The Fertilizing Fallopian Tubes

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Immunohistochemical staining of fallopian tube. Proteins expressed in ciliated cells (top) and secretory cells (bottom).

The fallopian tube mucosal layer is a simple columnar epithelium composed of secretory and ciliated epithelial cells, in order to provide the necessary environment for fertilization of the egg cell.

The fallopian tubes, also called the oviducts or uterine tubes, are paired tubes that extend from the uterus to connect the ovaries. The tube itself is composed of three layers: a mucosal membrane, a thick wall of smooth muscle and a serosal coat.

The mucosal layer is composed of a simple columnar epithelium layer of secretory and ciliated epithelial cells, and a thin lamina propria. The non-ciliated secretory cells produce a fluid containing nutrients for the ovum (egg cell). The oviductal glycoprotein 1 (OVGP1) is secreted into the lumen and is shown to play an important role in pre-fertilization events. PAX8 and BCL2 are two other proteins specific for secretory cells. Studies have proposed a link between epithelial ovarian carcinoma origin and PAX8 expression in fallopian tube. BCL2 is a apoptosis suppressor and regulates cell death by controlling the mitochondrial membrane permeability.

The fallopian tubes are also the site of fertilization of the egg by spermatozoa. Ciliated cells "beat" to cause movement in the fluid, excreted by secretory cells, in order to transport the egg cell towards the uterus. This requires several proteins involved in cilia function, beat and motility. The ER protein AGR3 controls cilia beat frequency, and RSPH9 is a radial spoke protein important for the mechanical movement of the cilia. C1orf87, an uncharacterized protein, is also shown to be expressed in cilia.

Learn more about fallopian tube histology here.

Feria Hikmet Noraddin