Chapter 02: The Female Reproductive System

Reference

Salustiano, R. (2024). The Normal Antepartal Period. In Dr. RPS Maternal & Newborn Care: A Comprehensive Review Guide and Source Book for Teaching and Learning (2nd ed., pp. 80-116). C&E Publishing, Inc.

The Vulva

The external genitalia of the female are collectively called the vulva. The pudenda is commonly designated the vulva.

The external soft, rounded, fatty pads that cushion over the symphysis pubis for protection is the mons veneris or mons pubis. This is the area covered by the triangular area known as the escutcheon, where curly hair grows after puberty.

The labia majora, “bigger lips”, are two folds of skin with sparse hair on either side of the vaginal opening. It contains fat and Bartholin’s glands (provides lubrication) that protects the labia minora and vaginal os. The labia minora, “smaller lips”, are two thinner folds of delicate tissue within the labia majora, usually not visible behind the non-separated labia majora in nulliparas but common to project beyond the labia majora in multiparas. It is hairless, moist, and reddish (as if a mucous membrane), and contains many sebaceous follicles and a few sweat glands.

• Each labia minora superiorly bifurcate then converge into two lamellae with each pair, the anterior or upper pair forms the prepuce, and the lower pair fuse to form the frenulum of the clitoris.
• Inferiorly, the labia minora simply converges into the fourchette. The labia minora act to protect and obscure the vestibule, urethral meatus, and vaginal os.

The clitoris is a small body of highly erectile, erogenous, and sensitive tissue protected by the prepuce. It is composed a glans, a corpus, and two crura. It measures less than 1 cm in width by 2 cm in length, with less than 0.5 cm in diameter. It is covered by stratified squamous epithelium that is richly supplied with nerve endings (more than 10,000!); the vessels of the clitoris are connected with the vestibular bulbs. As such, it is sensitive to touch, pressure, and temperature. This makes it the primary site of sexual arousal, excitement, and orgasm. The principal female erogenous organ.

• In obstetrics, the clitoris is used as a landmark to guide female catheterization.
• It is the site of syphilitic chancre (in young women) and leukoplakia (in mature women).

Bounded by the labia minora, clitoris, and fourchette, the almond-shaped area with six openings is called the vestibule. The six openings include the urethral meatus, vaginal opening, and two Skene’s glands and two Bartholin’s glands.

1. Urethral Opening/Meatus: the anterior opening set midline, 1 to 1.5 cm below the pubic arch, above the vaginal os, and below the clitoris. This is how the clitoris functions as a landmark for catheterization. The urethra’s short length predisposes women to urinary tract infection.
2. Vaginal Opening: the posterior opening, often hidden by overlapping labia minora in virginal women. An area called the fossa navicularis lies posterior to the vagina to the fourchette, usually only observed in nulliparous women.
   • Hymen: a thin membrane of various thickness, with no glandular or muscular elements and not richly supplied with nerve fibers. It surrounds the vaginal opening, and protects it. It also separates internal from external reproductive organs. It is very vascular in the newborn, thick and rich in glycogen in pregnant women, thin in menopausal women, and vary in thickness in adult women. It may be stretched or torn during physical activity, tampon insertion, vaginal examination, or sexual intercourse. Rupturing of this membrane may occasionally result in profuse bleeding. Its appearance cannot determine sexual activity.
     • Myrtiformes Caruncles are the remnants of the hymen after childbirth.
     • Imperforate Hymen is a rare lesion in which the vaginal os is occluded completely by the retention of menstrual blood and can be treated by surgical perforation.
3. Skene’s Glands or Paraurethral Glands: two small, palpable glands that open into the posterior urethral wall. They secrete mucus to lubricate the vestibule.
   • A common site of gonococcal infection and other sexually transmitted diseases.
4. Bartholin’s Glands or Vulvovaginal Glands: two small, palpable glands 0.5 to 1 cm in diameter situated beneath the vestibule on either side of the vaginal opening, with 1.5 to 2 cm long ducts that open on the vaginal orifice. At sexual arousal, these glands secrete alkaline mucoid material, altering the vaginal canal environment to favor motility and viability of sperms, particularly of androsperms (which are weak to acid).
   • The site of cyst (Bartholin’s cyst), infection (Bartholinitis), and abscess formation.
5. Vestibular Bulbs: almond-shaped aggregation of veins 3 to 4 cm long, 1 to 2 cm wide, and 0.5 cm to 1 cm thick. They lie beneath the mucous membrane on either side of the vestibule, terminate anteriorly at about the middle of the vaginal opening, and extend upward toward the clitoris. These may be injured or even ruptured during childbirth, forming a vulvar hematoma.

