The perimetrium is the outermost layer of the uterus, which is a key organ in the female reproductive system. It is a thin layer of tissue that provides support and protection to the uterus. The perimetrium is made up of connective tissue and is part of the broader structure of the uterus, which also includes the myometrium and endometrium. This layer plays a role in anchoring the uterus within the pelvic cavity and is involved in the overall function of the reproductive system. The perimetrium is also important during pregnancy, as it helps accommodate the growing uterus.