OVARIES

There is a pair of ovaries usually located on either side of the uterus below the fimbriated ends of the two fallopian tubes. The ovaries are attached to the posterior surface of the broad ligament and by the ovarian ligament to the uterus. Each ovary is a flat, almond-shaped structure and measures on average 1.5 cm wide, 3 cm long and 2 cm deep, weighing approximately 2–3 g.

The function of the ovaries is twofold in that they store the female germ cells, or oocytes, and produce the two major female reproductive hormones, oestrogen and progesterone. Structurally, the ovary is composed of an inner medulla containing supportive connective tissue directly attached to the broad ligament. The cortex of the ovary consists of highly vascular tissue where the ovarian follicles are embedded. Each primordial follicle contains an immature egg or germ cell encased in a layer of squamous-like follicle cells. The primary follicle is then surrounded by two or more layers of granulosa cells. These cells protect and nourish the germ cells until the follicle matures and ovulation occurs. Thus the primary germ cell, under the influence of the pituitary and ovarian hormones, becomes a fully developed graafian follicle. During a woman’s reproductive years, one germ cell usually matures each monthly cycle to be extruded from the ovary and engulfed by the fallopian tube fimbriae. This expulsion of the germ cell, or ovulation, occurs as a consequence of the stimulus of the gonadotrophic hormones, follicle stimulating and luteinizing hormones. After ovulation, the ruptured follicle transforms into a structure called the corpus luteum. In the absence of a pregnancy, the corpus luteum degenerates in approximately six months into a corpus albicans. If pregnancy occurs the corpus luteum is than maintained until the placenta is established, taking over the endocrine function^1,2.

Prior to birth, the fetal ovary contains over 2 million primordial follicles. By menarche (commencement of menstrual cycles), only approximately 200,000 remain, continuing then to decrease throughout a woman’s reproductive years. Only 300 to 400 are actually released by ovulation during the woman’s reproductive life. Of the remainder, a process termed atresia occurs in over 80%. This process involves the primordial and primary follicles becoming smaller and then being reabsorbed by the body¹.

FALLOPIAN TUBES

The fallopian tubes are also called uterine tubes or oviducts, of which there are two. Each tube is a slender, cylindrical and muscular structure approximately 10 cm long. The tube is an extension of the cornu of the uterus and travels to the side walls of the pelvis, turning downwards and backwards before reaching the ovaries. Both tubes communicate with the uterus at the medial end and the ovaries at the lateral end, being supported by the upper folds of the broad ligament. At the ovary end, the fallopian tubes form a funnel-shaped opening with fringed projections or fimbriae. These finger-like projections massage the ovaries at ovulation to help extract the mature ovum^1,2.

The primary function of the fallopian tubes is to provide a passageway for the ova and sperm to travel and possibly encounter, with fertilisation occurring. Most fertilisations occur within the outer one third of the fallopian tubes. This is assuming that sperm are present following recent coitus. Sperm are viable for 24–48 hours. An ovum can be fertilised up to 72 hours following ovulation.

Travel in the fallopian tubes occurs as a result of two factors:

Further, the fallopian tube provides a passageway through which tubal secretions can drain into the uterus. It should also be noted that the fallopian tube provides a direct passageway between the vagina and the peritoneal cavity. This is, therefore, a direct route for the entry of ascending infection into the peritoneal cavity^1,2.

UTERUS

The uterus is a thick-walled, muscular, pear-shaped, hollow structure located between the bladder and the rectum. In a woman that has never been pregnant (nulliparous), the uterus measures approximately 6 cm in length and 4 cm wide. Principally, the broad and round ligaments provide the uterus with support on both sides. The uterus is divided into three components, the fundus, the body or corpus and the cervix. Eighty percent of the uterus consists of the body, which is connected via the isthmus or neck to the cervix.

Most women have a forward-lying or anteverted uterus, with the uterine fundus and body resting on the bladder. It is possible, however, for the uterus to be in a number of other positions without causing any difficulties. These positions include anteflexion, retroflexion, or retroversion. This variation in position occurs in response to a variety of factors.

