Finish up the organization of the anterior body cavity. We're going to be talking about the membranes and cavities within the abdominal pelvic cavity. Now remember, we said that the abdominal pelvic cavity is that space inferior to or below the diaphragm, and the diaphragm is that major muscle of breathing. We're going to say that within that space are multiple overlapping spaces, and we've talked about some of these before. We'll go through those first and a little more quickly. First up, we have the abdominal cavity. That's the space below or inferior to the diaphragm, but still above or superior to the pelvis. There, we have things like the liver, most of your digestive organs, the pancreas, the spleen. And to this list, we'll add the kidneys. Then we had the pelvic cavity. The pelvic cavity is the space below or inferior to the abdomen and surrounded by the hip bones or the pelvis. There is the bladder, as well as any internal reproductive organs. So in females, ovaries and uterus, for example, and in males prostate, for example. To this now, we're going to add the peritoneal cavity. Remember the peritoneal cavity is a serous membrane-bound cavity, and the serous membrane that surrounds the peritoneal cavity is the peritoneum. Now, the peritoneal cavity is going to surround most abdominal organs and some superior pelvic organs, and that's because, remember, the abdominal and pelvic cavities, there's no hard dividing line between them like there is between the abdominal cavity and the thoracic cavity. So the peritoneum and the peritoneal cavity, while it's mostly in the abdominal cavity, can extend down into the pelvic cavity as well. Some organs in the pelvic cavity, such as the uterus, are going to be mostly wrapped by the peritoneal cavity. Well, things like the bladder, just the superior surface is going to be touching the peritoneum. Now we're going to add a completely new vocab word here, and this is going to be the retroperitoneum. The retroperitoneum is going to be the space behind or posterior to the peritoneum but still within the abdominal cavity. Now you can look at that word and it has that prefix retro, and you're probably familiar with like retro music or retro clothing. That's music or clothing from back in time. So retro means back or behind. The retroperitoneum is behind or in back of the peritoneum. What you're going to find there are the kidneys, as well as some other things like some of the pancreas, some of the rectum. But if there's a question about the retroperitoneum, it's quite often about the kidneys, so just keep that in mind. Let's look over in our anatomical model now. We have a sagittal view of the abdominal pelvic cavity. We know it's a mid-sagittal view because we can see the spine here. Now, first off, I notice I see all these organs in cross-section going down, but what we're really looking at here is the blue, and the blue is going to be the peritoneum and the peritoneal cavity. And you can see how it goes up and it surrounds all those different organs in what is a really complex shape to be able to do that. So we have some arrows here, and these arrows are just pointing to those organs surrounded by the peritoneum. We also have some arrows down here, though, and these arrows are going to be pointing to organs that are retroperitoneal organs, the organs behind the peritoneum, and that's going to be the rectum. And what you can't see here are the kidneys because they're more lateral to what this mid sagittal view can show. Alright. Before we go on, I just want to bring back our analogy of our plastic bag. So let's pretend that this plastic bag is the peritoneum, and I'm going to tie it off. So it's like the like a balloon. And remember, inside the bag where we can't access now is that peritoneal cavity. But with our other serous membranes,