The structure of the bronchial tree
Semey
State Medical University
:
“The structure of the bronchial tree”.
Prepared
by: Yerzhan L., 341-GMFby: Kozhanova S.K.
Semey
2015
The Tracheobronchial Tree
term "tracheobronchial
tree" or "respiratory tree" refers to the structures of bronchi
and bronchioles that terminate with the alveolar ducts, sacs, and, finally,
alveoli - that are contained within the lungs. These are
the structures through which air passes into the body (usually through the
nose/mouth then the trachea). Therefore these structures are also referred to
as "airways".
bronchial tree trachea
Trachea
trachea, also called the windpipe,
is part of the passageway that supplies air to the lungs. Any
prolonged blockage, even for a few minutes, can cause death.trachea is about
4.5 inches long and 1 inch in diameter, and is comprised of smooth muscle and
several c-shaped rings of cartilage. The rings of cartilage provide stability
and help to prevent the trachea from collapsing and blocking off the airways.
The trachea extends from the neck and divides into two main bronchi.trachea
divides to form the right- and left- primary bronchi (as shown). Each of these
divide into lobar bronchi - which supply air to each of the lobes of the
lung.lobar bronchi divide into segmental bronchi - which supply air to areas of
the lung that are called bronchoplumonary segments.
Bronchopulmonary segments are
functionally and anatomically distinct from each other - which matters because
a segment of diseased lung can be removed surgically without adversely
affecting the rest of the lung.
Areas of tracheobronchial tree furthest from the
trachea are collectively called the "distal respiratory tree".
Bronchi
similar to the trachea, the two
primary bronchi are located inside the lungs. The right
bronchus is slightly larger than the left one. Because of this, foreign objects
breathed into the lungs often end up in the right bronchus. The bronchi are
lined with the same type of mucus that lines the rest of the respiratory
tract.into the lungs, each bronchus is further divided into five smaller,
secondary bronchi, which provide air to the lobes of the lungs. The secondary
bronchi continue to branch off to form the tertiary bronchi, which are further
divided into terminal bronchioles. There are as many as 30,000 tiny bronchioles
in each lung. They lead to the alveoli by way of alveolar ducts.
Bronchial tree
, the trachea and the two primary
bronchi are referred to as the bronchial tree. At the end
of the bronchial tree lie the alveolar ducts, the alveolar sacs, and the
alveoli. tubes that make up the bronchial tree perform the same function as the
trachea: they distribute air to the lungs. The alveoli are responsible for the
primary function of the lungs, which is exchanging carbon dioxide and oxygen.
layer of protective mucus, called a mucus blanket, covers a large portion of
the membrane lining the bronchial tree. The mucus is an important air purifier.average
adult produces about 125 milliliters of mucus daily, which is slightly more
than half a cup. Microscopic, hair-like cilia move the cleansing mucus up to
the pharynx-part of the throat between the mouth and esophagus-from the lower
part of the bronchial tree. Cigarette smoke paralyzes the cilia, which allows
mucus to accumulate and leads to what is called smoker’s cough.bronchi
are lined with respiratory epithelium and have a similar overall structure to
the trachea, with two exceptions:
A smooth muscle layer intervenes between the
submucosa and the cartilagecartilagenous rings are smaller and less complete,
eventually disappearing when the bronchi become bronchioles.bronchioles are
lined by a simple cuboidal epithelium, and their wall is much thinner than the
bronchi. Their smooth muscle component is relatively larger.
Relations
right main bronchus passes posterior
to right pulmonary artery, inferior vena cava and ascending aorta. The
azygos vein passes over its superior surface to enter the inferior vena cava.
The oesophagus is posterior.
The left main bronchus passes
posterior to the left pulmonary artery, but anterior to the descending thoracic
aorta.vagus nerve passes anterior and posterior to the main bronchi, but mostly
posterior as the pulmonary plexus.
(lower airways)
shown above, the finest (narrowest)
of the bronchial air tubes are called
"terminal bronchioles".
lead to "respiratory bronchioles" which are even smaller tubes whose
structure is different from the terminal bronchioles.
Respiratory bronchioles are lined by ciliated
cuboidal epithelium surrounded by smooth muscle. The respiratory bronchioles
are covered by small "air cells" called alveoli. Alveolar ducts
connects alveoli to the respiratory bronchiole to which they are
attached.bronchioles and alveolar ducts occupy very similar positions on
diagrams but are distinguished physically by the differences between the
structure of their walls and the tissues that line them. E.g. respiratory
bronchioles are lined with simple ciliated cuboidal epithelium and Clara cells
whereas alveolar ducts are lined with flat nonciliated epithelium.of the
alveoli are covered by fine blood capillaries as shown in red for the top
aleveolar sace (above). Others are shown without the capillary network for
clarity of illustration of the alveoli.area shaded yellow is a cut-away section
to illustrate that the alveoli are notmany closed spheres but, rather, are many
microscopic blind-ending air pouches.
Each individual alveolus opens into
a larger sac (one of many such alveoli sacs, each having many individual
alveoli), that is connected to its terminal bronchiole via an alveoli duct. Also
note the alveoli-capillary membrane which seperates the air inside the alveolus
from the blood-carrying capillary on the outside of the alveolus. This is the
membrane through which the gases oxygen and carbon-dioxide are exchanged during
the breathing process (internal respiration).
Conclusion
The
bronchial tree is an essential part of the respiratory system. It consists
of several interacting structures, such as the bronchi, bronchioles, and
alveoli. These structures work together to provide a network system between the
lungs and the trachea <http://www.wisegeek.com/what-is-the-trachea.htm>.
Without this system, a person could not breathe properly.bronchial tubes are
the largest parts of this structure. There is one bronchial tube connected to
each lung. The connection occurs in an upper portion of the lung known as the
helium.the right and left bronchial tubes perform the same tasks, they are not
identical. The right bronchial tube, for example, is shorter than the left. It
is also wider than its counterpart.primary bronchi also branch off, forming two
smaller bronchial tubes known as the lobar bronchi, or secondary bronchi. There
are three lobar bronchi on the right side and two on the left. The bronchiole
tree’s parts continue reducing in size as these secondary bronchi become smaller
tubes known as the bronchioles.roots branch out in the ground, the bronchioles
branch out and cover the surface of the lungs. These muscular structures expand
and contract, controlling the exchange of gases with the alveoli. The alveoli
are tiny structures composed of ducts and air sacs. They allow the exchange of
the gases in the blood. Due to these tiny structures, carbon dioxide can be
transported out and oxygen can be processed in.bronchial tree provides a system
for the trachea to service the lungs. It is important to note, however, that
like the trachea, it does not include the lungs. The bronchial tree begins with
the primary bronchi and ends with the alveoli.