Female Internal Reproductive
Organs Anatomy
The female internal organs of reproduction include the uterus and
vagina and the paired ovaries and uterine (fallopian) tubes.
The uterus and ovaries are particularly affected by atrophy (shrinkage) after
the menopause.
Uterus
The uterus is a pear-shaped organ approximately 8 cm in
length. Its major component is the body (or corpus), which remains somewhat
enlarged after pregnancy. Inferiorly, the uterus tapers into the cylindrical
neck or cervix, which protrudes into the upper part of the vagina (Fig. 5.9).
The uterus is most commonly positioned with its body lying
on the superior surface of the bladder (Fig. 5.8). As
the bladder fills and empties, the uterine body moves on the relatively
immobile cervix. Thus, when the bladder is empty the uterine body is anteflexed
(bent forwards on the cervix), but when the bladder is distended the uterus may
become retroflexed.
Body
The uterine body possesses anteroinferior and
posterosuperior surfaces. The right and left borders give attachment to the
broad ligaments and superiorly give origin to the uterine tubes (Figs 5.8 & 5.11). The rounded upper end of the organ
between the attachments of the tubes is called the fundus.
On the posterosuperior surface of the uterus lie the
sigmoid colon or coils of ileum. Both surfaces are covered with peritoneum,
which continues laterally as the broad ligament (Fig. 5.11). Adjacent to the
uterus within each broad ligament is the uterine artery and its associated
plexus of veins. On each side, the ligament of the ovary and the round ligament
of the uterus attach to the uterine body close to the origin of the uterine
tube. These ligaments, remnants of the fetal gubernaculum, run laterally within
the broad ligament, often raising ridges in the peritoneum. The ligament of the
ovary attaches to the medial pole of the ovary, while the round ligament of the
uterus runs to the lateral pelvic wall and turns forwards in the
extraperitoneal tissues. Crossing the external iliac vessels, the round
ligament of the uterus enters the deep inguinal ring (Fig.
5.8), traverses the inguinal canal and terminates in the subcutaneous
tissues of the labium majus (Fig. 4.24).
The wall of the uterine body comprises a thick layer of
smooth muscle (myometrium) lined by a vascular mucosa (endometrium), the
thickness of which varies with the phases of the menstrual cycle. The uterine
cavity is narrow in sagittal section but triangular in coronal section, being
widest where the uterine tubes enter (Figs 5.10 & 5.11). Tapering
inferiorly, the cavity communicates via the internal os with the cervical canal.
The uterine cervix is thick-walled and has a narrow lumen,
the cervical canal (Figs 5.9 &
5.11). The canal communicates superiorly with the uterine cavity via the
internal os and opens inferiorly into the vagina at the external os. The
external os is circular before the first vaginal delivery but thereafter
presents an oval aperture. Although approximately in line with the body of the
uterus, the cervix lies roughly at right angles to the long axis of the vagina
(a position called anteversion). Structures close to the cervix are vulnerable
to the local spread of cervical carcinoma. Approximately half of the cervix
lies above the vagina (the supravaginal part) and is covered posteriorly by peritoneum passing from the uterine body onto the
vault of the vagina. The root of the broad ligament is attached to this part of
the cervix and contains the uterine artery (Fig. 5.13). The vessel runs
medially above the ureter then turns upwards at the side of the cervix near the
lateral fornix of the vagina. Anteriorly, the supravaginal part of the cervix
is related to the posterior surface of the bladder. The lower half of the
cervix protrudes through the anterior wall of the vagina, making it available
for clinical examination including cervical smear testing. Structures close to
the cervix, including both ureters, are vulnerable to the local spread of
cervical carcinoma.
The uterine body and cervix are supplied by branches of the
uterine artery, a branch of the internal iliac artery. Venous blood passes into
the uterine venous plexus, which drains into the internal iliac vein (Fig.
5.13).
Uterine tubes
The paired uterine tubes, each approxi- mately 10 cm long,
run in the free upper borders of the broad ligaments (Figs 5.8, 5.10 &
5.11) and convey ova from the ovaries to the uterine cavity. Near the ovary,
the lumen of each tube communicates with the peritoneal cavity via its pelvic
aperture. This opening leads into the funnel-shaped infundibulum, which bears a
series of finger-like processes, the fimbriae, one of which attaches to the
ovary. The infundibulum leads into the ampulla, which forms the comparatively
wide lateral part of the uterine tube. The medial part of the tube, the
isthmus, is narrower and continues through the uterine wall as the intramural
part of the tube.
The blood supply to the medial part of the uterine tube is
provided by terminal branches of the uterine artery. This vessel runs laterally
in the upper part of the broad ligament and anastomoses with the ovarian artery,
which supplies the lateral portion of the tube. Venous blood drains into veins
that accompany the arteries.
Fertilization of ova normally occurs in the uterine tube,
usually within its ampulla. Damage to the tubes, often as a result of
inflammation (salpingitis), is a common cause of infertility. Sometimes an
ectopic pregnancy occurs: a developing blastocyst may fail
to reach the uterine cavity but implants and grows within the uterine tube.
Rupture of the tube then leads to internal haemorrhage.
The ovaries lie close to the lateral pelvic walls,
suspended from the posterior surfaces of the broad ligaments (Fig. 5.8). Each
ovary is ovoid, approximately 4 cm long and 2 cm broad, with one pole directed
medially towards the uterus and the other laterally towards the fimbriated end
of the uterine tube. Each ovary is attached to the broad ligament by a sleeve
of peritoneum, the mesovarium, which conveys the ovarian vessels. However, most
of the ovarian surface is devoid of peritoneum. The ligament of the ovary
attaches to the medial pole of the organ and runs within the broad ligament to
reach the side of the uterine body. The ovary may lie in a shallow depression,
the ovarian fossa, on the lateral pelvic wall between the external and internal
iliac vessels. The ureter and the obturator nerve and vessels descend close to
the ovary (Figs 5.13 & 5.16). Ovarian disease that spreads to involve the
parietal peritoneum at this site, or the obturator nerve itself, may produce
pain referred to the medial side of the thigh.
The ovary is supplied by the ovarian artery (Fig. 5.13), a
direct branch of the abdominal aorta (p. 190). After crossing the pelvic brim,
this vessel traverses the suspensory ligament of the ovary (infundibulopelvic
ligament) to enter the broad ligament and divides into terminal branches within
the mesovarium. The ovary is drained by numerous veins (the pampiniform
plexus), which unite to form the ovarian vein. On the right, the ovarian vein terminates
in the inferior vena cava, while the left ovarian vein usually joins the left
renal vein (p. 194).
Vagina
The vagina is a midline tubular organ approximately 8–10 cm
long, which slopes downwards and forwards (Figs 5.8 & 5.9). Its upper
two-thirds, including the blind-ending vault, lie in the pelvic cavity. The
vagina pierces the pelvic floor and terminates inferiorly by opening into the
vestibule between the labia minora (p. 246). The anterior and posterior vaginal
walls lie in mutual contact so that the lumen forms a transverse cleft. The
lining possesses numerous transverse ridges (rugae; Fig. 5.12).
The uterine cervix pierces the upper part of the anterior
vaginal wall and an anular groove surrounds the intravaginal part of the
cervix. This groove is deepest superiorly where it is termed the posterior
fornix (Fig. 5.9). On either side are the lateral fornices, while below the
cervix is the comparatively shallow anterior fornix (Fig. 5.12).
Anteriorly, the vagina is closely applied to the posterior
wall of the bladder and urethra. Posteriorly lie the rectouterine pouch of
peritoneum and the ampulla of the rectum (Fig. 5.13). Lateral to its inferior
third are the medial borders of the levator ani muscles, which provide
important support to the vagina and uterus. Weakness of the pelvic floor
musculature may lead to prolapse (descent of the uterus into the vagina).
The blood supply to the vagina is provided by branches of
the uterine arteries and occasionally by vessels arising directly from the
internal iliac arteries (Fig. 5.32). Venous blood passes into an extensive
venous plexus surrounding the upper vagina and eventually reaches the internal
iliac veins.
