Female genitalia ( english )

source : " clinical anatomy "

• The vulva

The vulva (or pudendum) is the term applied to the female external genitalia. The labia majora are the prominent hair-bearing folds extending back from the mons pubis to meet posteriorly in the midline of the perineum. They are the equivalent of the male scrotum. The labia minora lie between the labia majora as lips of soft skin which meet posteriorly in a sharp fold, the fourchette.

Anteriorly, they split to enclose the clitoris, forming an anterior prepuce and posterior frenulum. The vestibule is the area enclosed by the labia minora and contains the urethral orifice (which lies immediately behind the clitoris) and the vaginal orifice. The vaginal orifice is guarded in the virgin by a thin mucosal fold, the hymen, which is perforated to allow the egress of the menses, and may have an annular, semilunar, septate or cribriform appearance.

Rarely, it is imperforate and menstrual blood distends the vagina (haematocolpos). At first coitus the hymen tears, usually posteriorly or posterolaterally, and after childbirth nothing is left of it but a few tags termed carunculae myrtiformes. Bartholin’s glands (the greater vestibular glands) are a pair of lobulated, pea-sized, mucus-secreting glands lying deep to the posterior parts of the labia majora. They are impalpable when healthy but become obvious when inflamed or distended. Each drains by a duct 1 in long which opens into the groove between the hymen and the posterior part of the labium minus. Anteriorly, each gland is overlapped by the bulb of the vestibule—a mass of cavernous erectile tissue equivalent to the bulbus spongiosum of the male. This tissue passe forwards, under cover of bulbospongiosus, around the sides of the vagina to the roots of the clitoris.

• The vagina

The vagina surrounds the cervix of the uterus, then passes downwards and forwards through the pelvic floor to open into the vestibule. The cervix projects into the anterior part of the vault of the vagina so that the continuous gutter surrounding the cervix is shallow anteriorly (where the vaginal wall is 3 in (7.5 cm) in length) and is deep posteriorly (where the wall is 4 in (10 cm) long). This continuous gutter is, for convenience of description, divided into the anterior, posterior and lateral fornices.

Relations

• Anteriorly — the base of the bladder and the urethra (which is embedded in the anterior vaginal wall).

• Posteriorly — from below upwards, the anal canal (separated by the perineal body), the rectum and then the peritoneum of the pouch of Douglas which covers the upper quarter of the posterior vaginal wall.

• Laterally— levator ani, pelvic fascia and the ureters, which lie immediately above the lateral fornices.

The amateur abortionist (or inexperienced gynaecologist) without a knowledge of anatomy fails to realize that the uterus passes upwards and forwards from the vagina; he pushes the instrument or IUCD (intra-uterine contraceptive device), which he intends to enter the cervix, directly backwards through the posterior fornix. To make matters worse, this is the only part of the vagina which is intraperitoneal; the peritoneal cavity is thus entered and peritonitis follows.

Blood supply

Arterial supply is from the internal iliac artery via its vaginal, uterine, internal pudendal and middle rectal branches. Avenous plexus drains via the vaginal vein into the internal iliac vein.

Lymphatic drainage

• Upper third to the external and internal iliac nodes.
• Middle third to the internal iliac nodes.
• Lower third to the superficial inguinal nodes.

Structure

Astratified squamous epithelium lines the vagina and the vaginal cervix; it contains no glands and is lubricated partly by cervical mucus and partly by desquamated vaginal epithelial cells. In nulliparous women the vaginal wall is rugose, but it becomes smoother after childbirth.

The rugae of the anterior wall are situated transversely; this allows for filling of the bladder and for intercourse. In contrast, the rugae on the posterior wall run longitudinally. This allows for sideways stretching to accommodate a rectum distended with stool and for the passage of the fetal head.

Beneath the epithelial coat is a thin connective tissue layer separating it from the muscular wall which is made up of a criss-cross arrangement of involuntary muscle fibres. This muscle layer is ensheathed in a fascial capsule which blends with adjacent pelvic connective tissues, so that the vagina is firmly supported in place. In old age the vagina shrinks in length and diameter. The cervix projects far less into it so that the fornices all but disappear.

• The uterus

The uterus is a pear-shaped organ, 3 in (7.5 cm) in length, made up of the fundus, body and cervix. The Fallopian (uterine) tubes enter into each superolateral angle (the cornu) above which lies the fundus.The body of the uterus narrows to a waist termed the isthmus, continuing into the cervix which is embraced about its middle by the vagina; this attachment delimits a supravaginal and vaginal part of the cervix.

