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Pulmonary Ventilation
Provide O2 to the tissues

• Main Functions of respiration
Remove CO2
•

By downward or upward
movement of the Diaphragm

Lungs can be expanded or contracted;

Elevation or depression of the ribs

• Normal quiet breathing - by the diaphragm
•

Muscles that raise the rib cage
1
...
SCM
3
...
Scaleni

Muscles that pull the rib cage downward
1
...
Internal intercostals

• Pleural pressure - pressure of the
fluid in the thin space bw the lung
pleura and the chest wall pluera
...
(Recoil pressure - elastic
forces that tend to collapse the lungs at
respiration)

Compliance of the lungs - extent the lungs will expand for each unit
increase in trans pulmonary pressure- 200 ml of air/cm H2O
• elastic forces of the heart - 1
...
EF by the surface tension of the fluid
determined by elastin and
that lines the inside walls of the alveoli
collagen

G

Surfactant • surface active agent in water, reduces the surface tension of water
...

• Phospholipids reduce the surface tension
...
Tidal Volume
Air inspired or expired with each
normal breath 500 ml
2
...
Expiratory reserve volume
Extra volume that can be expired 1100 ml
4
...
Inspiratory capacity = TV + IRV 3500 ml
2
...
Vital capacity = IRV + TV 4600 ml
4
...

Determines the conc
...


Dead space airSome air that a person breathes never reaches
the lungs but fills the nose, pharynx,
trachea (No gas exchange)
This air is expired first
150 ml

Pulmonary Circulation
• Lungs have 2 circulations

High pressure, low flow circulation
Supplies systemic arterial blood to the trachea,
bronchial tree

Low pressure, high flow circulation
Supplies venous blood from the body to the
alveolar capillaries

Pressures in the Right ventricle

Pressures in the pulmonary artery

1
...
Diastolic- 0- 1 mmHg

During systole = pressure in the right ventricle
• After the pulmonary valve closes at the end of systole,
ventricular pressure falls
...
of O2 in the air of the alveoli decreases below normal,
blood vessels constrict, increase vascular resistance
1
...
Decrease release of vasodilators - NO

• Extra blood flow through the lungs are achieved by,
1
...
Distending all the capillaries and increasing the rate of flow through
capillaries
3
...
8 second
When the cardiac output increases - 0
...
Pulmonary capillary pressure is low - 7 mmHg
2
...
Colloid osmotic pressure of the pulmonary interstitial fluid 14 mmHg
4
...

Tendency -4 mmHg



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