220 Respiratory System
Learning Outcomes
- Identify the structure and function of the respiratory system
The Respiratory System is vital 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
There are four processes of respiration. They are:
- Breather or ventilation
- External Respiration, which is the exchange of gases (oxygen and carbon dioxide) between inhaled air and the blood.
- Internal Respiration, which is the exchange of gases between the blood and tissue fluids.
- Cellular Respiration
In addition to these main processes, the respiratory system serves for:
- Regulation of Blood pH, which occurs in coordination with the kidneys,
- Defense against microbes
- Control of body temperature due to loss of evaporate during expiration
Respiratory System: Upper and Lower Respiratory Tracts
For the sake of convenience, we will divide the respiratory system in to the upper and lower respiratory tracts:
Upper Respiratory Tract
The upper respiratory tract, can refer to the parts of the respiratory system lying above the sternal angle (outside of the thorax), above the vocal folds, or above the cricoid cartilage. The tract consists of the nasal cavity and paranasal sinuses, the pharynx (nasopharynx, oropharynx and laryngopharynx) and sometimes includes the larynx. Its primary function is to receive the air from the external environment and filter, warm, and humidify it before it reaches the delicate lungs where gas exchange will occur.
Air enters through the nostrils of the nose and is partially filtered by the nose hairs, then flows into the nasal cavity. The nasal cavity is lined with epithelial tissue, containing blood vessels, which help warm the air; and secrete mucous, which further filters the air. The endothelial lining of the nasal cavity also contains tiny hairlike projections, called cilia. The cilia serve to transport dust and other foreign particles, trapped in mucous, to the back of the nasal cavity and to the pharynx. There the mucus is either coughed out, or swallowed and digested by powerful stomach acids. After passing through the nasal cavity, the air flows down the pharynx to the larynx.
Lower Respiratory Tract
The lower respiratory trac