The wall of the uterus consists of three layers. The outer serosal layer, derived from the abdominal peritoneum, is the perimetrium. This layer merges with the peritoneum that covers the broad ligament. The perimetrium is reflected over the bladder wall anteriorly and forms the vesicouterine pouch. Posteriorly, the perimetrium extends to form the cul-de-sac or pouch of Douglas. The proximity of the perimetrium to the bladder means that a bladder infection often causes uterine symptoms, especially during pregnancy.

The major portion of the uterine wall is the middle layer or myometrium. This layer has the amazing ability to change in length during pregnancy and labour. The inner layer of the uterus is the endometrium and is continuous with the inner layer of the fallopian tubes and vagina. There are then two layers of the endometrium, a basal and superficial layer. The superficial layer is shed during menstruation, but is then regenerated by the cells of the basal layer. Ciliated cells promote movement of tubal-uterine secretions out of the uterine cavity into the vagina^1,2.

CERVIX

In the nulliparous female, the cervix constitutes about 15%–20% of the uterus and is the part that invaginates or projects into the anterior wall of the vaginal canal. It is the outer portion, or ectocervix, that protrudes into the vagina. This ectocervix has a smooth, pinkish appearance due to the squamous epithelial cell covering. The inner, opening canal of the cervix is called the endocervix, containing a lining of columnar epithelial cells, giving it a rough, reddened appearance. Under hormonal influence, the columnar epithelium provides enough elasticity during labour for the cervix to adequately stretch to allow passage of a fetus. The squamocolumnar junction is where the two types of epithelial cells meet. This junction contains the optimal type of cells needed for an accurate Papanicolaou (Pap) test for malignancy screening. If there are endocervical cells present in the Pap test sample, this ensures that the squamocolumnar junction, or transformational zone, has been sampled.

The cervical canal or os, approximately 2–4 cm long, is tightly closed. The vaginal opening is termed the external os, and the internal os, the uterine opening. The os does, however, allow the passage of sperm to enter and menses to be expelled from the uterus. A rich supply of protective mucus is produced by glandular tissue in the endocervix, which changes in character and quantity during the menstrual cycle and pregnancy. Under the influence of oestrogen, the cervix produces mucus, which facilitates the entrance of sperm. Normally, the cervical mucus at ovulation becomes watery, more abundant, and can stretch several centimetres (spinnbarkeit). These conditions then allow the sperm to easily enter the cervical canal into the uterus. In contrast, the mucus becomes thick under the influence of progesterone following ovulation, inhibiting the passage of sperm. These physiological changes form the basis of natural family planning. The endocervical secretions also protect the uterus from infection and form a mucoid plug or operculum during pregnancy.

The cervix is richly supplied by blood from the uterine artery. This, therefore, can be a site of significant blood loss during birth. The cervix consists of a connective tissue matrix of glands and muscular tissue. This forms a firm fibrous structure that becomes soft and pliable under the influence of the hormones of pregnancy^1,2.

VAGINA

The vagina connects the internal and external genitalia, and is located behind the urinary bladder anteriorly and posteriorly adjacent to the rectum. The shape of the vaginal opening may be oval, circular, or sleeve-like, and may be partially or completely occluded. This occlusion may occur as a consequence of the presence of an intact or partially intact hymen. The hymen is a thin membrane of connective tissue, which varies the size of the vaginal opening from that of a pinhole to an opening large enough to permit two fingers to enter. It is a commonly held belief that an intact hymen indicates virginity. The hymen may, however, become stretched without tearing or becomes torn due to childhood activity, tampon usage or accidents.

