Respiratory System Question And Answers

Describe mechanics of respiration. (or) Muscles of respiration.
Answer:

Respiration:

• It is the process by which oxygen is taken in and carbon dioxide is taken out.
• Each respiratory cycle consists of 2 phases.

1. Inspiration:

• It is an active process.
• During inspiration, thorax is enlarge by.

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• • Ribs movement:
    • Due to the contraction of scaleni muscles, the first pair of ribs move upwards to a more horizontal position.
      1. This draws manubrium sterni – upwards and forwards.
    • 2nd 6th pair of ribs – upper costal series.
      • They move upwards and this movement is called pump handle movement.
      • It occurs due to contraction of external intercostal muscles.
      • It increases anteroposterior diameter of thoracic cage.
      • Central portion of these ribs move upwards and outwards and this movement is called Bucket handle movement.
      • It increases transverse diameter of thorax.
    • 7th-10th pair of ribs – lower costal series.
      • Shows bucket handle movement.
      • Increases transverse diameter of thorax.
    • 11th and 12 th pair of ribs – floating ribs.
      • Remain unchanged.
  • Diaphragmatic movements:
    • Diaphragm is a dome-shaped structure with convexity facing upwards.
    • During inspiration due to discharge in phrenic neurons, muscle fibers contract and central tendinuous portion is drawn downwards.
    • This flattens the diaphragm and increases the vertical diameter of the thoracic cage:
    • Movements of lungs.
    • During inspiration, as the enlargement of thoracic cage, negative pressure is increased in thoracic cavity.
    • This results in expansion of lungs.

2. Expiration:

• It is a passive process.
• During expiration, following changes occurs.
  1. Contraction of anterior abdominal wall muscles.
     • This increases intra-abdominal pressure.
     • Lowers the ribs to normal position.
     • Pushes diaphragm upwards.
  2. Internal intercostal muscles.
     • On contraction of these muscles, the upper ribs are pull down.
       Movement of lungs:
     • During expiration, as the thoracic cavity decreases in size, the pressure of thorax comes back to normal.
     • This compresses the lung tissues.