Uterine tube

The fallopian tubes, also known as uterine tubes or salpinges (singular salpinx) are uterine appendages, lined from inside with ciliated simple columnar epithelium, leading from the ovaries of female mammals into the uterus, via the uterotubal junction. They enable the passage of egg cells from the ovaries to the uterus. In non-mammalian vertebrates, the equivalent structures are just called oviducts.Fallopian tube The fallopian tubes, also known as uterine tubes or salpinges (singular salpinx) are uterine appendages, lined from inside with ciliated simple columnar epithelium, leading from the ovaries of female mammals into the uterus, via the uterotubal junction. They enable the passage of egg cells from the ovaries to the uterus. In non-mammalian vertebrates, the equivalent structures are just called oviducts. Its different segments are (lateral near the ovaries to medial near the uterus): the infundibulum with its associated fimbriae near the ovary, the ampullary region that represents the major portion of the lateral tube, the isthmus the visible medial third segment which is the narrower part of the tube that links to the uterus, and the interstitial (also known as intramural) part that transverses the uterine musculature. The ostium is the point where the tubal canal meets the peritoneal cavity, while the uterine opening of the fallopian tube is the entrance into the uterine cavity, the uterotubal junction. The average length of a fallopian tube is 11-12 cm. A cross-section of a fallopian tube shows four distinct layers, from outer to inner: serosa, subserosa, lamina propria and innermost mucosal. The serosa is derived from visceral peritoneum. Subserosa is composed of loose adventitious tissue, blood vessels, lymphatics, an outer longitudinal and inner circular smooth muscle coats. This layer is responsible for the peristaltic action of the fallopian tubes. Lamina propria is a vascular connective tissue. The inner layer is a single layer of simple columnar epithelium. The columnar cells have microscopic hair-like filaments (cilia) predominately throughout the tube, but are most numerous in the infundibulum and ampulla. Estrogen increases the production of cilia on these cells. Between the ciliated cells are peg cells, which contain apical granules and produce the tubular fluid. This fluid contains nutrients for spermatozoa, oocytes, and zygotes. The secretions also promote capacitation of the sperm by removing glycoproteins and other molecules from the plasma membrane of the sperm. Progesterone increases the number of peg cells, while estrogen increases their height and secretory activity. Tubal fluid flows against the action of the cilia, that is toward the fimbrial end. In view of longitudinal variation in histological features of tube, the isthmus has thick muscular coat and simple mucosal folds; whereas ampulla has complex mucosal folds. Embryos have two pairs of ducts to let gametes out of the body; one pair (the Müllerian ducts) develops in females into the fallopian tubes, uterus and vagina, while the other pair (the Wolffian ducts) develops in males into the epididymis and vas deferens. Normally, only one of the pairs of tubes will develop while the other regresses and disappears in utero. The homologous organ in the male is the rudimentary appendix testis. The tube allows passage of the egg from the ovary to the uterus. When an oocyte is developing in an ovary, it is encapsulated in a spherical collection of cells known as an ovarian follicle. Just prior to ovulation the primary oocyte completes meiosis I to form the first polar body and a secondary oocyte which is arrested in metaphase of meiosis II. This secondary oocyte is then ovulated. The follicle and the ovary's wall rupture, allowing the secondary oocyte to escape. The secondary oocyte is caught by the fimbriated end and travels to the ampulla of the uterine tube where typically the sperm are met and fertilization occurs; meiosis II is promptly completed. The fertilized ovum, now a zygote, travels towards the uterus aided by activity of tubal cilia and activity of the tubal muscle. The early embryo requires critical development in the fallopian tube. After about five days the new embryo enters the uterine cavity and on about the sixth day implants on the wall of the uterus.