Human Anatomy and Physiology - I. V. Gayvoronsky 2011

Anatomy of the Reproductive System. Human Reproductive Function and Development
Female Reproductive System

Structure OF THE genital Organs. The Internal Female Genitalia are located in the pelvic cavity. They include the Ovaries, uterine tubes, Uterus, and Vagina. The External female genitalia are situated in the perineal region: the mons pubis, Labia Majora and minora, vestibular bulb, Clitoris, and hymen (Fig. 11.5). The Mammary Glands are also considered part of the FEMALE Reproductive System.

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Fig. 11.5. Organs of the FEMALE Urogenital System:

1 — right Kidney; 2 — renal artery; 3 — renal vein; 4 — left kidney; 5 — Ureter; 6 — body of uterus; 7 — broad ligament of uterus; 8 — Uterine tube; 9 — fimbriae of uterine tube; 10 — Urinary Bladder; 11 — clitoris; 12 — external urethral orifice; 13 — vaginal orifice; 14 — greater vestibular glands; 15 — vestibular bulb; 16 — vagina; 17 — cervical canal; 18 — cervix of uterus; 19 — round ligament of uterus; 20 — Ovary; 21 — ampulla of uterine tube; 22 — fundus of uterus; 23 — uterine cavity

The ovary, ovarium (Greek *oophoron*), is a paired, ellipsoid-shaped gland attached by a peritoneal fold (the mesovarium) to the posterior surface of the broad ligament of the uterus (Figs. 11.6, 11.7). The ovary measures 4 cm in length, 2.5 cm in width, and 1 cm in thickness, with a mass of 5.5 g. It is connected to the uterus by the proper ligament of the ovary, which extends to its inferior pole. At the superior (tubal) pole, Blood Vessels and nerves approach the ovary, surrounded by Peritoneum known as the suspensory ligament of the ovary. The anterior border of the ovary attaches to the broad ligament of the uterus, while the posterior border remains free. The lateral surface faces the pelvic wall, and the medial surface faces the uterus. The organ features a small depression—the hilum—through which vessels and nerves enter the organ. Externally, the ovary is covered by the tunica albuginea, beneath which lie the stroma and parenchyma of the gland. The stroma consists of Connective Tissue, whereas the ovarian parenchyma comprises two layers: an outer cortical layer and an inner medullary layer situated closer to the hilum. The latter consists of connective tissue containing Blood Vessels and nerves.

Fig. 11.6. Organs of the female reproductive system (median section of the pelvis):

1 — uterus; 2 — rectouterine pouch; 3 — posterior fornix of vagina; 4 — rectum; 5 — cervix of uterus; 6 — anus; 7 — vagina; 8 — vesicouterine pouch; 9 — vestibule of vagina; 10 — Urethra; 11 — labium minus; 12 — labium majus; 13 — Pubic Symphysis; 14 — urinary bladder; 15 — round ligament of uterus; 16 — uterine tube; 17 — ovary

Fig. 11.7. Internal female reproductive organs (diagram):

1 — round ligament of uterus; 2 — proper ligament of ovary; 3 — ovary; 4 — fimbriae of uterine tube; 5 — ampulla of uterine tube; 6 — isthmus of uterine tube; 7 — uterine part of uterine tube; 8 — fundus of uterus; 9 — uterine cavity; 10 — broad ligament of uterus; 11 — mesovarium; 12 — suspensory ligament of ovary; 13 — cervix of uterus; 14 — cervical canal; 15 — vaginal rugae; 16 — vagina; 17 — isthmus of uterus; 18 — body of uterus

The ovarian cortex contains follicles at various stages of maturity, within which the formation and maturation of oocytes take place, alongside The production of Female Sex Hormones. In newborn girls, the ovarian follicles contain immature oocytes (approximately 400,000–500,000). The maturation of oocytes and their subsequent release from the follicles begin with the onset of Puberty (at ages 10–12). Normally, about one follicle matures each month. A mature follicle contains an oocyte and is referred to as a Graafian follicle (Fig. 11.8). The capacity for follicle and, consequently, oocyte maturation persists until ages 47–50. Over her lifetime, a woman matures only 400 to 500 oocytes.

