Ventilatory Systems Structure and Function

Learning Objectives

By the end of this session, you should be able to:

• Understand the purpose of the ventilatory system
• Evaluate the overall and specific structures of mammalian lungs and link them
  to their overall and specific function.
• Understand potential ventilatory diseases and disorders

What are Ventilatory Systems?

The ventilatory system or respiratory system is a series of organs and
structures which are used for the exchange of gases into and out of an
organism.
Both plants and animals use a variety of different ventilatory systems:
Animals: O2 into the organism, exchanged with CO2 which is removed from the
organism.
Plants: CO2 into the organism, exchanged with O2 which is removed from the
organism.

Overall Anatomy of Mammalian Lungs

O2
CO2
Trachea
Intercostal muscles
Ribs
Right Bronchus
Heart
Bronchiole
Air Sacs
Diaphragm

Anatomy of the Trachea and Bronchi

Trachealis Muscle

Smooth muscle tissue which connects
the open-section of the C-shaped
rings of cartilages and the
oesophagus. Aids in expelling air
during coughing

Larynx

Holds vocal cords allowing for speech
and vocalisation. Larynx muscles can be
constricted and relaxed to produce a cough
or clear the throat.

Tracheal Cartilage Rings

stacks of 16-20
C-shaped rings of hyaline cartilage. Maintains
the structural integrity and rigidity of the
windpipe, allowing free gaseous exchange

Primary Bronchi

Splits the trachea between the two
lungs

Secondary Bronchi

Multiple Bronchial splits leading into the
Alveoli

Anatomy of the Trachea and Bronchi Internal Structure

Oesophagus
D
Trachea
Hyaline Carilage
Cilia
Pseudostratified
Columnar
Epithelial Cells
The internal structure of the trachea is
lined with a thin epithelium lined with
multiciliated cells intersperse with
mucous producing goblet cells.
Collective movement of the cilia
within the trachea work together to
move bacteria, mucous and debris
out of the lungs and into the back of
the throat.

Anatomy of Mammalian Alveoli

CO
from pulmonary artery
Thin alveolar epithelium
Thin epithelium aids in rapid
gaseous exchange

• to pulmonary vein
  Bronchiole

Pulmonary Capillary

Multiple close single cell thick
blood vessels are pushed against
the alveolar sac walls allowing for
ease of gaseous exchange, also
high blood flow rapidly replaces
newly oxygenated blood with
deoxygenated blood

Alveolar Sacs

multiple linked,
spherical air pockets have a large
surface to volume ratio -> allowing
for increased rate of gaseous
exchange

Breathing in Mammals

Breathing In

Increased cavity space
results in a decrease in
pressure leading to air
rush in to normalise
the pressure
Intercostal
muscles
pull the ribs
upwards
further
increasing
the size of
the chest
cavity
Diaphragm contracts,
expanding the chest cavity

Breathing Out

Intercostal
muscles
relax
allowing the
ribs to push
against the
chest cavity
further
reducing the
cavity size
Decreased cavity
space results in an
increase in overall
pressure, leading to air
to rush out to
normalise pressure.
Diaphragm relaxes,
allowing the chest cavity to shrink

Ventilatory System Diseases: Asthma

Open Bronchiole
Relaxed Trachealis
Muscle
Thin protective
mucous layer
Closed Bronchiole
Allergen Present
Constricted
Trachealis Muscle
Thick protective
mucous layer

• Asthma is a long-term inflammatory disease of
  the airways of the lungs.
• Is characterised by reversible and short-term
  airflow obstructions.
• Symptoms include:
• Wheezing
• Tightness of the chest
  . Shortness of breath
• Coughing fits
• Reduced peak and forced expiratory
  volume
• A mixture of genetic and environmental
  factors cause asthma, including dust,
  chemical irritants, air pollution, and lower
  respiratory infections

