The document summarizes the structure and function of the respiratory system. It describes the conducting portion which includes the nasal cavities, pharynx, larynx, trachea, bronchi and bronchioles that warm, humidify and clean the air, but do not involve gas exchange. The respiratory portion includes respiratory bronchioles and alveoli where gas exchange occurs between the blood and air. It then provides detailed descriptions of the trachea, lungs, alveoli, alveolar epithelium consisting of Type-1 and Type-2 pneumocytes, blood-air barrier, interalveolar septum and alveolar phagocytes.

1. Dr. Samar Asker

2. It divided into
Conducting portion
& Respiratory
portion

3. Conducting portion:
no gaseous exchange
but warm, humidify,
clean entering air :
1.Nasal cavities.
2.Nasopharynx.
3.Oroopharynx.
4.Larynx.
5.Trachea.
6.Bronchi.
7.Bronchioles.

4. Respiratory portion:
gaseous exchange occurs.
This portion includes:
Respiratory bronchioles.
& lung Alveoli.
exchange of gases between the
blood and the inspired air
takes place.

5. TRACHEA
11 length x 2 cm width.
Starts at the end of the
Larynx & end by dividing
into 2 bronchi
The wall of the trachea
consists of 4 layers:
Mucosa,
Submucosa ,
Fibro-Cartilagenous coat
Adventitia.
11
2

6. Mucosa
submucosa
Fibro-Cartilagenous coat
Adventitia

7. Mucosa:
(A) Epithelium:
Pseudo-stratified columnar ciliated
with many goblet cells resting on
clear but thin basement membrane
(B) The C.T. Corium:
Thin infiltrated with lymphocytes
& contain blood vessels & nerves .
Rich in elastic fibres which
condenses to form elastic
membrane in the outer part.
L

8. Submucosa:
-Loose areolar
connective tissue
contains muco serous
tracheal glands which
Open into the surface
epithelium by short
ducts.

9. Fibro-Cartilagenous coat:
16-20 C-shaped rings of
hyaline cartilage embedded &
connected CT that fuse with
the perichondrium of the
cartilage plates.
The 2 ends of the cartilage
plates are connected by
transverse smooth muscle
fibres & flattened posteriorly
opposite the oesophagus
(4) Adventitia: Formed of CT

10. THE LUNG
The main part
of the respiratory
portion of the
respiratory tract &
consist of air
containing
chambers
called pulmonary or
lung alveoli

11. PULMONARY ALVEOLI
Structural & functional
units of the lung. Minute air
spaces that unit with each
other & form air sacs.
There are pores in () lung
alveoli to allow communication.
Separated from each other by
thin inter alveolar septum.
lined by two types of cells
called pneumocytes type-
1 & type-2..

12. Type-1- pneumocytes:
The most numerous as
they represent about 97%
of the lining epithelium.
L/M: - Flat squamous cells
with flat deeply stained
nucleus.

13. E/M: little cytoplasm contains few
organells
Cells attached to each other by
tight junctions to avoid escape of
tissue fluids to alveoli .
They can not divide.
Function: Provide a very thin membrane
through which gaseous exchange
takes place.

14. Type-2- Pneumocytes:
Less numerous 3% of the
alveolar lining cells.
L/M: Cuboidal cells with
vesicular rounded large
nuclei

15. EM:
Their apical surface have
microvilli.
 Vacuolated cytoplasm rich
in rER. Mitochondria, Golgi
Complex.
Can divide and give
the 2 types of pneumocytes.

16. They have
multilamellar
bodies
(cytosomes)
contain
phospholipids.

17. Function:
Secrete pulmonary surfactant
that forms a thin film over the
epithelial lining which reduce the
surface tension of lung alveoli &
help their expantion.
N.B.: surfactant is only
secreted late in pregnancy so
premature babies usually
have respiratory distress due
to deficiency of surfactant.

18. Interalveolar septum
Part in() lung Alveoli
Highly vascular C.T.
rich in
Reticular fibres &
elastic fibres which are
important for elasticity
& support of lung
tissue.

19. Blood air barrier:
Wall through which
gas exchange occur. It
is present in() blood in
the capillaries & air
within lung alveoli.

20. structure:
1)Thin film of pulmonary
surfactant
2)cytoplasm of
pneumocyte type I.
3)The fused basement
membrane of type I
pneumocyte and capillary
endothelium.
4)capillary endothelium.

21. Alveolar phagocytes
phagocytic
cells present in
the cavities of
lungs alveoli
or the
interalveolar
septum.

22. Origin: blood monocytes
Staining : vital stain as
trypan blue
Function : phagocytose
bacteria & dust particles &
rich in lysosomes.
Fate: coughed in the
sputum or they may die &
remain in the interalveolar
septum or the near by
lymph node.

23. Types:
Dust cells:
phagocytosed
dust or Carbon
particles that
are inspired
with air &
appear as black
particles .them

24. Heart failure cells:
Not in normal persons
but in patient with heart
failure. Congestion of
blood capillaries will lead
to their rupture & escape
of RBCs to alveolar
cavities. Macrophage
phagocytose HB&
destroy it to red colored
hemosidrin granules that
appear within them.

26. 1)The conducting portion of the
respiratory system includes :
a)Trachea.
b)Bronchi.
c)Terminal bronchioles .
d)Larynx.
e)All of the above

27. In the trachea, the corium is separated
from the submucosa by :
a)A complete layer of smooth muscle fibers.
b)A band of condensed fibro – elastic
membrane.
c)A band of elastic fibro cartilage.
d)A C- shaped ring of hyaline cartilage.
e)Irregular plates of hyaline cartilage.

28. 1)Concerning the alveolar epithelium, all are
correct except:
a)The epithelium rest on a very thick
basement membrane.
b)Type-I- pneumocyte constitute the
majority (97%).
c)Type II pneumocytes constitutes the
minority (3%).
d)For gas exchange and secretion of
pulmonary surfactant.
e)Type I pneumocytes are joined to

29. Regarding type –I pneumocyte, all are
correct except :
a)Constitute the majority of the alveolar
lining cells.
b)Flat squamous cells.
c)Can divide and give type II pneumocytes.
d)For gaseous exchange.
e)Joined to neighboring pneumocytes by
tight junction.

30. Each of the following is part of the blood
air barrier except:
a)Fused basement membrane of type I
pneumocyte and capillary endothelium
b)cytoplasm of pneumocyte type I.
c)Thin film of pulmonary surfactant
d)capillary endothelium.
e)A network of reticular fibers and
elastic fibers.

31. Alveolar phagocyte
Type-1pneumocytes:
Type-2pneumocytes: