Female Internal Reproductive Organs Anatomy and Physiology
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 Anatomy
and Physiology
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 ante- flexed (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 there- after 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 Anatomy
and Physiology
The paired uterine tubes, each approximately 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.
Ovaries Anatomy
and Physiology
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 Anatomy
and Physiology
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 levatorani 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.
