Anatomy and physiology of respiratory system

1. Basic Pulmonary Anatomy
Dr. Suva Nath
BHMS, MSc(Medical Physiology), MHA, PhD(Medicine)
Consultant Physician & Faculty of Medical Sciences

2. Basic Pulmonary Anatomy
The Upper and Lower Airways

3. Respiratory System

4. Upper Airways
 Nose
 Paranasal sinuses
 Pharynx

5. The Functions of the Nose
 Filter the air
 Humidify the air
 Warm the air
 Site for sense of
small
 To generate
resonance in speech

6. The Nose
 Rigid structure composed of cartilage
and bone
 Septal cartilage divides nasal cavity into
two nasal fossae
 Palate divides nasal cavity and oral
cavity
 Nose divided into 3 regions

7. Nasal structure

8. Nares and Nasal Cavity

9. Regions of the nose
 Nares or nostrils serve as opening for the
nasal fossae—two cavities in middle of
the face
 Vestibule/vestibular region
 Lined with stratified squamous epithelium
 Contain vibrissae-nasal hair, first line of
defense, function to filter inspired air

10. Sagital section of the head

11. Nasal regions
 Vestibular area contains sebaceous
glands; secrete sebum
 Keeps vibrissae soft and filter gases
 Olfactory region: pseudostratified
columnar epithelium and olfactory cells

12. Regions of the nose
 Respiratory—highly vascular; ciliated,
pseudostratified columnar
epithelium
 Contains turbinates or conchae;
increase surface area (166 cm2) for
humidification, heating/cooling and filtering
of air
 Mucous membranes provide up to 650-
1000 ml of water/day to humidify air

13. Respiratory region of nose
 Goblet cells in mucus membrane
secrete 100 ml/day of mucous; aids in
trapping inspired particles and prevents
them from entering lower respiratory
trace
 Each columnar cell contains 200-250
cilia; beat in waves toward oropharynx
(mouth), 2cm/min

14. Sinuses
 Air-filled cavities within the skull
(cranium)
 Aka paranasal sinuses (four pairs)
 Function not clear, lighten head and
provide voice resonance
 Lied with pseudostratified cliated
columnar epithelium and goblet cells

15. Paranasal Sinuses

16. Oral Cavity
 Alternate respiratory passage
 Anterior 2/3 of tongue located in oral
cavity
 Another “respiratory” muscle
 Lined with stratified squamous
epithelium

17. +Pharaynx
 (Throat), hollow, upper portion of the
airway and the digestive tract
 Subdivided into: nasopharynx,
oropharynx, laryngopharynx

Nasopharynx
 Pseudostratified ciliated columnar
epithelium

18. Pharynx

19. Nasopharynx
 Filters bacteria and foreign particles
from inspired air
 Carries this to the stomach
 Eustachian tube and auditory tube open
into lateral surfaces, connect
nasopharynx to middle each, equalizes
pressure of middle ear

20. Nasopharynx

22. Oropharynx
 Between soft palate above and base of
tongue below
 From tip of uvula to epiglottis
 Stratified squamous epithelium
 Gas conduction, filtering of air
 Defense mechanism: gag reflex

23. Oropharynx

24. Laryngopharynx
 Stratified squamous epithelium
 Gas conduction
 Connecting zone between upper and
lower airway (vocal cords and below)

25. Lower Airway
 Begins with true
vocal cords and
extends to alveoli
 Larynx
 Trachea
 Main stem bronchi
 Segmental bronchi
 Subsegmental
bronchi
 Bronchioles
 Terminal bronchioles
 Respiratory
bronchioles
 Alveolar ducts
 Alveolar sacs
 alveoli

26. Larynx
 Lies between base of tongue and
trachea
 Protrusion is the thyroid cartilage, aka
“Adam’s apple.”
 Houses the vocal cords, primary use is
vocalization
 Connection point-upper and lower
airways

27. Larynx

28. Larynx
 Extends from C3 to
C6
 Pseudostratified
ciliated columnar
epithelium
 Functions:
 Free flow of air to
the lungs
 During inspiration,
vocal folds abduct,
move apart, and
widen glottis
 Valsalva maneuver
and Muller maneuver

29. Larynx
 Composed of 3 single
cartilaginous structures:
 Epiglottis-flap, swings down
to meet larynx during
swallowing
 Thyroid-bulk of this forms
larynx
 Cricoid-circular, keeps head
of trachea open

