The Oviducts Flashcards
The oviducts are a pair of tubes that connect
to the uterus at one end and lie close to but not directly connected to an ovary at the other end (also known as the uterine or fallopian tubes)
They are divided structurally into the following sections:
i. The fimbriated infundibulum or fimbria
ii. The ampulla
iii. The isthmus
The fimbriated infundibulum or fimbria is
the ovarian end of the oviduct that flares out into a cone shape with thin finger-like projections that shroud the ovary. It is responsible for ovum pick-up after ovulation.
The ampulla is the
middle region and is the site of fertilization.
The isthmus is the
medial short narrow segment connecting the oviduct to the uterus.
The inner mucosal layer of the oviducts is covered with a single layer of columnar epithelium that can be subdivided into two distinct types:
ciliated epithelium and non-ciliate secretory epithelium.
The ratio of ciliated to secretory cells, the direction of ciliary beating and the height of the cells fluctuate in response to
estrogen and progesterone.
The mucosal layer of the oviduct contorts onto itself to form an intricate labyrinth of branching folds. These folds offer a large ciliated surface area that
potentiates the number of sperm that can be moved up the oviduct to the site of fertilization.
Sperm transport along the oviduct to the ampulla is brought about
by cilial propulsion and myosalpingeal contractions as well as by their own forward propulsion.
Secretions from the oviductal secretory epithelium supply fluid for the
movement of the sperm and oocytes, as well as nourishment to the gametes
Under the influence of estrogens the cilia of the isthmus and those in the ampulla region adjacent to the isthmus beat
in the direction of the ovary.
At the same time the cilia of the fimbria and those in the ampulla next to the fimbria
beat in the direction of the uterus.
In this fashion ovulated oocytes will be sequestered
within the middle of the ampulla.
If sperm enters the uterus at this time they will be ushered
into the oviduct and propelled to the awaiting oocyte.
The bi-directional movement of oviductal cilia facilitates
the fertilization process.
After ovulation in the presence of increasing concentrations of progesterone the cilia and myosalpingeal contractions all pulse from
the ovary toward the uterus moving the presumptive embryo towards the uterus for implantation.
