The lungs are located within the thoracic cavity and are surrounded by the pleural membranes. Each lung has a conical shape with an apex and base. The right lung is divided into three lobes and the left lung into two lobes by fissures. Over 300 million alveoli within the lungs provide a vast surface area for gas exchange to occur between the air in the alveoli and blood in the pulmonary capillaries.

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
 Conical in shape, apex, base, costal surface,
medial surface, hilus. Note various impressions
 Right lung
 Three lobes; superior, middle and inferior
 Oblique and horizontal fissure
 Left Lung
 Two lobes; superior and inferior also Lingula and
Cardiac notch, oblique fissure

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

5. 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

6. Surface Anatomy

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

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

9.  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

11. Trachea
Bronchu
s
Tertiary
bronchus
Bronchio
le
Respiratory
bronchiole
Epithelium Pseudost
ratified
 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 +

12. 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

13. Bronchiole
 Terminal bronchiole
-Columnar epithelium
-No cartilage
- smooth muscle +
-Clara cells present
 Respiratory bronchiole
-Cuboidal epithelium
-No mucous gland

15. Differences between Bronchi and
Bronchioles
Bronchioles
 No glands
 No cartilage
 No goblet cells
 Thick smooth muscle layer
 Presence of Clara cells
 Many elastic fibres

16. 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

18. Respiratory Bronchiole

20. 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

21. 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”

22. 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

24. Alveolar Sac

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

26. 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

27. Type I Pneumocytes

28. 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

30. 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.

31. Alveolar spaces - Septa
Type I
Pneumocytes
Type II
Pneumocyte

32. Alveolar Macrophages
Alveolar
macrophages: aka dust
cells, located in septa,
often contain
phagocytized material

33.  Synthesized by type II alveolar cells
 Increase pulmonary compliance.
 Reduces surface tension (prevents alveolar collapse during
expiration)
 Decreases the force that is needed to inflate alveoli during
inspiration.
 Prevent the lung from collapsing at the end of expiration.
 Prevents bacterial invasion
 Cleans alveoli surface

34. Composition
 Lipids : Over 90% of the surfactant
 Phosphatidylcholine: ~85% of the lipid in surfactant with
saturated acyl chains.
 Phosphatidylglycerol (PG): 11% of the lipids in surfactant
with unsaturated fatty acid chains that fluidize the lipid
monolayer at the interface.
 Neutral lipids and cholesterol are also present.
Proteins
 10% of surfactant.

36.  Surface active agent in water = reduces surface tension
of water on the alveolar walls
Pure water (surface
pressure)
72 dynes/cm
Normal fluid lining alveoli
without surfactant
(surface pressure)
50 dynes/cm
Normal fluid lining alveoli
with surfactant
5-30
dynes/cm

38. Lack of surfactant causes
respiratory distress syndromes
 The effect of surfactant on compliance and
elasticity Increase compliance and decrease
elasticity
 Premature infants: ordinarily a rise in levels of the
adrenal cortical hormone cortisol induces production
of surfactant before birth.
 In some adults with lung trauma from smoke
inhalation or toxic gas, surfactant production is
impaired

39. 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

40. 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

41. 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

42. 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

43. 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

45. Components of Alveolus

47. 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

49. 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

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

51. 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

52. 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.)

54. 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

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

56. 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

57. 57
Pleurae
 Serous membrane that covers the lung
parenchyma, mediastinum, diaphragm
and the rib cage
 Parietal pleura
 Covers the thoracic wall and superior face
of the diaphragm
 Continues around heart and between lungs

58. Pleurae
 Visceral, or pulmonary, pleura
 Covers the external lung surface
 Divides the thoracic cavity into three chambers
 The central mediastinum
 Two lateral compartments, each containing a lung
58

59. 59
Pressure Relationships
Figure 22.12

60. Histology
• Grossly: Normal pleura is a smooth, glistening,
semitransparent membrane.
• Light microscopy, pleural consist of five layers :
 Mesothalial layer
 Connective tissue layer
 Superficial elastic layer
 Loose subpleural connective tissue layer (rich in
vessels, nerves and lymphatics)
 Deep fibroelastic layer (in continuity with the
parenchymal structures of lung, diaphragm or the
thorax)

61. Pleural Fluid
 Fluid present between the parietal and visceral pleura, in
space called Pleural fluid.
 Fluid act as lubricant and allows the visceral pleura
covering the lung to slide along the parietal pleura lining
the thoracic cavity during respiratory movements.
 Volume :
 Mean amount of fluid in right pleural space in normal
individual is 8.4 +/- 4.3 ml.
 Normally the volume of fluid in right and left pleural
space is equal.

62.  Cells :
 Mean RBC count – 700 cells/mm3
 Mean WBC count – 1,716 cells/mm3
 Macrophages – 75 %
 Lymphocytes – 25 %
 Mesothilial, neutrophils, eosinophils ( < 2 % each )
 Eosinophil > 10 %

63.  Physiochemical factors :
• Protein – Pleural fluid is similar to that of serum except
that low molecular weight protein such as albumin present
in relatively greater quantities in plural fluid.
• Ions :
 Bicarbonates : increase by 20-25% to that in plasma.
 Sodium : reduce by 3-5% to that in plasma
 Chloride : reduce by 6-9% to that in plasma
 Potassium : nearly identical to that in plasma
• Glucose : similar to that in plasma- Less than 60 mg/dl .
• Pco2 : same as the plasma Pco2
• pH : due to elevated pleural fluid bicarbonate the pleural
fluid is alkaline with respect to plasma pH.

66. Question
 Outline the principal anatomical features of
the diaphragm that are important to its
function.

67. Thank You