4ZSS0167 Human Anatomy And Physiology


Refer to the physical principles that govern gas exchange and describe how the structure of lower respiratory systems facilitates gas exchanging.


The lower respiratory tract, or tract, comprises the trachea (bronchus), bronchioles, and bronchioles. Alveoli also includes lungs.

This system takes the oxygen from the upper respir system and releases it outside.

Other structures, such as the rib or thoracic cavity, and diaphragm, provide support and protection for these structures.

The function of the upper trachea is to inhale air and move it towards the windpipe or trachea.

There are bronchial and alveolar structures. The anatomy allows for the drawing of air and its processing in the lower respiratory tract. This facilitates gas exchange.

This essay discusses the structure and functions of the lower respiratory system that facilitates gaseous exchanging. It also discusses the physical principles that regulate the process.

The physical principles of gaseous exchanging include the diffusion of oxygen and carbon dioxide through respiratory membranes, ventilation, and the exchange of gases.

The lower respiratory tract is responsible for gaseous exchange. This is in accordance with the physical principles of gas trade.

The trachea, which is covered with cartilaginous rings and is tubeless, measures an inch in diameter.

It extends below the sternum and ends at the bottom of your larynx. From there it branches off into smaller tubes called bronchi.

When you inhale, the air is warm and filtered through the upper respiratory tract. This passes from the pharynx down into larynx then into the trachea which leads to bronchi or lungs (Cunningham and al.


These rings are C-shaped and have a gap on the posterior that help the trachea bend when the oesophagus presses down against food.

During exhalation the oxygenated air from the lungs is returned to the trachea.

The bronchi is the next structure. These are passageways that transport air inside and outside of the lungs.

From the bottom, the tubes of the primary and secondary bronchus branches off into further secondary and third-tier bronchi before finally becoming bronchioles.

These airways deliver oxygen-rich air to lungs via the trachea.

Deoxygenated blood containing high levels of carbon dioxide is exhaled through the reverse route.

Another mechanism occurs in the bronchioles. Bronchial smooth muscle relaxation causes dilation which allows greater ventilation. However, bronchoconstriction causes the opposite effect.

Lungs are essential for gaseous exchange in respiratory system.

This organ is responsible to the exchange of carbon dioxide and oxygen.

This organ is covered by the thoracic box, which is divided into left and right lungs.

The left lung is made up of two lobes. It has a slightly smaller volume than the right lung.

There is a curve in the heart’s accommodating notch.

The right lung has three lobes. They are slightly shorter because the diaphragm is muscle higher than where the liver is.

The oxygen from the air is absorbed into bloodstream through microscopic sacs known as alveoli and into surrounding capillaries. (Albertine 2016.

Deoxygenated air, or carbon dioxide waste, diffuses in an opposite direction from the capillaries to the alveoli.

The deoxygenated gas is expelled from the lungs by exhalation.

The physical principle of gaseous interchange takes place in this organ.

Through diffusion, the oxygen-taking and carbon dioxide-exchanging blood in the pulmonary arteries takes in oxygen.

This allows for the exchange of oxygen and carbon dioxide between blood and alveoli (Protti, et al.

The oxygen in the bloodstream diffuses from alveoli to the bloodstream, and the oxygen from the blood enters alveoli.

This diffusion requires a concentration gradient. The partial pressure or level of oxygen in the alveoli must be higher than that in blood. Additionally, the partial pressure or carbon dioxide concentration in alveoli should also be lower than in blood.

This would enable gaseous exchange in the lungs through diffusion (Mercer & Crapo 2015).

External respiration can also take place in the alveoli. These microscopic air sacs, which are located inside the lungs, facilitate gaseous exchange.

The terminal ends of the respiratory tract, where external respiration takes effect, called alveoli, are filled by air from the bronchioles during inhalation.

The oxygen is then pumped into the bloodstream through the pulmonary networks surrounding alveoli.

The deoxygenated blood then releases carbon dioxide through the exhalation of capillaries into the alveoli (Leong and Leong 2016).