A vagina consists of a fibromuscular tube approximately 7.5–10 cm in length, lined with mucus-secreting squamous epithelial cells. Vaginal secretions include cervical mucus, desquamated epithelium, and, during sexual stimulation, a direct transudate. The purpose of these secretions is to protect the vagina from infection. Consequently, the vaginal tissue is usually moist, with a pH maintained at 4–6, considered a bacteriostatic level, as further protection against vaginal infection. The squamous epithelial cells of the vagina store glycogen under the influence of oestrogen. The oestrogen levels also influence both the pH and keratinisation of these cells.

The vaginal walls’ muscular and erectile tissue allows enough dilatation and contraction to accommodate penetration of the penis during intercourse, as well as the passage of the fetus during birth. The membranous vaginal wall, which forms two longitudinal folds and several transverse folds or rugae, contributes to this dilatation^1,2.

MONS PUBIS (VENERIS)

The rounded eminence located anteriorly to the symphysis pubis of the bony pelvis is the mons pubis. This consists of a fat pad covered with skin and coarse hair that lies in an upside-down triangular pattern. Under the hormonal influence of puberty, the amount of fat and hair increases and the colour deepens. The skin is abundant with sebaceous glands, which may become infected for a variety of reasons, including changes in diet, normal variations, or poor hygiene. This is also the site of pubic lice infestation^1,2.

LABIA MAJORA

Beginning anteriorly at the base of the mons pubis and extending posteriorly to the anus are the outermost lips of the vulva called labia majora. This structure consists of folds of skin and fat, becoming covered with hair at the onset of puberty. The labia majora are rich in sebaceous glands and sweat glands and subject to the same types of problems as the mons pubis^1,2.

LABIA MINORA

Between the labia majora is the smaller delicate cutaneous structure of the labia minora, beginning anteriorly at the hood of the clitoris and ending posteriorly at the base of the vagina. This hairless structure consists of skin, fat and some erectile tissue, and is light pink in colour. The edges of the labia minora may be smooth or ragged and may protrude from the labia majora. During sexual arousal, the labia minora become distended with blood and enlarge, returning to normal following a period of labial throb. Sebaceous glands located in the labia minora secrete odoriferous fluid, both in the presence or absence of sexual arousal.

The vestibule is the area between the labia minora, extending anteriorly from the clitoris to the vagina posteriorly. This is a boat-shaped fossa that contains the ureteral and vaginal opening or introitus, and the Bartholin’s lubricating glands. These glands are located at the posterior and lateral aspects of the vaginal orifice where the labia minora end. The purpose of the Bartholin’s glands is to secrete a thin, mucoid material to lubricate the vestibular area. This is believed to contribute slightly to lubrication during sexual intercourse^1,2.

CLITORIS

Anteriorly, the two labia minora join, forming the clitoral hood or prepuce. Just below this structure, anterior to the urethral meatus, the clitoris is located. This structure consists of erectile tissue, rich in blood and nerve supply, which becomes distended during sexual stimulation. The clitoris is homologous to the male glans penis. Stimulation of the clitoris is an important part of sexual activity for women^1,2.

PERINEAL BODY

The perineal body or perineum is the tissue located posterior to the vagina and anterior to the anus. This area is composed of fibrous connective tissue and is the site of insertion of several perineal muscles. During childbirth, this area may be torn or incised (episiotomy) to facilitate birth of the baby^1,2.

FOLLICULAR PHASE

The follicular phase begins with the first day of menstrual bleeding and continues until immediately before ovulation occurs. This phase is initiated by the release of gonadotrophin releasing hormone (GnRH) from the hypothalamus, which in turn stimulates the secretion of two gonadotrophins, follicle-stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary gland. Under the influence of FSH, a number of follicles will begin to mature but one will mature more quickly than the others^1,4.

The main hormones produced by the ovary are oestrogen, progesterone and androgens⁴. Oestrogen comprises a number of compounds including oestriol, oestradiol and oestrone^1,5. LH stimulates the theca cells to produce androgens which are transported to the granulosa cells for conversion to oestrogen. FSH stimulates the granulosa cells to produce the enzymes that convert the androgens to oestrogen^1,4,6. Proliferation of the granulosa and theca cells occurs and the follicle further increases in size¹. The larger and more mature the Graafian follicle becomes, the greater the amount of oestrogen produced. As oestrogen levels rise, a negative feedback mechanism inhibits the production of FSH, ensuring that the growth and maturation of other follicles is controlled^1,4,5,6.

