Clinical Anatomy: Anatomy and Histology of the Respiratory System

Clinical Anatomy Lecture 13: Respiratory System

Clinical Anatomy
Lecture 13: Anatomy and Histology of the
Respiratory System

• Dr. Karyn Lumsden BSc, M.Ed., DC
• Assistant Professor
• Karyn.Lumsden@medready.org

Practice Questions are posted on Canvas

(c) 1999, Alvar W. Gustafson, Ph.D.

Learning Objectives: Air Entry and Lung Anatomy

1Learning
Objectives:

1. Trace air entry from the nostrils to the
   alveoli
2. Describe the anatomy of the lungs (e.g.
   layers of pleura, lobes, fissures, impressions,
   features)
3. Compare and contrast the right vs left lung
4. Describe the anatomy of the bronchial tree
5. Describe the contents of the hilum of the
   lung

• Be able to identify the histological features
  of lung tissue
• Be able to identify the histological features
  of the bronchial tree structures

The Respiratory System: Components

2The Respiratory System

• Nasal cavity
• Pharynx
• Larynx
• The Bronchial tree
• Trachea
• Primary (main) bronchi
• Secondary (lobar) bronchi
• Tertiary (segmental) bronchi
• Bronchioles
• Terminal bronchioles
  Conducting
• Respiratory bronchioles
• Alveolar ducts & sacs
• Individual alveoli
  Respiratory

-
Trachea
Left primary
bronchus
Secondary bronchus
Tertiary bronchi
Terminal bronchiole
Bronchioles
Respiratory
bronchiole
Alveolar
sac
LobuleThe Respiratory System

Conducting and Respiratory Zones

• Conducting zone
• Lined with pseudostratified columnar epithelium
• Conduit for air travel into body
• Cleans air
• Warms air
• Adds moisture
• Remove bacteria
• Moves air out and in
• Respiratory zone
• Lined with simple squamous epithelium
• Site of gas exchange
• 02 into blood
• CO2 out of blood

Frontal sinus
A
Sphenoidal sinus
Nasal cavity
Nasopharynx
Oropharynx
- Laryngopharynx
Larynx and vocal cords
Epiglottis
Esophagus
-Trachea
Right lung
Left
lung
Left
bronchus
Mediastinum
Right
bronchus
- Cardiac Notch
Diaphragm
Terminal
bronchiole
Thoracic
vertebra
Horizontal
cross section
of lungs
Visceral
pleura
Parietal
pleura
To pulmonary
vein
Alveoli
Wall of
thorax
Pleural space
Left lung
Right lung
Sternum
Rib
From pulmonary
artery
Alveolar
duct
Terminal
bronchiole
Capillaries
Section of lung enlargedThe Respiratory System

The Nasal Cavity

• The Nasal Cavity
• Nostrils - entrance
• Nasal Septum - divides cavity into
  right and left
• Concha (turbinate) - "shelf" of
  bone to trap/swirl air in cavity
• Sinuses - air filled spaces
  connected to cavity
• Also lined with mucosa
  Nasal Cavity - Parasagittal view
  Nasal mucosa - specialized lining of nasal cavity and associated
  structures
• Highly vascularized
• Pseudostratified columnar epithelium supported by lamina propria
• Cleans, warms, moistens air before it enters the pharynxThe Respiratory System

The Pharynx: Divisions and Function

• The Pharynx
• The "throat"
• Extends from base of skull to C3 body
• Common passage for both food and air
• Divisions of the Pharynx:
• 1. Nasopharynx: posterior to nose between
  base of skull and soft palate (air only)
• 2. Oropharynx: posterior to oral cavity (air
  and food)
• 3. Laryngopharynx: inferior portion of
  pharynx where it divides into larynx
  anteriorly and esophagus posteriorly
  Airway
  Foodway
  Naso-
  pharynx
  Oro-
  pharynx
  Laryngo-
  pharynxThe Respiratory System

The Larynx: Voicebox and Airway Protection

• The Larynx
• "voicebox" or glottis
• Contains vocal cords
• Extends from C3 to C6 vertebral body
• Passageway between pharynx and trachea
• Held open by cartilages
• 3 unpaired (cricoid, thyroid and epiglottis)
• 3 paired
• Entrance to trachea
• Contains elastic cartilage flap:
• Epiglottis covers trachea during swallowing
• Directs food and fluid into esophagus
• Prevents food from entering trachea
  Oro-
  pharynx
  -
  Laryngo-
  pharynx
  LARYNX
  TRACHEAThe Bronchial Tree = Trachea

