The human female reproductive system is a series of organs primarily located inside the body and around the pelvic region of a female that contribute towards the reproductive process. The female reproductive system is located entirely in the pelvis. The external part of the female reproductive organs is called the vulva, which means covering. Located between the legs the vulva covers the opening to the vagina and other reproductive organs located inside the body. The female reproductive organs (Fig. 1.1) are divided into external genitalia, which are visible from outside and the internal genitalia, which include the gonads and those supporting organs, which cannot be seen from outside.
EXTERNAL GENITALIA
The entrance to the vagina is surrounded by external parts that generally serve to protect the internal organs, this area is called ‘the vulva’ (Fig. 1.2). The vulva is made up of several female organs, which are external. The vulva is bounded anteriorly by the mons pubis, laterally by the labia majora and posteriorly by the perineum. The vulva consists of the following.
Mons Pubis
Mons pubis (mons veneris) is the fatty mound of tissue, made up of subcutaneous adipose connective tissues. It covers the pubic bone. Often called the ‘mons’. In the adult female it is covered by hair.
Labia Majora
Labia majora are the elevations of skin and subcutaneous tissue and are also called ‘large lips’. The labia majora pass from the mons pubis to end posteriorly in the skin over the perineal body. This flap of skin protects the vagina from foreign particles. The labia majora are covered with squamous epithelium and contain sebaceous glands, sweat glands and hair follicles. Below the skin, there are dense connective tissue and adipose tissue, which are richly supplied with venous plexus. The inner surface of the labia majora is hairless. The labia majora are homologous with the scrotum in the male.
Labia Minora
The labia minora are two thin folds of skin also named as ‘small lips’, which surround and protect the vaginal opening.2
The labia (singular labium) minora are flattened lengthwise into folds located with the cleft between the labia majora. These folds extend along either side of the vestibule. They are composed of connective tissue that is richly supplied with blood vessels, causing a pinkish appearance. In the back, near the anus, the labia minora merge with the labia majora, while in the front they converge to form a hood-like covering around the clitoris. It is homologous with the ventral aspect of the penis in the male.
Clitoris
The clitoris is a small cylindrical, erectile organ measuring about 2.5 cm located above the vaginal opening. It consists of a glans, covered by the frenulum of prepuce. The glans is covered by squamous epithelium and is richly supplied with nerves. The clitoris corresponds to the penis. The clitoris is well supplied with nerve endings and is extremely sensitive. During the coitus it becomes erect and plays an important role in inducing the orgasm in the female. It is also highly vascular. An injury to this causes heavy bleeding and can be very painful.
Vestibule
Vestibule is a triangular space bounded by clitoris anteriorly, fourchette in the posterior and labia minora on the either sides.
Openings in the Vestibule
There are three openings into the vestibule.
Urethral opening: This lies just posterior to the clitoris about 1.5 cm below the pubic arch. The paraurethral ducts open either on the posterior wall of the urethral orifice or directly into the vestibule.
Vaginal opening: This is situated in the posterior end of the vestibule. In virgins and nulliparae, the opening is closed by the labia minora, but in parous, it may be exposed.
Opening of Bartholin's ducts: Bartholin's glands are situated in the superficial perineal pouch close to the posterior end of the vestibule bulb. Bartholin's glands are pea sized (about 0.5 cm) and yellowish white in color. The Bartholin's gland corresponds to the bulbourethral gland of male. During sexual excitement, these glands produce alkaline mucus, which helps in lubrication. Each gland consists of a duct, which measures about 2 cm and opens into the groove between the hymen and the labium minus. The duct is lined by columnar epithelium, but near its opening, by stratified squamous epithelium.
Vestibular Bulbs
Vestibular bulbs are elongated masses of erectile tissues situated below the mucous membrane of the vestibule. Each bulb lies on either side of the vaginal orifice in front of the Bartholin's gland. They are similar to the single bulb of the penis and the corpus spongiosum in the male.
Perineum
A stretch of hairless, sensitive skin that extends from the bottom of the vagina till the anus. During childbirth, there may be injury in the perineum due to stretching.
Blood and Nerve Supply of the Vulva
Blood Supply
The internal and external pudendal arteries supply the vulvar areas. The veins from plexuses drain into internal pudendal vein, vesical venous plexus and long saphenous vein.
Nerve Supply
Bilateral spinal somatic nerves supply the vulva. The vulva is supplied by the labial and perineal branches of the pudendal nerve (S2–S4).
INTERNAL GENITAL ORGANS
The internal genital organs in female include vagina, uterus, fallopian tubes and the ovaries (Fig. 1.3). The midsagittal section of the female pelvis showing relative position of the pelvic organs is shown in Figure 1.4.
Vagina
The vagina (Latin: sheath) is a muscular tube or passage, which forms a part of the female sex organs and connects the neck of the uterus (called the ‘cervix’) with the external genitals. The vagina, which is approximately 2½ to 4 inches long, has muscular walls, which are supplied with numerous blood vessels. The posterior wall is 9 cm long and the anterior wall is 7 cm. These walls become erect when a woman is aroused, as extra blood is pumped into these vessels. The birth canal is directed upward and backwards forming an angle of 45° with the horizontal in erect posture. The long axis of the vagina is almost parallel to the plane of the pelvic inlet and at right angles to that of the uterus. The diameter of the canal is about 2.5 cm, which is widest in the upper part and narrowest at its introitus.
Transverse folds, which are present in the vaginal walls of nulliparae allow the vagina to stretch and dilate during coitus and parturition. These folds are partly obliterated in women who have borne many children.4
Many women (perhaps all) have a certain sensitive spot, a cluster of tissue surrounding the urethra, which can be felt and stimulated through the anterior vaginal wall. This tissue (which is probably identical or at least connected with the system of urethral glands) first swells under intense stimulation and then contributes to a specially intense orgasmic release. Anatomically, this sensitive area is known as the ‘Gräfenberg spot (G-spot)‘, after Ernst Gräfenberg who first described it in 1950.5
Fornices
The fornices are the clefts formed at the top of vagina due to the projection of the cervix through the anterior vaginal wall. There are four fornices—one anterior, one posterior and two lateral. The posterior fornix is deeper and the anterior is shallow.
Relations
Anterior: The upper one-third is related with the base of the bladder, the lower two-thirds are related with the urethra, the lower half of which is firmly embedded with its wall.
Posterior: The lower third of the vagina is related to the perineal body, the middle third to the ampulla of the rectum and the upper third to the anterior wall of the pouch of Douglas.
Lateral walls: The upper one-third is related to the pelvic cellular tissue at the base of broad ligament in which the ureter and the uterine artery lie about 2 cm from the lateral fornices. The middle third is blended with the levator ani and the lower third is related with the bulbocavernosus muscles, vestibular bulbs and Bartholin's glands.
Structure of Vagina
The layers of vagina are:
- Mucous coat, which is lined by stratified squamous epithelium without any secretory gland.
- Submucosal layer of loose areolar vascular tissues.
- Muscular layer consisting of inner circular and outer longitudinal layers.
