Pronunciation of Terminology
The respiratory system is an integrated arrangement of organs and structures which functions to extract oxygen from the atmosphere into the bloodstream and expel carbon dioxide, a waste product of metabolism, from the bloodstream into the atmosphere. It consists of the respiratory tract, the muscles used for breathing and the part of the brain that controls breathing.
Pulmonary is a medical term meaning pertaining to the lungs. Therefore, blood flow through the lungs is the pulmonary circulation. Some refer to the lungs and respiratory tract as the pulmonary system. Although pulmonary blood flow is actually part of the cardiovascular system it plays a vital role in delivering oxygen to and removing carbon dioxide from the body. For that reason doctors consider them one – the cardiopulmonary system.
The respiratory tract consists of the lungs, gas exchange areas within the lungs, and the tubular structures which transport air to the lungs. The lungs are the large spongy organs in the chest cavity where gas exchange occurs. The right lobe has three sections, upper, middle and lower lobes. The left lung has two sections, upper lobe and lower lobe. The left upper lobe has three divisions (lingulae). The lung parenchyma is the functional portion of the lungs where gas exchange occurs. It includes the alveoli, blood vessels and supporting tissue. The lung interstitium is the space between the cells of the parenchyma. Other structures of the respiratory tract are the nose, mouth, pharynx, larynx, trachea, bronchi, and bronchioles. The nostrils, nasal cavity, mouth, pharynx, and larynx form the upper respiratory tract. The trachea, bronchi, bronchioles, alveoli and lungs form the lower respiratory tract. Air enters the respiratory tract through the mouth or nose, and then passes through the pharynx, larynx, trachea, bronchi and bronchioles before reaching the alveoli in the lungs.
Muscles of respiration are those used to inhale air into the lungs and to exhale air from the lungs. They are in four locations of the body. The most important muscle is the diaphragm which moves up and down during breathing. It is between the cavities of the chest and abdomen. The next most important set of muscles for breathing is located in the chest wall and between the ribs. They are termed intercostal muscles. The least important and least used muscles for breathing are those of the abdominal wall and neck areas.
A region of the lower brainstem controls breathing by sending signals down the spinal cord into the nerves connected to the diaphragm and other breathing muscles. Those signals and muscle responses determine the rate and depth of breathing. The name of the part of the brain in which the breathing center is located is the medulla. The role of the breathing center explains why many individuals who suffer serious head injuries require mechanical ventilation.
Anatomical Terminology of the Respiratory System
Alveoli – Alveolus – sing. – Alveolar – adj. – The air sacs in the lungs at the very end of the bronchioles where gas exchange occurs between them and pulmonary capillaries.
Alveolar-capillary membrane – Is the thin tissue layer between the air sacs in the lungs and the capillaries, through which gases pass. It is composed of epithelium of the alveoli and endothelium of the pulmonary capillaries. In the case of oxygen, the exchange is from the alveoli into the capillaries. For CO2 it is vice versa.
Bronchi – Bronchus – sing. – Bronchial – adj. – The subdivided airways of the trachea which convey air to the lungs. They form additional branches known as lobar, segmental and subsegmental bronchi which become smaller the more they branch.
Dead space – Is the portion of the respiratory tract that not involved in gas exchange. Anatomical dead space consists of the nose, mouth, pharynx, larynx, trachea, bronchi and bronchioles. Alveolar dead space is the volume of air in alveoli which does not participate in oxygen–carbon dioxide gas exchange because of absent or deficient pulmonary capillary blood flow. Physiologic dead space is the sum of the anatomical dead space plus the alveolar dead space.
Larynx – laryngeal – adj. – The medical term for what lay people called the voice box. It houses the vocal cords, and is the portion of the respiratory tract where air enters after passing through the pharynx.
Nasal cavity – Is a dual cavity in the first portion of the respiratory tract into which air enters after passing through the nostrils. The wall dividing the right and left sides of the cavity is the nasal septum.
Pharynx – pharyngeal – adj. – Is the medical term for throat. It is the portion of the respiratory tract into which air enters after passing through the nasal cavity. The pharynx consists of three parts, the nasopharynx, the oropharynx and the laryngopharynx.
Pulmonary arteries – The two (one on the right and one on the left) vessels which transport oxygen short blood from the right ventricle to the lungs. The smaller divisions (pulmonary capillaries) absorb oxygen from the lungs and release carbon dioxide into the lungs, and then convey the blood back to the left atrium by means of the pulmonary veins.
Trachea – Tracheal – adj. – Is the medical term for windpipe. It is the largest tubular structure of the respiratory tract which receives air after it leaves the larynx and conveys it to the bronchi. It branches into the right and left main bronchi.