30. Larynx Posterior view

31. Epiglottis
 Covers the rima glottidis during
swallowing (glottis=cords & space)
 Larynx has poor lymphatic drainge,
prone to edema
 Epiglottitis is a life-threatening condition
(supraglottic croup), bacterial origin
 Narrowest part of lower airway in adult

32. Glottis

34. Thyroid
 Largest of the laryngeal cartilages
 Primary housing the vocal cords
 Inflammation below the vocal cords
known as laryngotracheobronchitis
 Croup
 Subglottic croup
 Viral orgins

35. Cricoid
 A complete cartilaginous ring
 Narrowest portion of the lower airway
in a neonate and infant
 Actual start of the lower airway

36. Larynx – superior view

37. Tracheobronchial Tree
 Series of branching
airways commonly
referred to a
“generations” or
“orders”
 The first generation
or order is zero (0),
the trachea itself.
 Bifucrates at the
carina

39. Two Types of Airways
 Cartilaginous
-serve only to
conduct air between
external environment
and the sites of gas
exchange
 Non-cartilaginous
 -serve both as
conductors of
inspired air and as
sites of gas
exchange

40. Tracheobronchial Tree
 Dichotomous branching (daughter
branches)
 Airways become progressively narrower,
shorter, and more numerous
 Cross-sectional area enlarges
 Common histology (at the nose) and
throughout until the bronchiole
generation

41. Histology
 Three major layers
 Epithelial lining
 Lamina propria
 Cartilaginous layer

42. Histology

43. Tracheal lining
 Pseudostratified columnar epithelium
with cilia; goblet cells, serous cells, and
specialized submucosal bronchial glands
 200+ cilia per cell, 5-7 microns long
 Beat cephalid (head) toward
oropharynx

44. Tracheal Lining

45. Epithelial lining
 Pseudostratified ciliated columnar
epithelium is homogenous until the
level of the bronchioles
 Cilia disappear in terminal bronchioles
 Cilia absent in respiratory bronchioles

47. Histology

48. Mucous blanket
 Covers the epithelial lining
 Composed of
 -95% water
 -glycoproteins
 Carbohydrate lipids
 DNA
 Cellular debris

49. Mucous
 Mucus produced by
 Goblet cells
 Found through terminal bronchioles
Submucosal (bronchial) glands
extend into laminar propria
Innervated by vagus nerve (parasympathetic)
Produce 100 ml of secretions/day
Disappear at end of terminal bronchioles

50. Mucous Blanket
 Two distinct layers
 Sol layer
 Gel layer
 Cilia move through
sol layer and strike
gel layer propelling it
toward mouth
 At a rate of 2
cm/minute

51. Mucocilliary Escalator
 Defense mechanism of lower airways
 Mucus propelled up airway to larynx
 Cough mechanism moves secretions
into oropharynx via sheering forces

52. Mucociliary transport & cough

53. Factors Which Slow
Mucocilliary Transport
 Cigarette smoke
 Dehydration
 Positive pressure
ventilation
 Endotracheal
suctioning
 High inspired
oxygen
concentrations
 Hypoxia
 Atmospheric
pollutants
 General anesthesia
 Parasympatholytic
drugs

54. Lamina Propria
 Submucosal layer
 Contains loose fibrous tissue with
 Tiny blood vessels
 Lymphatic vessels
 Branches of the vagus nerve
 Two sets of smooth muscle fibers which
continue/extend down to alveolar ducts

55. Lamina propria

56. Mast cells
 Found in lamina propria near
 Branches of vagus nerve and blood vessels
 Scattered throughout smooth muscle
 Loose connective tissue of skin and
intestinal mucosa
 Cell constituents of submucosal glands
 Important part of humoral immune response
(circulating antibodies) which defend against
antigens

57. Mast Cells
 Release histamine

58. Cartilaginous Layer
 Outermost layer of tracheobronchial
tree
 Consist of
 Trachea
 Mainstem bronchi
 Lobar bronchi
 Segmental bronchi
 Subsegmental bronchi

59. Trachea
 10-12 cm long
 1.5-2.5 cm wide
 Extends to second rib anteriorly and T4-
T5 posteriorly
 15-20 C shaped rings

60. Main Stem Bronchi
 Right bronchus
 Wider
 More vertical
 5 cm shorter
 Supported by C
shaped cartilages
 20-30 degree angle
 First generation
 Left bronchus
 Narrower
 More angular
 Longer
 Supported by C
shaped cartilages
 40-60 degree angle
 First generation