Asthma Management

Currently, there is no complete cure for asthma.
Trigger identification is currently the most effective form of treatment:
Removing the self from smoke, pets, food allergens etc.
Short-acting beta2-adrenoceptor agonists (SABA) is commonly used to treat
daily asthma attacks or to prevent attacks pre-exercise.
Corticosteroids can reduce Asthmatic exacerbation by reducing localised
inflammatory response
OH
IZ
HO
HO
Salbutamol
ALLEN & HANBURYS
Ventolin.
Evohaler
100 micrograms
200 meteved antaalicen

SABA: Mode of Action

Ca2+
Salbutamol
1
Adenylate
Cyclase
4
2
₿2 receptor
CAMP
ATP
3
Myosin Kinase

1. Salbutamol binds to the 32 receptors in
   trachealis and bronchi smooth muscle
   tissue.
2. Adenylate Cyclase is activated by the 32
   receptors which converts ATP into cyclic
   AMP (CAMP)
3. CAMP activates a myosin kinase starting
   a kinase cascade.
4. Kinase cascade blocks Ca2+ ions intake
   reducing intracellular concentration of
   Ca2+ within the smooth muscle cells.
5. This reduces bronchial and trachealis
   smooth muscle tissue constriction
   opening the bronchiole

Ventilatory System Diseases: Pneumonia

Pneumonia is an infection caused inflammation of the alveoli within the
lung.
Can be bacterial or viral in nature,
Commonly due to an upper respiratory tract infection which proceeds to a
lower respiratory infection.
Bacterial Pneumonia (such as Streptococcus pneumoniae) infects the
spaces between the alveoli and pulmonary capillaries, filling the alveoli
with pus and fluid as WBCs attack against these bacteria.

Pneumonia: Mode of Action

Normal Uninfected Alveoli Tissue

O2
CO2
Without fluid and debris, oxygen and
carbon dioxide is easily exchanged
across the Alveoli tissue.

Pneumonia Infected Alveoli Tissue

O2
CO2
Infection leads to increased pus/fluid
within the lung tissue. This fluid prevents
the easy exchange of gases across the alveoli
tissue.

Ventilatory System Diseases: Cystic Fibrosis

Cystic Fibrosis is a genetic disorder, which results in an increased
accumulation of thick mucus within a series of different organs.
Commonly associated with increased difficulty breathing and coughing
Gradually growing to increased risk of respiratory infections.
Mutations in the CFTR gene, results in the formation of a malfunctioning
CFTR protein which prevents the flow of Cl- ions out of the cell, resulting in
a reduction in the fluidity of the mucus and prevents cilia from clearing
this overly thick mucus.

Ventilatory System Diseases: Cystic Fibrosis Symptoms

Thin bronchi
walls
Thick bronchi
walls
Healthy bacterial
ecosystems
Maintained
bacterial
infections
Constricted/stiff
airway walls
Relaxed/flexible
airway wall
Clear, fluid-free
airways
Blood and excessively
thick mucus filled airways

Additional Affected Organs by Cystic Fibrosis

Increased risk of
bacterial sinusitis
infections
Altered sweat
(increased salt)
Blocked biliary ducts
within the liver
Increased accumulation
of thicker mucus within
the intestines prevents
nutrient absorption
Blocked
pancreatic
ducts
Fertility issues including
lack of the vas
deferens and reduced
sperm mobility

Cystic Fibrosis Inheritance

Unaffected
Mother
(Carrier)
Unaffected
Father
(Carrier)
R
r
R
r
R R
(Non-carrier)
R
r
R
r
r
r
(Carrier)
(Carrier)
(Affected)

• Cystic Fibrosis is caused by the lack of
  functional alleles of the gene CFTR
  (Cystic Fibrosis Transmembrane
  conductance Regulator).
• A F5084 (a phenylalanine deletion at
  point 508) is common (~4-5%) of
  Northern European ancestry.

Learning Outcome

You should now be able to:

• Understand the purpose of the ventilatory system
• Evaluate the overall and specific structures of mammalian lungs and link them
  to their overall and specific function.
• Understand potential ventilatory diseases and disorders