Trachea: Structure and Bifurcation

• Stiff/flexible tube that conducts 02
  into the lungs and allows C02 to
  exit lungs
• Approximately 4 inches in length
  and travels anterior to esophagus
  within superior mediastinum
• Is located inferior to the epiglottis
  (C6 body) & extends to its
  bifurcation point at T4/5
• Bifurcation of trachea occurs
  within middle mediastinum where
  the trachea splits into two primary
  airways called "Bronchi"
  ANTERIOR VIEW
  Larynx
  Trachea
  Right main
  (primary) bronchus
  Left main
  (primary) bronchus
  Secondary bronchus
  Tertiary
  bronchus
  BronchioleThe Bronchial Tree

Tracheal Wall and Carina

• Wall of Trachea:
• To maintain an open airway at all times, the wall
  of the trachea is held open by C-shaped rings of
  hyaline cartilage
• Posteriorly, the ends of the cartilage are
  connected by a band of smooth muscle known as
  the "trachealis" muscle
• The carina is the last full
  cartilage located at the
  bifurcation point of the
  trachea
  TRACHEALIS
  C
  O
  0
  ·
  Trachea and
  esophagus
  cross section
  Membranous
  part of
  trachea
  Carina
  A
  Tracheal
  cartilage
  Right main
  bronchus
  Left main
  bronchus
  PB
  The Bronchial Tree

Primary Bronchi: Right vs. Left

• Primary (main) bronchi: enter
  the lungs at the hilum (root)
  of the lung
• Walls will have plates/pieces of
  cartilage
  1. Right
• Wider and shorter
• Vertical orientation to trachea
• Travels under the arch of the
  azygous vein
  2. Left
• Narrower and longer
• Horizontal orientation to
  trachea
• Travels under arch of aorta and
  left pulmonary artery
  Esophagus,
  Thoracic duct
  Trachea
  - Left recurrent
  laryngeal nerve
  Vagus nerve
  Arch of
  azygos vein
  Aorta
  Right
  main
  bronchus
  DA
  Carina
  Left main
  bronchus
  Right
  bronchial
  artery
  Left
  bronchial
  artery
  Anterior
  vagal trunk
  ANTERIOR VIEWANTERIOR VIEW
  The Bronchial Tree

Secondary (Lobar) Bronchi

• Secondary (lobar) bronchi: enter
  each of the lobes of the lungs
• Walls will have plates of cartilage
• 3 secondary (lobar) bronchi
  branching from the R main
  bronchus
• RSLB = Right SUPERIOR lobar
  bronchus
• £
  RMLB = Right MIDDLE lobar
  bronchus
• RILB = Right INFERIOR lobar
  bronchus
• 2 secondary (lobar) bronchi
  branching from the L main
  bronchus
• LSLB = Left SUPERIOR lobar bronchus
• LILB = Left INFERIOR lobar bronchus
  RIGHT MAIN
  BRONCHUS
  LEFT MAIN
  BRONCHUS
  RSLB
  LSLB
  RMLB
  LILB
  RILBRight lung
  Left lung
  I
  II
  Bronchopulmonary
  Segments
  III
  Horizontal
  fissure
  IV
  IV
  Oblique
  fissure
  V
  Oblique
  fissure
  V
  VIII
  VII,VIII
  Bronchopulmonary segments: each has
  its own branch of airway, pulmonary
  artery and pulmonary vein
  I
  II
  IIIThe Bronchial Tree

Tertiary (Segmental) Bronchi

• Tertiary (segmental) bronchi:
  each supplies a separate
  bronchopulmonary segment
  within lobe of the lung
• Many tertiary bronchi per
  secondary bronchi
• NOT necessary to memorize
  all of the branching patterns
  here
• Walls will have small cartilage
  plates
  I
  II
  III
  IV
  V
  IV
  VI
  V
  VIII
  VII
  X
  IX
  Bronchopulmonary segments: each has
  its own branch of airway, pulmonary
  artery and pulmonary vein
  I
  II
  III
  VI
  VII, VII
  X
  IXThe Bronchial Tree

Bronchioles and Terminal Bronchioles

• Bronchioles
• Much thinner walls
• Cartilage is absent!
• Consists of a layer of smooth muscle and
  epithelial lining of the conducting zone
• Each bronchiole branches to 20-25
  terminal bronchioles
• End of the conducting zone
• Sparce smooth muscle lining
• Epithelium appears more cuboidal in
  nature
• Each terminal bronchiole branches to
  several respiratory bronchioles
  trachea
  main bronchus
  segmental
  bronchus
  bronchioles
  terminal
  bronchioles
  respiratory
  bronchioles
  conducting portion
  respiratoryThe Bronchial Tree