The perineum is the area between the vagina and the rectum, consisting of fibromuscular tissue. Most of the support for the perineum is provided by pelvic diaphragms, consisting of levator ani muscles plus the coccygeous muscles posteriorly, and urogenital diaphragms, which are external to the pelvic diaphragm and include the triangular area between the ischial tuberosities and the symphysis and are made up of deep transverse perineal muscles, constrictor of the urethra, and internal and external facial coverings.

• Blood supply: internal pudendal artery and its branches, the inferior rectal artery, and the posterior labial artery
• Nerve supply: primarily the pudendal nerve.

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Internal Female Reproductive Organs

The vagina is a vascular, tubular, and musculomembranous structure that extends from the vulva to the uterus between the urinary bladder (anteriorly) and rectum (posteriorly). Its length is 3” to 4”, with its posterior wall 10-cm long and anterior wall 7.5-cm long. It is the female organ of copulation, and the excretory canal of the uterus through which uterine secretions and menstrual flow escape. It also becomes a soft birth canal during labor.

• The vault is the upper end of the vagina.
• The posterior vaginal fornix is the largest fornix because the vagina is attached to the uterus at a higher level at the back than in the front.
• The anterior vaginal fornix lies in front of the cervix. Lateral vaginal fornices lie on either side.
• There are multiple vaginal layers:
  1. Inner lining: squamous epithelium, under which is a vascular connective tissue.
  2. Middle muscular layer: divided into a weak inner coat and a stronger outer coat of longitudinal fibers.
  3. Pelvis fascia: surrounding the vagina, forming a layer of connective tissue.
• The vagina has rugae (folds), transverse ridges of mucous membranes lining the vagina, which allow it to stretch during sexual intercourse and childbirth.
• Vaginal pH is normally 4 to 6 pH. This acidity is created by Doderlein’s bacilli consuming glycogen in the inner lining of the vagina, and producing lactic acid as a result.

The uterus is the hollow, muscular, pear-shaped (pyriform) organ; covered partially by the peritoneum or serosa, lying between the base of the bladder anteriorly and the rectum posteriorly. It is 7.5 cm by 5 cm by 2.5 cm, with each wall being 1.25 cm thick.

• Length varies, being 2.5 cm to 3.5 cm pre-puberty, 6 cm to 8 cm in adult nulliparous women, and 9 to 10 cm in multiparous women.
• Weight is ~60 grams while nonpregnant, to ~1,000 grams in pregnancy.
• The uterine walls consists of three layers:
  1. Endometrium: the inner mucosal layer; undergoes constant changes in response to estrogen (during the proliferative phase), and progesterone (during the secretory phase) in the menstrual cycle. It becomes highly specialized and is called the decidua during pregnancy.
  2. Myometrium: the middle muscular layer; the living ligatures that control bleeding during the third stage of labor. This responds to stimulation by oxytocic drugs.
  3. Perimetrium: the outer serosal layer formed by the peritoneum; continuous with broad ligaments on the sides of the uterus.

Various parts and regions make up the uterus:

1. Fundus: convex upper part between the insertion of the fallopian tubes; the most contractile portion of the uterus during labor.
2. Corpus or body: the upper, larger, triangular portion of the uterus.
3. Cornua: the portion or point from where the oviducts or the fallopian tubes emerge.
4. Isthmus: constricted area immediately above the cervix: the lower uterine segment; distends during pregnancy.
5. Cervix: the lower, smaller cylindrical portion with an internal os, the cervical canal, and an external os.

The uterus is partially mobile. It is free to move along the anteroposterior plane as the body moves. Normally, the uterus is almost horizontal when a nonpregnant woman stands erect. Depending on its position, it can be characterized as:

1. Anteversion: leaning forward
2. Anteflexion: bending forward on itself, with the fundus resting on the bladder. With anteversion, these positions prevent uterine prolapse.
3. Retroflexion: an abnormal position where the uterus bends back towards the cervix, resulting in a sharp angle at the point of bending.
4. Retroversion: turning back of the entire uterus in relation to the pelvic area.

The movement of the uterus is limited and supported by the pelvic floor and several ligaments, the most important of which are at the level of the cervix.

1. Broad Ligament: extends from the lateral margins of the uterus to the pelvic walls, thereby dividing the pelvic cavity into the anterior and posterior compartments. The lower border is thickened and strengthened to form the most important uterine support—the transverse cervical ligament—which, when damaged during labor, may cause the uterus to sag downward.
2. Round Ligaments: arises from the cornua of the uterus in front and below the insertion of each uterine tube and pass between the folds of the broad ligament to be inserted into each labium majus. Round ligaments have little value as a support but they help the broad ligament keep the uterus in place and tend to maintain the anteverted position of the uterus.
3. Ovarian Ligaments: arises from the cornua of the uterus but behind the uterine tubes and pass down between the folds of the broad ligament to the ovaries. The round ligament, the ovarian ligament, and the uterine tubes are very similar in appearance and arise from the same area in the uterus.
4. Cardinal Ligaments: the chief uterine supports; these ligaments fan out from the sides of the cervix to the side walls of the pelvis, suspending the uterus from the side walls of the true pelvis. They are also called transverse cervical ligaments or Mackenrodt’s ligaments.
5. Uterosacral Ligaments: pass backwards from the cervix to the sacrum and support for the uterus and cervix at the level of the ischial spines.
6. Pubocervical Ligaments: pass forward from the cervix, under the bladder, to the pubic bones.