FSH and LH function synergistically to complete maturation of the dominant follicle. The follicle continues to grow and as it reaches maturity, there is a marked rise in oestrogen production. This rise initiates a surge in LH secretion approximately 36 hours before ovulation occurs^1,4,6. Just prior to ovulation the primary oocyte completes its first meiotic division, becoming known as a secondary oocyte. The final stage of meiosis will take place on fertilization of the ovum¹.

The process of ovulation is assisted by the local secretion of prostaglandins and proteolytic enzymes which facilitate breakdown of collagen in the wall of the follicle¹. The oocyte escapes from the follicle still surrounded by the zona pellucida, some follicular fluid and cells⁶. Some women experience pain at the time of ovulation, known as mittelschmerz. The ovum released at ovulation remains fertile for up to 72 hours⁵.

LUTEAL PHASE

After ovulation has taken place, the walls of the follicle collapse inward. The remaining tissues become vascularised and change into the corpus luteum (yellow body)⁴. The function of the corpus luteum is to secrete the hormone progesterone, which has a profound influence on the preparation of the reproductive system for possible pregnancy. If pregnancy does occur, human chorionic gonadotrophin (HCG) maintains the corpus luteum and progesterone continues to rise. If pregnancy does not occur, the function of the corpus luteum declines by the end of the luteal phase and menstruation is triggered^5,6. The corpus luteum then atrophies, becoming the corpus albicans (white body). During this regression, there is a rapid decline in the production of progesterone and oestrogen. When levels become low enough, the anterior pituitary is stimulated to produce FSH and LH and a new ovarian cycle begins^1,4.

MENSTRUAL PHASE

This phase is characterised by vaginal bleeding, known as menstruation or menses. Menstruation typically lasts 3 to 6 days⁶. Although the first day of bleeding is considered to be the first day of the cycle, physiologically it is the end point of the cycle as it involves the shedding of the endometrium down to the basal layer⁵. If pregnancy does not occur, the function of the corpus luteum declines and levels of ovarian hormones fall. The endometrium undergoes vasospasm, ischaemic necrosis and sloughing of tissue⁴. Endometrial tissue and accompanying blood are discarded through menstruation with the aid of uterine contractions stimulated by prostaglandins. These contractions may cause pain, known as dysmenorrhoea. Normal blood loss during menstruation ranges from 30 to 80 mL⁴. The basal layer of the endometrium is not affected by the menstrual cycle and is, therefore, the foundation for endometrial regeneration⁶.

PROLIFERATIVE PHASE

This phase begins once menstruation has ceased and ends at the time of ovulation. After menstruation, the inner lining of the uterus or endometrium is very thin. During the proliferative phase, under the influence of oestrogens being produced by the maturing Graafian follicle, the endometrium thickens from 1 mm to 3–6 mm¹. The endometrium becomes more vascular and the endometrial glands proliferate. Increased levels of oestrogen also cause cyclical changes in the cervix, vagina and breasts⁶.

SECRETORY PHASE

This phase corresponds with the luteal phase of the ovarian cycle, spanning from ovulation to the onset of menstruation. Changes occurring during this phase are largely stimulated by the secretion of progesterone from the corpus luteum⁴. The endometrium and its supporting stroma continue to thicken, blood vessels proliferate, dilate and become coiled. Endometrial glands continue to hypertrophy and begin to secrete fluid rich in glycogen¹. Under the influence of oestrogen and progesterone, further changes to the reproductive system occur including to the alveolar system of the breasts, resulting in them feeling heavy and tender^4,6. The purpose of these changes is to prepare the reproductive system for implantation of a fertilised ovum and to begin preparation for lactation.