Respiratory System
The respiratory system could be divided into:Conducting portion:where conduction of air to and from the lung
.takes place as well as conditioning of air
-Nasal cavities and nasal sinuses.
-Nasopharynx.
-Larynx.
-Trachea.
-Bronchi.
-Bronchioles.
-Terminal bronchioles.
Respiratory portion: where exchange of gases between the
blood and the inspired air takes place.
-Respiratory bronchioles.
-Alveolar ducts.
-Alveolar sacs.
-Alveoli.
TRACHEA
The wall of the trachea consists of:
1- Mucosa
:Epithelium :it is formed of ،posteriorly folded
::cells of the epithelium are The.cells stratified columnar ciliated with goblet-Pseudo
.The cilia beat towards the larynx .columnar ciliated cells :Ciliated cells
Goblet cells.granules mucinogen have expanded apical parts distended with :
Basal cells:
Between the bases of the columnar cells
Act as reserve stem cells for the ciliated cells and the goblet cells.
Serous cells:
.Have apical electron dense granules
Produce a secretion of lower viscosity than that of the mucus.
Brush cells:
selender columnar with few luminal microvilli.
Interpreted as depleted goblet cells or intermediate between differentiation of the basal cells into goblet cells.
Neuro-endocrine cells:(cells Kulchitsky)
Granule containing cells have neuroendocrine function.
Secretes serotinin, calcitonin.
Migratory cells:
Lymphocytes
Globule leucocytes (mast cell like).
Corium (Lamina Propria):
Loose connective tissue.
Infiltrated with lymphocytes.
Rich in elastic fibres which condenses to form elastic membrane between the corium and the submucosa.
TRACHEA
2-Submucosa:
-Loose connective tissue contains tracheal glands.
-The tracheal glands have the following characters:
Tubulo-alveolar mixed (mucus and serous) glands.
Present in the intervals between the cartilaginous rings.
Open into the surface epithelium.
3-Fibro-Cartilagenous coat:
-Dense connective tissue contains 16-20 C-shaped
rings of hyaline cartilage.
-The hyaline cartilage rings the following charecters:
Arranged above each other.
-The gaps between the free edges are bridged by
smooth muscle fibres (facing the oesophagus).
-Connected together by fibro-elastic membrane
attached to the perichondrium
BRONCHI
The trachea ends by dividing into two main primary bronchi
.(bronchi extrapulmonary)
Inside the lung, each bronchus intrapulomnary)
passes to the lower lobe of lung )bronchus
dividing repeatedly along its course into smaller
.secondary and tertiary bronchi
Structure:
Extra-pulmonary bronchiresemble the trachea in :
.structure
Intra-pulmonary bronchithe wall of the intra pulmonary :
:bronchus is formed of
Mucosa:
Highly folded.
Formed of:
Epithelium:stratified columnar ciliated with few -pseudo
.goblet cells
Corium:.fibres connective tissue rich in elastic
Muscle Layer:around fibres spirally arranged smooth muscle
.the mucosa
Adventitia::contains fibres connective tissue rich in elastic
Hyaline cartilaginous plates
Mucous and serous tubuloalveolar glands.
Lymphatic nodules and lymphocytic infiltration.
The goblet cells and mucous glands diminish in
number as the bronchi become smaller and
end at the level of the bronchioles.
6- BRONCHIOLES
Diameter.mm ١less than :
The wall consists of:
Mucosa:
Epitheliumtwo types of cells contains ::
Ciliated cells simple columnar ciliated cells، become ciliated cubical in small :
.bronchioles
Non ciliated cells (Clara cells).columnar cells with rounded apex :
Possess microvilli.
Contain dense granules.
Represent 50% of the cells lining the terminal bronchioles.
Function.secrets serous fluid rich in protein :
Corium.fibres Thin layer of loose connective tissue very rich in elastic :
No goblet cells in the mucosa of the bronchioles .B.N
The absence of goblet .A viscous mucus in the bronchioles might result in their closure of these patency the cells and the abundance of Clara cells in the bronchioles ensure
.mm in diameter ١minute tubules that are less than
Muscle layer
Well developed.
Spirally arranged around the mucosa.
Outer connective tissue layer :with
No Cartilage
No glands
No lymphatic nodules
7- TERMINAL BRONCHIOLES
• They are the smallest and terminal part
of the conducting system.
• Lining epithelium: ciliated cubical cells
alternating with clara cells which
represent 50% of the lining cells.
(II) RESPIRATORY
PORTION
RESPIRATORY BRONCHIOLES -١
Arise.from the bifurcation of the terminal bronchioles
Diametermm ٠٫٥-٠٫٢ :
The wall is:
Interruptedby alveoli which directly open into its lumen it so called
.respiratory bronchiole
Lined by cubical ciliated epithelium which become low cubical and non
.ciliated in the subsequent branches
Surrounded and smooth muscle fibres by connective tissue، elastic
.fibres
ALVEOLAR DUCTS -٢
Long branching passages arise from respiratory bronchioles.
The wall is:
Interrupted.by numerous openings of alveoli and alveolar sacs
Lined.by low cubical non ciliated epithelium
Surrounded and smooth muscle fibres by connective tissue، elastic
.fibres
ALVEOLAR SACS -٣
( Is a group of alveoli which open into a common central space .)atrium
4- PULMONARY ALVEOLI
• Definition:minute air spaces represent the
functional and structural units of the
Open into the alveolar .respiratory tissue
ducts and to lesser extent into the respiratory
.bronchioles
• Structure:.alveolar epithelium (١)
• .septum Interalveolar (٢)
• .Alveolar pores (٣)
•
•
Alveolar epithelium (١)
:Pneumocytes -١-Type (A)
Number:constitute the majority of the alveolar lining
.(%٩٥(cells
L/M: flat squamous cells less than 0.2 m thickness
with slightly thickened area containing the nucleus.