- Fibrous coat derived from endopelvic fascia, which is tough and highly vascular.
Vaginal Epithelium
The vaginal epithelium is stratified squamous from birth till 10 to 14 days, which will become thinner with two layers during prepuberty and postmenopause due to the effect of decreased estrogen hormone. After puberty till menopause, the epithelium consists of three layers; basal cells, intermediate cells and superficial cornified cells. The intermediate and superficial cells contain glycogen under the influence of estrogen. These cells become continuous with the cells that cover the vaginal portion of the cervix. The superficial cells exfoliate constantly and more, so in inflammatory or neoplastic condition, replacement of the cells occurs from the basal cells.
Secretion
Just prior to the menstruation or in mid-menstrual period, during pregnancy and sexual excitement, the glands of the cervix, uterus, transudation of the vaginal epithelium and Bartholin's glands produce secretions. Normally, there is a presence of Doderlein's bacilli, which changes glycogen in the exfoliated squamous cells to lactic acid and maintains the pH between 4.9 and 3.5. The vaginal secretion consists of tissue fluid, epithelial debris, some leukocytes, electrolytes, proteins and lactic acid.
Functions of Vagina
The vagina serves four main functions:
- It provides a passageway for the menstrual flow from the uterus to the outside.
- It serves as a receptacle for a man's penis and his ejaculated sperm, which then may move on through the cervix.
- It provides a passageway for the baby during birth from the uterus to the outside.
- The vagina cleanses itself with its own secretions. It also possesses a special protection against infection.
Hymen
Hymen is a mucous membrane and is usually circular or crescentic in virgins. It usually ruptures at first coitus. It is a thin membrane of connective tissue, which is situated at the opening of the vagina. This hymen covers the opening of the vagina from birth until it is ruptured during sexual or non-sexual activity. The tissue may also be ruptured by vaginal penetration, pelvic examination, injury or certain types of activities such as horseback riding or gymnastics. Similarly, the presence does not necessarily indicate a lack of prior sexual activity, as it is possible for light activity to not rupture it or for it to be surgically restored. During childbirth, the hymen gets lacerated, which later becomes cicatrized nodules of varying sizes called the ‘carunculae myrtiformes’.
Blood Supply, Lymph Drainage and Nerve Supply
Arterial supply: Cervicovaginal branch of uterine artery, vaginal artery (branch of internal iliac artery), middle rectal artery and internal pudendal artery anastomose to form two azygos arteries (anterior and posterior). These two azygos arteries supply blood to vagina.
Venous drainage: A venous plexus, situated in the muscular wall, drains into the internal iliac veins.
Lymph drainage: This is through the deep and superficial iliac glands.
Nerve supply: The vagina is supplied by sympathetic and parasympathetic fibers from the pelvic plexus. The lower part is supplied by the pudendal nerve.
Uterus
The uterus (Latin word for womb) is a major female hormone-responsive reproductive sex organ. The uterus is a hollow, muscular pear-shaped structure situated deep in the pelvis and well protected by the pelvic bones. It lies in the pelvic cavity behind the bladder and in front of the bowel.
Position
Under normal circumstances the uterus is both ‘anteflexed’ (pointing forward relative to the cervix) and ‘anteverted’ (tipped forward).
Measurements
The uterus is about 3 inches (7.6 cm) long, 5 cm wide at the fundus and its walls are about 1.25 cm thick. Its weight varies from 50 to 80 g.
Relations
- Anteriorly, there is the presence of uterovesical pouch and below the internal os, it is separated from the base of the bladder by loose areolar tissues.
- Posteriorly, it is covered with peritoneum and forms the anterior wall of the pouch of Douglas.
- Laterally, the double folds of peritoneum (Fig. 1.5) of the broad ligament are attached between which the uterine arteries run up. Mackenrodt's ligament extends from the internal os down to the supravaginal cervix and lateral vaginal wall. At the left side, about 1.5 cm away of internal os, there is the crossing of the uterine artery and the ureter.
Parts of Uterus
A female uterus can be divided anatomically into four parts: the corpus, cervix and the isthmus.
Corpus or body: This is further divided into fundus and the body. The fundus is the part, which lies above the openings of fallopian tubes.7
The body lies between the openings of the tubes and the isthmus, and is triangular in shape. The superolateral angles of the body of the uterus that project outwards from the junction of the fundus and body are called cornua.
Isthmus: The isthmus is a constricted part measuring about 0.5 cm situated between the body and the cervix. It is limited above by the anatomical internal os and below by the histological internal os (Aschoff).
Cervix: The word cervix in Latin means ‘neck’. The cervix (or neck of the uterus) is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall.
The portion projecting into the vagina is referred to as the portio vaginalis or ectocervix. On average, the ectocervix is 3 cm long and 2.5 cm wide. It has a convex, elliptical surface and is divided into anterior and posterior lips. The ectocervix's opening is called the external os. The size and shape of the external os and the ectocervix varies widely with age, hormonal state and whether the woman has had a vaginal birth. In women who have not had a vaginal birth, the external os appears as a small, circular opening. In women who have had a vaginal birth, the ectocervix appears bulkier and the external os appears wider, more slit-like and gaping.
The passageway between the external os and the uterine cavity is referred to as the endocervical canal. The endocervical canal terminates at the internal os, which is the opening of the cervix inside the uterine cavity. There are pockets in the lining of the cervix known as cervical crypts, which function to produce cervical fluid.
The epithelium of the cervix is varied. The ectocervix is composed of non-keratinized stratified squamous epithelium. The endocervix is composed of simple columnar epithelium.
During most of the menstrual cycle, the cervix remains firm like the tip of the nose and is positioned low and closed. However, as woman approaches ovulation, the cervix becomes softer, and rises and opens in response to the high levels of estrogen present at ovulation. These changes, accompanied by 8the production of fertile types of cervical mucus, support the survival and movement of sperm.
Functions of the cervix
- During menstruation the cervix stretches open slightly to allow the endometrium to be shed. This stretching is believed to be part of the cramping pain that many women experience.
- During childbirth, contractions of the uterus will dilate the cervix up to 10 cm in diameter to allow the child to pass through.
- Stimulation of the cervix leads to orgasm for some women. During orgasm, the cervix convulses and the external os dilates.
Cavity of the Uterus
The uterine cavity is triangular with the base above and the apex below. It measures about 3.5 cm in length. The cervical canal is fusiform and measures about 2.5 cm.
Structure
The layers of the uterine body from innermost to outermost are as follows.
Endometrium: The lining of the uterine cavity is called the ‘endometrium’ (Fig. 1.6). It consists of the functional endometrium and the basal endometrium from which the former arises. The endometrium consists of lamina propria and surface epithelium. This surface epithelium is made up of ciliated columnar epithelium. The lamina propria contains stromal cells, endometrial glands, blood vessels and nerves. The gland contains mucus-secreting non-ciliated columnar epithelium that penetrates stroma.
