Human Anatomy - H. I. Koliadenko 2009

The Study of the Viscera (Splanchnology)
Urogenital System
Female Reproductive Organs

The Internal female reproductive Organs, whose Functions include the maturation of Female Germ Cells, as well as the development and gestation of the fetus, comprise the Ovaries, Uterus, uterine tubes (fallopian tubes), and Vagina (Fig. 117).

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Fig. 117. Cross-section of the internal FEMALE REPRODUCTIVE ORGANS:

1 — body of the uterus; 2 — cervix of the uterus; 3 — uterine cavity; 4 — Uterine tube (at the isthmus); 5 — ampulla of the uterine tube; 6 — infundibulum of the uterine tube; 7 — Ovary; 8 — proper ligament of the ovary; 9 — round ligament of the uterus; 10 — vagina; 11 — broad ligament of the uterus

The ovary (ovarium) is a paired female gonad responsible for the maturation of oocytes and The production of Female Sex Hormones. The ovaries are located in the lesser pelvis on both sides of the uterine fundus, inferior to the uterine tubes.

The ovary is ellipsoid in shape, bluish-white in color, with a bumpy surface. It measures 2.5–5 cm in length and 1.5–3 cm in width, with an average mass of 5–8 g in adult women.

The ovary features medial and lateral surfaces, as well as anterior and posterior borders. The anterior border connects the ovary to the broad ligament of the uterus and bears the hilum of the ovary, through which Blood Vessels and nerves enter and exit. The posterior border hangs freely within the pelvic cavity. Externally, the ovary is covered by a single layer of cuboidal epithelium, beneath which lies a thick tunica albuginea.

A cross-section of the ovary reveals its heterogeneous Structure. The superficial, or cortical, layer consists of glandular tissue. Beneath the cortical layer lies the medulla—the ovarian stroma—composed of loose Connective Tissue. The cortical layer has a connective tissue framework housing epithelial nests of round shape, known as follicles of varying diameters. This is because the follicles are at different Selection/3.html">Stages of development. The cells lining the follicles produce the female sex hormone estrogen (folliculin). Follicles mature gradually, starting from barely noticeable primary ovarian follicles. Immature germ cells, or oocytes, are already observable in primary follicles by the second month of intrauterine life.

The ovary of a newborn girl contains between 30,000 and 400,000 so-called primary ovarian follicles. Throughout a woman's life, 450 to 500 primary follicles mature, while the rest undergo atresia. Primary follicles develop into mature vesicular ovarian follicles, known as Graafian follicles. The release of the oocyte from these follicles (ovulation) begins with the onset of Puberty. Cavities form among the follicular cells and fill with clear follicular fluid. Over time, these cavities merge into a single continuous space, and the primary follicle transforms into a secondary vesicular follicle with a diameter of 2 cm, protruding from the ovarian surface. Fluid pressure within the follicle increases, its wall develops, and the oocyte, along with the follicular fluid, is expelled into the peritoneal cavity, from where it enters the uterine tubes and subsequently the uterine cavity. This process repeats approximately every 28 days and is termed ovulation. A corpus luteum forms at the site of the ruptured follicle. It regresses if Fertilization does not occur. In the event of Pregnancy, a corpus luteum of pregnancy develops, producing progesterone, which is vital during embryonic development. The corpus luteum functions throughout the entire pregnancy. After childbirth, it regresses, leaving behind a connective tissue scar.

The uterus (uterus) is a single hollow muscular organ situated in the lesser pelvis between the Urinary Bladder and the rectum. The mass of the uterus is about 50 g, and its length is 5 cm. Following gestation and childbirth, the dimensions and mass of the uterus double. The uterus is pear-shaped and consists of an upper expanded part—the fundus, a middle part—the body, and a lower narrowed part—the cervix. The body forms an anteriorly open angle relative to the cervix. The portion of the cervix that projects into the vagina is termed the vaginal part, while the portion lying above the vagina is the supravaginal part. The narrowed transition zone between the body and the cervix is called the isthmus. The uterine openings are located in the upper lateral angles of the uterine fundus, whereas in the lower angle, the uterine cavity transitions into the cervical canal, which is 2.5–3 cm long. The canal terminates in the external os of the uterus. In nulliparous women, the external os is rounded, whereas in multiparous women, it appears as a transverse slit.

The uterine wall consists of three layers: the outer serous layer (perimetrium), the middle muscular layer (myometrium), and the inner mucous layer (endometrium).

The mucous membrane, or endometrium, is lined with a simple columnar ciliated epithelium, with the cilia beating toward the vagina. The mucosa contains tubular uterine glands that secrete an alkaline fluid. The Glands of the cervical mucosa secrete a thick, viscous mucus that forms a plug, preventing microorganisms from entering the uterine cavity.

The muscular layer, or myometrium, consists of three layers of smooth Muscle containing connective tissue and elastic fibers. All three layers interlace and run in various directions, making the division into distinct layers somewhat indistinct.

