The respiratory system consists of a series of organs responsible for gas exchange. It includes the nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, and lungs. The trachea is a windpipe about 4 inches long that divides into two bronchi, one for each lung. The trachea and bronchi are lined with pseudostratified columnar epithelium containing ciliated, goblet, and basal cells. The bronchioles continue branching and lead to alveoli in the lungs where oxygen and carbon dioxide exchange occurs through a thin membrane between the air in the alveoli and blood in the capillaries.

1. Respiratory System
by Manash K. Paul
This ppt is for teaching purpose only

2. Respiratory System
Nasal
Cavitiy
Pharynx
Larynx
Trachea
Bronchi
Bronchiole
Lung
Respiratory System is a series of
organs responsible for taking in oxygen
and expelling carbon dioxide.
1. Conducting (Transports air)
• Nasal Cavities (NC)
• Pharynx
• Larynx
• Trachea
• Bronchi
2. Respiratory (gas exchange)
This ppt is for teaching purpose only

3. Windpipe
~ 4 inches long and less than an inch in diameter in most people.
Begins just under the larynx (voice box) and runs down behind the
breastbone (sternum).
20 rings of tough cartilage. The back part of each ring is made of
muscle and connective tissue.
Divides into two smaller tubes called bronchi: one bronchus for
each lung.
The trachea
This ppt is for teaching purpose only

4. Histology of Trachea
C-shaped
Cartilage
Epithelium
Transverse section of trachea
BM
GC
Ciliated
Cell
BC
BasalCell:BC,Clubcell:Club,GobletCell:GC

5. Pseudostratified columnar epithelium
(see previous page)
The diagram to the right illustrates the
organization of the epithelial cells and
submucosal glands in the trachea.
Important cell types
• Basal cells
• Columnar ciliated cells
• Goblet cells
Structure of Airway Epithelium
The airway epithelium plays a critical role in maintaining the conduit for
air to and from the alveoli. It is central to the defenses of the lung
against pathogens and particulates inhaled from the environment, with
the combined function of secretory and ciliated cells maintaining
efficient mucociliary clearance, and a variety of other host defense
processes
This ppt is for teaching purpose only

6. Basal cells are considered as the airway stem cells
Ciliated cells maintaining efficient mucociliary clearance. Cilia beats
upwards extruding the mucus enveloped dust as sputum
Goblet cells release mucus. Under the epithelium are submucosal glands
that secrete both mucus and fluid. Secretory cell number reduces in small
airway. Adult humans produces about 125 ml of mucus daily
Club or Clara cells are secretory cells as the airways branch from large to
small airways. Serous secretion includes glycoprotein, polysaccharide
and bacterosidic proteins
Airway Epithelial Cells
Stroma, blood vessel, nerve and immune cells
Goblet cell
Club cell
Fibroblast
Progenitor cell
Ciliated cell
Basal cell
DNA metabolic pulse-labeling
studies show that both basal
and columnar secretory cell
populations of the
pseudostratified epithelium
divide

7. Airway Epithelial Cells
EurRespirJ10:1655–1662,1997.

8. Airway Epithelial Cells
http://depts.washington.edu/envh/lung.html

9. Airway Mucous blanket
http://depts.washington.edu/envh/lung.htm

10. Main, Secondary and Tertiary Bronchi;
Bronchioles and Alveoli
Conducting Airways
Right bronchus
Secondary bronchus
Left bronchus
Tertiary bronchus
Alveoli
Bronchi:
Structurally similar to the trachea. C-shaped
cartilage rings are replaced by cartilage plates.
Smooth muscle fibers completely encircle the
wall, interior to the cartilage layer.
The right bronchus is slightly larger than the left
one. Because of this, foreign objects breathed
into the lungs often end up in the right bronchus.
The bronchi are lined with the same type of
mucus that lines the rest of the respiratory tract.
Each bronchus is further divided into five smaller, secondary bronchi,
which provide air to the lobes of the lungs. The secondary bronchi
continue to branch off to form the tertiary bronchi, which are further
divided into terminal bronchioles. There are as many as 30,000 tiny
bronchioles in each lung. They lead to the alveoli by way of alveolar
ducts.
The alveoli are responsible for the primary function of the lungs, which is
exchanging carbon dioxide and oxygen.

