Follicles at diﬀerent stages of maturation are distinguished by
their structure, which ranges from
with a sin-
gle layer of follicle cells surrounding the oocyte to more mature
follicles with several layers of granulosa cells. Te fully mature
, also called an
identiﬁed by its central ﬂuid-ﬁlled cavity called an
ure 27.13). When mature, the follicle extends from the deepest
part of the ovarian cortex and bulges from the surface of the
ovary, and its oocyte “sits proudly” on a stalk of granulosa cells
at one side of the antrum.
Each month in women of childbearing age, one of the rip-
ening follicles ejects its oocyte from the ovary, an event called
(see Figure 27.20,
). A±er ovulation, the ruptured
follicle is transformed into a very diﬀerent looking glandular
structure called the
te-um; “yellow body”;
plural: corpora lutea), which eventually degenerates (not shown
in Figure 27.13). As a rule, most of these structures can be seen
within the same ovary. In older women, the surfaces of the ova-
ries are scarred and pitted, revealing that many oocytes have
Check Your Understanding
Brieﬂy, what are the internal genitalia of a woman?
What two roles do the ovaries assume?
What name is given to the ﬂuid-ﬁlled cavity of a mature
For answers, see Appendix H.
held in place by several ligaments in the fork of the iliac blood
vessels within the peritoneal cavity. Te
chors the ovary medially to the uterus; the
anchors it laterally to the pelvic wall; and the
re-um) suspends it in between (see Figures 27.12
and 27.14). Te suspensory ligament and mesovarium are part
, a peritoneal fold that “tents” over the
uterus and supports the uterine tubes, uterus, and vagina. Te
broad ligament encloses the ovarian ligaments.
Te ovaries are served by the
, branches of
the abdominal aorta (see Figure 19.24c), and by the
branch of the uterine arteries
. Te ovarian blood vessels reach
the ovaries by traveling through the suspensory ligaments and
mesovaria (see Figure 27.14).
Like each testis, each ovary is surrounded externally by a ﬁ-
, which is in turn covered
externally by a layer of cuboidal epithelial cells called the
, actually a continuation of the peritoneum. Te ovary
has an outer
, which houses the forming gametes, and an
containing the largest blood vessels and nerves, but
the relative extent of each region is poorly deﬁned.
Embedded in the highly vascular connective tissue of the
ovary cortex are many tiny saclike structures called
. Each follicle consists of an immature egg, called an
egg), encased by one or more layers of
very diﬀerent cells. Te surrounding cells are called
if a single layer is present, and
when more than
one layer is present.
Antrum of a vesicular
Photomicrograph of a mammalian ovary showing follicles in different
Note that most follicles are in the cortex (3