The thin outer layer, featuring longitudinally arranged fibers, fuses with the subserosal layer. The middle circular layer is the most well-developed. It contains numerous Blood Vessels and is therefore also referred to as the vascular layer. The inner layer is the thinnest, with longitudinally oriented fibers.

The serous coat, or perimetrium, is formed by the Peritoneum. This membrane transitions from the urinary bladder onto the vesical surface of the uterus, forming the vesicouterine pouch. Continuing further, the serous coat covers the fundus, the intestinal surface of the uterine body, the cervix, and a small portion of the posterior vaginal wall. From this point, the peritoneum reflects onto the rectum. Consequently, a deep rectouterine pouch is formed between the uterus and the rectum.

The uterus is anchored by two pairs of ligaments. The largest of these is the broad ligament of the uterus, which consists of anterior and posterior folds of peritoneum extending to the floor of the lesser pelvis; its walls contain connective tissue cords with smooth muscle fibers. The broad ligament is conventionally divided into three parts: the uppermost part, bounded superiorly by the uterine tube and inferiorly by the ovary and its proper ligament, is the mesosalpinx; the portion of the posterior leaflet that extends to the mesovarian border of the ovary is the mesovarium; and the largest part of the ligament is the mesometrium.

The function of the uterus is related to fetal gestation, which lasts 9 months in humans. Over the course of pregnancy, the uterus enlarges 600-fold, reaching up to 2500 cm³, and returns to nearly its original size 1.5 to 2 months postpartum.

The round ligament of the uterus is 12–14 cm long, 3–5 mm in diameter, and resembles a fairly dense cord. The ligament originates from the upper margin of the uterus near the Water/144.html">Origin of the uterine tube, passes between the layers of the broad ligament to the deep inguinal ring. It then traverses the Inguinal Canal, emerges through the superficial inguinal ring, and terminates in the subcutaneous adipose tissue of the pubic tubercle and the labium majus. The round ligament is composed of connective tissue and smooth muscle cells, with its substance permeated by blood vessels, Lymphatic vessels, and nerves.

Fibers of the paired rectouterine muscle extend from the posterior surface of the cervix to the inferior region of the rectum.

The uterine, or fallopian, tube (tuba uterina) is a paired organ. The uterine tubes lie almost horizontally within the upper margin of the broad ligament of the uterus. The tubes open at one end into the uterine cavity and at the other into the peritoneal cavity. The length of the tube averages 10–12 cm, and its width is 0.5 cm. The uterine tube consists of several segments. The isthmus is the narrowest part of the tube connecting it to the uterus; the ampulla is the widened portion; and the infundibulum is the funnel-shaped expansion. Through the infundibulum, the tube opens into the peritoneal cavity. The margins of the infundibulum bear fimbriae that surround the ovary. One of the fimbriae (the ovarian fimbria) is the longest and attaches to the tubal pole of the ovary.

Externally and laterally, the uterine tube is covered by a serous coat, beneath which lies loose connective tissue, namely the subserosal layer. The muscular coat of the uterine tubes is three-layered and composed of smooth muscle. The mucosa is formed by a simple columnar ciliated epithelium, whose cilia beat toward the uterus. The movement of the infundibular fimbriae propels the oocyte from the peritoneal cavity into the uterine tube, through which it reaches the uterus via ciliary action and muscular contractions of the tube. Fertilization of the oocyte takes place in the tube, after which the embryo migrates toward the uterus and implants into its mucous lining, the endometrium.

The vagina (vagina) is a muscular tube, flattened anteroposteriorly, measuring 8–10 cm in length. Its upper end connects to the uterine cervix, while its lower orifice opens into the external genitalia. The upper end of the vagina forms a recess known as the vaginal fornix. In virgins, the vaginal orifice is partially closed by a fold of mucous membrane called the hymen.

The vaginal wall consists of two coats: muscular and mucosal. The mucosa is lined with stratified squamous epithelium, features numerous transverse folds known as vaginal rugae, and displays anterior and posterior longitudinal ridges called columns of rugae. The lower end of the anterior Column of rugae is termed the urethral carina of the vagina because the lower part of the Urethra opens into it.

The muscular coat of the vagina comprises an outer (circular) layer and an inner (longitudinal) layer. The anterior wall of the vagina is adjacent to the urinary bladder, and the posterior wall is adjacent to the rectum.

The External female genitalia include the Labia Majora and minora, Clitoris, Vestibule of the vagina, Perineum, and Mammary Glands.

The labia majora are paired, massive Skin folds running parallel to each other that laterally bound the pudendal cleft. They measure 7–8 cm in length and 2–3 cm in width, containing numerous sweat and Sebaceous Glands. Anteriorly and posteriorly, the labia majora merge via commissures.

The Labia minora are located medial to the labia majora and run parallel to them, though they are thinner and shorter. They define the BOUNDARIES OF THE vaginal vestibule.