The isthmus is 1.5 mm wide. The anatomical internal os marks its junction with the uterine body but its mucosa is histologically similar to the endometrium. The isthmus is that part of the uterus which becomes the lower segment in pregnancy. The cavity of the uterine body is triangular in coronal section, but in the sagittal plane it is no more than a slit. This cavity communicates via the internal os with the cervical canal which, in turn, opens into the vagina by the external os.
The nulliparous external os is circular but after childbirth it becomes a transverse slit with an anterior and a posterior lip.

The non-pregnant cervix has the firm consistency of the nose; the pregnant cervix has the soft consistency of the lips. In fetal life the cervix is considerably larger than the body; in childhood (the infantile uterus) the cervix is still twice the size of the body but, during puberty, the uterus enlarges to its adult size and proportions by relative overgrowth of the body. The adult uterus is bent forward on itself at about the level of the internal os to form an angle of 170°; this is termed anteflexion of the uterus. Moreover, the axis of the cervix forms an angle of 90° with the axis of the vagina—anteversion of the uterus. The uterus thus lies in an almost horizontal plane.

In retroversion of the uterus, the axis of the cervix is directed upwards and backwards. Normally on vaginal examination the lowermost part of the cervix to be felt is its anterior lip; in retroversion either the os or the posterior lip becomes the presenting part. In retroflexion the axis of the body of the uterus passes upwards and backwards in relation to the axis of the cervix. Frequently these two conditions co-exist.

They may be mobile and symptomless—as a result of distension of the bladder or purely as a development anomaly. Indeed, mobile retroversion is found in a quarter of the femal population and may be regarded as a normal variant. Less commonly, they are fixed, the result of adhesions, previous pelvic infection, endometriosis or the pressure of a tumour in front of the uterus.

Relations

• Anteriorly—the body is related to the uterovesical pouch of peritoneum and lies either on the superior surface of the bladder or on coils of intestine. The supravaginal cervix is related directly to bladder, separated only by connective tissue. The infravaginal cervix has the anterior fornix immediately in front of it.

• Posteriorly—lies the pouch of Douglas, with coils of intestine within it.

• Laterally—the broad ligament and its contents , the ureter lies 12 mm lateral to the supravaginal cervix.

The ureter is readily infiltrated by lateral extension of a carcinoma of the uterus; bilateral hydronephrosis with uraemia is a frequent mode of termination of this disease. The close relationship of ureter to the lateral fornix is best appreciated by realizing that a ureteric stone at this site can be palpated on vaginal examination. (This is the answer to the examination question: ‘When can a stone in the ureter be felt?’)

Blood supply

The uterine artery (from the internal iliac) runs in the base of the broad ligament and crosses above and at right angles to the ureter to reach the uterus at the level of the internal os. The artery then ascends in a tortuous manner alongside the uterus, supplying the corpus, and then anastomoses with the ovarian artery. The uterine artery also gives off a descending branch to the cervix and branches to the upper vagina. The veins accompany the arteries and drain into the internal iliac veins, but they also communicate via the pelvic plexus with the veins of the vagina and bladder.

Lymph drainage

1. The fundus (together with the ovary and Fallopian tube) drains along the ovarian vessels to the aortic nodes, apart from some lymphatics which pass along the round ligament to the inguinal nodes.

2. The body drains via the broad ligament to nodes lying alongside the external iliac vessels.

3. The cervix drains in three directions—laterally, in the broad ligament, to the external iliac nodes; posterolaterally along the uterine vessels to the internal iliac nodes; and posteriorly along the recto-uterine folds to the sacral nodes. Always examine the inguinal nodes in a suspected carcinoma of the corpus uteri—they may be involved by lymphatic spread along the round ligament.

Structure

The body of the uterus is covered with peritoneum except where this is reflected off at two sites, anteriorly on to the bladder at the uterine isthmus and laterally at the broad ligaments. Anteriorly, the peritoneum is only loosely adherent to the supravaginal cervix; this allows for bladder distension. The muscle wall is thick and made up of a criss-cross of involuntary fibres mixed with fibroelastic connective tissue. The mucosa is applied directly to muscle with no submucosa intervening.

The mucosa of the body of the uterus is the endometrium, made up of a single layer of cuboidal ciliated cells forming simple tubular glands which dip down to the underlying muscular wall. Below this epithelium is a stroma of connective tissue containing blood vessels and round cells. The cervical canal epithelium is made up of tall columnar cells which form a series of complicated branching glands; these secrete an alkaline mucus which forms a protective ‘cervical plug’ filling the canal.

