Biomedical Engineering Reference
In-Depth Information
Chapter 2
The Human Respiratory System
2.1 Anatomy and Structure
Respiration is the act of breathing, namely inhaling (inspiration) oxygen from the at-
mosphere into the lungs and exhaling (expiration) into the atmosphere carbon diox-
ide [
53
]. The respiratory system is made up of the organs involved in breathing, and
consists of the nose, pharynx, larynx, trachea, bronchi, and lungs, as depicted in
Fig.
2.1
.
The respiratory system can be divided into two major parts: the upper airways
part and the lower airways part. The upper respiratory tract includes the nose, with
its nasal cavity, frontal sinuses, maxillary sinus, larynx, and trachea. The lower res-
piratory tract includes the lungs, bronchi and the alveoli.
The lungs take in oxygen, which is required by all the cells throughout the body
to live and carry out their normal functions. The lungs also get rid of carbon dioxide,
a waste product of the body's cells. The lungs are a pair of cone-shaped organs made
up of spongy, pinkish-gray tissue. They take up most of the space in the chest, or
the thorax (the part of the body between the base of the neck and diaphragm).
The lungs are separated from each other by the mediastinum, an area that con-
tains the following:
•
heart and its large vessels;
•
trachea;
•
esophagus;
•
thymus;
•
lymph nodes.
The right lung has three sections, called lobes. The left lung has only two lobes.
When one breaths, the air enters the body through the nose or the mouth, travels
down the throat through the larynx (voice box) and trachea (windpipe) and goes
into the lungs through the tubes called main-stem bronchi. One main-stem bronchus
leads to the right lung and the other one leads to the left lung. In the lungs, the main-
stem bronchi divide into smaller bronchi and then into even smaller tubes called
bronchioles, which finally end in tiny air sacs called alveoli. At this level, the act of