EM
• Perinuclear cytoplasm contains:
• Small Golgi complex.
• Few mitochondria.
• Occasional profiles of rER.
• The cytoplasm of the thin portion is devoid of
organelles.
• Attached by occluding junction to each other and to
type-2 pneumocytes.
• Have thin basement membranes fuse with basement
membranes of nearby capillaries (favorable for gas
exchange).
• Function:
• They are differentiated cells. They can not divide.
• Provide a very thin membrane through which
gaseous exchange takes place.
B) Type-2- Pneumocytes )
Number: represent 5% of the alveolar lining cells.
L/M: Cuboidal cells with rounded central nuclei.
E/M: Commonly located near the angles of the interalveolar septa.
Thicker than type-1 pneumocytes with rounded apical surface projecting above the level of the
surrounding epithelium.
Alveolar surface.microvilli covered by short :
Joined.by tight junctions ١-type pneumocytes to the neighboring
Nucleus.irregular with small clumps of heterochromatin :
Cytoplasm:contains
Extensive rER.
Many mitochondria.
Prominent Golgi Complex.
Multivesicular bodies.
Lamellar bodies.and surrounded by membrane phospholipid globules، rich in lamellated electron dense :
Function:
Have the capacity to divide and to act as progenitor cells for type-1 and type-2 pneumocytes.
They are secretory cells, secrete phospholipid substance known as pulmonary surfactant.
Pulmonary Surfactant:
Is a complex mixture of phospho-lipids, mainly diplamitoyl phosphatidylcholine complexed with
protein and carbohydrate.
Secreted by type-2 pneumocytes and spreads lining the inside aspects of the alveoli.
Very important in reduction of the surface tension (intermolecular forces between the H2O
molecules), so facilitating the inflation of the alveoli.
factant content by theIt is imperative for the lungs to have developed an adequate sur :.B.N
.time a newborn baby draws his first breath of air
•
2-Interalveolar septum
،formed of :
Alveolar epithelium on either
sides
Capillary network pulmonary )
.)capillary bed
Supporting network of:
•
Reticular fibres.
•
Elastic fibres.
•
C.T. cells:
•
Septal cells (interstitial
fibroblasts) which are the most
abundant.
•
Mast cells and few lymphocytes.
•
Extravasated leucocytes.
Basement membranes:
Basement m. of alveolar epithelium.
Basement m. of capillary beds.
In certain sites, the membranes fuse
together forming alveolar
capillary membrane.
3- Alveolar pores
• (: septa are interalveolar The
interrupted by holes called alveolar
These pores .)kohn pores of(pores
are important for communication
.between the alveoli
• BLOOD AIR BARRIER
• It is the wall separating the air in the
alveoli from the blood in the
capillaries.
• Formed of three components:
•
•
•
The surface lining and cytoplasm of the
alveolar cells.
The fused basal laminae of the alveolar
and endothelial cells.
The cytoplasm of the endothelial cells of
the capillaries.
ALVEOLAR MACROPHAGES
• Definition:Alveolar macrophages are the principal
mononuclear phagocytes of the lungs and represent the
.first line of defense against infection
• Site: .septum interalveolar In the • Free cells migrating over the luminal surface of the lung
alveoli.
• Origin:and are interstitium enter the monocytes blood
there transformed into macrophages that migrate into the
.lumen of the lung alveoli
• Number:Outnumber all other cell types of the lung and
:are constantly being eliminated and replaced
• M/E :
• Size ٤٠ – ١٥ : um
• Cell membrane.irregular with numerous pseudopodia :
• Nucleus.irregular :
• Cytoplasm: vacuolated & contains
» Small Golgi
» Short profiles of rER
» Glycogen particles
» Many lysosomes
•
•
•
•
•
•
•
•
Types Of ALVEOLAR MACROPHAGES :
:Dust cells (١)
These phagocytose dust or coal particles that are inspired with
air.
In cigarette smokers, the cytoplasm is crowded with large
irregular – shaped membrane limited bodies with heterogenous
electron densities.
:Heart failure cells (٢)
These phagocytose the extravasated RBCs, which escape from
the congested capillaries into the alveoli.
In persons with heart failure, the cytoplasm contains many
vacuoles with haemosiderin granules.
Fate:
Many of them migrate from the alveoli to the surface of the
action through the upper airway to ciliary bronchi and carried by
the pharynx where they are swallowed with saliva or expelled in
.)through coughing(the sputum
TEM of a Dust Cell (Alveolar Macrophage)
THE PLEURA
• A double walled serous membrane applied to the
and invests the lung )parietal pleura(thoracic cavity
.(visceral pleura)
The parietal pleura:
• Consists of fibr-elastic membrane.
• Lined on the inside by simple squamous epithelium.
The visceral pleura:
• Consists of fibro-elastic membrane.
• Continuous with the interlobular septa of the lung.
• Lined on the outside by simple squamous epithelium.
• The visceral and parietal layers of the pleura are
separated by a thin film of fluid to lubricate the sliding
movement of the visceral pleura and lung over the
parietal pleura.
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Practical
poster & Slides
Intrapulmonary Bronchus
Intrapulmonary Bronchus
Pseudostratified Ciliated Epithelium with Goblet
Cells