The lungs are located in the thoracic cavity and surrounded by the pleural membranes. They have an apex, base, lobes, and hilum where structures enter and exit. The lungs contain branching airways down to terminal bronchioles and alveoli, which are the gas exchange surfaces. Alveoli are made of type I and II cells and contain surfactant. The blood-air barrier is very thin to allow for gas exchange by diffusion. The lungs receive blood flow from the pulmonary and bronchial circulations and have lymphatic drainage.

1. Basic Pulmonary Anatomy
Dr. Mohanad

2.  Lung is porous, highly elastic and
spongy
 It crepitates on touch and floats on
water
Color :
 -In new born it is rosy pink
 -Becomes darker slat grey due to
deposition of carbonacious
particles
Lungs

3. Lungs Located within the thoracic cavity,
surrounded by the double-layered pleural
membrane –
parietal pleura – lines cavity wall
visceral pleura – covers the
lungs

4. Lungs- Anatomical Features
Apex – extends 1” above
clavicle
Base – rests on diaphragm
Right
lung
Left
lung
Superior
lobe
Middle lobe
Inferior
lobe
Horizontal
fissure
Oblique
fissure
Superior lobe
Inferior lobe
Oblique fissure
Cardiac notch
Hilum – at medial surface;
where primary bronchus,
pulmonary artery & veins
enter/exit lung

5. Hilum
Cardiac
notch of Lt.
lung
Lung – medial surface
Groove for aorta

6. Right lung
Upper lobe
Middle lobe
Lower lobe
Left lung
Upper lobe
Lower lobe
Right lung Left lung

7.  Each lung has a primary
bronchus entering at the
Hilus.
 Each lobe of a lung has a
secondary (a.k.a. lobar)
bronchus
 Lobes are functionally divided
into bronchopulmonary
segments & each segment has
a tertiary (segmental)
bronchus
 Segments are functionally
divided into many lobules &
each lobule receives a terminal
bronchiole
Airways within Lungs

9. Trachea Bronchus Tertiary bronchus Bronchiole
Respiratory
bronchiole
Epithelium Pseudostra
tified
 Columnar  Cuboidal
Goblet cells +++ ++ ++ + Absent
Clara cells Absent Absent Absent + +
Muscularis
mucosae
Absent + ++ +++ +++
Mucous glands +++ ++ + Absent Absent
Cartilage +++ ++ + Absent Absent
Alveoli Absent Absent Absent Absent +

10. Terminal Bronchioles
 16th
to 19th
generation
 Average diameter is 0.5 mm
 Cilia and mucous glands begin to
disappear totally
 End of the conducting airway
 Canals of Lambert-interconnect this
generation,provide collateral ventilation

12. Respiratory Zone
 Defined by the presence of alveoli; begins as terminal
bronchioles feed into Respiratory bronchioles
 Respiratory bronchioles lead to alveolar ducts, then to
terminal clusters of alveolar sacs composed of alveoli
Approximately 300 million alveoli:
 Account for most of the lungs’ volume
 Provide tremendous surface area for gas exchange

13. Alveoli
 200-300 million in a normal lung
 Between 75 µ to 300 µ in diameter- Total
area-75 square meters
 Most gas exchange takes place at alveolar-
capillary membrane
 85-95% of alveoli covered by small
pulmonary capillaries
 The cross-sectional area or surface area is
approximately 70m2

14. Alveoli are expanded
chambers of epithelial tissue
that are the exchange
surfaces of the lungs
Multiple alveoli usually share
a common alveolar duct,
creating “alveolar sacs”

15. Acinus or Lobule
 Each acinus (unit) is approximately 3.5 mm
in diameter
 Each contains about 2000 aveloli
 Approximately 130,000 primary lobules in
the lung

17. Alveolar Sac

18. Alveolar epithelium
 Two principle cell types:
 Type I cell, squamous pneumocyte
 Type II cell, granular pneumocyte

19. Type I Cell (Pneumocytes)
 95% of the alveolar surface is made up
of squamous pneumocyte cells
 Between 0.1 µ and 0.5µ thick
 Major site of gas exchange
 Preventing leakage of blood from
capillaries to the alveolar lumen
 Form Blood Air barrier

20. Type I Pneumocytes

21. Type II Cell
 5% of the surface of alveoli composed
of granular pneumocyte cells
 Cuboidal in shape with microvilli
 Primary source of pulmonary surfactant
 Involved with reabsorption of fluids in
the dry, alveolar spaces

23. Type II pneumocytes
 Also known as Septal cells
 Rounded or cuboidal secretory cells with microvilli
 Secretory granules are made of several layers- Multilamellar
bodies.
 Is constantly renewed.
 Pulmonary Surfactant – is the fluid secreted that spreads
over the alveolar surface.

