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MECHANISM OF BREATHING
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MECHANISM OF BREATHING
Accessory Inspiratory Muscles-
- Sternocleidomastoid
- Scalene
- Alae Nasi
- Serratus Anterior
MUSCLES INVOLVED
COMPLIANCE
It is defined as the change in the lung volume per unit change in pressure.
The measure of the distensibility of the lungs.
Compliance of the normal lung – 200mL/cm of H₂O
Mathematically,
Compliance= △V
△P
CLINICAL ASPECT
Pneumothorax
Abnormal collection of air or gas in the pleural space that causes an uncoupling of the lung from the chest wall.
SURFACTANT
SURFACE TENSION
- At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other than to the molecules in the air.
SURFACTANT
- It is a surface-active lipoprotein complex
- Formed by type II alveolar cells.
- Present in the liquid lining the alveoli
- Reduces surface tension.
Composition
- Dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.
- Surface apoproteins and the Calcium ions are required for faster spread of surfactant
MECHANISM
- Dipalmitoylphosphatidylcholine (DPPC)
- Other phospholipids
- Surface Apoproteins
- Cholesterol
- Calcium ions
- Surfactant- hydrophilic and hydrophobic regions.
- Adsorbes to the air-water interface of alveoli
- Hydrophilic head-orients towards water
- Hydrophobic tails-towards the air.
DEAD SPACE
THANK YOU
FUNCTIONS
- Anatomical
- Physiological
Alveolar Ventilation
Total amount of air entering the alveoli each minute
WORK OF BREATHING
Workdone=P/V
- Reduces the surface tension
- Increases the alveolar radius
- Keeps alveoli dry
- Stabilization of the alveoli
- To increase pulmonary compliance.
CLINICAL ASPECTS
WITHOUT SURFACTANT
- Atelectasis
- Infant Respiratory Distress Syndrome (IRDS)
WITH SURFACTANT
STABILISATION OF ALVEOLI
By LaPlace's Law,
P= 2xT
R
P- Alveolar pressure
T- Surface Tension
R- Radius
PRESSURE CHANGES
INSPIRATORY MUSCLES
INTRA-ALVEOLAR PRESSURE
TYPES OF BREATHING
TRANSPULMONARY PRESSURE
- Diaphragm
- External Intercostal muscles
- The difference between the alveolar pressure and the intrapleural pressure in the lungs
- Ptp = Palv – Pip
- Pressure within the alveoli
- Determines whether airflow will flow into or out of the lungs.
- Thoraco-abdominal
- Abdomino-thoracic
PRESSURE CHANGES DURING VENTILATION
ACCESSORY INSPIRATORY MUSCLES
- Alae Nasi
- Sternomastoid
- Serratus anterior
- Scalene
ACCESSORY EXPIRATORY MUSCLES
- Rectus Abdominis
- Internal intercostals
- Internal and external obliques
- Transversus abdominis
Types Of Individual Pressures
- Intrapleural Pressure
- Intra alveolar Pressure
- Transpulmonary Pressure
INTRA-PLEURAL PRESSURE
- The pressure within the pleural cavity
- Allows lung distension
- Pressure is sub-atmospheric (negative)
- Due to the recoil of the lungs