The endometrium builds a lining periodically, which is shed or reabsorbed, if no pregnancy occurs. Shedding of the functional endometrial lining in humans is responsible for menstrual bleeding throughout the fertile years of a female. During pregnancy, it is designed to provide a home and nutrition for the baby. Endometrium during pregnancy is called ‘decidua’.
Myometrium: The uterus mostly consists of thick bundle of smooth muscle known as ‘myometrium’. The myometrium allows the uterus to expand as the baby grows. During pregnancy, three layers can be identified in myometrium, outer longitudinal layer, middle interlacing layer and inner circular layer.
These muscles contract during labor in order to push the baby out of the birth canal.
Perimetrium: The serous coat that surrounds the uterus except on the lateral border is called the ‘perimetrium’. The job of the perimetrium is to protect the other linings of the uterus. Various ligaments help to keep the perimetrium in place inside the uterus.
Secretions
A little amount of watery substance is secreted by the endometrium. The cervical glands secrete alkaline mucus with pH 7.8. This mucus is rich in fructose, glycoprotein and mucopolysaccharides. It also contains sodium chloride. Fructose is nutrition for the spermatozoa. With the help of estrogenic effect, glycoprotein facilitates the sperm ascent. Cervical mucus contributes in the formation of mucus plug to close the cervical canal during pregnancy.
Functions of the Uterus
The uterus provides structural integrity and support to the bladder, bowel, pelvic bones and organs. The uterus helps to separate and keep the bladder in its natural position above the pubic bone and the bowel in its natural configuration behind the uterus. The uterus is essential in sexual response by directing blood flow to the pelvis and to the external genitalia including the ovaries, vagina, labia and clitoris. The uterus is needed for uterine orgasm to occur.
The reproductive function of the uterus is to accept a fertilized ovum, which passes through the uterotubal junction from the fallopian tube. It then becomes implanted into the endometrium and derives nourishment from blood vessels, which develop exclusively for this purpose. The fertilized ovum becomes an embryo, develops into a fetus and gestates until the childbirth.
Blood Supply, Lymph Drainage and Nerve Supply
Arterial supply: Blood is supplied by uterine arteries, branches of the internal iliac arteries. The uterine arteries pass up the lateral aspects of the uterus between the two layers of the broad ligaments. These arteries also supply the fallopian tubes and join with the ovarian arteries to supply the ovaries.
Venous drainage: The veins follow the same route as the arteries and eventually drain into the internal iliac veins.
Lymph drainage: Deep and superficial lymph vessels drain lymph from the uterus and fallopian tubes to the aortic lymph nodes and group of nodes associated with the iliac blood vessels.
Nerve supply: The parasympathetic nerves supplying the uterus and the uterine tubes consist of fibers from S2 to S4 and ends in the ganglia of Frankenhauser that lies on the either sides of the cervix. The sympathetic nerves supplying the uterus consist of the fibers from T10 to L1 spinal segments.
Supporting Structures
The uterus is primarily supported by the pelvic diaphragm, perineal body and the urogenital diaphragm. Secondarily, it is supported by ligaments and the peritoneum (broad ligament of uterus).
Major Ligaments
Major ligaments are held in place by several peritoneal ligaments, of which the most important (there are two of each) are given in Table 1.1.10
Other ligaments near the uterus, i.e. the broad ligament, the round ligament and the suspensory ligament of the ovary, the infundibulopelvic ligament have no role in the support of the uterus.
Fallopian Tubes
The fallopian tubes (named after the 16th century anatomist Fallopius) are also called the ‘oviducts’ or ‘uterine tubes’. There are two fallopian tubes on either side of the uterus. They extend out from the uterus, like arms reaching for the ovaries, which are positioned near them. Each of these tubes is roughly 10 cm long and ranges in width from about 1 inch at the end next to the ovary to the diameter of a strand of thin spaghetti. The width varies at different parts along the length, being more towards the ovarian side and thinner, but more muscular towards the uterine side. Its widest part, the ampulla lies next to the fimbria and its importance lies in the fact that fertilization of the ovum by the sperm usually occurs in this region.
Each tube has two openings. One opening connects to the uterus. The other opening is larger, wider and has a number of finger-like projections all around it called the ‘fimbriae’. The fimbriae lie near the ovary of the same side and picks up the ovum at the time it is released from the ovary (ovulation). It is the fimbria that each month urges an egg to exit the ovary and begin its trip towards the uterus. Microscopic hairs called ‘cilia’ line the inner side of the tube and help in propelling the ovum towards the uterus.
Parts of Fallopian Tubes
There are four parts (Fig. 1.7), from medial to lateral they are:
- Intramural or interstitial lying in the uterine wall, which measures 1.25 cm in length and 1 mm in diameter.
- Isthmus almost straight and measures about 2.5 cm long and 2.5 mm in diameter.
- Ampulla—tortuous part, which is 5 cm long and is the widest part where most of the time fertilization takes place.
- Infundibulum, which measures 1.25 cm in length and 6 mm in diameter.
The beating projections, along with muscle contractions, force the ovum down into the funnel's small end, which opens into the uterus. Inside the tube, there are innumerable hair-like growths called cilia (singular: cilium) whose movements, together with muscular contractions of the tubal wall, sweep the egg towards the uterus. After sexual intercourse, sperm swim up into this funnel from the uterus.
The lining of the tube and its secretions sustain both the egg and the sperm, encouraging fertilization and nourishing the egg until it reaches the uterus.
Structure of Fallopian Tube
Fallopian tube consists of three layers:
- Serous: This layer consists of peritoneum on all sides except along the attachment of mesosalpinx.
- Muscular layer: This layer is arranged in two layers, outer longitudinal and inner circular layer.
- Mucous membrane: It is a longitudinal folds lined by columnar epithelium, partly ciliated, others secretary non-ciliated and ‘peg cells’. Below the epithelium is the delicate vascular reticulum of connective tissue. During the menstrual cycle, there are changes in this tubal epithelium.
Functions
The functions of the uterine tubes are as follows:
- Transport of the gametes.
- Facilitates the fertilization.
- Survival of zygote through its secretion.
Blood Supply, Lymph Drainage and Nerve Supply
Blood supply: Arterial supply is from the uterine and ovarian arteries. Venous drainage is through the pampiniform plexus into the ovarian veins.
Lymph drainage: Deep and superficial lymph vessels drain lymph from the uterus and fallopian tubes to the aortic lymph nodes and group of nodes associated with the iliac blood vessels.
Nerve supply: The nerve supply is derived from the uterine and ovarian nerves.
Ovaries
The ovaries are a pair of oval or almond-shaped glands, which lie on either side of the uterus and just below the opening to the fallopian tubes. They are pinkish-white in color and is 3 cm in length, 2 cm in breadth and 1 cm in width approximately. The ovary is located in the lateral wall of the pelvis in a region called the ovarian fossa. The fossa usually lies beneath the external iliac artery in front of the ureter and the internal iliac artery. They are not attached to the fallopian tubes, but to the outer layer of the uterus via the ovarian ligaments.
