Question

Question 22 0.4 pts During active expiration, which of the following occurs first? pleural pressure becomes less negative thoracic volume increases air flows into the lungs alveolar pressure becomes less than atmospheric

Answer 1

Ans:- a) pleural pressure become less negative.

Concept :- according to boyls law pressure is inversely proportional to vol.

so when we expire vol decrease and intrapleural pressure increase and become -2.5 from -6 mm hg. I.e it become less negative.

other option.

During expiration air move out of lung so C) is wrong.

Option d) will cause suction of air into alveoli

Option b) also OCCURE during inspiration

BOYLE'S LAW 00:00:49 Pressure of a gas (P) is inversely proportional to the volume of the gas (v). pot in physiology, V = 500 ml of air = Tidal volume P = 3 lung pressures = 1. Intra pleural pressure 2. Alveolar presure 3. Transpulmonary pressure PRESSURES IN LUNG 00:02:29 D)Pressure at the level of pleura : Intra Pleural pressure (IPP) • At rest, the intra pleural pressure: Negative -2.5 mm Hg) or -3.4 cm HO CimmHg = 1.36 CM HO ) • Intra Pleural Pressure becomes positive only during forceful expiration. why Intra Pleural Pressure is negative at rest? Astretchy →inward Outwarda си um chest الصيا Lung \→ Pleura Zipp: Negative • The pleura is attached to both the lungs and the chestwall. • Normal tendency of the chest wall is to move out / expand • Normal tendency of the lung is to collapse inward.

• Thus the pleura is always under stretch by a opposing forces (chest wall pulling it outwards + lung pulling it inwards] Vacum like state produced in between Intra Pleural Pressure negative • Intra Pleural Pressure changes * During inspiration Volume D So, Intra Pleural Pressure tipos C-comm Hg or -8cm H2O) That is, during inspiration Intra Pleural Pressure becomes more negative. * during expiration = Kolume D According to Boyles Law, Intra Pleural Pressure 1 [-2.5mm Hg)