Page 862 - Atlas of Histology with Functional Correlations

(plastic section). ×130.

FUNCTIONAL CORRELATIONS 21.3 ■ Uterine

Tubes

The uterine tubes perform important reproductive functions. Just before
ovulation and rupture of the mature follicle, the finger-like fimbriae of the
infundibulum that are close to the ovary begin to sweep its surface to capture

the released oocyte. This function is accomplished by gentle peristaltic
contractions of smooth muscles in the uterine tube wall and fimbriae. In
addition, the ciliated cells on the fimbriae surfaces create a current toward the
uterus that guides the released oocyte into the infundibulum of the uterine

tube. The cilia action and the muscular contractions of the uterine tube
transport the captured oocyte, or fertilized egg, through the uterine tube
toward the uterus.

The uterine tubes also serve as the site of oocyte fertilization, which

occurs in the ampulla. The nonciliated (peg) secretory cells in the uterine
tube contribute nutritive material for the oocyte, the initial development of
the fertilized ovum, and the embryo. The uterine secretions also maintain the
viability of sperm in the uterine tubes and allow them to undergo
capacitation, a complex biochemical and structural process that activates the

sperm and enables them to bind to and fertilize the released oocyte. The
fertilization triggers the ovulated secondary oocyte to undergo the second
meiotic division and produce an ovum that can be fertilized by the sperm.

When the sperm reaches the secondary oocyte, it must first penetrate the

protective corona radiata layer around the oocyte. In order to fertilize the
oocyte, the sperm must also penetrate the surrounding zona pellucida and
bind to zona pellucida receptors to complete capacitation. This binding
produces the acrosome reaction, which releases the hydrolytic enzymes

from the acrosome on the sperm nucleus into the zona pellucida allowing its
passage into the oocyte. As the sperm penetrates the oocyte, proteases
released from the cortical granules present in the ovum cover the zona
pellucida with a barrier and produce a block to polyspermy called the

cortical reaction. This reaction allows the penetration of only one sperm to
fertilize the egg.

The epithelium in the uterine tubes exhibits changes that are associated
with the ovarian cycle. The height of the uterine tube epithelium is at its

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