5. RESPIRATORY TRACT
(AIRWAY)
Its conducting portion is composed of
interconnected hollow organs, thus forming a
branching out passageway, which has hard
elements (bones, cartilages, ligaments) in its
walls. Those elements maintain to keep
lumina of hollow organs patent, because they
prevent collapsing of walls of air passages.
6. Two Major Subdivisions of
Conducting Portion of Airway:
a) Upper part/airway (nasal cavity with
paranasal air sinuses, oral cavity, nasopharynx,
oropharynx and upper portion of
laryngopharynx);
b) Lower part/airway (larynx, trachea,
extrapulmonary bronchi, intrapulmonary
bronchi, regular and terminal bronchioles). It
includes bronchial trees.
10. RESPIRATORY TRACT
(AIRWAY)
Its respiratory portion – “Respiratory Tree”:
consists of functional units “Acini”, which
include respiratory bronchioles, alveolar ducts,
alveolar atria or vestibules and alveolar sacs
with alveoli. Acini are attached to the smallest
elements of the bronchial tree – the terminal
bronchioles.
13. Outside air:
Varies in temperature. At the alveolar surface it must
be at body temperature
Varies from very dry to very humid. At the alveolar
surface it must be saturated with water vapour
Contains dust and debris. These must not reach the
alveolar wall
Contains micro-organisms, which must be filtered out
of the inspired air and disposed, before they reach the
alveoli, enter the blood and cause possible problems.
It is easy to see that the temperature and humidity of
inspired air will increase as it passes down a long
series of tubes lined with a moist mucosa at body
temperature. The mechanisms for filtering are not so
obvious though the turbulence of inspired air could
play some role in it.
15. LUNGS
Lungs are paired parenchymatous organs,
which consist of lobes, bronchopulmonary
segments and lobules.
They also include intrapulmonary bronchi,
bronchioles and numerous Respiratory Trees or
functional units: Acini, which contain
Respiratory Membranes (air-blood barriers).
Latter serve for gas exchange between
atmospheric air and blood. Transport of gases
with the blood to and from lungs is provided via
the pulmonary circulation.
17. ADDITIONAL STRUCTURES
INVOLVED IN PULMONARY
VENTILATION
They include the:
–Visceral and parietal pleurae
–Two plural cavities (right & left)
–Bones and joints of the thoracic cage
–Muscles of respiration with their blood and
nerve supply)
18. Mechanism of breathing.
In order to grasp the way in which we breathe we have
to grasp the following facts:
– Each lung is surrounded by a pleural cavity or sac, except
where the plumbing joins it to the rest of the body, rather like
a hand in a boxing glove.
The glove has an outer and inner surface, separated by a layer
of padding. The pleura, similarly, has two surfaces, but the
padding is replaced by a thin layer of fluid.
– Each lung is enclosed in a rib cage bounded below by the
diaphragm and at the sides by the chest wall and the
mediastinum.
– Breathing works by making the cage bigger: the pleural
layers slide over each other and the pressure in the lung
is decreased, so air is sucked in. Breathing out does the
reverse, the cage collapses and air is expelled.
