The uterus is a hollow muscular organ of thick walls in front of the rectum and behind the urinary bladder in the pelvic cavity. Its shape is like inverted pear and its size is about 7.5 centimeter long, 5 centimeter broad on the upper side and 2.5 centimeter thick and its weight is about 30 grams but in the condition of pregnancy its size starts to increase (6-7 folds) and reaches into its previous form after delivery but it becomes some large comparison to a woman who is unmarried or has no child till this time.
There are round ligaments just below the entry of uterus of both sides of fallopian tubes which bends to the uterus forwardly over the urinary bladder. The uterus is attached to the lateral wall of pelvis by two broad ligaments. These ligaments are extended to the floor of pelvic cavity and lateral wall from the uterus. Two uterosacral ligaments are extended to the sacrum from the upper portion of the cervix. Posterior ligament connects uterus to the rectum and anterior ligament connect uterus to the urinary bladder.
Upper broad portion of the uterus is called fundus. Fallopian tubes open on the both sides by coming under the fundus. The middle portion of the fundus of uterus which is becoming narrow slowly is called body which gets dissolved into the contracted cervix at the lower side and opens into the mouth of vagina. The portion between the body and the cervix is called isthmus. The mouth of cervix which opens is called cervix or external os through which the cervical cavity is attached with vaginal cavity. The cervix is attached with the body of uterus by internal os. The portion between internal os and external os is called cervical canal. The uterus of the woman who is not pregnant is some flat and because of this reason the uterine cavity appears only a cleavage. Generally, the uterus bends above the urinary bladder forwardly on the right angle of the vagina.
The uterus is made of three layers of tissues.
It is the serous membrane of the most outer peritoneum of uterus which is extended on the different surfaces in different ways. On the front side, it is extended on the fundus and on some portion of the body from where it makes vesicouterine pouch by reverting over the upper layer of urinary bladder. At the back side, it is extended to the fundus, body and cervix and then it reverts over the rectum and makes rectouterine pouch. On the lateral sides, it covers only fundus and makes two broad ligaments which connects uterus to the lateral walls of pelvis.
It is a muscular layer of middle and most of portion of the uterus wall is made of this layer. This smooth muscle is made of three fibrous layers. From outside to inside they are arranged perpendicularly and in all the directions and in anguine way. There are blood ducts and nerves. There is flexibility in them of which the size of uterus keeps on enlarging during the growth of embryo. They get contracted too at the time of orgasm of woman. The length of myometrium is one centimeter but its thickness becomes much at the time of pregnancy.
It is the most internal layer of the uterus made by special mucus membrane. There are enough blood vessels and mucus excreting cells in it. Endometrium is made of two layers-stratum functionalis and stratum basilis. Each month, endometrium gets prepared for the possible implantation of the fertilized ovum by the process of estrogen hormone. Progesterone hormone helps in developing active glands of which sufficient nutrition gets available in the endometrium and gets ready to adopt fertilized ovum. If there is no implantation, the stratum functionalis layer comes down and flows with the blood and other excretions of glands through the cervix and vagina. There is menstrual flow because of breaking endometrium in this way and this process is called menstruation. The layer stratum basilis is permanent layer and a new stratum functionalis layer originates after 3 to 5 days of menstrual period.
If the ovum gets fertilized and implanted, the uterus provides nutrition by keeping the developing embryo inside its muscular walls safe. In the continuity of pregnancy, the estrogen hormone develops the smooth muscle of the uterus walls for the preparation of delivery.