? Gross features
? Bronchial Tree
? Microscopic features of different part
? Functional correlations
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? Clinical correlatesIntroduction
? Provide molecular oxygen for cellular oxidation
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? Remove carbon dioxide generated? Vascular or circulatory transport AND Air/Gas transport
Gross Anatomy
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Bronchopulmonary SegmentsContinued.....
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Continued.....Functional Requirements
? The Respiratory System has tubular components for air/gas
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conduction
? Plus respiratory components for gas exchange.
? Inspiratory pressure tends to collapse the conducting tubes. They
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must be held open.
? Other essential functions include: warming; moistening; cleansing by
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removal of particulate matter; detoxification by absorption of harmfulgases; and entrapment of harmful bacteria and viruses.
Conduction
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? The nasal cavity is held open by bone and cartilage.
? Most of the additional functions are carried out by
pseudostratified columnar ciliated epithelial cells and goblet
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cells (mucous secretors).
? The cilia beat rhythmically in one direction only
? Move debris and pathogen-laden mucous to the oropharynx
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and mouth where it is expectorated or swallowed.
Continued.....
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? Air temperature control is by the profuse capillary beds that
are beneath the epithelium
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? Which warm or cool inspired air.? Extensive venous plexus, largely replace capillaries in the
nasal cavities to modify air temperature
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TracheaBronchus and Bronchial Tree
? The trachea typifies the
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conducting system.
? The cilia are paralyzed by
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cigarette smoke.? At rest, smooth muscle
contraction decreases
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tracheal (and bronchial)
diameter to decrease
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respiratory dead space.Continued......
? Bronchioles - lumen of 1mm or less in diameter.
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? The epithelium ciliated columnar.? Cartilage and glands disappear
? Bronchiole is held open by the surrounding lung tissue.
? The smooth muscle in the wall may excessively narrow the
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lumen in asthma.--- Content provided by FirstRanker.com ---
Bronchiole? Bronchioles with a lumen of 1
mm or less in diameter.
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? Epithelium becomes ciliated
columnar.
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? Cartilage and glands disappear? The bronchiole is held open by
the surrounding lung tissue.
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? The smooth muscle may
excessively narrow the lumen in
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asthma.Bronchiole
? Bronchioles continue to
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divide and decrease in size
? Terminal Bronchioles
? Respiratory Bronchioles ,
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which give the alveolar
ducts, alveolar sacs and
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alveoli.Terminal and Respiratory Bronchioles
? Epithelium - non-ciliated
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cuboidal and goblet cells
disappear.
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? Gas exchange - in therespiratory alveoli
? That bud from the
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respiratory bronchioles.
Alveoli
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? The alveoli - functional unit? Out-pocketings of respiratory
bronchioles, alveolar ducts and
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alveolar sacs.? The most conspicuous feature of
the alveolar wall -Presence of
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many small capillaries in the
septae between them.
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? Opposite the septae the alveoliare open to allow air entry.
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Epithelium? Type I are the flattened epithelial cel s
(squamous pneumocytes) that have
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cytoplasmic extensions about 0.1 - 0.3
um thick and have no microvil i.
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? In some areas the basal lamina of thetype I cel is fused to the capil ary
? Endothelium - possible areas of gas
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exchange.
? Type I , the large alveolar cel s (granular
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pneumocytes) are cuboidal withoutbroad cytoplasmic extensions and
occupy about 5% of the alveolar surface.
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Epithelium
? Type II Cells produce Surfactant, a stabilizing, surface-active material
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consisting mainly of the phospholipid lecithin.? Surfactant is crucial to lung function
? Its high viscosity and low surface tension, stabilizes the diameter of
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alveoli preventing collapse after expiration, while retaining residualair in the alveoli after each breath;
? Because alveoli are already partially open, energy expenditure in
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subsequent inspirations is much less.
Continued....
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? Acting as a detergent surfactant facilitates the removal of amnioticfluid from the lungs at birth, before the first breath.
? Dust cells (macrophages) usually lie free in the alveoli and air
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passageways.
? Their role is to clear the lungs of invading bacteria and inspired
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particulate material (e.g. dust and carbon particles).--- Content provided by FirstRanker.com ---
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
MCQs
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Question :- Which of the following is correct regarding Clara cell?
a. Ciliated secretory cuboidal cells
b. Present in larger terminal bronchiole
c. Present in smaller terminal bronchiole
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d. Number decreases in small bronchiole