Each ovary has an outer thick lining called the ‘cortex’ and an inner part called the ‘medulla’. Ovaries in females are homologous to testes in males, in that they are both gonads and endocrine glands.
Ovarian Ligaments
In human, the paired ovaries lie within the pelvic cavity on either side of the uterus to which they are attached via a fibrous cord called the ovarian ligament. The ovaries are uncovered in the peritoneal cavity, but are tethered to the body wall via the suspensory ligament of the ovary. The part of the broad ligament of the uterus that covers the ovary is known as the mesovarium. Thus, the ovary is the only organ in human body, which is totally invaginated into the peritoneum, making it the only interperitoneal organ (not to be confused with intraperitoneal).
Structure
The surface of the ovaries is covered with epithelial tissue. Beneath the ovarian epithelium there are thousands of microscopic structures called ovarian follicles (Fig. 1.8), which are embedded in a connective tissue matrix known as ‘stroma’.12
The follicles contain the ova and after puberty they are present in varying stages of development.
The section of the ovary in a newly born child shows the following:
- The outermost layer is called the germinal epithelium.
- The tunica albuginea covers the cortex.
- The ovarian cortex consists of ovarian follicles and stroma in between them. Follicles include the cumulus oophorus, membrana granulosa (the granulosa cells inside it), corona radiata, zona pellucida and primary oocyte. The zona pellucida, theca of follicle, antrum and liquor folliculi are also contained in the follicle. Also, in the cortex is the corpus luteum derived from the follicles.
- The innermost layer is the ovarian medulla. It can be hard to distinguish between the cortex and medulla, but follicles are usually not found in the medulla.
Functions
The ovaries have two primary functions:
- They produce and store the female gametes (ova) that are contained in small spheres called primary follicles (primordial follicles). A girl baby is born with about 60,000 of these cells, which are contained in sac-like depressions in the ovaries. During the reproductive life, i.e. from puberty to menopause, the cortex contains numerous ‘graafian follicles’ at different stages of development. Every month a graafian follicle in one of the ovaries matures and releases an ovum. This phenomenon is called ‘ovulation’. During woman's lifetime, only about 400 follicles reach maturity. A woman attains menopause when the number of follicles 13in her ovaries decreases below a critical level. The ovaries shrink in size and become whitish in color. They also secrete lesser amounts of estrogen and progesterone.
- They also serve as endocrine glands by releasing the female sex hormones, the estrogens (primarily estradiol) and progesterone. Estrogen is responsible for the appearance of secondary sex characteristics of females at puberty and for the maturation and maintenance of the reproductive organs. Progesterone functions with estrogen by promoting cyclic changes in the endometrium (it prepares the endometrium for pregnancy), as well as by helping to maintain the endometrium in a healthy state during pregnancy.
Blood Supply
Arterial supply: This is by ovarian arteries, which branch from the abdominal aorta.
Venous drainage: The pampiniform plexus join to form the ovarian veins, which drain into inferior vena cava in the right side and the left renal vein in the left side.
Nerve supply: The ovaries are supplied by parasympathetic nerves from the sacral and sympathetic nerves from the lumbar outflow.
MENSTRUATION
Females at reproductive age experience cycles of hormonal activity that repeat at about 1-month intervals (menstru means ‘monthly’, hence the term menstrual cycle). With every cycle, a woman's body prepares for a potential pregnancy, whether or not that is the woman's intention.
The term menstruation refers to the periodic shedding of uterine lining. Menstruation is the periodic discharge of blood, mucus and epithelial cells from the uterus. It usually occurs at monthly intervals throughout the reproductive period, except during pregnancy and lactation, when it is usually suppressed.
There are four major hormones involved in the menstrual cycle:
- Follicle-stimulating hormone (FSH).
- Luteinizing hormone (LH).
- Estrogen.
- Progesterone.
The menstrual cycle is controlled by the cyclic activity of the FSH and LH from the anterior pituitary and progesterone and estrogen from the ovaries. In other words, FSH acts upon the ovary to stimulate the maturation of a follicle and during this development, the follicular cells secrete increasing amounts of estrogen.
Menstrual Cycle
The average menstrual cycle takes about 28 days and occurs in phases—the menstrual phase, the follicular/proliferative phase (ov-ulation) and the luteal/secretory phase.
Menstrual Phase
Days 1 to 5—this is known as the menstrual phase. A lack of signal from a fertilized egg influences the drop in estrogen and progesterone production. A drop in progesterone results in the sloughing off of the thick endometrial lining, which is the menstrual flow. This occurs for 3 to 5 days.
Follicular/Proliferative Phase
Days 6 to 14—this is known as the proliferative phase. A drop in progesterone and estrogen stimulates the release of FSH from the 14anterior pituitary. FSH stimulates the maturation of an ovum with graafian follicle. Near the end of this phase, the release of LH increases causing a sudden burst like release of the ovum, which is known as ovulation.
Luteal/Secretory Phase
Days 15 to 28—this is known as the secretory phase. High levels of LH cause the empty graafian follicle to develop into the corpus luteum. The corpus luteum releases progesterone, which increases the endometrial blood supply, endometrial arrival of the fertilized egg. If the egg is fertilized, the embryo produces human chorionic gonadotropin (hCG). The hCG signals the corpus luteum to continue to supply progesterone to maintain the uterine lining. Continuous levels of progesterone prevent the release of FSH and ovulation ceases (Fig. 1.9).
Menopause
Menopause is the cessation of menstruation. This usually occurs in women between the ages of 45 and 50. Some women may reach menopause before the age of 45 and some after the age of 50. In common use, menopause generally means cessation of regular menstruation. Ovulation may occur sporadically or may cease abruptly.
Periods may end suddenly, may become scanty or irregular or may be intermittently heavy before ceasing altogether. Markedly diminished ovarian activity, i.e. significantly decreased estrogen production and cessation of ovulation causes menopause.
From Menarche to Menopause
While we tend to think that the female reproductive system remains dormant until a girl is somewhere between 10 and 14 years of age, her sex hormones actually begin to function in the first few months after conception. In fact, gonadotropin-releasing hormone (GnRH), FSH and LH start to circulate in the fetus shortly after the ovaries develop. The levels of FSH and LH in the developing baby are very similar to those found in postmenopausal women.
After a rather turbulent first year during which the newborn baby's system makes the final transition from reliance on her mother's hormones to her own, the reproductive system enters a dormant phase. FSH and LH levels fall to their lowest levels, by the time girls are about 2 years old and then start to rise slowly again between the ages of 4 and 10.
At the age of 6, circulating levels of the male hormone androgen starts to increase. This rise in androgen causes the development of hair under the arms and in the pubic area. Meanwhile, estrogen stimulates breast development and the sex hormones and glands begin to gear up for menarche, the onset of menses. However, at some point between the ages of 8 and 14, LH is secreted at a rate 2 to 4 times higher at night than during the day. This causes estrogen and FSH levels to rise and puberty is underway.
