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RESPIRATORY ORGANS
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Its main function is gas exchange.
Functionally 2 parts airways respiratory
surface extrapulmonary intrapulmonary nasal
cavity bronchi nasal part of pharynx
bronchioli nasal part of oral cavity
bronchioli respiratorii larynx
alveolar ducts trachea alveolar
sacs principal bronchi
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Nasal cavity cavum nasi 3 histological
parts regio cutanea regio respiratorica reg
io olfactoria Regio cutanea vestibulum nasi. The
stratified squamous keratinized epithelium of
outer integument turns inside the nasal cavity.
Many sebaceuos glands, sweat glands and
vibrissae. Regio respiratorica lower and
medial concha nasalis covered by mucous
membrane. Lamina epithelialis pseudostratified
ciliated columnar epitheliumgoblet
cells endoepithelial serous and mucous
glands Lamina propria loose connective tissue
with lymphocytes and plasma cells wide venous
sinusoids filled with blood Regio olfactoria
yellowish pigmented mucous membrane. Lamina
epithelialis pseudostratified columnar
epithelium without motile cilia and goblet
cells. Instead olfactory cells primary sensory
cells, support cells. Lamina propria
connective tissue, contionuous with periosteum,
glands of Bowman (branched tubuloalveolar
gland producing binding proteins)
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Regio respiratorica Regio olfactoria with an
olf. dendrite
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Nasopharynx
Histology is similar to that of regio
respiratorica of nasal cavity. Lymphatic cells
are especially abundant at tuba auditiva
(tonsilla tubaria) and in the middle of dorsal
wall (tonsilla pharyngea). Seromucous glands are
also present. The crossing point of digestive and
respiratory system
Oropharynx
Nasopharynx
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Larynx
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Epiglottis
Perichondrium Elastic cartilage
lymphocytes
Glands
Pharyngeal surface
Laryngeal suface
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Trachea
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Histological layers of trachea Tunica
mucosa lamina epithelialis pseudostratified
ciliated columnar epithelium goblet
cells lamina propria collagen and elastic
fibers, cell-rich loose CT
seromucous glands this layer is
continuous with the perichondrium C shaped
hyaline cartilage, the two ends of C are bound
together with a bundle smooth
muscle Tunica adventitia loose CT binds the
trachea to the surrounding tissues and the
esophagus Note the open end of
cartilages faces towards the esophagus the
dorsal side contains continuous smooth muscle
bundle called paries membranaceus, also
containing elastic fibers Principal
bronchi The histology is similar to that of the
trachea.
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• The lung tree
• Principal bronchus
• Lobar bronchus
• Segmental bronchus
• Terminal bronchus
• Beginning of lobulus
• pulmonis
• 6. Trachea
• 7. Larynx
• 8. Thyroid cartilage
• 9. Cricoid cartilage

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Bronchopulmonary segment pyramidal shaped unit
of the lung one bronchus with its all branches
surrounded by CT septa rich in elastic
fibers. Note blood vessels branch together with
the airways.
Arteria pulmonalis Vena pulmonalis End of
bronchus Arteria broncialis
Bronchiolus Terminal bronchiolus
Acinus pulmonis smaller unit one
terminal bronchiole with its branches (200-300
alveoli)
bronchiolus respiratorius ductus
alveolaris alveolus
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• Bronchi
• The bronchus tree follows the histology
• of the trachea, but
• Cartilages loose their C shape, become
• fragmented and disappear below the
• diameter of 1 mm.
• Instead of cartilage smooth muscle takes
• over the place.
• - The lining epithelium is pseudostratified
• columnar, but at smaller diameters it is
• getting to be lower.
• The lamina propria is also thinning as
• the diameter of airways decreases

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Bronchioli star-shaped lumen Airways with a
diameter less than 1 mm. They lack cartilage and
glands but still have smooth muscle.
Simple columnar epithelium (ciliated) Lamina
propria Smooth muscle bundles
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Bronchiolus respiratorius simple cuboidal
epithelium, no cilia.
Alveoli appear in the wall. The smooth muscle
disappears. Alveoli are made up by a simple
squamous epithelium
Alveolar duct made up by a series of alveoli
SEM
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Clara cells cuboidal non-ciliated cells in the
terminal bronchiole. Their apical portion is
dome-shaped. They contain secretory granules of
protein-nature. Their functions
SP-A and SP-D proteins opsonin-like action on
bacteria CCP protein reduces inflammatory proces
ses.
ICC- LM
SEM
RER Secretory granule Nucleus Nucleolus
TEM
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The alveolar system Alveoli are small
thin-walled spheric structures covered with a
dense capillary network. In lung there are 3-400
million of alveoli, ensuring a very large
respiratory surface (hundreds of m2)
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Schematic drawing of the alveolar wall
Alveolar macrophage
Entrance to the alveolus
Elastic fiber in cross-section
Type I. pneumocyte
Type II. pneumocyte
capillaries
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The layers through which the gas-exchange takes
place Blood-air barrier
Alveolar epithelium (pneumocyte I.)
Common lamina basalis
Capillary endothelium
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Type II. pneumocytes and their function Cuboidal
cells scattered among type I. pneumocytes.
Pneumocyte II.
Pneumo- cyte I.
Their lamellar bodies contain surfactant phospholi
pid-protein which does not allow the alveoli to
collapse even at exspiration.
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Alveolar macrophages dust-cells, members of
the mononuclear phagocytotic system (MPS) keep
clean the respiratory surface
LM
TEM
SEM
Phagosomes Nucleus
Bacteria
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The interstitium of the lung Outer surface
pleuraCT capsule rich in elastic fibers CT septa
around bronchopulmonary segments intersegmental
septa CT septa around lobuli interlobular
septa Elastic fibers enmesh the tissue
(resoric-fuchsin staining)
Elastic fibers at the entrance of alveoli
Lumen of alveoli