Thus, the ovaries develop and mature Female Germ Cells (oocytes) and also produce female sex hormones that enter the BLOOD AND Lymph (see below).

The uterus, uterus (Greek *metra*, *hystera*), is an unpaired, hollow muscular organ measuring approximately 7.5 cm in length and 5 cm in width. It is located in the middle of the pelvic cavity between the urinary bladder—toward which its anterior (vesical) surface faces—and the rectum, which faces its posterior (intestinal) surface. The uterus comprises the fundus (the convex upper part), the body (which narrows inferiorly), the isthmus, and the cervix. Normally, the cervical canal is filled with dense mucus. In nulliparous women, the cervix is cylindrical with a pin-point external os, whereas in multiparous women, it is oval with a slit-like os (Fig. 11.9). The fundus and body of the uterus are normally anteflexed relative to the isthmus and cervix; this position is termed *anteflexio*. Additionally, the uterus is tilted forward relative to the pelvic axis, known as *anteversio*.

Fig. 11.8. Graafian follicle:

1 — ovarian parenchyma; 2 — follicular cells; 3 — follicular cavity; 4 — cumulus oophorus; 5 — oocyte

The uterus has a triangular-shaped cavity lined with a mucous membrane, the endometrium. It consists of two layers: a superficial, thick layer called the functional layer (functionalis), and a deep layer, the basal layer (basalis). The functional layer is named for the characteristic changes it undergoes during the Menstrual cycle, being almost entirely shed during menstruation. The basal layer does not change significantly during menstruation; it is preserved and serves as the foundation for the regeneration of the functional layer. The middle and thickest tunic of the uterus, the myometrium, is composed of powerful smooth Muscle arranged in three layers: outer and inner longitudinal layers, and a middle circular layer. The serous coat of the uterus, the perimetrium, is represented by the peritoneum. It covers the entire uterus except for the cervix, transitioning from the uterus onto adjacent organs and pelvic walls. Consequently, a peritoneum-lined vesicouterine pouch is formed between the uterus and the urinary bladder, and a rectouterine pouch between the uterus and the rectum. Laterally from the isthmus and the supravaginal part of the cervix, subperitoneal parametrial tissue (parametrium) is located.

Fig. 11.9. Shapes of the cervix in a nulliparous (a) and multiparous (b) woman:

1 — posterior lip; 2 — external os of cervix; 3 — anterior lip; 4 — anterior fornix; 5 — posterior fornix

Fixation of the uterus is largely provided by its paired ligaments. The broad ligament of the uterus consists of two folds of peritoneum extending from the vesical and intestinal surfaces of the uterus to the lateral pelvic wall. The upper part of this ligament encloses the uterine tube, while the ovary is attached to its posterior fold by the mesovarium. The round ligament of the uterus is composed of connective and Cytology/cytology/32.html">Smooth Muscle tissue, forming a cord that runs within the broad ligament from the uterine body to the deep inguinal ring. It passes through the Inguinal Canal and terminates within the labia majora, anchoring to the pubic bone. Near the Water/144.html">Origin of the round ligament, the proper ligament of the ovary attaches to the uterus. The rectouterine and pubocervical ligaments consist of connective tissue bundles extending from the uterine isthmus to the respective organs. The cardinal ligaments secure the organ to the lateral pelvic walls.

The uterus is designed for the implantation of a fertilized oocyte, The Development of the embryo, and the gestation of the fetus. During childbirth, contractions of its muscular wall expel the fetus from the body. The position and dimensions of the uterus change significantly during Pregnancy. As the fetus grows, the pregnant uterus gradually enlarges, virtually reaching the level of the xiphoid process of the Sternum. Following childbirth, it involutes and resumes its original position.

The uterine (Fallopian) tube, tuba uterina (Greek *salpinx*), is a paired hollow organ approximately 11 cm in length. It comprises the uterine part (located within the uterine wall), the isthmus (a narrowed section), and the ampulla (an expanded segment). The ampulla of the uterine tube terminates in a funnel-shaped infundibulum, from which numerous finger-like projections, the fimbriae, extend toward the ovary.

