for life?
Breathing is the physical process of moving air into and out of the lungs to facilitate gas exchange with the environment. It is essential for life as it allows the body to take in oxygen (O₂), which is required by all cells for cellular respiration to produce energy. Simultaneously, it enables the removal of carbon dioxide (CO₂), a waste product of metabolic processes.
2. How does the mechanism of breathing work in humans?
The mechanism of breathing is driven by the diaphragm and intercostal muscles and involves two main phases:
- Inhalation: The diaphragm contracts and moves down, while the rib muscles contract to lift the rib cage up and out. This increases the volume of the chest cavity, creating lower pressure inside the lungs compared to the outside air, which causes air to rush in.
- Exhalation: The diaphragm and rib muscles relax, decreasing the volume of the chest cavity. This increases the pressure inside the lungs, forcing air out.
3. What are the main organs of the human respiratory system?
The human respiratory system is a complex network of organs and tissues. Its primary components include:
- The Nose and Nasal Cavity for filtering, warming, and moistening air.
- The Pharynx (throat) and Larynx (voice box) which guide air towards the trachea.
- The Trachea (windpipe), which is the main airway to the lungs.
- The Bronchi and Bronchioles, which are branching airways within the lungs.
- The Lungs, the main organs of respiration.
- The Alveoli, tiny air sacs where the actual exchange of oxygen and carbon dioxide takes place with the blood.
4. Why is it generally better to breathe through your nose than your mouth?
Breathing through the nose is more beneficial than mouth breathing because the nasal passages are specifically adapted to prepare air for the lungs. The hairs and mucus in the nose act as a natural filter, trapping dust and pathogens. The nasal cavity also warms and humidifies incoming air, protecting the delicate lung tissues. Furthermore, nasal breathing releases nitric oxide, which helps improve oxygen circulation in the body.
5. How is lung capacity measured and what are some key respiratory volumes?
Lung capacity is measured using a device called a spirometer, which assesses how much air the lungs can hold and move. Key measurements as per the CBSE 2025-26 syllabus include:
- Tidal Volume (TV): The volume of air inhaled or exhaled during a normal breath.
- Vital Capacity (VC): The maximum amount of air a person can exhale after taking the deepest breath possible.
- Total Lung Capacity (TLC): The total volume of air the lungs can hold after a maximum inhalation, which is typically around 6 litres in a healthy adult male.
6. What is the key difference between breathing and cellular respiration?
Breathing is a physical or mechanical process involving the inhalation of oxygen and exhalation of carbon dioxide. In contrast, cellular respiration is a biochemical process that occurs inside the body's cells. It uses the oxygen supplied by breathing to break down glucose and generate ATP, the energy currency of the cell. In essence, breathing facilitates the gas exchange needed for cellular respiration to occur.
7. If water (H₂O) contains oxygen, why can't humans breathe underwater?
The oxygen atom in a water molecule (H₂O) is chemically bonded to two hydrogen atoms. Human lungs are designed to extract gaseous oxygen (O₂) from the air, not to break these strong chemical bonds in water. Fish use specialised organs called gills to extract the small amount of O₂ gas that is dissolved in water, which is a different process entirely from breaking down the water molecule itself.
8. How does the nervous system control the rate of breathing?
Breathing is primarily regulated by the respiratory centre in the brainstem, specifically the medulla oblongata and pons. This centre automatically controls the rhythm of breathing. However, the rate can be modified based on feedback from chemoreceptors in the body. These receptors are highly sensitive to the level of carbon dioxide in the blood. An increase in CO₂ is the most powerful stimulus to increase the rate and depth of breathing to restore balance.
9. How does the human respiratory system differ from that of an insect?
Humans and insects have vastly different respiratory structures. Humans have a centralized system featuring a pair of lungs. Oxygen is transported from the lungs to the body's cells via the circulatory system, using haemoglobin in the blood. Insects, however, have a decentralized network of air tubes called the tracheal system, which opens to the exterior through small pores called spiracles. This system delivers oxygen directly to the tissues without relying on a transport medium like blood.
10. What physiologically limits how long a person can hold their breath?
The primary factor limiting breath-holding time is not the lack of oxygen, but the buildup of carbon dioxide (CO₂) in the blood. As CO₂ levels rise, the blood becomes more acidic. This change is detected by chemoreceptors in the brain and major arteries, which then send powerful, involuntary signals to the respiratory centre. This creates an overwhelming and uncontrollable urge to breathe, forcing a person to exhale and inhale.
