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GLOSSARY OF SIGNIFICANT RESPIRATORY SYSTEM STRUCTURES AND TERMS
Rona Alexander, PhD, CCC-SLP
Speech-Language Pathologist
PO Box 26734
Wauwatosa, Wisconsin 53226-0734
ALVEOLI PULMONIS Small pits or depressions in the walls of the terminal bronchioles and air sacs of the
lung; alveolar wall has an intricate capillary network with only a thin barrier between it and the
alveolar air, facilitating rapid exchanges of oxygen and carbon dioxide.
BRONCHI Tubes extending from the trachea to the lungs and then branching further into a form,
generally referred to as the bronchial tree; divide into the main stem bronchi, the lobar or
secondary bronchi, and the segmental or tertiary bronchi.
BRONCHIOLES Final division of the bronchi; they are tubes less than 1mm in diameter generally;
continue to subdivide until give rise to the terminal bronchioles which communicate directly with
the alveolar ducts, opening into the air sacs of the lung with the alveoli.
BRONCHOPULMONARY SEGMENTS Further division of the lobes of the lungs.
COSTAL PLEURA Part of the parietal pleura lining the inner surface of the rib cage.
DIAPHRAGM Divides the trunk into the thoracic and abdominal cavities; dome-shaped musculotendinous
structure, higher on the right side than on the left; the muscular fibers that take their origin from
the margins at the outlet of the thorax course upward and inward inserting on the edges of the
central tendon; the 3 parts of the muscular portion of the diaphragm are the sternal, costal, and
vertebral portions; the central tendon or aponeurosis of the diaphragm consists of several layers
of fibers that intersect each other at different angles, increasing the strength of the central
tendon.
DIAPHRAGMATIC PLEURA Part of the parietal pleura covering the diaphragm.
FISSURES Separate the lobes of each lung; each lung has an oblique fissure; the right lung also has a
horizontal fissure.
HILUM Opening in the mediastinal surface of the lung through which major airways, blood vessels,
lymphatics, and nerves pass.
LARYNX Modification of the upper most tracheal cartilages; a musculocartilaginous structure with the
primary function to open and close the airway during specific biologic and phonatory functions.
LOBES Upper, middle, and lower lobes of the right lung; upper and lower lobes of the left lung.
LUNGS Paired, cone-shaped organs that lie in the left and right pleural cavities; the left lung is narrower
than the right due to the protrusion of the heart and mediastinum; the right lung is shorter than
the left due to the elevation of the right side of the diaphragm by the liver; the lungs extend from
the diaphragm up to and slightly above the clavicles; lungs conform closely to the borders of the
thoracic cage with an apex, base, costal surface, and mediastinal surface as well as anterior,
inferior, and posterior borders; composed of highly elastic, spongy, and porous material with only
a few smooth muscle fibers; each lung's volume is 90% gas and 10% tissue.
GLOSSARY OF SIGNIFICANT RESPIRATORY. . . PAGE 2
MAIN STEM BRONCHI Connect the trachea to the lungs; each main stem bronchi is slightly greater than
half the diameter of the trachea; right bronchus is larger in diameter, shorter, and more direct in
line with the trachea than is the left bronchus; foreign material entering the trachea is more liable
to get into the right bronchus and possibly into the right lung; the right bronchus divides into 3
secondary bronchi corresponding to each lobe of the right lung and then the secondary bronchi
subdivide into 10 tertiary bronchi, each supplying a lung segment; the left bronchus divides into 2
secondary bronchi and then into 8 tertiary bronchi, each supplying an individual lung segment.
MEDIASTINAL PLEURA Part of the parietal pleura lining the mediastinum.
MEDIASTINUM Space in the central thorax between the left and right pleural cavities; anterior
mediastinum lies between the sternum and pericardium and contains the thymus gland and
lymph nodes; middle mediastinum contains the pericardium, heart, great vessels, phrenic nerve,
and upper portions of the vagus nerve, trachea, main stem bronchi, and their lymph nodes;
posterior mediastinum lies between the pericardium and the vertebral column and contains the
esophagus, thoracic aorta, thoracic duct, sympathetic chains and lower parts of the vagus nerve,
and lymph nodes.
NASAL CAVITY Two narrow chambers separated by the nasal septum; anteriorly from the nostrils or
anterior nares and posteriorly to the choanae (posterior nares) of the nasopharynx; lateral walls
of the nasal cavities are the superior, middle, and inferior nasal conchae; floor of the cavities are
formed by the maxillae and palative bones while the roof is "pierced" by the foramina in the
cribriform plate of the ethmoid bone.
ORAL CAVITY Bounded anteriorly and laterally by the teeth and alveolar processes, superiorly by the
hard and soft palates, posteriorly by the palatoglossal arch and inferiorly by the muscular floor
with the tongue its predominant structure.
