The intraplural pressure becomes more negative simply because as the inspriatory muscles (diaphragm, external intercostals) act to increase thoracic volume, the intrapleural space increases in volume somewhat, thereby decreasing the pressure (Boyle's Law).
Its explained well in most Physiological texts if that doesn't help
firstly the intraplural cavity is a closed space and pressure change is due to increased volume. For example with the contraction of the diaphram causing the intraplural cavity to increase in size and therefore reducing the pressure causing inspiration. Since the intraplural space is attached to the lungs, the lungs also expands, theoretically increasing space and therefore reducing volume. So if the intraplural pressure down, lung pressure will also go down and vise versa with exhilation. hope that helps.
Intrathoracic pressure, intrapleural pressure, and transmural pulmonary vascular pressure exhibit rhythmic variations with respiration. These variations are important for normal breathing mechanics and gas exchange in the lungs.
The intrapulmonary pressure is the pressure in the alveoli. Intrapulmonary pressure rises and falls with the phases of breathing, but it ALWAYS eventually equalizes with the atmospheric pressure.
Positive selection pressure favors traits that increase an organism's fitness, leading to the evolution of beneficial characteristics. Negative selection pressure eliminates traits that decrease fitness, resulting in the removal of harmful characteristics from a population. Both types of selection pressure drive the evolution of a species by shaping its genetic makeup over time.
Positive selection pressure favors traits that increase an organism's chances of survival and reproduction, leading to the evolution of beneficial traits. Negative selection pressure, on the other hand, eliminates traits that decrease an organism's chances of survival and reproduction, resulting in the removal of harmful traits from a population. Overall, positive selection pressure drives the evolution of advantageous traits, while negative selection pressure helps to maintain the fitness of a species by removing detrimental traits.
Intrapleural pressure is most negative at the completion of inspiration.
Intrapleural pressure is maintained by the opposing forces of the elastic recoil of the lung and chest wall. During inspiration, the diaphragm contracts and the intercostal muscles expand the thoracic cage, causing a decrease in intrapleural pressure. This negative pressure helps keep the lungs inflated.
During quiet breathing, the intrapleural pressure decreases during inspiration as the diaphragm contracts and the thoracic cavity expands, leading to a decrease in pressure inside the lungs. During expiration, intrapleural pressure increases as the diaphragm relaxes and the thoracic cavity decreases in volume, causing an increase in pressure inside the lungs.
Because the negative pressure is the major factor preventing the lungs from collapsing. If the intrapleural pressure became equal to atmospheric pressure the lungs would recoil and collapse.
The lung will collapse (atelectasis) because the negative intrapleural pressure gradient that keeps the lung inflated has is now at equilibrium with atmospheric pressure.
Intrapleural pressure becomes positive during forced expiration or coughing when the muscles contract forcefully to increase the pressure within the thoracic cavity. This positive intrapleural pressure helps to push air out of the lungs.
Intrathoracic pressure
Intrathoracic pressure is the pressure inside of the pleural cavity. It is also called intrapleural pressure and the normal pressure is called negative pressure.
Inspiration happens when the pressure inside the lungs is lower than the atmospheric pressure (outside) and air rushes into the lungs. Expiration is when the air inside the lungs is higher than the atmospheric pressure and the air rushes out of the lungs. If the intrapleural pressure (pressure within the pleura of the lungs) isn't maintained then the pressure in the lungs can't differentiate between inspiration and expiration and so the lung collapses.
Negative intrathoracic pressure is the normal pressure in the area between the pleura of the lungs and the chest wall. The pressure is considered negative because it is less than the atmospheric pressure.
firstly the intraplural cavity is a closed space and pressure change is due to increased volume. For example with the contraction of the diaphram causing the intraplural cavity to increase in size and therefore reducing the pressure causing inspiration. Since the intraplural space is attached to the lungs, the lungs also expands, theoretically increasing space and therefore reducing volume. So if the intraplural pressure down, lung pressure will also go down and vise versa with exhilation. hope that helps.
intrapleural pressure