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Anatomy & Physiology - Body Systems

The Respiratory System

The branches of science that will help you understand the body parts and functions are anatomy and physiology. Anatomy deals with the study of the human body (the component parts, structure and position) and physiology the study of how the body functions.

Body Systems

The body comprises a number of systems including the: Cardiovascular system, Digestive system, Endocrine system, Muscular system, Neurological system, Respiratory system and the Skeletal system.

The Respiratory System

The respiratory system comprises of the nose, mouth, throat, larynx, trachea, bronchi and lungs. The function of the respiratory system is to facilitate gaseous exchange to take place in the lungs and tissue cells of the body.

Oxygen is required by cells in the body to allow various metabolic reactions to take place and to produce energy and is therefore essential to life.

The respiratory system may be defined as the organs and tissues through which air is passed into and out of the body to allow the necessary gaseous exchanges to take place.

External respiration is the means by which oxygen from the air passes into the bloodstream for transportation to the tissue cells and carbon dioxide is collected and transferred back to the lungs and expelled from the body.

Internal respiration involves the vital chemical activities that take place in every living cell requiring oxygen and glycogen to combine and release energy, water and carbon dioxide.

Organs of the respiratory system

Respiratory system

The normal rate of inspiration and expiration, the respiration rate, is about 16 times a minute in an adult. Breathing is controlled by specialized centres in the brainstem, which automatically regulate the rate and depth of breathing depending on the level of carbon dioxide in the blood.

A-VO2 diff

Arterio-venous oxygen difference (A-VO2 diff) is the difference between oxygen concentration in the arteries and the oxygen concentration in the veins.

Composition of Air

The composition of the air that we breathe in and out is approximate as follows:

Breathed In Gas Breathed Out
20.94% Oxygen 17%
78.08% Nitrogen 78%
0.04% Carbon Dioxide 4%
0.94% Tracer Gases 1%

Haemoglobin and Myoglobin

Haemoglobin is a protein in red blood cells which enables the cells to carry oxygen and myoglobin is an oxygen-binding protein found in heart and skeletal muscles.

Effect of exercise on the respiratory system

In the Cardiovascular system, the benefits of exercise were discussed in relation to the improved functioning of the heart and the lowering of blood pressure. Combined with increased maximum oxygen consumption (VO2 max), or lung capacity, these are all vital contributors to being fit and healthy.

An athlete who has not properly trained their cardiovascular system is likely to incur other injuries more easily by the rapid onset of fatigue and the consequent lowering of motivation and mental awareness. For anyone competing at varying altitudes, they must allow themselves a considerable period to acclimatise before an event. Even climbing to a moderate altitude decreases the maximum uptake by 7% to 8% due to the change in atmospheric pressure. This decrease in oxygen being supplied to the muscles may decrease performance by 4 to 8% depending on the duration of the competition, a considerable disadvantage at the finish line.

Even the athlete who prepares and acclimatises well may still not match natives of high-altitude areas such as the Andes, who have a larger chest capacity, more alveoli, larger capillary beds and higher red blood cell count. Since people may suffer from altitude sickness when moving from low to high altitudes, sufficient time must also be allowed for these symptoms to disappear before starting intensive training.

Related References

The following references provide additional information on this topic:

  • DEMPSEY, J. A. et al. (2012) Respiratory System Limitations to Performance in the Healthy Athlete: Some Answers, More Questions. Deutsche Zeitschrift fur Sportmedizin, 63 (6), p. 157-162
  • IONESCU, C. M. (2013) The human respiratory system: an analysis of the interplay between anatomy, structure, breathing and fractal dynamics. Springer

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (2001) Physiology - Respiratory System [WWW] Available from: [Accessed

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