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Marco Zaccaria: Archimyometrium – The Innermost and Phylogenetically Oldest Layer of the Myometrium

Marco Zaccaria/LinkedIn

Aug 26, 2026, 18:20

Marco Zaccaria: Archimyometrium – The Innermost and Phylogenetically Oldest Layer of the Myometrium

Marco Zaccaria, Global Product Manager at H.S. Hospital Service SpA, shared on LinkedIn։

“The archimyometrium is the innermost, phylogenetically oldest portion of the uterine myometrium: from a radiological standpoint, it corresponds to the junctional zone, the interface located immediately below the endometrium.

Unlike the outer layer of the uterus (called the neomyometrium), the archimyometrium has unique biological, embryological, and functional characteristics.

Embryologically, it develops from the fusion of the paramesonephric (Müllerian) ducts, the same tissue from which the endometrium originates.

It consists mainly of densely packed circular muscle fibers. Their distinctive arrangement creates a median structure known as the fundocorneal raphe.

The archimyometrium is constantly active throughout a woman’s entire life and reproductive cycle, not just during childbirth.

It acts like a true peristaltic pump. It generates rhythmic contractions and waves that change direction depending on the phase of the menstrual cycle.

During the ovulatory phase, peristalsis moves retrograde (from the cervix toward the fundus), facilitating the directed transport of sperm toward the fallopian tube containing the dominant follicle.

During menstruation, the movements become antegrade (from the fundus toward the cervix) to facilitate the expulsion of menstrual blood.”

Archimyometrium, Myometrial layers