PERICARDIUM Parietal pericardium; a loose, membranous sac that contains the heart.
PHARYNX Muscular tube connecting the nasal and oral cavities to the larynx and esophagus; extends
from the base of the skull to the level of the 6th cervical vertebra (in adults) and the cricoid
cartilage.
PLEURAE Serous membranes that are highly vascular containing lymphatics and nerves; parietal pleura
lines the inner surface of the thoracic cavity, the thoracic surface of the diaphragm, and the
mediastinum; visceral pleura covers the lungs extending into the hilar bronchi and vessels as well
as into the fissures; help to protect each lung separately, one in each pleural cavity.
PLEURAL CAVITY Intrapleural space; between the visceral and parietal pleurae; is a "potential" space
occupied by a thin layer of serous fluid, which allows the pleurae to glide over one another
without friction during every breathing cycle; helps changes in chest wall and diaphragm
movement to impact the lung tissue.
PULMONARY SURFACTANT Produced by the Type II alveolar cells; it is a substance which intersperses
with liquid molecules on the alveolar surfaces to decrease surface tension.
RIB CAGE Skeletal framework of respiration composed of the ribs, thoracic vertebrae, and sternum.
GLOSSARY OF SIGNIFICANT RESPIRATORY. . . PAGE 3
RIBS Twelve pairs; first 7 ribs articulate with the thoracic vertebrae posteriorly and the sternum anteriorly
and are called the true or vertebrosternal ribs; rib pairs 8 through 10 articulate indirectly with the
sternum via a long costal cartilaginous band anteriorly and with the thoracic vertebrae posteriorly
and are called the false or vertebrochondral ribs; rib pairs 11 and 12 have vertebral attachments
to the rib cage posteriorly but no direct or indirect structural attachments anteriorly and are called
the vertebral or floating ribs.
SECONDARY LOBULES Subdivision of the bronchopulmonary segments of the lungs containing clusters
of 3-5 terminal bronchioles.
STERNUM Breastbone; prominent midline structure of the anterior, upper thoracic wall and rib cage; the
uppermost segment is called the manubrium which articulates with the medial end of the
clavicles, the costal cartilage of the 1st rib, and the costal cartilage of the 2nd rib and body of the
sternum at the sternal angle; the largest part of the sternum is the body or corpus with its long,
narrow shape as it articulates with the costal cartilages of ribs 2 through 7 laterally and with the
most inferior aspect of the sternum called the xiphoid (ensiform) process.
SUPRASTERNAL NOTCH Depression on the superior border of the manubrium of the sternum.
THORACIC CAGE Skeletal framework of respiration composed of the rib cage and shoulder girdle
complex.
THORACIC VERTEBRAE Twelve vertebra that are part of the vertebral or spinal column (which consists of
a total of 32-33 individual vertebrae, joined together by intervertebral cartilages and a complex
system of ligaments); distinctive from other vertebrae by the articular facets on their transverse
processes and vertebral bodies that serve as points of attachments for the ribs; thoracic
vertebrae increase in size from T1 throughT12.
THORAX Chest cavity; extends from the area of the clavicles, 1st ribs, and superior aspect of the
manubrium of the sternum down to its floor at the diaphragm; contains the esophagus, trachea,
lungs, heart, and great vessels.
TRACHEA Tubular structure which extends from the larynx at the level of the cricoid cartilage down
through the neck to the articulation between the manubrium and body of the sternum (angle of
Louis) at which point it divides into the 2 main stem bronchi; composed of 16-20 horseshoeshaped cartilaginous rings, one on top of the other with a space in between containing a
fibroelastic membrane; the tracheal rings are open at the back (where it contacts the esophagus)
with a space filled with fibrous tissues and the trachealis muscle; the 1st tracheal ring is slightly
larger than the others; the last cartilage is called the carina and is a ridge like structure at its level
of bifurcation.
GLOSSARY OF SIGNIFICANT RESPIRATORY. . . PAGE 4
RESOURCES
Barral, J-P. The thorax. Seattle, WA: Eastland Press, 1991.
Dickson, D., & Maue-Dickson, W. Anatomical and physiological bases of speech. Austin, Texas: Pro-Ed,
1982.
Myer, C., Cotton, R., & Shott, S. (Eds.). The pediatric airway: An interdisciplinary approach. Philadelphia:
J.B. Lippincott, 1995.
Othersen, H.B. (Ed.). The pediatric airway. Philadelphia: W.B. Saunders, 1991.
Scanlon, C., Wilkins, R., & Stoller, J. Egan's fundamentals of respiratory care (7th ed.). St. Louis: Mosby,
1999.
Zemlin, W. Speech and hearing science: Anatomy and physiology (4th ed.). Boston: Allyn & Bacon,
1998.
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