Describe what peristalsis is and how it allows you to drink water while hanging upside down.

Peristalsis is a series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. The process of peristalsis begins in the esophagus when a bolus of food is swallowed. The strong wave-like motions of the smooth muscle in the esophagus carry the food to the stomach, where further processing occurs.

Now, how does this allow you to drink water while hanging upside down?

When you're upright, gravity helps to move the water down your esophagus and into your stomach. However, when you're upside down, gravity is working against this process. This is where peristalsis comes in.

Even when you're upside down, the muscles in your esophagus continue to contract in a wave-like manner, which helps to push the water against gravity and into your stomach. So, while it might be a bit slower, you can indeed drink water while hanging upside down thanks to peristalsis.