Human Anatomy: Female Internal-External Genital Organs (Lecture Notes)

HUMAN ANATOMY
FEMALE INTERNAL-EXTERNAL GENITAL ORGANS

(Lecture Notes)

Necdet Ersöz
Gazi University Medical School

Female External Genital Organs: Vulva, Mons Pubis, Labia Majora, Labia Minora, Clitoris, Perineum

Female Internal Genital Organs: Vagina, Cervix, Uterus, Fallopian Tubes, Ovaries

Uterus

This is a muscular organ whose function is to provide a nidus for the developing embryo. In the virginal state, it is shaped of a flattened pear. Its size is about 8 x 5 x 3 cm. It possesses a fundus, body, and cervix. It receives the uterine tubes, and the cervix protrudes and opens into the vault of the vagina. The fundus is the part above the entrance of the tubes. It is convex and measures about 5 cm from side to side and about 3 cm thick. It possesses             a serous coat of pelvic peritoneum which continues downwards over the front and back of the body. The body of the uterus tapers downwards from the fundus and is flattened anteroposteriorly. Each upper angle (cornu), at the junction of fundus and body, receives the uterine tubes. The body is enclosed by peritoneum which laterally becomes the broad ligament. The intestinal surface of the body faces upwards with coils of intestine lying upon it while the vesical surface rests on the bladder with the peritoneum of the vesicouterine pouch intervening. The cavity of the uterus occupies the body. A narrow slit in the virgin, it enlarges during pregnancy by growth of the uterine walls to accommodate the fetus.

The lowest half centimetre of the body which becomes continuous with the cervix is the isthmus and forms what obstetricians call the lower uterine segment at full term. The cervix of the uterus tapers below the body and its lower end is clasped by the vault of the vagina, into which it protrudes. It thus has vaginal (lower) and supravaginal (upper) parts, the latter like the body of the uterus having intestinal and vesical surfaces. The deep sulcus which surrounds the protruding cervix is the fornix of the vagina, and is deepest posteriorly. The intestinal surface is covered by peritoneum that continues from the body on to the upper part of the fornix, forming the anterior wall of the rectouterine pouch (of Douglas). The vesical surface has no peritoneal covering, being deep to the vesicouterine pouch and attached to the bladder above the trigone by rather dense connective tissue. The ureter, by lying first lateral to and then in front of the fornix, comes to pass about 1-2 cm from the cervix. The body of the uterus is rarely exactly in the midline; when deviated to one side the cervix becomes deflected to the opposite side, so one ureter may be closer to the cervix than the other.

Cervix

The canal of the cervix is continuous with the cavity of the body at what is commonly called the internal os. The lower opening into the vagina is the external os; this is circular in the nulliparous but usually a transverse slit after childbirth, with anterior and posterior lips. The external os is normally on a level with the ischial spines. The cervical opening to the vagina is small.

Nerve supply

The nerves of the uterus are branches from the pelvic plexus.

Uterus Ligaments

ü  Broad ligament

ü  Round ligament

ü  Cardinal ligament

ü  Utero-sacral ligament

Broad Ligament: The broad ligament is not strictly speaking a ligament in the usual sense, since it consists of no more than a lax double fold of peritoneum lying lateral to the uterus, and it plays little part in uterine support. Its medial edge is attached to the side wall of the uterus and flows over its intestinal and vesical surfaces as its serous coat. The lateral edge is attached to the side wall of the pelvis, hence the two layers of its inferior edge or base pass forwards and backwards to line the pelvic cavity; the posterior wall most importantly has the ureter adhering underneath it.

The line of lateral attachment crosses the obturator nerve, superior vesical or obliterated umbilical vessels, and the obturator artery and vein. The upper border of the broad ligament is free, forming the mesosalalpinx and containing the uterine tube, and the lateral quarter of this upper edge forms the suspensory ligament of the ovary (formerly         the infundibulopelvic ligament), which contains the ovarian vessels and lymphatics. The anterior layer of the broad ligament is bulged forwards by the round ligament of the uterus just below the uterine tube. The posterior layer bulges backwards as the mesovarium, suspending the ovary.

Broad ligament serves as a mesentery for the uterus, ovaries, and the uterine tubes. It helps in maintaining the uterus in its position. Between the two layers is a mass of areolar tissue, the parametrium, in which lie the uterine and ovarian vessels and lymphatics, the round ligament of the ovary, and vestigial remnants of mesonephric tubules (the epoophoron and paroophoron)

Round Ligament: Extends from the junction of the uterus and tube to the deep inguinal ring. Originates at the uterine horns, in the parametrium. It lies in the anterior layer of the broad ligament below the uterine tube. The round ligament passes through the inguinal canal and is attached at its distal extremity to the fibrofatty tissue of the labium majus of the vulva. Function is maintenance of the anteversion of the uterus.

