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Anatomy and function of the uterus.
Where do babies come from? That’s the age-old awkward question that our parents hate to hear. They might have bought some time by telling you that they found you in a cabbage patch or perhaps that you were delivered by a stork. Of course, we know better now, but what did you know about the oven that bakes the bun? Stick around to find out in our short tutorial about the uterus.
The uterus, also known as the womb, is located in the pelvic cavity of a female. You could try to look for it in males, but no luck there. It is a thick-walled muscular structure that lies in the midline as we can see here in our image of the abdominopelvic cavity. The uterus is about eight centimeters in length and it's actually roughly the size and shape of an upside-down pear. If we change our perspective so we can see a sagittal section of the abdominopelvic cavity, we can understand the location of the uterus and its relationship to other structures a little better. As we can see, the uterus sits between the bladder and the rectum and is connected to the vagina inferiorly.
Okay, now that we're familiar with the location of the uterus, let's explore some of its anatomy.
The uterus can be divided into four key parts – the fundus, the body, the isthmus, and the cervix. Let’s move on to look at these in more detail starting with the fundus. As you can see here, the fundus is at the top of the uterus and is situated above the entry points of the uterine tubes. Moving inferiorly, we have the body of the uterus, which is also known as the corpus. As we can see in our illustration, the cavity of the body is shaped like an inverted triangle due to its connection to the isthmus and both uterine tubes. Implantation of the blastocyst normally occurs here.
Next, we have the isthmus. The isthmus is about one centimeter long and, as you can see, is the constricted part of the uterus between the body and the cervix.
Lastly, we have the cervix which connects the uterine cavity to the lumen of the vagina. The cervix is approximately two point five centimeters long and has two openings – the internal os which opens into the uterus and the external os which opens into the vagina.
Now it's time to have a brief look at some associated structures of the uterus. The first structure that we're going to talk about is the broad ligament of the uterus, which is a double layer of peritoneum. This ligament connects the uterus to the lateral walls of the pelvis and contains the uterine and ovarian arteries. Next, we have the uterine tube which is also known as the fallopian tube. We have two uterine tubes along which eggs travel from the ovaries to the uterus.
Okay, let's move on to look at the ovary, which produces and releases eggs. As you can see, you also have two ovaries. I mentioned earlier that the uterus is connected to the vagina inferiorly. The vagina serves as a conduit for menstrual blood from the uterus, accommodates the penis during intercourse and, during childbirth, the baby passes through the vagina to reach the external environment. As you can see, this was a very brief overview of associated structures, but if you came for more, then visit our website for more in-depth tutorials on these topics.
Okay, so let's move on to the blood supply, innervation, and lymphatics of the uterus. The uterus is supplied by the uterine artery, which we can see here highlighted in green and the uterine branch of the ovarian artery. The venous drainage of the uterus is carried out by the uterine vein.
Okay, so let's move on now to talk about the innervation of the uterus. The sympathetic supply is derived from the inferior hypogastric plexus, which we can see here highlighted in green, whereas the parasympathetic supply is derived from the pelvic splanchnic nerves.
Lastly, we have the lymphatic drainage of the uterus. Lymph from the body and cervix drains mostly to the internal and external iliac nodes, which we can see here highlighted in green. Lymph from the fundus drains to the para-aortic nodes.
It’s time to move on to our next topic, which is the functions of the uterus. Once a blastocyst has implanted in the body of the uterus, the uterus carries out various functions to aid the growth and development of the baby or the fetus. Firstly, it provides mechanical protection preventing any physical damage to the fetus. It also provides nutritional support which is essential for growth and removes waste keeping the fetal environment nice and clean.
I mentioned earlier that the uterus sits in the pelvic cavity; however, during pregnancy, the uterus expands up into the abdominal cavity as the baby grows. When the baby is ready, the muscular wall of the uterus contracts to help push the baby out at the time of delivery. If fertilization of the egg doesn't occur and there's no implantation of the blastocysts, the uterus will eventually shed its lining in a process known as menstruation.
Now that we’re clued up on the uterus and its functions, let's get clinical.
In today's clinical notes, we're going to talk about a procedure known as the hysterectomy. A hysterectomy is the surgical removal of the uterus and there are several types. If the entire uterus is removed, it is a total hysterectomy. If only the part of the uterus is removed, it is called a subtotal hysterectomy.
Sometimes, the ovaries and the fallopian tubes are also removed, which is known as a total hysterectomy and bilateral salpingo-oophorectomy. This surgery is a very common procedure and has various indications including reproductive malignancy, uterine prolapse, endometriosis, and major postpartum hemorrhage.
As with any surgery, a hysterectomy comes with a risk of complications including hemorrhage, infection, pain, and general anesthetic complications. Depending on the type of procedure, you can take six to eight weeks to fully recover from a hysterectomy.
So that brings us to the end of our short tutorial on the uterus.