Question

Inspiration occurs when there is a negative pressure in the lungs with respect to atmospheric pressure. This negative pressure is achieved when
A)Intrapulmonary pressure is less than the atmospheric pressure
B)Intrapulmonary pressure is greater than the atmospheric pressure
C)Intrapulmonary pressure is equal to the atmospheric pressure
D)Intrapleural pressure becomes more than the intra-alveolar pressure

Answer 1

Breathing is an important mechanism of all living entities. The human body needs oxygen to carry out its functions. The breathing process is differentiated into two different phages i.e inspiration and expiration. Inspiration is the inhalation of air and expiration is the exhalation of air

Complete answer:
-Inspiration is a process during which atmospheric air enters an expiration is the process by which alveolar air releases out. This movement of air moving inside and outside of the lung is generally carried out by generating a pressure gradient between the lung and atmosphere.
-Inspiration only occurs when intrapulmonary pressure within the lung is less than the atmospheric pressure. therefore negative pressure generated in the lungs with respect to atmospheric pressure.
-Expiration only occurs when intrapulmonary pressure within the lungs is greater than the atmospheric pressure.
-There is a specialized set of muscles i.e external and internal intercostal between the ribs and the diaphragm. They both help in creating the gradients between lungs and atmospheric pressure.

Additional Information: -When the diaphragm is contracted, it increases the volume of the thoracic chamber which is present in the anteroposterior axis.
-When the external intercostal muscle is contracted, it lifts up the ribs and sternum. They both cause an increase in the volume of the thoracic chamber which is present in the dorsoventral axis.
-So an increase in the thoracic volume causes the same increase in pulmonary volume and decreases the intrapulmonary pressure to become less than atmospheric pressure. Hence forces the air to move into the lung. This process is called inspiration.
So, the correct answer is, "intrapulmonary pressure is less than atmospheric pressure".

Note: -A healthy human breath 12 to 16 times per minute.
-Humans have the ability to increase the power of inspiration and expiration with the help of abdomen muscles. For example: after the exercise the breathing rate increases from the normal breathing rate.