How does ventilation occur in humans

Muscular breathing movements and recoil of elastic tissues create the changes in pressure that result in ventilation. Pulmonary ventilation involves three different pressures:. Atmospheric pressure is the pressure of the air outside the body. Intraalveolar pressure is the pressure inside the alveoli of the lungs.

Intrapleural pressure is the pressure within the pleural cavity. So please, read on. Simply put, ventilation is breathing — the physical movement of air between the outside environment and the lungs. Air travels through the mouth and nasal passages, then down the pharynx. Upon reaching the vocal cords, air flows into the trachea, transitioning from the upper airway into the lower airway.

Here, it continues distally to the carina, then through the primary bronchi, various branches of bronchioles, and eventually arriving in the alveoli. This is inhalation. Air movement in a reverse pathway from alveoli to mouth and nose, is exhalation.

Inhalation, followed by exhalation, equals one ventilation. This is what you observe chest rise and fall when determining the breathing rate. A ventilation can only take place if the brainstem, cranial and associated peripheral nerves, the diaphragm, intercostal musculature and lungs are all functional.

Combining the function of all these structures, the pulmonary ventilation mechanism establishes two gas pressure gradients. One, in which the pressure within the alveoli is lower than atmospheric pressure — this produces inhalation.

The other, in which the pressure in the alveoli is higher than atmospheric pressure — this produces exhalation. These necessary changes in intrapulmonary pressure occur because of changes in lung volume. So, how does the lung volume change? Quite simply, it is a combination of muscle contractions stimulated by the central nervous system , and the movement of a serous membrane within the thorax called the pleura.

The pleura is made of two layers: a parietal layer that lines the inside of the thorax and a visceral layer that covers the lungs and adjoining structures blood vessels, bronchi, and nerves.

Between the visceral and parietal layers is a small, fluid-filled space, called the pleural cavity. The initiation of ventilation begins with the brainstem, where impulses action potentials generate within the medulla oblongata, then travel distally within the spinal cord. The impulse traverses individually through cervical nerves three, four and five until just above the clavicle.

Here, the three cervical nerves merge into one large nerve called the phrenic nerve, which attaches distally to the diaphragm. Imagine these two nerves resembling a pair of suspenders on the anterior chest. The delivered impulse from the phrenic nerve initiates diaphragm contraction.

The intercostal muscles are a group of intrinsic chest wall muscles occupying the intercostal spaces. They are arranged separately in three distinct layers external intercostal muscles, internal intercostal muscles, and innermost intercostal muscles. The intercostal nerves that stimulate these muscles originate from the spinal cord thoracic nerves Inhalation is initiated as the dome-shaped diaphragm is stimulated. As it contracts and flattens, the thorax expands inferiorly.

But how does it work? Breathing uses chemical and mechanical processes to bring oxygen to every cell of the body and to get rid of carbon dioxide. Our body needs oxygen to obtain energy to fuel all our living processes. Carbon dioxide is a waste product of that process. The respiratory system, with its conduction and respiratory zones, brings air from the environment to the lungs and facilitates gas exchange both in the lungs and within the cells. Nurses need a solid understanding of how breathing works, and of vital signs of breathing and breathing patterns, to be able to care for patients with respiratory problems and potentially save lives in acute situations.

Citation: Cedar SH Every breath you take: the process of breathing explained. Nursing Times [online]; 1, It is also often the first question asked about newborns and the last one asked about the dying.

Why is breathing so important? What is in the breath that we need so much? What happens when we stop breathing? These might seem obvious questions, but the mechanisms of respiration are often poorly understood, and their importance in health assessments and diagnostics often missed.

This article describes the anatomy and physiology of breathing. We need energy to fuel all the activities in our bodies, such as contracting muscles and maintaining a resting potential in our neurons, and we have to work to obtain the energy we use.

Green plants take their energy directly from sunlight and convert it into carbohydrates sugars. We cannot do that, but we can use the energy stored in carbohydrates to fuel all other reactions in our bodies. To do this, we need to combine sugar with oxygen.

We therefore need to accumulate both sugar and oxygen, which requires us to work. As a matter of fact, we spend much of our energy obtaining the sugar and oxygen we need to produce energy. We source carbohydrates from green plants or animals that have eaten green plants, and we source oxygen from the air. Green plants release oxygen as a waste product of photosynthesis; we use that oxygen to fuel our metabolic reactions, releasing carbon dioxide as a waste product.

Plants use our waste product as the carbon source for carbohydrates. To obtain energy we must release the energy contained in the chemical bonds of molecules such as sugars. The foods we eat such as carbohydrates and proteins are digested in our gastrointestinal tract into molecules such as sugars and amino acids that are small enough to pass into the blood.

The blood transports the sugars to the cells, where the mitochondria break up their chemical bonds to release the energy they contain. Cells need oxygen to be able to carry out that process. As every cell in our body needs energy, every one of them needs oxygen. The energy released is stored in a chemical compound called adenosine triphosphate ATP , which contains three phosphate groups.

When we need energy to carry out an activity, ATP is broken down into adenosine diphosphate ADP , containing only two phosphate groups. Breaking the chemical bond between the third phosphate group and ATP releases a high amount of energy. Our lungs supply oxygen from the outside air to the cells via the blood and cardiovascular system to enable us to obtain energy.

As we breathe in, oxygen enters the lungs and diffuses into the blood. It is taken to the heart and pumped into the cells. At the same time, the carbon dioxide waste from the breakdown of sugars in the cells of the body diffuses into the blood and then diffuses from the blood into the lungs and is expelled as we breathe out.

One gas oxygen is exchanged for another carbon dioxide. This exchange of gases takes places both in the lungs external respiration and in the cells internal respiration. Fig 1 summarises gas exchange in humans. Our respiratory system comprises a conduction zone and a respiratory zone. This respiratory process takes place through hundreds of millions of microscopic sacs called alveoli. Oxygen from inhaled air diffuses from the alveoli into pulmonary capillaries surrounding them.

It binds to hemoglobin molecules in red blood cells, and is pumped through the bloodstream. Meanwhile, carbon dioxide from deoxygenated blood diffuses from the capillaries into the alveoli, and is expelled through exhalation.

The bloodstream delivers oxygen to cells and removes waste carbon dioxide through internal respiration, another key function of the respiratory system.

In this respiratory process, red blood cells carry oxygen absorbed from the lungs around the body, through the vasculature. When oxygenated blood reaches the narrow capillaries, the red blood cells release the oxygen.

It diffuses through the capillary walls into body tissues. Meanwhile, carbon dioxide diffuses from the tissues into red blood cells and plasma. The deoxygenated blood carries the carbon dioxide back to the lungs for release. Phonation is the creation of sound by structures in the upper respiratory tract of the respiratory system.