374
UNIT 3
Organ Systems
Figure 19-3A.
Overview of the ovary.
H&E, left
3
17; right
3
129
The
ovaries
are paired organs covered by a simple, usually cuboidal, mesothelium (sometimes called
germinal epithelium
) and a
tunica albuginea (connective tissue). Each ovary is divided into a
cortex
and a
medulla
. The
cortex
contains various stages of fol-
licles including
primordial follicles, primary follicles, secondary follicles
, and, occasionally,
graa±
an follicles
. It may also contain the
corpus luteum
, a temporary endocrine gland formed by components of an ovulated follicle. A degenerated corpus luteum persists
in the ovary as the
corpus albicans
. Most follicles degenerate (undergo
atresia
) before ovulation and are then called
atretic follicles
.
The
medulla
contains connective tissue with blood vessels, nerve F
bers, and lymphatic vessels.
Ligament
of ovary
Germinal epithelium
Germinal epithelium
Germinal epithelium
Tunica albuginea
Tunica albuginea
Tunica albuginea
Primordial
Primordial
follicle
follicle
Primordial
follicle
Primary follicle
Primary follicle
(multilaminar)
(multilaminar)
Primary follicle
(multilaminar)
Medulla
Medulla
Medulla
Secondary
follicles
Cortex
Cortex
Cortex
A
D.Cui
D.Cui
Theca interna
Granulosa cells
Corona radiata
(granulosa cells)
Cumulus
oophorus
Zona pellucida
Theca externa
Theca interna
Granulosa cells
Granulosa cells
Zona pellucida
Theca externa
Oocyte (1°–2°)
Oocyte (1 )
o
Antrum
Antrum
Antrum
Antrum
Antrum
Antrum
Graafian follicle
Secondary follicle
Granulosa cell
Follicular
(squamous)
cell
Granulosa
(cuboidal)
cell
Primordial follicle
Primary follicle (unilaminar)
Primary follicle (multilaminar)
Basement
membrane
Basement
membrane
Oocyte (1 )
o
Oocyte (1 )
o
Oocyte (1 )
o
Zona
pellucida
B
Figure 19-3B.
Development of the ovarian follicles.
This illustration shows
ovarian follicles
from early to late stages: the
primordial (resting) follicle,
the unilaminar
primary follicle,
the multi-
laminar
primary (growing) follicle,
the
secondary (antral
or
vesicular) follicle
, and the
graa± an (preovulatory) follicle
. Each of these follicles
contains a
primary (1
0
)
oocyte
, which is an immature ovum. A
secondary oocyte
is formed shortly before ovulation, when the oocyte com-
pletes the F rst meiotic division. The secondary oocyte does not undergo the second meiotic division unless fertilization occurs. Note that the
follicles are not drawn to scale; a graaF an (preovulatory) follicle is approximately 1,000 times the diameter of a primordial follicle.
Ovaries
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