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Mechanism of respiration. corrected

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Mechanism of respiration. corrected

  1. 1. Topic – Mechanism of breathing Roll No. 65-73 • Rahul Rai- 65 • Raman – 66 • Rashid – 67 • Rishima Jain – 68 • Ritika Goel – 69 • Rititka Kishore Sahay – 70 • Sachet Nangia – 71 • Sai dev vrat – 72 • Sanjukta – 73
  2. 2. Mechanism of breathing.. • BREATHING is an involuntary process which involves two processes – Inspiration and Expiration. • The two processes involves certain bones and muscles. • At rest an adult breathes at a rate of 12-14 breaths/min and the amount of air inspired or expired per breath is approx. 500ml. Thus 6-7 litres of air is breathed in or out of the lungs per minute called PULMONARY VENTILATION
  3. 3. Inspiration • An active process . • Thoracic cavity expands. • Pleural cavity pressure decreases. • Movement of ribs outwards and upwards.(rib movements) • Descent of diaphragm.(diaphragmatic movements) • Due to these movements the volume inside the lungs increases , leading to decrease in pressure inside the lungs. • This decrease in pressure in the lungs relative to atmospheric pressure(760 mm hg) leads to movement of air from atmosphere to the lungs.
  4. 4. RIB MOVEMENTS • 1ST pair of ribs moves and bring about increase in anteroposterior diameter. • 2nd -6th ribs slope downwards and forwards from their joints with the spinal column.(pump handle movements). • 7th _10th ribs swing outwards and upwards.(bucket handle movements).
  5. 5. diaphragmatic movements. • Responsible for 75% of inspiratory effort • Thin dome-shaped muscle attached to the lower ribs, xiphoid process, lumbar vertebra • Innervated by Phrenic nerve (Cervical segments 3,4,5) • During contraction of diaphragm – Abdominal contents forced downward & forward causing increase in vertical dimension of chest cavity – Rib margins are lifted & moved outward causing increase in the transverse diameter of thorax – Diaphragm moves down 1cm during normal inspiration – During forced inspiration diaphragm can move down 10cm
  6. 6. Clinical significance. • Patients with bilateral nerve palsy but, with intact innervation of intercoastal muacles have their respiration somewhat laboured but, it is adequate to maintain • Transection of spinal chord above 3rd spinal segment is fatal but, below 5th cervical segment is not because phreic nerve remains Intact. Exhalation dysfunction: – Pump handle: ribs are stuck down in the front and up in the back – Bucket handle: ribs are stuck down and in – Caliper: ribs are stuck pincing in • Inhalation dysfunction: – Pump handle: ribs are stuck up in the front and down in the back – Bucket handle: ribs are stuck up and out – Caliper: ribs are stuck pincing out
  7. 7. Accesory muscles of inspiration. These muscles assist with forced inspiration during periods of stress or exercise Scalene Muscle • Attach cervical spine to apical rib • Elevate the first two ribs during forced inspiration Sternocleidomastoid Muscle • Attach base of skull (mastoid process) to top of sternum and clavicle medially • Raise the sternum during forced inspiration
  8. 8. EXPIRATION. The Passive Phase Of Breathing Cycle • Chest muscles & diaphragm relax contraction.Elastic recoil of thorax & lungs return to equilibrium. • Pleural & alveolar pressures rise.Gas flows passively out of the lung. Active expiration requires abdominal & internal intercostals muscle contraction. Rectus abdominus/abdominal oblique muscles – Contraction raises intra-abdominal pressure to move diaphragm upward – Intra-thoracic pressure raises and forces air out from lung Internal intercostals muscles – Assist expiration by pulling ribs downward & inward – Decrease the thoracic volume – Stiffen intercostals spaces to prevent outward bulging during straining. Accessory muscles --adductor muscles of vocal chords. --their contraction is not complete so their main function is protective.
  9. 9. Pressure changes during ventillation- intra –pulmonary pressure. • In quiet breathing at end inspiration and expiration this is equal to atmospheric .ie.760 mm hg. • As inspiration begins,the volume increases and the pressure decreases to about 1 mm hg below the atmospheric. • When expiration follows passively,the elastic recoil causes the intra-pulmonary pressure to swing slightly towards the positive mm hg.
  10. 10. • At the end expiratory position, tendency of lungs to recoil from the chest wall is just balanced by the tendency of the chest wall to recoil in the opposite direction. • This causes a slight subatmospheric pressure of about -2mm hg between the 2 layers pf pleura at the start of inspiration. • -ve intra pleural pressure is directly proportional to the amount of thorasic expansion which occurs. • During quiet inspiration, lungs are pulled into a more expanded condition causing intra pleural pressure to decrease to about - 6mmhg. • At end expiration, where the recoil pressure of lungs and chest wall balance ,intra pleural pressure returns back t0 -2mmhg. INTRA PLEURAL PRESSURE.
  11. 11. Vertical movement • Vertical expansion is achieved by lowering of the Diaphragm.
  12. 12. Bucket handle movement • Transverse (Lateral) increase happens at the rib cage. • This movement is sometimes referred to as BUCKET HANDLE. • The movement comes from the lower portion due to CARTLIDGE as well as the shape of the ribs. • Lower ribs are shaped in direction of movement. • Upper ribs are more horizontal. • It is the outward movement which assists the diaphragm as well as providing more space for the lungs
  13. 13. Pump handle movement • This movement is less efficient (5-10%) • Increases the size of the cavity from the upper chest, from sternum. • It is called PUMP HANDLE MOTION. • It is less flexible not as much breath can be taken. • The expansion will not allow the intake of much breath.
  14. 14. Factors affecting intra pulmonary and intra pleural pressure.Valsalva manouvre- forced expiration against a closed glottis, may produce a positive intra pulmonary pressure of more than 100 mm hg above the atmospheric value. Muller’s manouvre- forced inspiration against a closed glottis can reduce the intra pulmonary pressure to less than 80 mm hg below the atmospheric value PHYSIOLOGICAL fACTORS DEEP INSPIRATION-pressure lowers as much as 30 mm hg. VALSALVA MANOUVRE-pressure increases by 60 – 70 mm hg. EFFECT OF GRAVITY.-in standing pressure decreases by -7mmhg, and sitting pressure decreases by – 2 mm hg. PATHOLOGICAL FACTORS. EMPHYSEMA-loss or decrease in lung elasticity, so it increases intra pleural pressure. INJURY TO THORACIC WALL-causes equalzation of intrapleural and atmospheric pressure thus causing collapse of lungs , thus causing pneumothorax.
  15. 15. Letting goooooo……. • Breath itself is nominal. It is a concept. It is about shaping the shapeless, snatching order from chaos. Creation. Breath is the intellectual emanation that creates the eye of the storm. How can an emanation support the physical action of speaking? Through allowance, ease and trust. • thank u ..