Respiratory Bronchioles and Alveolar Ducts

• Beginning of respiratory zone:
• Respiratory bronchioles
• The beginning of the
  respiratory zone
• Lined by simple squamous
  epithelium
• No smooth muscle in wall
• Open up into approximately 2-
  11 alveolar ducts
• Alveolar duct
• Several alveoli are found
  attached to an alveolar sac
• Lined by simple squamous
  epithelium
  Trachea
  Main Bronchus
  Lobar Bronchus
  Segmental Bronchus
  Conducting Bronchiole
  Terminal Bronchiole
  Respiratory Bronchiole
  We have about 480
  million alveoli ... that's
  a lot of oxygen
  potential!

Alveoli
Alveolar duct
Respiratory
bronchioles
Alveolar duct
Terminal
bronchiole
-
Alveolar
sacThe Bronchial Tree

Alveoli: Functional Unit of the Lung

The end of the bronchial tree

• Alveolus / Alveoli
• Balloon-like air sacs
• Functional unit of the lung
• Alveolar cells
• Type 1 - simple squamous cells
• Type 2 - cuboidal like cells
• Gas exchange between air and
  blood occurs at the respiratory
  membrane
• Fused basement membranes of
  capillary endothelium and
  alveolar epithelium (type 1 cells)
  Alveolar
  connective
  tissue
  Nucleus of capillary
  endothelial cell
  Erythrocyte
  Nucleus
  of alveolar
  type I cell
  Erythrocyte
  Capillary
  Pulmonary
  capillaries
  Alveolar
  type I cell
  Alveolar
  type II cell
  Diffusion of CO2 Diffusion of O2
  Alveolar
  macrophages
  Alveolus
  Alveolar epithelium
  Alveolar pores
  Interalveolar
  septum
  Respiratory
  membrane
  Fused basement membranes
  of the alveolar epithelium and
  the capillary endothelium
  Capillary endothelium
  a
  b
  Alveolus
  Air
  in and out
  CO2
  2
  O
  2
  -
  Blood vessel
  (capillaries)Gas Exchange in the Lungs:

Gas Exchange and Blood Supply

• Gas exchange occurs in
  respiratory zone of
  bronchial tree:
• Respiratory bronchioles
• Alveolar ducts
• Alveolar sacs
• Pulmonary arterioles
  bring in deoxygenated
  blood to lungs
• Oxygenated blood travels
  via pulmonary venules to
  left atrium
  bronchiole
  lobule
  blood
  flow
  pulmonary
  arteriole
  blood flow
  pulmonary
  artery
  pulmonary
  vein
  blood flow
  alveoli
  pulmonary
  venule
  Blood supply of alveoli
  Capillary network of one alveolus
  Each alveolus is surrounded by an extensive capillary bed where
  C02 diffuses from blood into alveolus and is exhaled and 02 from
  inhaled air diffuses into blood and is carried back to heartPOLLING QUESTION 1:

Polling Question: Bronchial Tree Order

Which of the following is correct in order from larger to smaller?

• A. Respiratory bronchiole, Terminal bronchiole, Bronchiole
• B. Trachea, bronchiole, bronchi
• C. Bronchi, alveoli, bronchiole
• D. Alveoli, respiratory bronchiole, bronchi
• E. Bronchiole, terminal bronchiole, respiratory bronchioleThe Lungs

Pleura: Layers and Cavity

• There are 2 layers of pleura
  surrounding the lungs:
  1. Parietal pleura - outer layer that
  lines the thoracic cavity
  1. Costal part (touches ribs)
  2. Medistinal part (faces mediastinum)
  2. Visceral pleura - integrated with
  lung surface
  ANTERIOR VIEW
  Pleural cavity - the space between the parietal and visceral
  pleura; Filled with serous pleural fluidThe Lungs

Pleural Spaces and Recesses

• Pleural Spaces:
• Pleural cavity: the space between the
  parietal and visceral pleura
• Filled with small amount of serous fluid
  PA
  LATERAL
  R
  L
  X-ray views:
  Look for nice
  sharp angle
  on the
  postero-
  lateral aspect
  of the
  diaphragm
  Endothoracic
  fascia
  0
  Parietal
  pleura
  Visceral
  pleura
  Costodiaphragmatic
  recess
  Diaphragm
  Costodiaphragmatic
  sinus
  Costodiaphragmatic
  (costophrenic) recess
• Postero-lateral recess
• Potential space for
  abnormal fluid
  collection
  section of the right costodianhranmatic recess and sinus