Between Two Lungs Biography
(Source google.com)
In humans, the trachea divides
into the two main bronchi that enter the roots of the lungs. The bronchi
continue to divide within the lung, and after multiple divisions, give rise to
bronchioles. The bronchial tree continues branching until it reaches the level
of terminal bronchioles, which lead to alveolar sacs. Alveolar sacs, are made
up of clusters of alveoli, like individual grapes within a bunch. The
individual alveoli are tightly wrapped in blood vessels and it is here that gas
exchange actually occurs. Deoxygenated blood from theheart is pumped through
the pulmonary artery to the lungs, where oxygen diffuses into blood and is
exchanged for carbon dioxide in thehaemoglobin of the erythrocytes. The
oxygen-rich blood returns to the heart via the pulmonary veins to be pumped
back into systemic circulation."Lung Disease & Respiratory Health Center
Human lungs are located in two
cavities on either side of the heart. Though similar in appearance, the two are
not identical. Both are separated into lobes by fissures, with three lobes on
the right and two on the left. The lobes are further divided into segments and
then into lobules, hexagonal divisions of the lungs that are the smallest
subdivision visible to the naked eye. The connective tissue that divides
lobules is often blackened in smokers. The medial border of the right lung is
nearly vertical, while the left lung contains acardiac notch. The cardiac notch
is a concave impression molded to accommodate the shape of the heart. Each lobe is surrounded by a
pleural cavity, which consists of two pleurae. The parietal pleura lies against
the rib cage, and the visceral pleura lies on the surface of the lungs. In
between the pleura is pleural fluid. The pleural cavity helps to lubricate the
lungs, as well as providing surface tension to keep the lung surface in contact
with the rib cage.
Lungs are to a certain extent
'overbuilt' and have a tremendous reserve volume as compared to the oxygen
exchange requirements when at rest. Such excess capacity is one of the reasons
that individuals can smoke for years without having a noticeable decrease in
lung function while still or moving slowly; in situations like these only a
small portion of the lungs are actually perfused with blood for gas exchange.
Destruction of too many alveoli over time leads to the condition emphysema,
which is associated with extreme shortness of breath. As oxygen requirements
increase due to exercise, a greater volume of the lungs is perfused, allowing
the body to match itsCO2/O2 exchange requirements. Additionally, due to the
excess capacity, it is possible for humans to live with only one lung, with the
one compensating for the other's loss. The environment of the lung is very
moist, which makes it hospitable for bacteria. Many respiratory illnesses are
the result of bacterial orviral infection of the lungs. Inflammation of the
lungs is known as pneumonia; inflammation of the pleura surrounding the lungs
is known as pleurisy. Vital capacity is the maximum volume of air that a person
can exhale after maximum inhalation; it can be measured with a spirometer. In
combination with other physiological measurements, the vital capacity can help
make a diagnosis of underlying lung disease.
The lung parenchyma is strictly
used to refer solely to alveolar tissue with respiratory bronchioles, alveolar
ducts and terminal bronchioles. However, it often includes any form of lung
tissue, also including bronchioles, bronchi, blood vessels and lung
interstitium.
To understand the anatomy of the
lungs, the passage of air through the nose and mouth to the alveoli must be
studied. The progression of air through either the mouth or the nose, travels
through the nasopharynx, oropharynx, larynx, and the trachea (windpipe). The
air passes down the trachea, which divides into two main bronchi; these branch
to the left and right lungs where they progressively subdivide into a system of
bronchi and bronchioles until the alveoli are reached. These many alveoli are
where the gas exchange of carbon dioxideand oxygen takes place. Breathing is
driven by muscular action; in early tetrapods, air was driven into the lungs by
thepharyngeal muscles via buccal pumping, which is still found in amphibians.
Reptiles, birdsand mammals use their musculoskeletal system to support and
foster breathing. Medical terms related to the lung often begin with pulmo-,
such as in the (adjectival form:pulmonary) or from the Latin pulmonarius
("of the lungs"), or with pneumo- (from Greekπνεύμων
"lung").
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