 Hey everybody, Dr. O. In this short video we're going to talk about primarily peristalsis which you can see here in segmentation. So in the intro to this chapter we talked about propulsion, the movement of material from your mouth towards your anus. That can be broken down into two parts, the voluntary part which is swallowing so we'll cover that later. So you're in control of swallowing or at least the initiation of swallowing but after that the movement of material from one organ or structure in your GI tract to the next is going to be controlled by smooth muscle contraction and it's called propulsion. So propulsion and segmentation just make it real simple. Propulsion is when something is moving from the mouth towards the anus. Segmentation involves somewhat similar smooth muscle contractions but it's occurring on both sides of whatever is inside your gut so it's going to cause a mixing. So propulsion, think movement forward from the mouth to the anus, segmentation, think mixing. So here we do see, we see peristalsis. Think about like squeezing a tube of toothpaste from the bottom. You're squeezing behind what you're swallowing or what you're moving and that's going to push it forward from the mouth to the pharynx that's going to be swallowing and then from the pharynx to the esophagus, the esophagus to the stomach, etc., etc. That's going to be peristalsis, a one-way movement of material, one-way movement of food. Here we see segmentation. Now we have smooth muscle contractions happening on both sides. Imagine shoving something back and forth, pushing something back and forth. I always think about like when you're mixing ingredients in a mixing bowl. So this churning up process, nothing's moving forward. It's moving forward but then back, forward, back. So this churning process is mixing things up. It is not actually moving something from your small intestine to your large intestine for example. So this mixing segmentation occurs the most in the duodenum which is why I call it the mixing bowl of your small intestine. About 12 times a minute these contractions occur just continually churning and mixing things up. So what's being mixed in the duodenum, this is an example. The kind that comes from your stomach is going to be mixed with the bicarbonate, the buffer from the pancreas, digestive enzymes from the pancreas, and bile from the liver and gallbladder. So all this is going to be getting churned up together in this process of segmentation. So propulsion, movement, forward, segmentation, mixing which mixes things together and makes digestion occur better and also helps with absorption. Okay that is peristalsis versus segmentation. I hope that helps. Have a wonderful day. Be blessed.