It is supplied by a branch of the ovarian artery in the broad ligament and by a branch from the inferior epigastric artery in the inguinal canal. It consists largely of visceral muscle, and it acts to hold the uterus forwards in anteflexion and anteversion, especially when forces tend to push the uterus backwards (e.g. distension of the bladder, gravity during recumbency).

Cardinal Ligament: The extraperitoneal tissue (pelvic fascia) condensed in certain places to form named ligaments which contain some visceral muscle fibres unfortunately they are often difficult to appreciate in dissecting specimens because they become athrophic in old age, but they are supremely important for uterine stability, in particular those called the lateral and uterosacral ligaments. The lateral ligament, otherwise known as the lateral cervical cardinal oe Mackenrodt’s ligament, consists of thickenings of connective tissue in the base of each broad ligament, extending from the cervix and vaginal fornix laterally to the side wall of the pelvis. The ureter, uterine artery and inferior hypogastric plexus lie on the upper surface of this tissue and the cervical branch of the uterine artery of this tissue and the cervical branch of the uterine artery passes through it. It imparts lateral stability to the cervix.

Cardinal ligament is located at the base of the broad ligament of the uterus. Importantly, in contains the uterine artery and uterine vein. It provides support to the uterus.

Utero-sacral Ligament: The utero-sacral ligaments are similar condensations of very variable size that extend backwards from the cervix below the peritoneum, embracing the rectouterine pouch and rectum and becoming attached to the fascia over piriformis. They are best palpated on rectal (not vaginal) examination. They keep the cervix braced backwards against the forward pull of the round ligaments on the fundus and so maintain the body of the uterus in anteversion. It passes along the lateral wall of the pelvis from the uterine cervix to sacrum and serves to support the uterus and hold it in place.

Position of the Uterus

It lies in centre of the pelvic cavity, between bladder anteriorly, and rectum posteriorly,  usually it is anteversion and anteflexion. Anteversion is axis of uterus at 90 degree with that of vagina. Anteflexion is axis of body of uterus is bent forward with that of the cervix forming an angle of about 170 degree (body of the uterus is bent slightly forward at isthmus).

Ovaries

ü  Mesovarium

ü  Broad ligament

ü  Ovarian ligament

ü  Fimbria

ü  Fallopian tubes

The Ovary is ovoid in shape, smaller than the testis. It is firm to the touch, being composed of rather dense fibrous tissue in which the ova are embedded. It projects into the pelvic cavity, attached to the posterior leaf of the broad ligament by a double fold of peritoneum, the mesovarium.

The mesovarium is attached equatorially around the ovary, but does not invest the surface of the gland, which is covered with low columnar epithelium. The ovary often lies flush within the posterior leaf of the broad ligament, in which case there is no mesovarium, but traction on the ovary will pull up the peritoneum into a temporary mesovarium.

The ovary lies on the peritoneum of the side wall of the pelvis, in the shallow ovarian fossa in the angle between the internal and external iliac vessels, on the obturator nerve. The ovary in its normal position can just be reached through the vagina by the tip of the examining finger. It is overlaid by the coils of sigmoid colon and ileum that occupy the rectouterine pouch of Douglas. It usually lies with its long axis oblique, its tubal extremity uppermost and medial. It is attached at its uterine extremity to the upper angle of the uterus by the ligament of the ovary. This is a mass of smooth muscle and fibrous tissue lying between the two layers of the broad ligament, and continuous with the round ligament, the whole being the remnant of the gubernaculum.

Blood Supply of Ovary

The ovary is supplied by the ovarian artery, a branch of the abdominal aorta just below the renal artery. The vessel runs down behind the peritoneum of the infra-colic compartment and the colic vessels, crossing the ureter obliquely, on the psoas muscle. It crosses the brim of the pelvis and enters the suspensory ligament (formerly the infundibulopelvic ligament) at the lateral extremity of the broad ligament. It gives off a branch to the uterine tube which runs medially between the layers of the broad ligament and anastomoses with the uterine artery, and it ends by entering the ovary.

The ovarian veins form a plexus in the mesovarium and the suspensory ligament (the pampiniform plexus like the testis). The plexus drains into a pair of ovarian veins which accompany the ovarian artery. They usually combine as a single trunk before their termination. That on the right joins the inferior vena cava, that on the left renal vein.

Lymph Drainage

The lymphatics of the ovary drain to para-aortic nodes alongside the origin of the ovarian artery, just above the level of the umbilicus (L2).