Puberty is traditionally defined by three events—development of the breasts, appearance of pubic hair and the beginning of menstruation. It is important to remember that the time it takes for these changes to occur is extremely variable. While one girl may appear to be fully developed by age 11, her friend next door may not reach puberty until age 14 or 15. Both schedules are considered ‘normal’.
After puberty, the reproductive system continues its regular cycles until around age 40 after which the perimenopausal years begin. At this point, ovarian function and the monthly menstrual cycle tend to become less regular and many of the effects of estrogen in the body start to wane. Menopause (the cessation of the monthly cycle and the end of reproductive capacity) usually occurs between the ages of 45 and 55 in American women, the average age is about 51.
During fetal life, there are about 6 to 7 million eggs. From this time, no new eggs are produced. The vast majority of the eggs within the ovaries steadily die, until they are depleted at menopause. At birth, there are approximately 1 million eggs and by the time of puberty, only about 300,000 remain. Of these, 300 to 400 will be ovulated during a woman's reproductive lifetime. The eggs continue to degenerate during pregnancy, with the use of birth control pills and in the presence or absence of regular menstrual cycles.
PELVIC FLOOR
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus and associated connective tissue, which span the area underneath the pelvis. The pelvic floor separates the pelvic cavity above from the perineal region (including perineum) below.
Functions
- Pelvic floor plays an important role during the coitus.
- During childbirth, the pelvic floor influences the movements of the fetus through the birth canal and relaxes to allow delivery of the baby.
Muscle Layers
The muscles of the pelvic floor are arranged in two layers, the superficial layer and the deep layer.
Superficial Muscle Layer
The superficial fascia is very thick, areolar in texture and contains much fat in its meshes. This layer is composed of five muscles, which are as follows.
Sphincter ani externus (external sphincter ani): This is a flat plane of muscular fibers, elliptical in shape. It measures about 8 to 10 cm in length, from its anterior to its posterior extremity and is about 2.5 cm broad opposite the anus. It consists of two strata, superficial and deep. The superficial constituting the main portion of the muscle arises from a narrow tendinous band, the anococcygeal raphé, which stretches from the tip of the coccyx to the posterior margin of the anus, it forms two flattened planes of muscular tissue, which encircle the anus and meet in front to be inserted into the central tendinous point of the perineum. The deeper portion forms a complete sphincter to the anal canal. Its fibers surround the canal, closely applied to the sphincter ani internus and in front blend with the other muscles at the central point of the perineum. Posteriorly, they are continuous with those of the opposite side behind the anal canal.
Nerve supply: A branch from the fourth sacral and twigs from the inferior hemorrhoidal branch of the pudendal supply the muscle.
The action of this muscle is as follows:
- It keeps the anal canal and orifice closed
- It can be put into under the influence of the will, so as more firmly to occlude the anus, in expiratory efforts unconnected with defecation
- Taking its fixed point at the coccyx, it helps to fix the central point of the perineum, so that the bulbocavernosus may act from this fixed point.
Sphincter ani internus (internal sphincter ani): It is a muscular ring, which surrounds about 2.5 cm of the anal canal. It is about 5 mm thick and is formed by involuntary circular fibers of the intestine. Its lower border is about 6 mm from the orifice of the anus. Its action is entirely involuntary. It helps the sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces (Fig. 1.10).
Superficial transverse perineal muscle: This is a narrow muscular slip, which arises by a small tendon from the inner and forepart of the tuberosity of the ischium.
This is inserted into the central tendinous point of the perineum, joining in this situation with the muscle of the opposite side, the sphincter ani externus behind and the bulbocavernosus in front. The simultaneous contraction of the two muscles serves to fix the central tendinous point of the perineum.
Bulbocavernosus (sphincter vaginae): This surrounds the orifice of the vagina. It covers the lateral parts of the vestibular bulbs and is attached posteriorly to the central tendinous point of the perineum, where it blends with the sphincter ani externus. Its fibers pass forward on either side of the vagina to be inserted into the corpora cavernosa clitoridis, a fasciculus crossing over the body of the organ so as to compress the deep dorsal vein. The bulbocavernosus diminishes the orifice of the vagina. The anterior fibers contribute to the erection of the clitoris, as they are inserted into and are continuous with the fascia of the clitoris, compressing the deep dorsal vein during the contraction of the muscle.
Ischiocavernosus (erector clitoridis): This is smaller than the corresponding muscle in the male. It covers the unattached surface of the crus clitoridis. It is an elongated muscle, situated on the side of the lateral boundary of the perineum. It arises by tendinous and fleshy fibers from the inner surface of the tuberosity of the ischium, behind the crus clitoridis, from the surface of the crus and from the adjacent portion of the ramus of the ischium. The ischiocavernosus compresses the crus clitoridis and retards the return of blood through the veins and thus serves to maintain the organ erect.
Sphincter urethral membrane (constrictor urethrae): This like the corresponding muscle on the male, consists of external and internal fibers. The external fibers arise on either side from the margin of the inferior ramus of the pubis. They are directed across the pubic arch in front of the urethra and pass around it to blend with the muscular fibers of the opposite side, between the urethra and vagina. The innermost fibers encircle the lower end of the urethra.
Deep Muscle Layer
The deep muscle layer consists of levator ani muscles. The levator ani is a broad, thin muscle, situated on the side of the pelvis. It is attached to the inner surface of the side of the lesser pelvis and unites with its fellow of the opposite side to form the greater part of the floor of the pelvic cavity (Fig. 1.11). It supports the viscera in pelvic cavity and surrounds the various structures, which pass through it. The right and left levator ani lie almost horizontally in the floor of the pelvis, separated by a narrow gap that transmits the urethra, vagina and anal canal. The levator ani is usually considered in three parts: pubococcygeus, puborectalis and iliococcygeus. In combination with the coccygeus muscle, it forms the pelvic diaphragm.
The pubococcygeus arises from the back of the pubis and from the anterior part of the obturator fascia and is directed backward almost horizontally along the side of the anal canal towards the coccyx and sacrum to which it finds attachment. Between the termination of the vertebral column and the anus, the two pubococcygei muscles come together and form a thick, fibromuscular layer lying on the raphé (anococcygeal raphé) formed by the iliococcygei. The greater part of this muscle is inserted into the coccyx and into the last one or two pieces of the sacrum. The fibers, which form a sling for the rectum, are named the ‘puborectalis or sphincter’ recti. They arise from the lower part of the symphysis pubis and from the superior fascia of the urogenital diaphragm.18
They meet with the corresponding fibers of the opposite side around the lower part of the rectum and form a strong sling. Relaxation reduces the angle between rectum and anus, allowing defecation in conjunction with relaxation of the internal and external sphincters.
The iliococcygeus arises from the ischial spine and from the posterior part of the tendinous arch of the obturator fascia and is attached to the coccyx and anococcygeal raphé, it is usually thin and may fail entirely or largely replaced by fibrous tissue. It is part of the levator ani group of muscles. Puborectalis is part of the levator ani group of muscles.
