Basic Pulmonary Anatomy
The Upper and Lower Airways
Respiratory System
Upper Airways
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Nose
Paranasal sinuses
Pharynx
The Functions of the Nose
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Filter the air
Humidify the air
Warm the air
Site for sense of
small
To generate
resonance in speech
The Nose
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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
Nasal structure
Nares and Nasal Cavity
Regions of the nose
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Nares or nostrils serve as opening for the
nasal fossae—two cavities in middle of
the face
Vestibule/vestibular region
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Lined with stratified squamous epithelium
Contain vibrissae-nasal hair, first line of
defense, function to filter inspired air
Sagital section of the head
Nasal regions
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Vestibular area contains sebaceous
glands; secrete sebum
Keeps vibrissae soft and filter gases
Olfactory region: pseudostratified
columnar epithelium and olfactory cells
Regions of the nose
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Respiratory—highly vascular; ciliated,
pseudostratified columnar
epithelium
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Contains turbinates or conchae;
increase surface area (166 cm2) for
humidification, heating/cooling and filtering
of air
Mucous membranes provide up to 6501000 ml of water/day to humidify air
Respiratory region of nose
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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
Sinuses
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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
Paranasal Sinuses
Oral Cavity
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Alternate respiratory passage
Anterior 2/3 of tongue located in oral
cavity
Another “respiratory” muscle
Lined with stratified squamous
epithelium
+Pharaynx
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(Throat), hollow, upper portion of the
airway and the digestive tract
Subdivided into: nasopharynx,
oropharynx, laryngopharynx
Nasopharynx
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Pseudostratified ciliated columnar
epithelium
Pharynx
Nasopharynx
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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
Nasopharynx
Oropharynx
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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
Oropharynx
Laryngopharynx
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Stratified squamous epithelium
Gas conduction
Connecting zone between upper and
lower airway (vocal cords and below)
Lower Airway
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Begins with true
vocal cords and
extends to alveoli
Larynx
Trachea
Main stem bronchi
Segmental bronchi
Subsegmental
bronchi
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Bronchioles
Terminal bronchioles
Respiratory
bronchioles
Alveolar ducts
Alveolar sacs
alveoli
Larynx
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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
Larynx
Larynx
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Extends from C3 to
C6
Pseudostratified
ciliated columnar
epithelium
Functions:
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Free flow of air to
the lungs
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During inspiration,
vocal folds abduct,
move apart, and
widen glottis
Valsalva maneuver
and Muller maneuver
Larynx
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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
Larynx Posterior view
Epiglottis
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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
Glottis
Thyroid
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Largest of the laryngeal cartilages
Primary housing the vocal cords
Inflammation below the vocal cords
known as laryngotracheobronchitis
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Croup
Subglottic croup
Viral orgins
Cricoid
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A complete cartilaginous ring
Narrowest portion of the lower airway
in a neonate and infant
Actual start of the lower airway
Larynx – superior view
Tracheobronchial Tree
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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
Two Types of Airways
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Cartilaginous
-serve only to
conduct air between
external environment
and the sites of gas
exchange
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Non-cartilaginous
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-serve both as
conductors of
inspired air and as
sites of gas
exchange
Tracheobronchial Tree
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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
Histology
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Three major layers
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Epithelial lining
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Lamina propria
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Cartilaginous layer
Histology
Tracheal lining
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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
Tracheal Lining
Epithelial lining
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Pseudostratified ciliated columnar
epithelium is homogenous until the
level of the bronchioles
Cilia disappear in terminal bronchioles
Cilia absent in respiratory bronchioles
Histology
Mucous blanket
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Covers the epithelial lining
Composed of
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-95% water
-glycoproteins
Carbohydrate lipids
DNA
Cellular debris
Mucous
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Mucus produced by
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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
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Mucous Blanket
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Two distinct layers
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Sol layer
Gel layer
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Cilia move through
sol layer and strike
gel layer propelling it
toward mouth
At a rate of 2
cm/minute
Mucocilliary Escalator
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Defense mechanism of lower airways
Mucus propelled up airway to larynx
Cough mechanism moves secretions
into oropharynx via sheering forces
Mucociliary transport & cough
Factors Which Slow
Mucocilliary Transport
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Cigarette smoke
Dehydration
Positive pressure
ventilation
Endotracheal
suctioning
High inspired
oxygen
concentrations
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Hypoxia
Atmospheric
pollutants
General anesthesia
Parasympatholytic
drugs
Lamina Propria
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Submucosal layer
Contains loose fibrous tissue with
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Tiny blood vessels
Lymphatic vessels
Branches of the vagus nerve
Two sets of smooth muscle fibers which
continue/extend down to alveolar ducts
Lamina propria
Mast cells
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Found in lamina propria near
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Branches of vagus nerve and blood vessels
Scattered throughout smooth muscle
Loose connective tissue of skin and
intestinal mucosa
Cell constituents of submucosal glands
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Important part of humoral immune response
(circulating antibodies) which defend against
antigens
Mast Cells
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Release histamine
Cartilaginous Layer
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Outermost layer of tracheobronchial
tree
Consist of
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Trachea
Mainstem bronchi
Lobar bronchi
Segmental bronchi