The wall of the tube consists of three tunics: an inner mucosal coat, a middle muscular coat, and an outer serous coat. Ciliated epithelial Cells of the mucous membrane facilitate The transport of the oocyte toward the uterus. The peristalsis of the muscular coat also AIDS in moving the oocyte along the uterine tube. Thus, the uterine tube serves to convey the oocyte from the ovary into the uterine cavity. Occasionally, implantation of a fertilized oocyte occurs within its lumen, resulting in an ectopic Tubal Pregnancy.

The vagina (Greek colpos) is an unpaired muscular tube, 7–10 cm in length, that connects the uterus to the external genitalia. The vagina serves as the passage for menstrual flow and for copulation. It also forms part of the birth canal through which the fetus is expelled from the mother's body.

The vaginal wall is relatively thick and yet, owing to its structural features, highly distensible. The interior of the vagina is lined with a grayish-pink mucous membrane, which becomes more vivid during menstruation. The mucous membrane is virtually devoid of glands. During sexual intercourse, vaginal lubrication is produced by transudation («oozing») of fluid from the vascular plexus surrounding the organ. An acidic environment is maintained within the vagina due to the presence of abundant microorganisms—Döderlein's bacilli (Lactobacillus acidophilus and others)—which produce lactic acid. This mechanism serves a protective function, preventing pathogenic microflora from entering the organ. A recess known as the vaginal fornix is located between the cervix and the vaginal walls. The cervix faces the posterior, deepest part of the fornix.

The muscular coat consists of an inner circular layer and an outer longitudinal layer. Externally, the vagina is covered by adventitia, except in the region of the posterior fornix, which is covered by peritoneum.

Fig. 11.10. Female external genitalia:

1 — mons pubis; 2 — anterior commissure of the labia majora; 3 — prepuce of the clitoris; 4 — clitoris; 5 — frenulum of the clitoris; 6 — labium minus; 7 — external urethral orifice; 8 — Vestibule of the vagina; 9 — vaginal orifice; 10 — vestibule fossa; 11 — Perineum; 12 — anus; 13 — posterior commissure of the labia majora; 14 — hymen; 15 — labium majus

Fig. 11.11. Mammary gland:

1 — nipple; 2 — lactiferous ducts; 3 — deep Fascia of the breast; 4 — pectoralis major muscle; 5 — body of the gland; 6 — lobes of the gland; 7 — adipose tissue; 8 — Skin

Before the onset of sexual activity, the vaginal entrance is partially covered by the hymen, a fold of mucous membrane containing small apertures for the outflow of menstrual blood. The hymen is typically ruptured during first sexual intercourse, leaving small remnants known as carunculae hymenales.

In some women, the hymen is exceptionally elastic and may remain intact until childbirth.

The mons pubis is a triangular prominence of the anterior abdominal wall located anterior to the pubic symphysis (Fig. 11.10). In this area, the skin is covered with Hair and features a well-developed layer of subcutaneous adipose tissue. Inferiorly, the mons pubis transitions into the labia majora.

The labia majora are paired, rounded folds approximately 7 cm long and 2 cm wide. The skin on their outer surface is covered with hair. The bulk of the labia is formed by subcutaneous adipose tissue. Anteriorly and posteriorly, they are joined by corresponding commissures. The labia majora bound the pudendal cleft (urogenital fissure). Under normal conditions, they remain closely apposed, closing the vaginal entrance.

The Labia minora are situated between the labia majora as paired, delicate, longitudinal skin folds of smaller size. Anteriorly and posteriorly, these folds also unite to form commissures, with the anterior commissure enclosing the clitoris. The labia minora contain no adipose tissue but are rich in elastic fibers. They enclose a space called the vestibule of the vagina. Opening into the vestibule are the external urethral orifice, the vaginal orifice, and the ducts of the greater and lesser vestibular glands. The secretion of these glands moistens and lubricates the vestibule while neutralizing its acidic environment.

The clitoris corresponds structurally and topographically to the corpora cavernosa of the Penis. Its posterior portion is anchored to the pubic bones, while the anterior portion terminates in the glans clitoridis, which is densely supplied with sensory nerve endings, forming one of the primary female erogenous zones.