Nerve Supply

Sympathetic (vasoconstrictor) fibres reach the ovary from the aortic plexus along its blood vessels; the preganglionic cell bodies are in T10 and T11 segments of the cord. Some parasympathetic fibres may reach the ovary from the inferior hypogastric plexus via the uterine artery and are vasodilator. Autonomic fibres do not reach the ovarian follicles; an intact nerve supply is not required for ovulation. Sensory fibres accompany the sympathetic nerves, so that ovarian pain may be periumbilical, like appendicular pain.

Uterine Tubes

Each tube is 10 cm long. The proximal 1 cm (uterine part, formerly called the intramural or interstitial part) is embedded in the uterine wall. Emerging from the cornu, the tube then lies in the upper edge of the broad ligament, the peritoneal fold embracing it being the mesosalpinx. The part adjacent to the uterus (the isthmus of the tube) is straight and narrow but distally it becomes wider as the ampulla and finally ends as a trumpet-shaped expansion, the infundibulum or fimbriated end, with a number of finger-like processes. This open end lies behind the broad ligament adjacent to the lateral pelvic wall and ovary, whose liberated ova should drop into it. The tube, formed of two layers of visceral muscle (inner circular and outer longitudinal, like the gut).

Blood Supply of Uterine Tubes

The uterus is supplied by the uterine artery, a branch of the internal iliac. It passes medially across the pelvic floor in the base of the broad ligament, above the ureter, to reach the side of the supravaginal part of the cervix. Giving a branch to the cervix and vagina, the vessel turns upwards between the layers of the broad ligament to run alongside the uterus as far as the entrance of the tube where it anastomoses end on with the tubal branch of the ovarian artery. In its course it freely gives off branches which penetrate the uterine walls.

The uterine tube is supplied by the tubal branch of the ovarian artery. The tubal artery runs below the tube, between the layers of the broad ligament, to anastomose with the uterine artery.

The veins of the uterus course below the artery at the lower edge of the broad ligament where they form a wide plexus across the pelvic floor. This communicates with the vesical and rectal plexuses and drains to the internal iliac veins. The tubal veins join the ovarian veins.

Lymph Drainage

The body and fundus of the uterus normally drain mainly to external iliac nodes, but it is also possible for lymph to reach the inguinal nodes via the round ligament and the inguinal canal. There is only scanty lymphatic drainage along the tube and ovarian vessels to aortic nodes. The cervix drains to external and internal iliac nodes by lymphatic channels that run respectively in front of or behind the ureter, and also to sacral nodes via the uterosacral ligaments. Note that while lymph from the body of the uterus may reach inguinal nodes, that from the cervix does not.

Vagina

The tubular vagina lies in approximately the same direction as the pelvic brim. For much of its total length (about 10 cm) the anterior and posterior walls are in opposition, i.e. the lumen is transverse, but the vaginal orifice (introitus) is an anteroposterior slit. The vagina extends from the uterine cervix to the labia minora of the pudendal cleft of the vulva; its lower end is thus in the perineum. It lies in front of the rectum, anal canal, and perineal body, and behind the bladder and urethra. The upper end is slightly expanded and receives the uterine cervix which projects into it forming round the margin of the cervix a circular groove or vaginal fornix, which for descriptive convenience is usually subdivided into anterior, posterior, and lateral fornices. The uppermost parts of the vagina are the posterior and lateral fornices. The posterior fornix is covered by peritoneum of the front of the rectouterine pouch (of Douglas); this is the only part of the vagina to have a peritoneal covering. The ureter is first adjacent to the lateral fornix and then passes over the front of the anterior fornix to ender the bladder.

Below the cervix, the anterior wall of the vagina is in contact with the base (posterior surface) of the bladder, and below the bladder the urethra is embedded in the vaginal wall. The vagina passes down between the pubovaginalis parts of levator ani, through the urogenital diaphragm and perineal membrane (i.e. through the deep perineal space) into the superficial perineal space to become the vestibule of the vagina. Here it may show internally the remains of the hymen, and the duct of the greater vestibular (Bartholin’s) gland opens on each side just below the hymen in the posterolateral wall. Lateral to the vestibule is the bulb of the vestibule covered by the bulbospongiosus muscle and with the greater vestibular gland under cover of the posterior end of the bulb. The urethra opens immediately in front of the vaginal orifice, which is below by the labia minora and the minute openings of the lesser vestibular gland are behind the urethral orifice.

Blood Supply of the Vagina

The vaginal branch of the internal iliac artery is an obvious supply, but other sources include the uterine, inferior vesical and middle rectal vessels, whose branches all make good anastomotic connexions on the vaginal wall. This variety of branches may help to keep the organ adequately supplied during the extreme dilatation of childbirth. Veins join the plexuses on the pelvic floor to drain into the internal iliac vein.

