 Hey everybody, Dr. O'Hare. Let's talk about the penis. So we're going to end our conversation with the memory production track by talking about the penis. So here we see both the circumcised and uncircumcised penis. Let's look at just the parts of the penis. We'll start with the circumcised one. We have the penis itself, the corona there, and then the glans penis or the head of the penis. On the left you see an uncircumcised penis. The skin from the penis forms this collar around the glans penis or head of the penis called the prepuse, which we usually call the foreskin. The foreskin does have a lot of nerve endings. The glans penis has a lot of nerve endings as well. Obviously, they play a role in pleasure and sensitivity when it comes to sexual intercourse. Let's talk about circumcision for a moment. Then we'll look inside the penis at the vascular chambers. Globally, 35 to 40% of men are circumcised. It widely varies, depends on cultural and religious reasons, et cetera. At this point, about 75% of American men are, but the number is slowly dropping. 32% in Canada, 7% in New Zealand, almost 0% in Honduras, and 7% in Spain. I think those are some of the numbers that I looked up. Pros and cons. I'm not telling you what to do. I'm not in that business, but the pros of circumcision would be decreased urinary tract infection risk, especially in the first year of life. Very, very likely lower risk of sexually transmitted infections. I've seen multiple studies that have said that. A much lower risk of penile cancer, but penile cancer is very rare to begin with, but it is a much lower risk of penile cancer. I think the main thing is better genital hygiene. If you've ever worked with people in nursing homes and stuff, if you don't take care of the penis, it can get dirty and infected and all sorts of things. Having a foreskin does make that more complicated. There are cons to having circumcisions as well. The surgical procedure and the loss of sensitivity, too. I completely understand. People giving pause and thinking about whether or not this is a good idea, but my personal vote is that it is. If you've ever seen what happens to someone's penis that doesn't take good care of it and the infection risk and those kind of things, the foreskin does make it worse. With good genital hygiene, having one can certainly be no problem whatsoever. No condemnation or judgment from me ever. The penis itself. Here we see a flaccid penis. I'll show you an erect one in just a moment. The penis, it is our organ of copulation, the male organ of copulation or sexual intercourse leading to reproduction. The shaft of the penis does surround the urethra, which you can see there at the bottom. This would be called the penile or spongy urethra, so the longest portion of the urethra. Obviously, the penis also plays a role in mixturition or urination. A flaccid penis is involved in mixturition or urination and an erect penis is involved in sexual intercourse. There are three chambers. The key thing to remember about the anatomy of the penis is these three chambers. You see those two large corpora cavernosa. They're going to be what produce the most of the volume of the penis and they're going to get the most rigid during an erection. Then on the bottom, you have the corpus spongiosum, which can't get as rigid because it has to allow semen to leave through the urethra. Those would be the three key chambers, the two corpora cavernosa, and then you have that one corpus spongiosum. Let's look at an erection then. What actually happens here? The technical term for an erection is vasocongestion. What you see is the penis enlarges and becomes more rigid because there's more arterial blood flowing into it than there is venous blood leaving it. During arousal, during sexual arousal, nitric oxide is released. Nitric oxide is a vasodilator and that's going to cause the blood vessels in this corpora cavernosa and spongiosum to enlarge and more blood. The relaxation of the smooth muscles is causing more blood to rush into the penis, which is filling it with blood and why it becomes rigid because of the vasodilation. I've already said that. Then on the other side, though, this rapid filling makes it impossible. It actually puts pressure on the veins and venules in the penis. This blood is rushing in, but the veins get pinched off so the blood cannot escape. It prevents the drainage of blood from the penis. More blood flows in, then can drain away. That's why the penis fills with blood and becomes erect. Increased blood flows, it does that. Then after ejaculation or whenever, this blood flow will return back to normal and the amount of blood entering and leaving the penis will equalize and the erection will go away. That is the structure of the penis and also how an erection occurs. I hope this helps. Have a wonderful day. Be blessed.