What are the two main phases of respiration?

Respiration consists of two alternating phases: inspiration (intake of air into the lungs) and expiration (expulsion of air from the lungs). Inspiration increases thoracic volume, while expiration decreases it.

How does the thoracic cavity change during inspiration?

During inspiration, the thoracic cavity increases in three dimensions: vertical diameter increases via diaphragm contraction, anteroposterior diameter increases via pump-handle movement of the sternum, and transverse diameter increases via bucket-handle movement of the ribs.

Is expiration an active or passive process?

Expiration can be passive or active. Quiet expiration is passive, relying on elastic recoil of alveoli and muscle relaxation. Forced expiration is active, involving muscles like internal intercostals and abdominal muscles.

What muscles are used during quiet respiration?

During quiet respiration, inspiration primarily involves the diaphragm and external intercostal muscles, while expiration is passive with no muscle action.

What is the difference between deep and forced respiration?

In deep respiration, inspiration uses additional accessory muscles like scalene and sternocleidomastoid, but expiration is passive. In forced respiration, all inspiratory muscles are active, and expiration becomes active with muscles like internal intercostals and abdominal muscles.

Why do asthma patients adopt a specific posture during an attack?

Asthma patients often sit leaning forward to aid breathing. This asthmatic posture helps by lowering the diaphragm for better lung expansion and fixing the scapulae so muscles like the pectorals can elevate the ribs more effectively.

What is the normal resting respiratory rate for adults?

The normal adult resting respiratory rate is approximately 18 breaths per minute. This rate can vary, being faster in children and slower in elderly individuals.

Mechanism of Respiration – Pump-Handle & Bucket-Handle

❓ Frequently Asked Questions