Subsegmental bronchi
Trachea
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10-12 cm long
1.5-2.5 cm wide
Extends to second rib anteriorly and T4T5 posteriorly
15-20 C shaped rings
Main Stem Bronchi
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Right bronchus
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Wider
More vertical
5 cm shorter
Supported by C
shaped cartilages
20-30 degree angle
First generation
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Left bronchus
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Narrower
More angular
Longer
Supported by C
shaped cartilages
40-60 degree angle
First generation
Lobar Bronchi
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R main stem divides
into:
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Upper lobar
bronchus
Middle lobar
bronchus
Lower lobar
bronchus
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L main stem divides
into:
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Upper lobar
bronchus
Lower lobar
bronchus
Segmental Bronchi
3rd generation
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R lobar divides into
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Segmental bronchi
10 segments on right
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L lobar divides into
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Segmental bronchi
8 segments on left
Subsegmental Bronchi
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4th to 9th generations
Progressively smaller airways
1-4 mm diameter
At 1 mm diameter connective tissue
sheath disappears
Noncartilagenous Airways
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Bronchioles
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10-th to 15th
generation
Cartilage is absent
Lamina propria is
directly connected
with lung
parenchyma
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Surrounded by spiral
muscle fibers
Epithelial cells are
cuboidal
Less goblet cells and
cilia
With no cartilage,
airway remains open
due to pressure
gradients
Terminal Bronchioles
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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
Gas exchange zone
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Respiratory bronchioles
Acinus (aka primary acinus; aka primary
lobule)—respiratory bronchioles to the
alveoli
Ducts, sacs, alveolar
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Squamous epithelium
The Functional Units of Gas
Exchange
Functional Units of Gas
Exchange
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Three generations of respiratory
bronchioles
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Three generations of alveolar ducts
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15-20 clusters--sacs
Gas exchange terminology
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All of the structures arising from a
single terminal bronchiole are called
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Primary lobule
Acinus
Terminal respiratory unit
Lung parenchyma
Functional units
Acinus/Primary lobule
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Respiratory bronchioles with some
alveoli arising from their walls
Alveolar ducts arise from respiratory
bronchioles--alveoli whose septal wall
contain smooth muscle
Alveoli
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Ca. 300 million alveoli
Between 75 µ to 300 µ in diameter
Most gas exchange takes place at
alveolar-capillary membrane
Anatomic Arrangement of
Alveoli
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85-95% of alveoli covered by small
pulmonary capillaires
The cross-sectional area or surface area
is approximately 70m2
Acinus or Lobule
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Each acinus (unit) is approximately 3.5
mm in diameter
Each contains about 2000 aveloli
Approximately 130,000 primary lobules
in the lung
Acinus
Alveolar epithelium
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Two principle cell types:
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Type I cell, squamous pneumocyte
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Type II cell, granular pneumocyte
Type I Cell
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95% of the alveolar surface is made up
of squamous pneumocyte cells
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Between 0.1 µ and 0.5µ thick
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Major site of gas exchange
Type II Cell
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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
Type II Pneumocyte
Pore of Khon
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Small holes in the walls of adjoining
alveoli (alveaolar septa)
Between 3 to 13 µ in diameter
Formation of pores may be due to:
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Desquamation due to disease
Normal degeneration due to aging
Movement of macrophages leaving holes
Canals of Lambert/Pores of
Kohn
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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
Pores of Kohn
Alveolar macrophages
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So-called Type III cell
Remove bacteria and foreign particles
May originate as
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Stem cells precursors in bone marro
Migrate as monocytes through the blood
and into the lungs
Intersitium/interstial space
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Surround, supports, and shapes the
alveoli and capillaries
Composed of a gel like substance and
collagen fibers
Contains tight space and loose space
areas
Alveolar-Capillary Site-Interstitial Space
Interstitium
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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
Blood Supply to the
Pulmonary System
Two Systems
Bronchial Blood Supply
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Bronchial arteries
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From aorta to temrinal bronchioles
Merge with pulmonary arteries and
capillaries
1% of total cardiac output (left ventricle)
Bronchial arteries
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Also nourish
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Mediastinal lymph nodes
Pulmonary nerves
Some muscular pulmonary arteries and
veins
Portions of the esophagus
Visceral pleura
Bronchial venous system
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1/3 blood returns to right heart
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Azygous
Hemiazygous
Intercostal veins
This blood comes form the first two or
three generations of bronchi
Bronchial venous return
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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.)
Pulmonary Vascular System
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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
Pulmonary Capillaries
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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
Lymphatic System
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Lymphatic vessels
remove fluids and
protein molecules
that leak out of the
pulmonary
capillaries
Transfer fluids back
into the circulatory
system
Lymphatics
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Lymphatic vessels arise within loose
spaces of connective tissue
Vessels then follow bronchial airways,
pulmonary airways, pulmonary arteries
and veins to the hilum
Lymphatics
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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
Lymphatics
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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)
Lymphatic vessels
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Thoracic duct carries
lymph fluid coming
from tissues inferior
to diaphragm and
from left side of
upper body
Eventually empties
into left subclavian
vein
Lymphatic vessels
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Right lymphatic duct drains the right
half of the body superior to the
diaphragm
Empties into the right subclavian vein