Nerve supply: The levator ani muscles are mostly innervated by the pudendal nerve, perineal nerve and inferior rectal nerve in concert. In addition, sacral spinal nerves (S3, S4) innervate the muscles directly as well. Sometimes, the inferior rectal nerve innervates the levator ani muscles independently of the pudendal nerve.
ANATOMY OF OTHER ORGANS RELATED TO GYNECOLOGY
Urinary Bladder
The urinary bladder is a musculomembranous sac, whose shape is affected by factors including the person's age and sex as well as the volume of urine it contains at the time. It has a considerable power of distension. Its capacity is about 450 mL, but can retain as much as 3 to 4 L of urine. When it distends it gives ovoid shape. The bladder is located on the floor of the pelvic cavity, in front of the uterus and upper vagina. The bladder consists of an apex, superior surface, base, two inferolateral surfaces and neck, which is continuous with the urethra.
Relations
The superior surface is related with the peritoneum of the uterovesical pouch. The base is infront of the supravaginal cervix and the anterior fornix. The ureters enter the bladder on its lateral angles. The inferolateral surfaces 19are related with the space of Retzius. The neck lies over the superior layer of the urogenital diaphragm.
Structure of Bladder
The bladder consists of four layers (Fig. 1.12):
- Outer surfaces of the bladder: The upper and side surfaces of the bladder are covered by peritoneum. This is the serous membrane of the abdominal cavity, sometimes referred to as ‘serosa’. This transparent membrane consists of mesothelium and elastic fibrous connective tissue. It is ‘visceral peritoneum’ that covers the bladder and other abdominal organs, while ‘parietal peritoneum’ lines the abdomen walls.
- Muscular: The detrusor muscle is the muscle of the urinary bladder wall. It consists of three layers of smooth (involuntary) muscle fibers. Most of the fibers of the external layer are arranged longitudinally. Those of the middle layer are mostly arranged in a circular configuration and the muscle fibers of the internal layer have a longitudinal arrangement.
- Submucous: This is a thin layer of areolar tissue that loosely connects the muscular layer with the mucous layer, being itself intimately attached to the mucous layer.
- Mucus: The innermost layer of the wall of the urinary bladder is the mucous membrane, which contains transitional epithelium tissue that can stretch. The stretching ability of this tissue allows variability of the bladder when it is filled and emptied several times per day. Because it is only loosely attached to the muscular layer, the mucosa falls into many folds known as ‘rugae’ when the bladder is empty or is only filled to a small extent.
The features observable inside the bladder are the ureter orifices, the trigone and the internal orifice of the urethra. The trigone is a smooth triangular region between the openings of the two ureters and the urethra.
This area has a pale color than the rest of the interior of the bladder and does not present at any rugae even when the bladder is empty—because this area is more tightly bound to its outer layer of bladder tissue.
The internal urethral sphincter is a sphincter (circular) muscle located at the neck of the bladder and formed by a thickening of the detrusor muscle. It closes the urethra when the bladder has emptied.
Functions of the Bladder
- The purpose of the urinary bladder is to store urine prior to elimination of the urine from the body.
- The bladder also expels urine into the urethra by a process called micturition (also known as urination). Micturition involves the actions of both voluntary and involuntary muscles. Lack of voluntary control over this process is referred to as incontinence.
Pelvic Ureters
The ureters are the two tubes, which convey the urine from the kidneys to the urinary bladder. It is usually placed on a level with the spinous process of the first lumbar vertebra. The ureter proper measures from 25 to 30 cm in length and is a thick-walled narrow cylindrical tube, which is directly continuous near the lower end of the kidney with the tapering extremity of the renal pelvis.
Course and Relations
In female, the ureter forms, as it lies in relation to the wall of the pelvis, the posterior boundary of a shallow depression named the ovarian fossa in which the ovary is situated. It then runs medialward and forward on the lateral aspect of the cervix uteri and upper part of the vagina to reach the fundus of the bladder. In this part of its course, it is accompanied for about 2.5 cm by the uterine artery, which then crosses in front of the ureter and ascends between the two layers of the broad ligament. The ureter is distant about 2 cm from the side of the cervix of the uterus. The ureter is sometimes duplicated on one or both sides and the two tubes may remain distinct as far as the fundus of the bladder. On rare occasions, they open separately into the bladder cavity.
Structure
The ureter is composed of three coats: fibrous, muscular and mucous coats (Fig. 1.13).
Fibrous coat (tunica adventitia): This is continuous at one end with the fibrous tunic of the kidney on the floor of the sinus, while at the other it is lost in the fibrous structure of the bladder.
Muscular coat (tunica muscularis): It consists of two layers, longitudinal and circular. The longitudinal fibers become lost upon the sides of the papilla at the extremities of the calyces.
The circular fibers may be traced surrounding the medullary substance in the same situation. In the ureter proper the muscular fibers are very distinct and are arranged in three layers: an external longitudinal, middle circular and an internal, less distinct than the other two, but having a general longitudinal direction.
Mucous coat (tunica mucosa): This is smooth and presents a few longitudinal folds, which become effaced by distension. It is continuous with the mucous membrane of the bladder below, while it is prolonged over the papilla of the kidney above. Its epithelium is of a transitional character and resembles that found in the bladder. It consists of several layers of cells of which the innermost cells are in contact with the urine are somewhat flattened, with concavities on their deep surfaces into which the rounded ends of the cells of the second layer fit. The intermediate cells more or less resemble columnar epithelium and are pear shaped with rounded internal extremities, which fit into the concavities of the cells of the first layer, and narrow external extremities, which are wedged in between the cells of the third layer. The external or third layer consists of conical or oval cells varying in number in different parts and presenting processes, which extend down into the basement membrane. Beneath the epithelium and separating it from the muscular coats, is a dense layer of fibrous tissue containing many elastic fibers.
Functions of the Ureters
- The ureters transport urine from the renal pelvis of the kidney to the bladder.
- Both the ureters pass beneath the urinary bladder, which results in the bladder compressing the ureters and hence preventing backflow of urine when pressure in the bladder is high during urination.
Blood Supply and Nerve Supply
Blood supply: The arteries supplying the ureter are branches from the renal, internal spermatic, hypogastric and inferior vesical.
Venous drainage: It corresponds to the arterial supply.
Nerve supply: The nerves are derived from the inferior mesenteric, spermatic and pelvic plexuses.
Urethra
The female urethra is a narrow membranous canal, about 4 cm long, extending from the internal to the external urethral orifice. It is placed behind the symphysis pubis, imbedded in the anterior wall of the vagina and its direction is obliquely downward and forward. It is slightly curved with the concavity directed forward. Its diameter when undilated is about 6 mm. It perforates the fascia of the urogenital diaphragm. The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control [i.e. it is innervated by the somatic nervous system (SNS)]. Its external orifice is situated directly in front of the vaginal opening and about 2.5 cm behind the glans clitoridis. The lining membrane is thrown into longitudinal folds one of which is placed along the floor of the canal is termed the urethral crest. Many small urethral glands open into the urethra.
