Lungs and Respiratory System of the Chest



The respiratory system of the upper abdomen and chest includes the structures involved in the vital delivery of atmospheric air and the exchange of gases between the body and atmospheric air. The human body requires a constant supply of oxygen from the atmosphere for the cellular growth and metabolism that keep the body alive. At the same time, carbon dioxide that forms as a waste product of cellular metabolism must be eliminated from the body and released into the atmosphere before reaching toxic levels.

Atmospheric air enters the body through the mouth and nose and arrives in the chest through the trachea, or windpipe. The trachea is a large open tube lined with rings of cartilage. The cartilage of the trachea provides a flexible rigidity that maintains an open airway to and from the lungs at all times. At its inferior end the trachea branches into two bronchi that each enter one of the lungs. Inside the lung each bronchi further branches into several smaller secondary bronchi, which in turn further branch into many smaller tertiary bronchi and finally branch into many tiny, flexible bronchioles. These air passages are collectively known as the bronchial tree and serve to deliver air to the millions of tiny cup-like alveoli found throughout each lung.

The respiratory system of the head and neck



The respiratory system of the head and neck marks the starting point for where oxygen enters the body. The system begins at the nose and mouth where oxygen is inhaled. The areas of the respiratory in the head and neck allow air to flow in and out of the lungs.

The important parts of the respiratory system in the head and neck include the nasal cavity, which processes the airflow on its way through to the lungs. Connected to the nasal cavity is the pharynx that is actually a part of the respiratory and digestive systems. It allows for the passage of both food and air. It lies behind and to the sides of the larynx, or voice box, which forms part of a tube in the throat that carries air to and from the lungs and houses the epiglottis. At rest, the epiglottis is upright and allows air to pass through the larynx and into the rest of the respiratory system. During swallowing, it folds back to cover the entrance to the larynx, preventing food and drink from entering the windpipe. The trachea, or windpipe, allows the head and neck to twist and bend during the process of breathing.

All of these parts in the head and neck play a significant role in directing oxygen to the lungs so that the body can breathe in oxygen.

Physiology of the respiratory system



Pulmonary Ventilation
Pulmonary ventilation is the process of moving air into and out of the lungs to facilitate gas exchange. The respiratory system uses both a negative pressure system and the contraction of muscles to achieve pulmonary ventilation. The negative pressure system of the respiratory system involves the establishment of a negative pressure gradient between the alveoli and the external atmosphere. The pleural membrane seals the lungs and maintains the lungs at a pressure slightly below that of the atmosphere when the lungs are at rest. This results in air following the pressure gradient and passively filling the lungs at rest. As the lungs fill with air, the pressure within the lungs rises until it matches the atmospheric pressure. At this point, more air can be inhaled by the contraction of the diaphragm and the external intercostal muscles, increasing the volume of the thorax and reducing the pressure of the lungs below that of the atmosphere again.

To exhale air, the diaphragm and external intercostal muscles relax while the internal intercostal muscles contract to reduce the volume of the thorax and increase the pressure within the thoracic cavity. The pressure gradient is now reversed, resulting in the exhalation of air until the pressures inside the lungs and outside of the body are equal. At this point, the elastic nature of the lungs causes them to recoil back to their resting volume, restoring the negative pressure gradient present during inhalation.