11. http://depts.washington.edu/envh/slide17.gif
Airway cast-trimmed. Airway cast-untrimmed.
Pulmonary Anatomy

12. A higher power view of the bronchus shows the epithelium (E) of
mainly pseudostratified ciliated columnar cells with a few goblet cells.
Bronchial branches less than about 5 mm in diameter
lack supporting cartilage and are called bronchioles
Typical section of lung tissue including many bronchioles, some of
which are respiratory bronchioles (RB) cut lengthwise, and showing the
branching continuity with alveolar ducts (AD) and sacs (AS).
The Respiratory Segment

13. The Respiratory Segment
An alveolus (plural: alveoli) is a hollow cavity found in the lung
parenchyma, and is the basic unit of respiration.
Respiratory Bronchioles branch to form alveolar ducts and alveoli
Alveolar ducts give off alveoli
Alveolar sacs: spaces surrounded by clusters of alveoli
Alveoli: sites of gas exchange with the blood as well.
The alveolar membrane is the gas-exchange surface. CO2 rich blood
is pumped from the rest of the body into the alveolar blood
vessels where, through diffusion, it releases its CO2 and absorbs
oxygen.

14. http://antranik.org/the-respiratory-system/

16. http://depts.washington.edu/envh/slide17.gif
The Respiratory Segment

17. The Cells of the Respiratory Segment
Type I Alveolar epithelium
Cuboidal, lines alveoli, thin flat cells, extended gas exchange surface
Gas exchange between blood
Type II Alveolar epithelium
Responds to damage of the vulnerable type I cell by dividing and acting
as a progenitor cell for both type I and type II cells.
Synthesizes, stores and releases pulmonary surfactant and acts to
optimize conditions for gas exchange.
Club Cells
Goblet Cells
Alveolar Macrophage
• Two major classes of lung macrophages are recognized.
• The most abundant is alveolar macrophages, which reside within the
lumen of the alveolus, directly exposed to air and the environment
but closely apposed to the alveolar epithelium.

18. The Cells of the Respiratory Segment

19. Type I Type II
Flattened Squamous cells
Line the alveolar surfaces and
are extremely attenuated
Make up 97% of the alveolar
surface
Have occluding junctions and
desmosomes
They are roughly cuboidal in
shape
Interspersed among the type I
alveolar cells with which they
have occluding and
desmosome junctions
Make up 3% of the alveolar
surface
Contains lamellar bodies that
store pulmonary surfactants
Type I and Type II Cells: comparision

20. TEM of a type II alveolar cell protruding into the alveolar lumen
TEM of a transversely sectioned capillary (C) in an
interalveolar septum shows areas for gas exchange between
blood and air in three alveoli
Type I and Type II Cells: comparision

21. Mechanism of gas exchange

22. The purpose of the respiratory system is to perform gas exchange.
Partial preassure: The pressure exerted by each type of gas in a
mixture
Concentration of a gas in a liquid determined by its partial pressure and
its solubility coefficient
Ventilation: Movement of air into and out of the lungs,
Perfusion: Flow of blood in the pulmonary capillaries.
Hemoglobin: Iron-containing substance in red blood cells that
transports oxygen from the lungs to the rest of the body; it consists of a
protein (globulin) and heme (a porphyrin ring with iron at its center)
Oxyhemoglobin: the form of hemoglobin, loosely combined with
oxygen, present in arterial and capillary blood
Mechanism of gas exchange

23. Basic Composition of Air
• 79% Nitrogen
• 21% Oxygen
• ~ 0% Carbon Dioxide
•In a mixture of gases, each gas exerts a partial pressure proportional to
its mole fraction
Total Pressure = sum of the partial pressures of each gas
Total Pressure (at sea level)
Pbarometric = 760 mm Hg
Each gas has a specific solubility
O2 Solubility coefficient = 0.003 ml/100 ml Blood
C02 = 0.06 ml/100 ml Blood (x 20 of 02)
Gases dissolve in fluids by moving down a
Partial Pressure gradient rather than a concentration gradient
.
Mechanism of gas exchange

24. Mechanism of gas exchange

25. THANKS