Diaphragm, which is an organ that supplies muscle for breathing, forms the floor for the thoracic cavity.

This organ controls the physical process that is involved in breathing, including exhalation and inhalation.

The contraction of diaphragm occurs during inhalation. This causes movement to the abdomen cavity.

This allows the volume of the lung and thoracic cavity (Weibel 2015) to rise when deep breathed.

Normal exhalation is characterized by relaxation of the diaphragm and external intercostals muscles. As air is expelled, the thoracic cavity and thoracic cavities decrease.

The physical properties of gaseous exchanging are at the heart of all organ’s functions and structures.

The primary function and purpose of the human respiratory system is to exchange gases, carbon dioxide and oxygen.

There are three major principles involved in the exchange gas (oxygen and CO2) from the outside environment to the lungs. They flow in the bloodstream through ventilation, perfusion, diffusion.

The ventilation mechanism is where air moves within and outside the lungs.

Diffusion, another mechanism, is the spontaneous movement between gas in alveoli and blood in capillaries in the lungs.

The gaseous exchange mechanism where the heart pumps oxygenated air throughout the lungs is also affected by perfusion.

Partial pressure is essential for oxygen exchange between cells and the external environment.

The surface area of the 75-square-metre alveoli and capillaries has 75-square metres.

Similar to internal respiration there is intracellular oxygen that can be used for ATP production and simple diffusion along partial pressure gradients.

The actual blood flow through the pulmonary circulation is called pulmonary perfusion.

Due to its large surface area, and thinness the alveolar-capillary skin facilitates gas exchange at the interface air-blood.

Blood is pumped into the lungs through the right ventricle via the pulmonary artery.

This artery is split into right and left branches that supply blood to both the lungs.

These parts are divided and supply blood to both lungs with 2% blood pumping from right ventricle. However, this blood does not enter the alveolar capillaries.

This blood is known as shunted and it drains into the left-side heart without the involvement of alveolar gaseous Exchange (Gilbert Barness, Spicer, Steffensen (2014)

It can be seen that the lower respiratory tract structure allows for efficient exchange of carbon dioxide and oxygen.

This mechanism describes the physical principles that allow for gaseous exchange to take place in the lower respiratory tract.

Due to diffusion towards a concentration gradient, diffusion occurs in the alveoli of the lungs.

The warm air passes through the traphea, which heats it and filters it down to the trachea before reaching the lungs.

Bronchi function as passageways to transport oxygen rich air through the trachea and into the lungs.

Because lungs are the essential organs that alveoli rely on, they play an important role in gaseous exchange. Here oxygen diffuses into alveoli.

The same happens with carbon dioxide, which is deoxygenated blood. It diffuses from capillaries through diffusion and is expelled by exhalation.

This is how lower respiratory tract facilitates gaseous exchanging efficiently in accordance with the physical principles.

Refer to

Anatomy of lungs.

Murray and Nadel’s Textbook of Respiratory Medicine Sixth Edition (pp.


Williams Obstetrics. 24e.

Respiratory system.

Handbook of Pediatric Autopsy Pathology (pp.

The human respiratory system.

The Human Respiratory System (pp.

Leong F.J.W.M.

Anatomy of the Human Lung.

A Color Atlas of Comparative Pathology of Pulmonary Tuberculosis. p. 31.

Crapo, J.D.

The gas exchange region in the lungs.

Comparative Biology of the Normal Pulmonary (Second Ed.) (pp.

Marie Krogh: One hundred years worth of pulmonary function testing. A perspective on ‘The diffusion gas through the lungs of men’.

The Journal of physiology. 593(2). pp. 351-352.

Protti A. Andreis D.T. Milesi M. Iapichino G.E. Monti M. Comini B. Pugni P. Melis V. Santini A. Dondossola D. and Gatti S.

Lung anatomy and energy load.

How alveolar epithelial cell tricks work to create a healthy lung.

American journal for respiratory and critical care medicine 191(5), pages 504-513.