24. Pulmonary Surfactant
 Surfactant contains
phospholipids, proteins and
glycosaminoglycans, reduces
the surface tension and prevents
collapse of the alveolus during
expiration.
 The reduced surface tension in
the alveoli decreases the force
that is needed to inflate alveoli
during inspiration.
 Therefore surfactant
stabilizes the alveolar
diameters, facilitates their
expansion and prevents
their collapse by
minimizing the collapsing
forces.
 Surfactant also has
bactericidal properties

26. Canals of Lambert/Pores of Kohn
 Provide for collateral ventilation of
difference acinii or primary lobules
 Additional ventilation of blocked units
 May explain why diseases spread so
quickly at the lung tissue (paremchymal)
level

27. Alveolar macrophages
 So-called Type III cell
 Remove bacteria and foreign particles
 May originate as
 Stem cells precursors in bone marro
 Migrate as monocytes through the blood
and into the lungs

28. Intersitium/interstial space
 Surround, supports, and shapes the
alveoli and capillaries
 Composed of a gel like substance and
collagen fibers
 Contains tight space and loose space
areas

29. Interstitium
 Water content in loose space can increase
by 30% before there is a significant change
in pulmonary capillary pressure
 Lymphatic drainage easily exceeded
 Collagen limits alveolar distensibility

30. Respiratory Membrane
 Respiratory membrane
 Alveolar wall – type I and type II alveolar cells
 Epithelial basement membrane
 Capillary basement membrane
 Capillary endothelium
 Very thin – only 0.5 µm thick to allow rapid diffusion of
gases
 Permit gas exchange by simple diffusion

32. Components of Alveolus

34. Blood Air Barrier
 Consist of a thin layer of surfactant
 Basement membrane of Pneumocytes I
 Basement membrane of capillary endothelial cell
 It exists to prevent air bubbles form forming in the blood, and
from blood entering alveoli

36. Nutrition of the lung
The lung gets nutrition from two sources:
1.Conducting part up to the beginning of respiratory
bronchiole is supplied by Bronchial artery
2. Respiratory part is supplied by pulmonary artery via
Pulmonary capillary plexus
•Primary purpose is to deliver blood to lungs for gas exchange
•Right lung has one bronchial artery and left lung has two
Bronchial artery

37. Bronchial arteries
 Also nourish
 Mediastinal lymph nodes
 Pulmonary nerves
 Some muscular pulmonary arteries and
veins
 Portions of the esophagus
 Visceral pleura

38. Bronchial venous system
 1/3 blood returns to right heart
 Azygous
 Hemiazygous
 Intercostal veins
 This blood comes form the first two or
three generations of bronchi

39. Bronchial venous return
 2/3 of blood flowing to terminal bronchioles drains
into pulmonary circulation via “bronchopulmonary
anastomoses”
 Then flows to left atrium via pulmonary veins
 Contributes to “venous admixture” or “anatomic
shunt” (ca. 5% of C.O.)

40. Pulmonary Capillaries
 Walls are les than 0.1µ thick
 Total external thickness is about 10µ
 Selective permeability to water,
electrolytes, sugars
 Produce and destroy biologically active
substances

41. Lymphatic System
 Lymphatic vessels remove
fluids and protein
molecules that leak out of
the pulmonary capillaries
 Transfer fluids back into
the circulatory system

42. Lymphatics
 Lymphatic vessels arise within loose spaces of
connective tissue, not in the walls of the alveoli.
 Vessels then follow bronchial airways,
pulmonary airways, pulmonary arteries and
veins to the hilum
 Vessels end in pulmonary and
bronchopulmonary lymph nodes within and
outside of lung parenchyma

43. Thank You