The greater vestibular glands (Bartholin's glands) lie at the Base of the labia majora, with their excretory ducts opening onto the Medial surface of the labia minora. Small in size (about the size of a pea), they secrete a whitish mucus that lubricates the vaginal entrance.

The clitoris is a finger-like projection composed of small corpora cavernosa, a glans, and crura. The body of the clitoris is 1.5–2.5 cm long. The crura of the corpora cavernosa diverge at an angle and attach to the inferior rami of the pubic bones.

The vaginal vestibule is the space between the labia minora, forming a small depression bounded anteriorly by the clitoris, posteriorly by the frenulum of the labia minora, and laterally by the medial surfaces of the labia minora. Below the clitoris and above the vaginal vestibule, the urethral orifice opens on a small mucosal elevation.

The perineum is the region situated between the anus and the external genitalia. Forming the pelvic floor, it is bounded anteriorly by the pubic arch, posteriorly by the tip of the coccyx, and laterally by the ischial tuberosities. The perineum is composed of Muscles, fascia, adipose tissue, and skin.

The mammary gland is a paired female organ belonging to the Reproductive System. The gland consists of 15–20 lobes, which are modified sweat and sebaceous Skin glands. Each lobe has its own excretory duct that expands terminally into a lactiferous sinus. All ducts open onto the nipple, which is located in the center of the pigmented areola.

Changes in the mammary gland during pregnancy begin as early as the second month and become pronounced by the 4th to 5th month. The glands increase in size due to the proliferation of glandular tissue, and the Blood and Lymphatic vessels undergo significant dilation. Following the cessation of Lactation, the mammary gland undergoes involution, though it does not fully return to its pre-pregnancy size.

Embryogenesis OF THE Female Reproductive Organs

The reproductive organs develop from the primary Kidney, known as the mesonephros (or Wolffian body). During embryonic development, the Wolffian body and the Wolffian duct undergo regression. Only rudiments of the cranial and caudal ends of the tubules of the primary kidney remain. Concurrently, the Müllerian ducts develop progressively and participate in The formation of the female reproductive tract. Their paired sections transform into the uterine tubes. The epithelium of the uterus develops from the cranial part of the unpaired section of the Müllerian ducts, while the vaginal epithelium develops from its caudal part. In later stages of embryonic development, the single-layered columnar mesodermal epithelium of the vagina is replaced by ectodermal epithelium that grows out from the urogenital sinus and the caudal ends of the Wolffian ducts. The germinal epithelium gives rise to the ovarian follicles and the ovary.

Age-Related Structural Features of the Female Reproductive Organs

In newborns, the ovaries are most often located outside the pelvic cavity, as The process of descent is not completed until 5–6 years of age. After 35–40 years, the ovaries begin to decrease in size. At ages 45–50, ovulation typically ceases, marking the onset of the Climacteric period. Ovarian follicles disappear from The surface of the ovary, causing it to become wrinkled as connective tissue develops in place of the follicles.

In newborns, the uterine tubes are tortuous and straighten out only gradually. The uterus is narrow with a pointed apex; up to the age of 10, the cervix is longer than the uterine body. It acquires its characteristic pear shape by 12–14 years of age. During the climacteric period, the uterus gradually decreases in size by almost half.

The vagina in newborns is short and narrow, lengthening and widening by 9–10 years of age, and particularly during puberty (12–14 years).

Development of the Urinary Organs

In their development, the Kidneys pass through three successive stages: the pronephros, the mesonephros, and the metanephros. These stages of kidney development distantly mirror phylogeny. For instance, the pronephros is found only in lower fish. In higher fish and amphibians, the primary kidney functions. In birds and mammals, the pronephros and mesonephros appear only transiently, after which they disappear and the definitive kidney forms.

In the human embryo, the pronephros is laid down in the third week of development as 8–10 segmental tubules formed from the ventromedial mesoderm at the level of the cervical somites. It persists for only 40 hours before disappearing.

The primary kidney (mesonephros) is formed from segmentally arranged convoluted tubules. One end of each tubule ends blindly, while the other opens into the mesonephric duct, which persists from the pronephros. Under the pressure of an invading capillary tuft (glomerulus), the blind end invaginates to form the double-walled capsule of the renal corpuscle.

The definitive kidney (metanephros) is laid down at the end of the second month of embryonic development, caudal to the primary kidney. Mesoderm, or nephrogenic tissue, accumulates around the mesonephric duct. Medial to the mesonephric duct (also known as the Wolffian duct), an outgrowth forms that invades the nephrogenic tissue. It is within this tissue that the renal tubules arise, connecting at one end with the diverticulum of the Wolffian duct. The diverticulum gives rise to the renal pelvis and Ureter, while the opposite end of the tubule forms the glomerular capsule. The definitive kidney begins to function during the second half of embryonic development.

The three stages of kidney development in ontogeny recapitulate the evolutionary pathway of the Cytology/cytology/86.html">Urinary organs in vertebrate phylogeny.

The kidneys of newborns are insufficiently developed and only reach a structural maturity approaching that of an adult kidney by 8–10 years of age.