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The Respiratory System
11 THE RESPIRATORY SYSTEM
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Introduction
T he Respiratory System is crucial to every human being. Without it, we would cease to live
outside of the womb. Let us begin by taking a look at the structure of the respiratory system and
how vital it is to life. During inhalation or exhalation air is pulled towards or away from the lungs, by
several cavities, tubes, and openings.
The organs of the respiratory system make sure that oxygen enters our bodies and carbon dioxide
leaves our bodies.
The respiratory tract is the path of air from the nose to the lungs. It is divided into two sections:
Upper Respiratory Tract and the Lower Respiratory Tract. Included in the upper respiratory tract
are the Nostrils, Nasal Cavities, Pharynx, Epiglottis, and the Larynx. The lower respiratory tract
consists of the Trachea, Bronchi, Bronchioles, and the Lungs.
As air moves along the respiratory tract it is warmed, moistened and filtered.
Functions
In this chaper we will discuss the four processes of respiration. They are:
1. BREATHING or ventilation
2. EXTERNAL RESPIRATION, which is the exchange of gases (oxygen and carbon
dioxide) between inhaled air and the blood.
3. INTERNAL RESPIRATION, which is the exchange of gases between the blood and
tissue fluids.
4. CELLULAR RESPIRATION
In addition to these main processes, the respiratory system serves for:
REGULATION OF BLOOD pH, which occurs in coordination with the kidneys, and as a
DEFENSE AGAINST MICROBES
Breathing and Lung Mechanics
Ventilation is the exchange of air between the external environment and the alveoli. Air moves by
bulk flow from an area of high pressure to low pressure. All pressures in the respiratory system are
relative to atmospheric pressure (760mmHg at sea level). Air will move in or out of the lungs
depending on the pressure in the alveoli. The body changes the pressure in the alveoli by changing the
volume of the lungs. As volume increases pressure decreases and as volume decreases pressure
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