The primary responsibility of the uterus is to receive and nurture the blastocyst, the fertilized egg which is developing into an embryo. The walls of the uterus provide a lining that is suitable for implantation. Prenatal development follows a course of approximately nine months which provides full term time for the completion of gestation. When gestation has reached completion, the walls of the uterus also have an active participation in delivery. Shaped like a pear, the uterus is really a hollow cavity organ that has very thick walls and ample muscle. Positioned near the lower division of the pelvic cavity, the uterus is in close proximity to the bladder, and the rectum sandwiched in between the two. Auterus is designed to change shape invariably throughout pregnancy. A uterus that is not pregnant measures about 7 cm long and 5 cm wide, with a 1 inch diameter.


The fundus is the anatomical segment of the uterus which encompasses the uppermost dome shaped section located superior to the fallopian tube entrance. The body of the uterus, which is a sophisticated empty cavity, is the distended main segment. The segment of the uterus which remains constricted and is positioned behind the vaginal opening is the cervix. To create the unification with the vagina at a right angle, the cervix protrudes posteriorly and inferiorly. The break within the fundus and the body of the uterus creates the uterine cavity. Extending through the cervix, the cervical canal begins from its narrow origin and expands into the lumen. The isthmus of the uterus is the area where the cervical canal and the uterine cavity form their own conjuncture. The uterine ostium is created by the cervical canal opening into the vagina.


Image: Uterus

Muscles originating from the pelvic floor and ligaments which extend from either the pelvic girdle or the body wall provide the structural support necessary to keep the uterus in its proper place. The vagina and uterus are essentially held up mostly by the pelvic diaphragm, more specifically the muscle referred to as the levator ani. During an active pregnancy, the ligaments go through the process of hypotrophy in order to provide support to the uterus as it grows. In a state of post partum the ligaments experience the process of regression in order to retain the original position of the uterus. These ligaments also experience a state of atrophy in the post-menopausal female body. This atrophy is often partially responsible for a condition known as a prolapsed uterus after menopause, which means the uterus has sloped down too far.


Within the pelvic cavity there are 4 sets of paired ligaments which hold the uterus in place. Folds of the peritoneum which protrude from the pelvic walls create the set of broad ligaments. These also come up from the floor of the pelvic floor to provide support. Additionally, the peritoneum continues in order to create the next pair of ligaments known as the rectouterine folds. These follow the natural curve of the pelvic wall laterally and on the lateral sides of the rectum connecting the sacrum and the uterus. Within the broad ligament there are fibrous bands which from the vagina and the cervix, protrude laterally and traverse the pelvic floor. Here, the lateral cervical ligaments (or cardinal ligaments) anchor to the wall of the pelvis. Smooth muscle tissue and nerves and vessels comprise the cardinal ligaments. These vessels and nerves deliver blood and sensation to the cervix and the vagina. The final pair of ligaments are round which in reality are a continuation of ligaments which provide support for the ovaries, the ovarian ligaments. Just below the point of attachment of the uterine tube to the lateral pelvic wall, these round ligaments extend around the lateral edge of the uterus. Each individual round ligament continues through the inguinal canal so that they can attach deep within the labium majus tissue.
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