Structure
Muscular coat: This is continuous with that of the bladder. It extends the whole length of the tube and consists of circular fibers. In addition to this, between the superior and inferior fascia of the urogenital diaphragm, the female urethra is surrounded by the sphincter urethral membrane.
Erectile layer: It is a thin layer of spongy erectile tissue, containing a plexus of large veins, intermixed with bundles of unstriped muscular fibers, lies immediately beneath the mucous coat.
Mucous coat: It is pale and is continuous externally with that of the vulva and internally with that of the bladder. It is lined by stratified squamous epithelium, which becomes transitional near the bladder. Its external orifice is surrounded by a few mucous follicles.
Functions
The urethra is the passageway through which urine is discharged from the body.
Physiology of Micturition
Micturition is fundamentally a spinobulbospinal reflex facilitated and inhibited by higher brain centers such as the pontine micturition center and like defecation, subject to voluntary facilitation and inhibition.
In healthy individuals, the lower urinary tract has two discrete phases of activity—the storage (or guarding) phase, when urine is stored in the bladder and the voiding phase, when urine is released through the urethra.
Storage phase
The urine comes into the bladder drop by drop at the rate of 0.5 to 5 mL/minute through the ureteric openings. When the bladder fills, the walls of the bladder stretches to maintain a constant muscle tone. The intravesical pressure is raised to remain almost steady at the level of 10 cm.
The muscles controlling micturition are controlled by the autonomic and somatic nervous systems. During the storage phase, the internal urethral sphincter remains tense and the detrusor muscle relaxed by sympathetic stimulation. During micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. The external urethral sphincter (sphincter urethrae) is under somatic control and is consciously relaxed during micturition.
It is commonly believed that in infants, voiding occurs involuntarily (as a reflex). However, the practice of elimination communication (EC), suggests otherwise. The ability to voluntarily inhibit the micturition develops by the age of 2 to 3 years, as control at higher levels of the central nervous system develops. In adult, the volume of urine in the bladder that normally initiates a reflex contraction is about 300 to 400 mL.
Voiding phase
Voiding begins when a voluntary signal is sent from the brain to begin urination and continues until the bladder is empty. Nerve supply of the vesicourethral unit is shown in Figure 1.14.
Bladder afferent signals ascend the spinal cord to the periaqueductal gray, where they project both to the pontine micturition center and to the cerebrum. At a certain level of afferent activity, the conscious urge to void and becomes difficult to ignore. Once the voluntary signal to begin voiding has been issued, neurons in pontine micturition center fire maximally causing excitation of sacral preganglionic neurons.23
The firing of these neurons causes the wall of the bladder to contract. As a result a sudden, sharp rise in intravesical pressure occurs. The pontine micturition center also causes inhibition of Onuf's nucleus, resulting in relaxation of the external urinary sphincter. When the external urinary sphincter is relaxed, urine flows from the urinary bladder when the pressure is great enough to force urine to flow through the urethra. The micturition reflex normally produces a series of contractions of the urinary bladder.
The flow of urine through the urethra has an overall excitatory role in micturition, which helps to sustain voiding until the bladder is empty. After urination, the female urethra empties by gravity. Urine remaining in the urethra of the male is expelled by several contractions of the bulbospongiosus muscle.
Rectum
At the level of the middle sacrum, the sigmoid colon loses its mesentery and gradually becomes the rectum. At the upper limit of the pelvic diaphragm it ends in the anal canal. It is about 15 cm long and widens below as the ampulla, which is very distensible. The rectum follows the sacrococcygeal curve. At the anorectal junction, the gut curves backward and its concavity is held by the puborectal sling, which can be palpated per anum. The rectum presents three or more lateral curvatures, which correspond to transverse rectal folds in the interior of the gut. It has neither 24mesentery nor haustra and it has an almost complete outer longitudinal muscular coat rather than taenia.
Relations
In the upper third of the rectum, its front and sides are covered by peritoneum; in its middle third, the front only; its lower third is devoid of peritoneum. The rectovesical and rectouterine pouches descend within about 7 to 8 cm and 5 to 6 cm, respectively of the anus. Below the pouches, condensations of parietal pelvic fascia are found and the rectum is surrounded by visceral pelvic fascia from the superior fascia of the pelvic diaphragm. Anteriorly, the rectum is related to coils of small intestine in the rectouterine pouch above and to the back of the vagina below. Laterally, the rectum is related to the ileum or sigmoid colon. Posteriorly, the rectum is related to the sacrum, coccyx and pelvic diaphragm.
Structure
Rectum consists of three layers—muscular layer, submucous layer and mucous membrane. Rectum is surrounded by rectal fascia. Muscles of rectum consist of outer longitudinal and inner circular fibers. Submucosal layer is loose and contains venous plexuses. Mucous membrane is lined by columnar epithelium.
The median section of rectum and anal canal is given in Figure 1.15.
Anal Canal
The anal canal is the terminal part of the large intestine. It is situated between the rectum and anus below the level of the pelvic diaphragm. It lies in the anal triangle of perineum in between the right and left ischiorectal fossa. It is approximately 2.5 to 4 cm long, extending from the anorectal junction to the anus and is directed downwards and backwards. It is surrounded by inner involuntary and outer voluntary sphincters, which keep the lumen closed in the form of an anteroposterior slit. It is differentiated from the rectum by the transition of the internal surface from endodermal to skin-like ectodermal tissue.
Relations
The anal canal is surrounded by the levatores ani the anal canal passes through the pelvic diaphragm and the anorectal junction is held forward by the puborectal sling. Below the pelvic diaphragm, the anal canal is surrounded by the sphincter ani externus and the ischiorectal fossa is situated laterally.
Anal Sphincters
Internal anal sphincter: It is involuntary in nature, which is formed by thickening of circular layer of the upper two third of the anal canal.
External anal sphincter: It is voluntary in nature and surrounds the entire length of the canal. It consists of three parts:
The subcutaneous part surrounds the lowermost portion of the canal.
The superficial part, situated above the subcutaneous division, is attached to the perineal body and coccyx.
The deep part, more or less continuous with the superficial division, surrounds the uppermost portion of the canal and is associated with the puborectalis posteriorly.
Epithelial Linings
The upper two third is lined by columnar epithelium, but the lower third is lined by stratified squamous epithelium.25
Blood Supply, Nerve Supply and Lymph Drainage
Blood supply: The rectum and anal canal are supplied by the superior rectal artery (the continuation of the inferior mesenteric artery) with assistance from the middle and inferior rectal arteries and by the median sacral artery. The submucosal venous plexus above the pectinate line drains into the superior rectal veins (portal system). The submucosal plexus below the pectinate line drains into the inferior rectal veins, which may become varicose resulting in hemorrhoids or piles.
Nerve supply: Parasympathetic fibers supply the smooth muscle including the internal sphincter. Sympathetic fibers are mainly vasomotor. Somatic motor fibers supply the external sphincter. Sensory fibers are concerned with the reflex control of the sphincters and with pain. The anal canal is very sensitive below the pectinate line, so that external hemorrhoids may be very painful.