Lymphatic Drainage

The lymphatics of the vagina, like those of the cervix, drain to external and internal iliac and sacral nodes, but the lowest part (below the hymen level) drains like other perineal structures to superficial inguinal nodes.

Nerve Supply

The lower end of the vagina receives sensors fibres from the perineal and posterior labial branches of the pudendal nerve, and (with the anterior part of the vulva) from the ilioinguinal nerve. Sympathetic fibres from the hypogastric plexuses supply blood vessels and the smooth muscle of the vaginal wall. The upper vagina is said to be sensitive only stretch, the afferent fibres running with sympathetic nerves.

Female Urethra

The female urethra is about 4 cm long, passing from the neck of the bladder at the lower angle of the trigone to the external urethral meatus, which is in the vestibule of the vagina in front of the vaginal orifice and 2.5 cm behind the clitoris. The urethra is not simply in front of the vagina throughout its short course, but all except its uppermost end is embedded within the vaginal wall. As it leaves the bladder, fibres of the pubovaginalis part of levator ani lie adjacent to it, and although these periurethral fibres are not connected to the urethra they play some part in compressing it. There is no internal urethral sphincter in the female.

Blood Supply

The upper part of the urethra is supplied by the inferior vesical and uterine arteries, with the lower end receiving contributions from the perineal branch of the internal pudendal artery. Veins drain to the vesical plexus and the internal pudendal vein.

Lymph Drainage

Lymph vessels pass mainly to internal iliac nodes but some reach the external iliac group.

Nerve Supply

Fibres reach the urethra from the inferior hypogastric plexuses and from the perineal nerve.

The Female External Genitalia

Collectively they form the vulva. All the formations and structures seen in the male are present in the female, but greatly modified for functional reasons. The essential difference is the failure in the female of the midline fusion of the genital folds.

The mons pubis is the mound of hairy skin and subcutaneous fat in front of the pubic symphysis and pubic bones. It extends backwards on either side as the labia majora which are fatty cutaneous folds forming the boundary of the pudendal cleft. The round ligaments of the uterus end in front of each labium. The labia are joined in front as the anterior commissure; at the back they fade away approaching the anus behind the vagina, and this area forms the posterior commissure. The labia minora are cutaneous folds without fat lying internal to the labia majora and forming the boundaries of the vestibule of the vagina. Their front ends split to form the (dorsal) prepuce and (ventral) frenulum of the clitoris, while at the back they unite by a small skin fold, the frenulum of the labia. The clitoris lies at the front ends of the labia minora. Although homologous with the penis, it is not associated with the urethra, so it is formed by two miniature corpora cavernosa without any corpus spongiosum. Its free extremity, the glans, is highly sensitive to sexual stimulation and is usually overlapped by the prepuce. The vestibule of the vagina, bounded by the labia minora, contains the external urethral meatus and the vaginal orifice and the ducts of the greater vestibular glands.

The female perineal membrane is wider but weaker than in male, being pierced transversely by the vagina (although the opening of the vagina in the vulva is longitudinal). It gives attachment to the crura of the clitoris, each of which is covered by an ischiocavernosus muscle. Medial to each crus, attached to the perineal membrane at the side of the vagina, is a mass of erectile tissue, the bulb of the vestibule, one on each side of the orifices of the vagina and urethra. They join in front of the urethral orifice and pass forwards to the glans of the clitoris. Each bulb is covered by a bulbospongiosus muscle, whose fibres extend from the perineal body round the vagina and urethra to the clitoris. They form a perineal sphincter for the vagina in addition to its pelvic sphincter (the pubovaginalis parts of levator ani).

The greater vestibular glands (of Bartholin) form pea-shaped masses less than 1 cm in diameter lying at the side of the vaginal opening, one behind the posterior end of each bulb and deep to bulbospongiosus (at 4 and 8 o’clock viewed from the lithotomy position). Each opens by a single duct 2 cm long into the posterolateral part of the vaginal orifice, in the groove between the labium minus and the hymen or its remains. The duct is subject to cyst formation, and the gland to ascending infection (bartholinitis). The glands may play a minor role in lubricating the lower vagina and are homologous with the bulbourethral (Cowper’s) glands of the male, but note that the glands in the male are deep to the perineal membrane, i.e. within the deep perineal pouch; in the female they are superficial to the membrane, so their ducts do not have to pierce it as they do in the male. The lesser vestibular glands are very small mucous glands with minute openings between the urethral and vaginal openings. The hymen is a mucosal fold of variable extent and thickness at the margins of the vaginal opening. It may be absent or may even completely close the opening, in which case it must be incised at the age when menstruation begins. Its remains after rupture by the first intercourse may form small tags (hymenal carunculae).

Note: These notes are taken from Gazi University Faculty of Medicine Prof. Dr. Rabet GOZIL’s anatomy lectures.