Critical Thinking Questions pg 24, #1,4

1. a. The pleura is the double-layered membrane that surrounds the lungs and lines the ribcage. When the pleura is inflamed, pleurisy is developed.
b. The pleura protects and smooths the surface of the lungs as they inflate and deflate within the rib cage. Usually, a thin, fluid-filled gap (the pleural space) allows the two layers of the pleural membrane to slide gently past each other.
c. John's condition is so painful because the added fluid in the membrane puts pressure on the lungs, which reduces their ability to move freely. This extra fluid can become infected and cause shortness of breath. Every time John coughs, sneezes, or even just breathes, the roughened surfaces rub together painfully.
4. When we are dehydrated, we usually feel thirsty, which causes us to drink fluids. The thirst sensation is part of a negative feedback control system. All negative feedback mechanisms have the same goal which is to prevent severe changes within the body. There are so many variables that need to be regulated throughout the body. So when we become thirsty, the negative feedback system tells us we need to drink fluids so we do not become faint, or light-headed. It helps us control dehydration.