The vaginal aspect of the cervix is covered with a stratified squamous epithelium continuous with that of the vagina. The mucosa of the corpus undergoes extensive changes during themenstrual cycle which may be briefly summarized thus:

1. first 4 days—desquamation of its superficial two-thirds with bleeding

2. subsequent 2–3 days — rapid reconstitution of the raw mucosal surface by growth from the remaining epithelial cells in the depths of the glands

3. by the 14th day the endometrium has reformed; this is the end of the proliferative phase

4. from the 14th day until the menstrual flow commences is the secretory phase,the endometrium thickens, the glands lengthen and distend with fluid and the stroma becomes oedematous and stuffed with white cells.

At the end of this phase three layers can be defined:

1 a compact superficial zone;
2 a spongy middle zone—with dilated glands and oedematous stroma;
3 a basal zone of inactive non-secreting tubules.

With degeneration of the corpus luteum there is shrinkage of the endometrium, the arteries retract and coil, producing ischaemia of the middle and superficial zones, which then desquamate. It is probable that spasm of the vessels in the basal layer (which remains non-desquamated) prevents the woman bleeding to death. Only very slight desquamation and bleeding takes place in the mucosa of the cervical canal.

• The Fallopian tubes

The Fallopian, or uterine, tubes are about 4 in (10 cm) long; they lie in the free edge of the broad ligaments and open into the cornu of the uterus. Each comprises four parts.

1 The infundibulum — the bugle-shaped extremity extending beyond the broad ligament and opening into the peritoneal cavity by the ostium. Its mouth is fimbriated and overlies the ovary, to which one long fimbria actually adheres (fimbria ovarica).

2 The ampulla—wide, thin-walled and tortuous.

3 The isthmus—narrow, straight and thick-walled.

4 The interstitial part—which pierces the uterine wall.

Structure

Apart from the interstitial part, the tube is clothed in peritoneum. Beneath this is a muscle of outer longitudinal and inner circular fibres. The mucosa is formed of columnar, mainly ciliated cells and lies in longitudinal ridges, each of which is thrown into numerous folds. The ova are propelled to the uterus along this tube, partly by peristalsis and partly by cilial action.

• The ovary

The ovary is an almond-shaped organ, 1.5 in (4 cm) long, attached to the back of the broad ligament by the mesovarium. The ovary has two other attachments, the infundibulopelvic ligament, (sometimes called the suspensory ligament of the ovary), along which pass the ovarian vessels and lymphatics from the side wall of the pelvis, and the ovarian ligament, which passes to the cornu of the uterus.

Relations

The ovary is usually described as lying on the side wall of the pelvis opposite the ovarian fossa, which is a depression bounded by the external iliac vessels in front and the ureter and internal iliac vessels behind and which contains the obturator nerve. However, the ovary is extremely variable in its position and is frequently found prolapsed into the pouch of Douglas in perfectly normal women. The ovary, like the testis, develops from the genital ridge and then descends into the pelvis. In the same way as the testis, it therefore drags its blood supply and lymphatic drainage downwards with it from the posterior abdominal wall.

Blood supply, lymph drainage and nerve supply

Blood supply is from the ovarian artery which arises from the aorta at the level of the renal arteries. The ovarian vein drains, on the right side, to the inferior vena cava, on the left, to the left renal vein, exactly comparable to the venous drainage of the testis. Lymphatics pass to the aortic nodes at the level of the renal vessels, following the general rule that lymphatic drainage accompanies the venous drainage of an organ. Nerve supply is from the aortic plexus (T10). All these structures pass to the ovary in the infundibulopelvic ligament.

Structure

The ovary has no peritoneal covering; the serosa ends at the mesovarian attachment. It consists of a connective tissue stroma containing Graafian follicles at various stages of development, \ corpora lutea and corpora albicantia (hyalinized, regressing corpora lutea, which take several months to absorb completely). The surface of the ovary in young children is covered with a so-called ‘germinal epithelium’ of cuboidal cells. It is now known, however, that the primordial follicles develop in the ovary in early fetal life and do not differentiate from these cells. In adult life, in fact, the epithelial covering of the ovary disappears, leaving only a fibrous capsule termed the tunica albuginea. After the menopause the ovary becomes small and shrivelled; in old age the follicles disappear completely.