? Microscopic features of different part
? Functional correlations
? Clinical correlates
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Introduction? Provide molecular oxygen for cellular oxidation
? Remove carbon dioxide generated
? Vascular or circulatory transport AND Air/Gas transport
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Gross Anatomy
Bronchopulmonary Segments
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Continued.....
Continued.....
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Functional Requirements? The Respiratory System has tubular components for air/gas
conduction
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? Plus respiratory components for gas exchange.
? Inspiratory pressure tends to collapse the conducting tubes. They
must be held open.
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? Other essential functions include: warming; moistening; cleansing by
removal of particulate matter; detoxification by absorption of harmful
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gases; and entrapment of harmful bacteria and viruses.Conduction
? The nasal cavity is held open by bone and cartilage.
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? Most of the additional functions are carried out bypseudostratified columnar ciliated epithelial cells and goblet
cells (mucous secretors).
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? The cilia beat rhythmically in one direction only
? Move debris and pathogen-laden mucous to the oropharynx
and mouth where it is expectorated or swallowed.
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Continued.....
? Air temperature control is by the profuse capillary beds that
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are beneath the epithelium
? Which warm or cool inspired air.
? Extensive venous plexus, largely replace capillaries in the
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nasal cavities to modify air temperature
Trachea
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Bronchus and Bronchial Tree
? The trachea typifies the
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conducting system.? The cilia are paralyzed by
cigarette smoke.
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? At rest, smooth muscle
contraction decreases
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tracheal (and bronchial)diameter to decrease
respiratory dead space.
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Continued......
? Bronchioles - lumen of 1mm or less in diameter.
? The epithelium ciliated columnar.
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? Cartilage and glands disappear? Bronchiole is held open by the surrounding lung tissue.
? The smooth muscle in the wall may excessively narrow the
lumen in asthma.
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Bronchiole
? Bronchioles with a lumen of 1
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mm or less in diameter.
? Epithelium becomes ciliated
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columnar.? Cartilage and glands disappear
? The bronchiole is held open by
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the surrounding lung tissue.
? The smooth muscle may
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excessively narrow the lumen inasthma.
Bronchiole
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? Bronchioles continue to
divide and decrease in size
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? Terminal Bronchioles? Respiratory Bronchioles ,
which give the alveolar
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ducts, alveolar sacs andalveoli.
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Terminal and Respiratory Bronchioles? Epithelium - non-ciliated
cuboidal and goblet cells
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disappear.
? Gas exchange - in the
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respiratory alveoli? That bud from the
respiratory bronchioles.
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Alveoli
? The alveoli - functional unit
? Out-pocketings of respiratory
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bronchioles, alveolar ducts and
alveolar sacs.
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? The most conspicuous feature ofthe alveolar wall -Presence of
many small capillaries in the
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septae between them.
? Opposite the septae the alveoli
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are open to allow air entry.Epithelium
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? Type I are the flattened epithelial cel s(squamous pneumocytes) that have
cytoplasmic extensions about 0.1 - 0.3
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um thick and have no microvil i.
? In some areas the basal lamina of the
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type I cel is fused to the capil ary? Endothelium - possible areas of gas
exchange.
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? Type I , the large alveolar cel s (granular
pneumocytes) are cuboidal without
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broad cytoplasmic extensions andoccupy about 5% of the alveolar surface.
Epithelium
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? Type II Cells produce Surfactant, a stabilizing, surface-active materialconsisting mainly of the phospholipid lecithin.
? Surfactant is crucial to lung function
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? Its high viscosity and low surface tension, stabilizes the diameter ofalveoli preventing collapse after expiration, while retaining residual
air in the alveoli after each breath;
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? Because alveoli are already partially open, energy expenditure in
subsequent inspirations is much less.
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Continued....? Acting as a detergent surfactant facilitates the removal of amniotic
fluid from the lungs at birth, before the first breath.
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? Dust cells (macrophages) usually lie free in the alveoli and air
passageways.
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? Their role is to clear the lungs of invading bacteria and inspiredparticulate material (e.g. dust and carbon particles).
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Summary? Massive surface area for gas exchange (75 square metres)
? As lumen decreases so do cartilage, cilia, epithelial height and mucous
? Smooth muscle controls diameter, but excessively narrowing in
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asthma
? Surfactant is thick in polycystic fibrosis
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EmphysemaBronchiectasis
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MCQsQuestion :- Which of the following is correct regarding Clara cell?
a. Ciliated secretory cuboidal cells
b. Present in larger terminal bronchiole
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c. Present in smaller terminal bronchioled. Number decreases in small bronchiole