Encyclopedia of Health and Medicine

THE PULMONARY SYSTEM
The pulmonary system brings oxygen into the body and expels metabolic wastes in the form of gases. Physician specialists
who treat conditions of the pulmonary system are internists who have subspecialty certifications in pulmonary
medicine (pulmonologists). Physician specialists who operate on the LUNGS and related structures are thoracic surgeons.
This section, “The Pulmonary System,” presents an overview of the structures and functions of the pulmonary
system, a discussion of pulmonary health and disorders, and entries about the health conditions that can affect the
lungs and related structures.
TRACHEA
BRONCHUS
bronchiole
ALVEOLUS
PLEURA
left lung
upper lobe
Structures of the Pulmonary System
lingula (lingular segment)
lower lobe
right lung
upper lobe
middle lobe
lower lobe
DIAPHRAGM
Functions of the Pulmonary System
The LUNGS bring life-giving oxygen into the body
and remove toxic gaseous wastes from it. An
asymmetrical pair, these spongy structures rhythmically
expand and compress about 15 to 20
times a minute. Expansion, or inhalation, draws
air and oxygen into the lungs; compression, or
exhalation, expels carbon dioxide and other gases
that are metabolic waste byproducts of cellular
activity. The structures of the nasal cavity and the
upper airway (THROAT) bring air, containing about
21 percent oxygen, into the body. The NOSE and
SINUSES warm and moisturize the air.
Carrying that air to the lungs are the TRACHEA,
bronchi, and bronchioles—a branching structure of
progressively smaller airways. The air’s destination
is the alveoli, tiny membranous sacs that cluster
grapelike at the ends of the bronchioles. A webbing
of capillaries (tiny blood vessels) surrounds each
ALVEOLUS, carrying erythrocytes (red BLOOD cells)
waiting to receive oxygen molecules and release
carbon dioxide molecules. This process, the OXY-
GEN–CARBON DIOXIDE EXCHANGE, gives the body life.
LOBES AND SEGMENTS OF THE LUNGS
Right Lung
Left Lung
Right upper lobe Left upper lobe
apical segment apical-posterior segment
posterior segment anterior segment
anterior segment superior lingular segment (lingula)
Right middle lobe inferior lingular segment (lingula)
lateral segment Left lower lobe
medial segment superior segment
Right lower lobe anterior basal segment
superior segment lateral basal segment
anterior basal segment posterior basal segment
medial basal segment
lateral basal segment
posterior basal segment
The lungs: asymmetry in synchronization The
lungs fill the thoracic cavity from neck to
DIAPHRAGM and sternum to spine. Though paired,
the lungs differ somewhat in structure. The right
lung is larger than the left lung, containing three
lobes to the left lung’s two. The left lung must
accommodate the HEART, which nestles into an
indentation called the cardiac notch. Some
anatomists consider the small tail of tissue in the
left lung that drops behind the heart, called the
lingula, as a structure separate from either lobe of
the left lung though most designate it a segment
of the left upper lobe. Each lobe of the lung further
contains structural divisions called bronchopulmonary
segments, 10 among the three
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