The Fundus of the Uterus

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The fundus of the uterus is the region of the uterus farthest from the cervix. It is the thickest and most muscular part of the uterus, making it essential for labor and delivery of a newborn. The fundus also acts as the roof of the uterus, spanning the area between the fallopian tubes.

Anatomy

The uterus is one of the major organs of the female reproductive system. It is a pear-shaped organ that consists of three major regions: the fundus, body, and cervix. The fundus is the most superior region of the uterus that spans the area between the fallopian tubes and forms the roof of the hollow uterine cavity.

The fundus of the uterus forms part of the uterine wall and, as such, is made of three distinct tissue layers.

Lining the interior of the uterus is the endometrium, a thick layer of highly vascularized mucous membrane. Simple columnar epithelium makes up the surface layer of the endometrium and folds into deep endometrial glands that penetrate through most of the thickness of the endometrium. Deep into the epithelial layer is a thick layer of areolar connective tissue that contains many blood vessels and supports the epithelium. The middle layer of the uterine wall, known as the myometrium, is the thickest layer and is responsible for the bulk of the fundus. Several layers of smooth muscle tissue are arranged so that their fibers can constrict the uterus in all directions during childbirth. Blood vessels and nerves in the myometrium support and control the contraction of the smooth muscle tissue. The perimetrium is the outermost layer of the uterine wall. It is a serous membrane made of simple squamous epithelial tissue covering a thin layer of areolar connective tissue that anchors it to the myometrium. The perimetrium forms a very smooth surface for the uterus and secretes a slimy serous fluid to lubricate the surface and prevent friction between the uterus and its neighboring organs. It covers the entire uterus and extends beyond the uterus to merge with the serous membranes of the other pelvic organs.

Physiology

The fundus of the uterus plays several important roles in the function of the female reproductive system. As the top of the uterus, it acts as a barrier during pregnancy to protect the developing fetus from external trauma and infection. During labor and delivery, the thick muscularis of the fundus comes into play to help contract the uterus and push the fetus into the vagina. The hormone oxytocin stimulates the myometrium through a positive feedback cycle to produce ever stronger waves of contraction until the fetus is expelled from the uterus.