61. Lobar Bronchi
 R main stem divides
into:
 Upper lobar
bronchus
 Middle lobar
bronchus
 Lower lobar
bronchus
 L main stem divides
into:
 Upper lobar
bronchus
 Lower lobar
bronchus

63. Segmental Bronchi
3rd generation
 R lobar divides into
 Segmental bronchi
 10 segments on right
 L lobar divides into
 Segmental bronchi
 8 segments on left

64. Subsegmental Bronchi
 4th to 9th generations
 Progressively smaller airways
 1-4 mm diameter
 At 1 mm diameter connective tissue
sheath disappears

66. Noncartilagenous Airways
 Bronchioles
 10-th to 15th
generation
 Cartilage is absent
 Lamina propria is
directly connected
with lung
parenchyma
 Surrounded by spiral
muscle fibers
 Epithelial cells are
cuboidal
 Less goblet cells and
cilia
 With no cartilage,
airway remains open
due to pressure
gradients

67. 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

68. Gas exchange zone
 Respiratory bronchioles
 Acinus (aka primary acinus; aka primary
lobule)—respiratory bronchioles to the
alveoli
 Ducts, sacs, alveolar
 Squamous epithelium

69. The Functional Units of Gas
Exchange

70. Functional Units of Gas
Exchange
 Three generations of respiratory
bronchioles
 Three generations of alveolar ducts
 15-20 clusters--sacs

71. Gas exchange terminology
 All of the structures arising from a
single terminal bronchiole are called
 Primary lobule
 Acinus
 Terminal respiratory unit
 Lung parenchyma
 Functional units

72. Acinus/Primary lobule
 Respiratory bronchioles with some
alveoli arising from their walls
 Alveolar ducts arise from respiratory
bronchioles--alveoli whose septal wall
contain smooth muscle

73. Alveoli
 Ca. 300 million alveoli
 Between 75 µ to 300 µ in diameter
 Most gas exchange takes place at
alveolar-capillary membrane

75. Anatomic Arrangement of
Alveoli
 85-95% of alveoli covered by small
pulmonary capillaires
 The cross-sectional area or surface area
is approximately 70m2

76. 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

77. Acinus

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

80. Type I Cell
 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

81. 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

82. Type II Pneumocyte

83. Pore of Khon
 Small holes in the walls of adjoining
alveoli (alveaolar septa)
 Between 3 to 13 µ in diameter
 Formation of pores may be due to:
 Desquamation due to disease
 Normal degeneration due to aging
 Movement of macrophages leaving holes

84. 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

85. Pores of Kohn

86. 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

87. 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

88. Alveolar-Capillary Site--
Interstitial Space

90. 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
 Area of scarring, making for stiffer or
non-compliant lungs

91. Blood Supply to the
Pulmonary System
Two Systems

92. Bronchial Blood Supply
 Bronchial arteries
 From aorta to temrinal bronchioles
 Merge with pulmonary arteries and
capillaries
 1% of total cardiac output (left ventricle)

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

94. 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

95. 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.)

96. Pulmonary Vascular System
 The second source of blood to the lungs
 Primary purpose is to deliver blood to
lungs for gas exchange
 Also delivers nutrients to cells distal to
terminal bronchioles
 Composed of arteries, arterioles,
capllaries, venules, and veins

97. 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

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

99. Lymphatics
 Lymphatic vessels arise within loose
spaces of connective tissue
 Vessels then follow bronchial airways,
pulmonary airways, pulmonary arteries
and veins to the hilum

100. Lymphatics
 Vessels end in pulmonary and
bronchopulmonary lymph nodes within
and outside of lung parenchyma
 Nodes acts as filters to keep particles
and bacteria from entering the blood

101. Lymphatics
 Lymphatic vessels are not in
the walls of the alveoli.
 Within the interstial spaces
to help drain fluids and
foreign materials.
 More lymphatic vessels on
surface of lower lobes than
on upper and middle lobes
(dependent portions)

102. Lymphatic vessels
 Thoracic duct carries
lymph fluid coming
from tissues inferior
to diaphragm and
from left side of
upper body
 Eventually empties
into left subclavian
vein

103. Lymphatic vessels
 Right lymphatic duct drains the right
half of the body superior to the
diaphragm
 Empties into the right subclavian vein