The uterus is a primary reproductive organ, functioning for menstruation, pregnancy or gestation, and labor:

1. Menstruation: under the influence of the ovarian hormones estrogen and progesterone, the uterine endometrium thickens (proliferative stage), becomes vascular, is ready for implantation (secretory stage), and is then sloughed off if implantation does not take place (menstrual stage).
2. Pregnancy/Gestation: housing and nourishment of the baby.
3. Labor: contractile tissue for the propulsion of the products of conception into the vaginal canal.

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The Oviducts

Also known as the fallopian tubes, these are two muscular canals/tubes 8 to 14 cm (average 10 cm) in length that extends from the uterine cornua to a site near the ovaries; enveloped in the upper fold of the broad ligament. It is the site of normal fertilization (mostly the ampullary portion), and are the ducts through which the ova travel from the ovaries to the uterus.

• They are covered by peritoneum folds that drape down below as broad ligaments and extend at the sides to form the infundibulopelvic ligaments.
• The lumen of the oviducts is lined by a ciliated mucous membrane called the ciliated cubical epithelium. This membrane produces a current of lymph that facilitates the movement of the ovum along the tube.
• The oviducts, as mentioned, are muscular. They rhythmically contract at a rate that varies with hormonal changes in the ovarian cycles.

Parts
Interstitial Portion	1.25 cm long and has a lumen that is 1 mm in diameter; embodied within the uterine muscular wall.
Isthmus	a narrow portion immediately after the uterus and extends 2.5 cm from it, or about one-third of the length of the tube.
Ampulla	the widest portion, 5 cm long and makes up about half of the length of the tube; site of fertilization (conception).
Infundibulum	the funnel-shaped passage that has a fringed end that is composed of the fimbriae. One of the fimbriae (the fimbra ovarica/ovarian fimbria) is elongated and connected to the ovary.
Layers
Inner epithelium	Lining of the mucous membrane of the ciliated cubical epithelium thrown into complicated longitudinal mucosal folds known as plicae, most prominent in the ampullary region; these folds slow the ovum down on its way to the uterus. - The mucosal surface contains cilia, hair-like structures that move to propel the ovulated egg from the ovary towards the uterus, and distributing tubal fluid throughout the tube. Nearing ovulation, estrogen and progesterone increase the rate of beating of the cilia. - Goblet cells in the inner lining produce a secretion containing glycogen to nourish the ovum. - Beneath the lining is a layer of vascular connective tissue.
Smooth middle muscle coat	Consists of one inner circular layer and one outer longitudinal layer; they allow for peristaltic movement of the tubes.
Outer peritoneum	The outer covering. The infundibulum passes through it to open into the peritoneal cavity. The mucosal lining of the tubes and the peritoneal lining of the pelvis are in direct contact, allowing the spread of infection from the tubes to the peritoneum and vice versa. This is called pelvic inflammatory disease (PID).

• Blood Supply: uterine and ovarian arterial and drains.
• Lymphatic Drainage: to the lumbar glands.
• Nerve Supply: from the ovarian plexus.

Abnormalities

1. Ectopic Pregnancy: condition that is most commonly associated with the fallopian tubes; implantation of a fertilized egg in any part of the fallopian tube due to a delay in its transport towards the uterus; may cause tubal rupture (discussed in Chapter 06: High-Risk Pregnancy).
2. Salpingitis: inflammatory disease that leads to the thickening of the tubes. Two types of salpingitis:
   • Salpingitis isthmica nodosa: involves the formation of nodules inside the isthmus section of the tubes.
   • Non-nodular salpingitis: usually caused by an infection, such as those associated with pelvic inflammatory disease (PID).
3. Hydrosalpinx: when one or both tubes are swollen and filled with fluid; may be due to tubal infections or obstruction of one or both ends of the tubes.
4. Tubal torsion/adnexal torsion: twisting of the fallopian tube affecting its blood supply; can affect fertility.
   • Tubal infertility: inability to conceive a pregnancy due to issues with the fallopian tubes (congenital abnormalities, infections). One of the most common causes of tubal factor infertility is chlamydia complications.
   • Tubal cancer: a rare primary cancer of the fallopian tube (less than one percent of gynecologic cancers); more likely to be the result of metastasis from another site (ovarian cancer, uterine cancer, cervical cancer).

