Question

During inhalation and exhalation which of the following is seen
(This question has multiple correct options)
A. Ribs move up and outward, diaphragm moves down.
B. Ribs move down and inwards, diaphragm moves up.
C. Ribs move down and outwards, diaphragm moves down.
D. Ribs move up and inwards, diaphragm moves down.

Answer 1

Hint:-The process of breathing consists of two steps. They are inspiration or inhalation and expiration or exhalation. Inspiration is an active process in which atmospheric air is taken into the lungs. Expiration is the passive process in which air from the lungs is expelled out to the atmosphere. The uptake of air into lungs and expulsion of air from the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere.

Complete Answer:-
Different muscles are involved in the process of breathing: diaphragm, internal and external intercostal muscles and abdominal muscles. During inspiration, the diaphragm contracts, moves downwards and attains a flattened position. Intercostal muscles also contract, which are 11 pairs of muscles present between 12 pairs of ribs. The contraction of external intercostal muscles lifts the ribs and sternum upward and outward, causing an increase in the volume of thoracic cavity, dorsoventrally and laterally. As the volume of thoracic cavity increases, volume of intrapulmonary cavity increases and intrapulmonary pressure decreases than atmospheric pressure. Thus, inspiration occurs. So in inspiration,the ribs move up and outward and the diaphragm moves down. Thus, Option A is correct.
Expiration or exhalation is a passive process which involves the relaxation of diaphragm and external intercostal muscles which returns the diaphragm, sternum and ribs to their normal position, thereby reducing the volume of the thoracic cavity. The diaphragm moves up to attain its original dome shape. The intercostal muscles relax and make the ribs and sternum move downward and inward. The decrease in the volume of thoracic cavity decreases the intrapulmonary volume and increases the intrapulmonary pressure than the atmospheric pressure. Thus, expiration is caused. For expiration, Option B is correct. Ribs move down and inward, diaphragm moves up.
Thus, the correct answer is Option A and Option B.

Note:- The diaphragm and the ribs move upwards and downwards during the process of breathing, in order to maintain the volume of lungs within the thoracic cavity. Inspiration can occur, if there is negative pressure in the lungs with respect to the atmospheric pressure, that is, the pressure in the lungs should be less than the atmospheric pressure. For expiration, the pressure inside the lungs should be greater than the atmospheric pressure so that the air can move from the lungs to outside. The diaphragm and rib cage helps to maintain the intrapulmonary volume and pressure.