The vestibular bulb (bulbus vestibuli) is structurally analogous to the corpus spongiosum of the male penis. It is located within the thickness of the labia majora. During sexual arousal, the Veins OF THE vestibular bulb become engorged with blood.

The mammary gland, glandula mammaria (Greek mamma, mastos), is a large glandular organ that produces milk. The disc-shaped body of the gland is surrounded by adipose tissue and situated on the anterior thoracic wall (Fig. 11.11). It consists of 15–20 radially arranged lobes from which lactiferous branchlets originate. These converge into larger ducts directed toward the nipple, where they open externally via minute punctate openings.

The function of the gland is closely linked to the hormonal activity of the ovaries. Stimulated by Ovarian Hormones during puberty, the glandular tissue proliferates. The mammary gland acquires its characteristic shape and size, which in turn depend on age, body type, and the functional state of the female Organism (Phases of the menstrual cycle, pregnancy, and Lactation).

Urethra. The female urethra is an unpaired tubular organ, slightly curved, measuring 2.5–3.5 cm in length and 8–12 mm in diameter. It begins at the neck of the bladder with the internal urethral orifice and terminates at the external orifice, which opens into the vestibular space approximately 2 cm below the clitoris. The upper portion of the anterior urethral wall lies posterior to the pubic symphysis, whereas its posterior wall is fused with the anterior vaginal wall. Descending inferiorly, the urethra pierces the Muscles and fascia of the perineum, at which point it is encircled by bundles of muscle fibers forming the external sphincter. The urethral wall comprises mucous, muscular, and adventitial layers. The mucous membrane is well developed and features longitudinal folds.

Menstrual Cycle. Unlike the Male Reproductive System, the female reproductive system exhibits a distinct cyclical pattern. This strict sequence of physiological Changes in the female body is referred to as the menstrual cycle. In most women, it repeats regularly at intervals of approximately 28 days. The menstrual cycle comprises the menstrual phase (bleeding), the postmenstrual phase, and the premenstrual phase.

Conventionally, the cycle begins on the first day of menstruation. The menstrual phase (desquamation—the shedding of the functional layer of the endometrium) is accompanied by mild discomfort, lasts on average 3–5 days, and involves a blood loss of 50–100 ml per day.

During the postmenstrual phase, under the Influence of the pituitary follicle-stimulating hormone (FSH), a single ovarian follicle begins to mature, harboring the future oocyte. The growing follicle secretes female sex hormones—estrogens—which stimulate the proliferation of the uterine lining (endometrium) and trigger a surge in pituitary luteinizing hormone (LH). Beginning on days 3–5 of the cycle, the postmenstrual phase culminates on day 14 in ovulation, the rupture of the follicular wall and release of the oocyte. By this time, the functional endometrial layer has fully regenerated. The postmenstrual phase encompasses the regeneration phase (epithelialization of the endometrium) and the proliferation phase (restoration of endometrial thickness).

On day 15 of the cycle, the premenstrual phase (secretory phase) begins: the endometrium becomes edematous and accumulates nutrients essential for the implantation of a fertilized ovum. During this period, the cavity of the ruptured follicle fills with yellowish cells that, driven by luteinizing hormone, enlarge to form the corpus luteum—a temporary endocrine gland producing progesterone. Progesterone inhibits the maturation of remaining follicles. The oocyte is swept by the fimbriae into the uterine tube, where Fertilization most frequently occurs. Simultaneously, nutrients accumulate within the endometrium. Thus, optimal conditions for blastocyst implantation are established in the uterine mucosa during this window.

If fertilization does not occur, the premenstrual phase concludes on the 13th day following ovulation (the 28th day of the cycle), giving way to the bleeding (menstrual) phase. This phase is triggered by the withdrawal of estrogens and a decline in progesterone secretion by the corpus luteum. The hormonal support sustaining the thickened endometrium ceases, causing it to slough off along with the unfertilized oocyte and blood clots, which are expelled from the body. Toward the end of menstruation, falling progesterone levels prompt the Pituitary Gland to release follicle-stimulating hormone once again, and the cycle repeats.