The oviducts (Fallopian tubes, uterine tubes) are long
tortuous ducts that measure 20 to 30 cm in length when
fully extended in horse mares. Cilia are present on
the epithelium of the oviduct and produce a current
directed toward the uterus. The oviduct is divided into
three parts: the infundibulum (funnel-shaped portion
nearest the ovary), the ampulla (expanded middle portion),
and the isthmus (narrowed portion that connects
the ampulla to the uterine horn). The cranial edge of the
infundibulum attaches to the lateral surface of the
mare’s ovary (see Figures 1-5 and 4-7). At ovulation,
this fan-shaped structure envelopes the ovulation fossa
to facilitate ovum entry into the oviduct. Cannulation
of the infundibulum is possible through a fl ank
approach, which has been used for such clinical and
research procedures as oocyte transfer to a recipient
mare, gamete intrafallopian transfer (GIFT) (instillation
of both sperm and oocyte into a recipient mare), and
fl ushing to determine oviductal patency. The ampulla is
the middle part of the oviduct (see Figure 1-6 ) where
fertilization and early cleavage of fertilized ovum
occur. The highly muscular isthmus (see Figure 1-7 )
serves both as sperm reservoir and as a conduit to transport
sperm from the uterus to the ampulla and fertilized
ova (embryos) from the site of fertilization into the uterine
lumen (see Figure 1-6 ). The oviduct enters the uterus
just caudal to the blunt end of the uterine horn through
a distinct papilla (oviductal papilla) that is easily visualized
from the uterine lumen (see Figure 4-35 ). Normal
oviducts are not usually palpable per rectum.