MECHANISM OF RESPIRATION

ANATOMY OF RESPIRATORY SYSTEM

STEPS OF RESPIRATION

• PULMONARY VENTILATION• EXTERNAL RESPIRATION OR PULMONARY

RESPIRATION• TRANSPORT OF GASES IN BLOOD• INTERNAL RESPIRATION OR TISSUE

RESPIRATION

STEPS OF RESPIRATION

MECHANICS OF BREATHING

• 2 PROCESSES-

• Inspiration-Inlow of atmospheric air into lungs.• Expiration-Outflow of air from lungs into

atmosphere.

Important Pressures

• Atmospheric Pressure –Pressure exerted by the air surrounding the body i.e 0cm water pressure

• Intrapulmonary Pressure /intraalveolar pressure–pressure exerted by the air within the lungs

• Intrapleural Pressure /intrathoracic pressure-pressure within the pleural cavity exerted by pleural fluid.

• Transpulmonary Pressure/recoil pressure

MUSCLE OF INSPIRATION

• Muscle of normal tidal inspiration-• Diaphragm• External intercostal• Accessory Muscle of inspiration-i. Sternocleidomastoidii. Scaleneiii. Serratus Anterioriv. Pectoralis major and minor• Laryngeal muscle

MUSCLE OF EXPIRATION

• Internal intercostal• Abdominal muscles include-i. Abdominal Rectiiii. Transversus Abdominisiii. Internal oblique

MUSCLES OF RESPIRATION

BOYLE’S LAW

• Pressure of gas is inversely proportional to volume of thoracic cavity.

• Normal size• Gas molecules strike wall and exert pressure.

• If volume increases,less pressure is exerted

• If volume decreases,more pressure is exerted

COMPLIANCE

Ease with which lungs can be stretched.

Compliance of lung is determined by-•Elastic forces of lung tissue.•Alveolar surface tension.

COMPLIANCE

Low compliance

• Supine position• High standing diaphragm• Pulmonary fibrosis• Surgical intervention• Hydrothorax• Pneumothorax

High compliance

• Emphysema• Old age

SURFACE TENSION IN LUNGS

• Thin layer fluid lines alveoli.• Surface tension due to attraction between water

molecule.• Surface tension=force for alveoli to collapse or resist

expansion

SURFACE TENSION

• Increase tendency of alveoli to collapse.• Increase work of breathing.• Causes pulmonary oedema.• Alveolar instability.

TO OVERCOME SURFACE TENSION

• Surfactant secreted from type II cells. • Important components-• Dipalmitoylphosphatidylcholine• Surfactant apoproteins• Calcium ions

WORK OF BREATHING

• INCREASE IN –

• Exercise• Obstructive lung diseases• Restrictive lung diseases

Thank You