Final answer:
The larynx contributes to increased abdominal pressure assisting the diaphragm and abdominal muscles in maintaining a closed airway during the Valsalva maneuver. This action aids important body processes like defecation, urination, and childbirth by increasing the pressure in the abdominal cavity.
Step-by-step explanation:
The larynx plays a role in manoeuvres that require increased abdominal pressure by contributing to the closure of the airway, effectively allowing the diaphragm and abdominal muscles to increase pressure in the abdominal cavity. When engaging in the "Valsalva maneuver", a person attempts to forcibly exhale while keeping the mouth and nose closed, which involves the larynx. This leads to a rise in pressure within the thoracic cavity, which cannot escape due to the closure of the larynx. As a result, when the abdominal muscles contract, they increase the pressure in the abdominal cavity, aiding in processes like defecation, urination, or childbirth. These actions are facilitated by the diaphragm's position, which remains lower due to the trapped air above it, not allowing it to move up when the abdominal muscles contract. To summarize the physiological process: during activities that require an increase in abdominal pressure, the diaphragm contracts and stays in a downward position, while the abdominal muscles contract. This traps air within the thoracic cavity due to the closed larynx, leading to an increase in abdominal pressure.