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Ovaries

Two almond-shaped organs sized 2.5 to 5.0 cm in length, 1.5 to 3.0 cm in breadth, and 0.6 to 1.5 cm thick. They weigh 6 to 10 grams each, and are situated in the upper part of the pelvic cavity, attached to the posterior surface/back of the broad ligament within the peritoneal cavity.

• Covered in a single layer of cuboidal epithelial cells called germinal epithelium; no peritoneal covering for the ovaries. The lack of covering allows the mature ovum in erupting, but allows for easier spreading of malignant cells from cancer of the ovaries.

The ovaries appear smooth with a dull-white surface through which glisten several small follicles; more corrugated in older women and markedly convoluted in elderly women. They consist of three layers:

1. Tunica albuginea: dense and dull white; protective layer.
2. Cortex: contains the ovarian follicles in different stages of development (ova, Graafian follicles, corpura lutea, degenerated corpora lutea/corpora albicantia, degenerated follicles) held together by the ovarian stroma. There are about 200,000 primordial follicles in the ovarian cortex at birth.
3. The inner part of the cortex, the medulla is composed of loose connective tissues, it contains nerves, blood vessels, and lymphatic vessels. The hilum where these vessels enter lies just where the ovary is attached to the broad ligament. This area is called the mesovarium.
   • The motor and sensory sympathetic and parasympathetic nerves follow the ovarian artery across the infundibulopelvic ligament to reach the ovary. The ovaries are insensitive unless they are distended and squeezed.
   • Mittelschmerz is a mid-cycle pain marked during ovulation when the ovum is released and the Graafian follicle bursts, as the peritoneum becomes irritated by blood or fluid escaping along with the ovum.

The ovaries are the female gonads, and are responsible for both reproductive and endocrine functions:

1. Oogenesis: the process of developing a mature ovum in a Graafian follicle.
   • When primordial follicles mature and become cystic, they are termed Graafian follicles. The ovum is situated at the end of a Graafian follicle, encircled by a narrow perivitelline space and surrounded by a clump of cells called discus proligerus, which radiate outwards to form the corona radiata. The very clear innermost outer coat of the follicle is the external limiting membrane. Around this lies the theca, and area of compressed ovarian stroma.
2. Ovulation: the monthly expulsion of a mature ovum from the Graafian follicle into the pelvic cavity.
3. Endocrine Function: secretion of female hormones estrogen and progesterone; maturing follicles secrete estrogen, while the corpus luteum secretes estrogen and primarily progesterone.
   • Ovaries: primary source of estrogen; adrenal cortex (extraglandular sites) produce a minute amount of estrogen.
   • Estgrogen: develops female secondary sex characteristics.
   • Progesterone: the hormone of pregnancy; its effects on the decidua (thickened and more vascular) allow pregnancy maintenance.

• Blood Supply: blood flows through the ovarian arteries and veins. The right ovarian vein joins the inferior vena cava, but the left ovarian vein returns blood to the left renal vein.
• Lymphatic Drainage: to the lumbar glands.
• Nerve Supply: from the ovarian plexus.

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Mammary Glands (Breasts)

Located under the skin, over the pectoralis major muscles. It is made of fibrous, adipose, and glandular tissue. The glandular tissue is arranged in about 15 to 25 lobes. Each lobe is composed of lobules, which in turn are composed of alveoli with secreting cells (acinar cells) that produce milk; and excretory ducts that lead from each lobe to an opening in the nipple composed of erectile tissue and muscle fibers that have a sphincter-like action in controlling the flow of milk. The smooth muscle of the nipple causes the erection of the nipple on contraction.

• The areola is a pigmented area of skin surrounding the nipple.
• Size varies on adipose tissue rather than glandular tissue. Estrogen during puberty develops breast size. Size is not a significant factor in successful breastfeeding.
• Milk secretion (lactation) is used for nourishment and transfer of maternal antibodies. It is also a site of sexual stimulation.

Maternal Reflexes

1. Prolactin Reflex: the milk secretion reflex; a high prolactin level stimulates the alveoli, particular the acini cells. Milk is then stored in the breast tubules. High levels of estrogen and progesterone induce alveolar and duct growth as well as stimulate milk secretion. In pregnancy, milk secretion is not stimulated because of low prolactin as a result of high estrogen secretion by the placenta.
2. Let-down Reflex: draught reflex; oxytocin-induced flow of milk after stimulation by sucking on a lactating breast. It is also affected by maternal emotions.
3. Milk Ejection Reflex: controls the expulsion of milk from the breast tubules, also under the influence of oxytocin secreted by the PPG.