Lymphatics: The lymphatics from the rectum and upper third of the anal canal drain into internal iliac and preaortic nodes, while the lower third of the anal canal drains into the superficial inguinal nodes.
Pelvic Peritoneum
The pelvis is covered internally with a thin, translucent, serous peritoneal membrane, continuous with that of the abdominal cavity. 26It is described as either parietal or visceral, depending on the underlying structures. The vesical peritoneum anteriorly is hardly noticeable unless the bladder is filled and when it remains as extraperitoneal organ covered by parietal peritoneum. Thus, the inferior most portion of the vesicouterine pouch represents the anterior junction of the parietal and visceral parts. As the membrane drapes upward anteriorly over the uterus, round ligaments and uterine tubes, it invests these organs with visceral peritoneum. Posteriorly, these organs and their ligamentous structures continue to be covered by visceral peritoneum as it drapes abruptly, medially and continues downward to the uterine cervix. There it becomes parietal peritoneum, covering the sacrouterine ligaments, which form as a condensation of endopelvic fascia posterolaterally to the cervix and between them. As it reaches the rectum, the visceral peritoneum is reflected upward and circumferentially covering the upper half of the rectum and sigmoid colon, and forming their respective mesenteries posterolaterally. The ‘broad ligament’ actually a mesentery, adjacent to the uterus laterally on either side, is comprised of anterior and posterior parietal peritoneum, with vessels between them. Only the ovaries remain without peritoneum. The small mesentery for the uterine tube is called the mesosalpinx and that for the ovary, the mesovarium. During pregnancy, the peritoneal sac is greatly distorted as the body and fundus grow and distend upward carrying the adnexa and adjacent structures with them.
Female Perineum
The perineum in the female is much like that of the male (Fig. 1.16). It has a central point, which converge the external sphincter ani from behind the superficial transverse perinei muscles from each side and the bulbocavernosus muscles from the front. The ischiocavernosus muscles lie along the rami of the pubes. These superficial muscles are reinforced by the deep transverse perinei muscle, which comes from the ramus of the ischium on the side to insert by its anterior fibers around the urethra (compressor urethra), its middle fibers into the vaginal wall and its posterior fibers at the central point of the perineum.
Also, the levator ani muscle inserts into the lower end of the vagina anteriorly then into the central point of the perineum, next into the lower end of the rectum and finally into the coccyx. The deep layer of the superficial fascia (Colles’ fascia) and the triangular ligament being pierced by the vagina are not so marked as in the male between them lies the ischiocavernosus, bulbocavernosus and superficial transverse perinei muscles.
Ligaments
The ligaments of the uterus are eight in number—one anterior, one posterior, two lateral or broad, two uterosacral and two round ligaments.
One Anterior Ligament
The anterior ligament consists of the vesicouterine fold of peritoneum, which is reflected to the bladder from the front of the uterus, at the junction of the cervix and body.
One Posterior Ligament
The posterior ligament consists of the rectovaginal fold of peritoneum, which is reflected from the back of the posterior fornix of the vagina on to the front of the rectum. It forms the bottom of a deep pouch called the rectouterine excavation, which is bounded in front by the posterior wall of the uterus, the supravaginal cervix and the posterior fornix of the vagina. Behind, it is bounded by the rectum and laterally by two crescentic folds of peritoneum.
Two Uterosacral Ligaments
The rectouterine excavation is bounded laterally by two folds of peritoneum, which pass backward from the cervix uteri on either side of the rectum to the posterior wall of the pelvis. These folds are named the sacrogenital or rectouterine folds. They contain a considerable amount of fibrous tissue and non-striped muscular fibers, which are attached to the front of the sacrum and constitute the uterosacral ligaments.
Two Lateral/Broad Ligaments
The two lateral or broad ligaments (ligamentum latum uteri) pass from the sides of the uterus to the lateral walls of the pelvis. Together with the uterus they form a septum across the female pelvis dividing that cavity into two portions. In the anterior part contains the bladder, in the posterior part the rectum and in certain conditions some coils of the small intestine and a part of the sigmoid colon. Between the two layers of each broad ligament it contains:
- The uterine tube superiorly.
- The round ligament of the uterus.
- The ovary and its ligament.
- The epoöphoron and paroöphoron.
- Connective tissue.
- Unstriped muscular fibers.
- Blood vessels and nerves.
The portion of the broad ligament, which stretches from the uterine tube to the level of the ovary is known by the name of the mesosalpinx. Between the fimbriated extremity of the tube and the lower attachment of the broad ligament is a concave rounded margin called the infundibulopelvic ligament.
Infundibulopelvic ligament (suspensory ligament of the ovary) includes the portion of the broad ligament, which extends from the infundibulum of the fallopian tube to the lateral pelvic wall. It contains ovarian vessels, nerves and lymphatics from the ovary, fallopian tube and body of the uterus.28
Ligamentum transversalis colli (Mackenrodt's ligament/cardinal ligament) is located at the base of the broad ligament of the uterus on either side of the cervix uteri. It is attached to the side of the cervix uteri, vault and lateral fornix of the vagina and is continuous externally with the fibrous tissue, which surrounds the pelvic blood vessels.
Importantly, it contains the uterine artery and uterine vein. There is a pair of cardinal ligaments in the female human body. It thus provides support to the uterus and also provides lateral stabilization to the cervix at the level of ischial spine. It may be of clinical significance in hysterectomy.
Two Round Ligaments
The round ligaments (ligamentum teres uteri) are two flattened bands of 10 to 12 cm in length, situated between the layers of the broad ligament in front and below the uterine tubes. Commencing on either side at the lateral angle of the uterus, this ligament is directed forward, upward and lateralward over the external iliac vessels. It then passes through the abdominal inguinal ring and along the inguinal canal to the labium majus in which it becomes lost. The round ligaments consists principally of muscular tissue prolonged from the uterus, also some fibrous and areolar tissue besides blood vessels, lymphatics and nerves enclosed in a duplicature of peritoneum, which in the fetus is prolonged in the form of a tubular process for a short distance into the inguinal canal. This process is called the canal of Nuck. It is generally obliterated in the adult, but sometimes remains pervious even in advanced life. It is analogous to the saccus vaginalis, which precedes the descent of the testis.
Different ligaments of the pelvis are shown in Figure 1.17.
The function of the round ligament is maintenance of the anteversion of the uterus (a position where the fundus of the uterus leans ventrally). When the uterus grows during pregnancy, these ligaments can stretch causing pain.
Perineal Body
The perineal body is a pyramidal fibromuscular structure in the midline between the anus and vagina with the rectovaginal septum at its cephalad apex. Below this, muscles and their fascia converge and interlace through the structure. Attached to the perineal body are the rectum, vaginal slips from the pubococcygeus, perineal muscles and the anal sphincter, it also contains smooth muscle, elastic fibers and nerve endings. During childbirth, the perineal body distends and then recoils. It is an important part of the pelvic floor; just above it is the vagina and the uterus. Acquired weakness of the perineal body gives rise to elongation and predisposes to defects such as rectocele and enterocele.
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