Female Reproductive System PDF

Female Reproductive System  e female reproductive system consists of internal sex organs and external genital structures. Internal: ovaries, uterine tubes, uterus, and vagina External: mons pubis, labia majora and minora, clitoris, vestibule and opening of the vagina, hymen, and extern...

Female Reproductive System  e female reproductive system consists of internal sex organs and external genital structures. Internal: ovaries, uterine tubes, uterus, and vagina External: mons pubis, labia majora and minora, clitoris, vestibule and opening of the vagina, hymen, and external urethral ori ce. Female reproductive organs undergo regular cyclic changes from pube y to menopause. Ovaries, uterine tubes, uterus of the sexually matured female undergo marked structural and functional changes related to neural activity and changes in hormone levels during each menstrual cycle and during pregnancy. Menarche occurs in females between 9 and 14 years of age and marks the end of pube y. Menopause or climacterium (commonly called the change of life) happens between ages 45 to 55. Production of gametes and steroid hormones are the two major functions of the ova. Oogenesis Developing gametes are called oocytes; mature gametes are called ova. Steroid hormones (estrogen and progesterone are secreted by the ovaries) Estrogen: growth and maturation of internal and external sex organs responsible for the female sex characteristics promote breast development Progesterone: prepare the internal sex organs, mainly the uterus, for pregnancy by promoting secreto changes in the endometrium prepare the mamma gland for lactation Ovarian Structure e ovaries are paired, almond-shaped, pinkish white structures Each ovaries is attached to the posterior su ace of the broad ligament by a peritoneal fold, the mesovarium. e superior (or tubal) pole of the ova is attached to the pelvic wall by suspenso ligament of the ova , which carries the ovarian vessels and ne es. e inferior (or uterine pole) is attached to the uterus by the ovarian ligament.  e ova is composed of a co ex and a medulla. medulla or medulla region: (central po ion) contains loose connective tissue, a mass of relatively large conto ed blood vessels, lymphatic vessels, and ne es co ex or co ical region: (on the periphe ) contains ovarian follicles embedded in a richly cellular connective tissue “Germinal epithelium” instead of mesothelium covers the ova. e su ace of the ova is covered by a single layer of cuboidal, and in some pa s, almost squamous cells. is cellular layer, known as the germinal epithelium, is continuous with the mesothelium that covers the mesovarium. A dense connective tissue layer, the tunica albuginea, lies between the germinal epithelium and the underlying co ex. Ovarian follicles provide the microenvironment for the developing oocyte. Ovarian follicles of various sizes, each containing a single oocyte, are distributed in the stroma of the co ex. Normally, only one oocyte reaches full maturity and is released from the ova during each menstrual cycle. During reproductive life span, a woman produces only about 400 mature ova. Most of the estimated 600,000 to 800,000 prima oocytes present at bi h do not complete maturation and are gradually lost through atresia, the spontaneous death and subsequent resorption of immature oocytes. Follicle development ree basic types of ovarian follicle can be identi ed on the basis of developmental state: primordial follicles; growing follicles, which are fu her subcategorized as prima and seconda (or antral) follicles; and mature follicle or Graa an follicles  e primordial follicle is the earliest stage of follicular development. e primordial follicle rst appear in the ovaries during the third month of fetal development. Early growth of the primordial follicle is independent of gonadotrophin stimulation. A single layer of squamous follicle cells surrounds the oocyte. ee cytoplasm of the oocyte, referred to as ooplasm, contains a Balbiani body - localized accumulation of Golgi membranes and vesicles, endoplasmic reticulum, centrioles, numerous mitochondria, and lysosomes. In addition, human oocytes contain annulate lamellae.  e prima follicle is the rst stage in the development of the growing follicle. e surrounding attened follicle cells proliferate and become cuboidal. Now, identi able as prima follicle. As the oocyte grows, it secretes speci c proteins that are assembled into an extracellular coat called the zona pellucida. e zona pellucida in humans is composed of three classes of sulfated acidic ZP glycoproteins. ZP-1: has not yet been functionally characterized ZP-2: seconda spermatozoa-binding protein ZP-3: spermatozoa-binding receptor and inducer of the acrosome reaction Follicle cells undergo strati cation to form the granulosa layer of the prima follicle. rough rapid mitotic proliferation, the single layer of follicle cells gives rise to a strati ed epithelium, the membrana granulosa (stratum granulosum), surrounding the oocyte. e follicle cells are now identi ed as granulosa cells. Connective tissue cells form the theca layers of the prima follicle. As the granulosa cells proliferate, stromal cells immediately surrounding the follicle form a sheath of connective tissue cells, known as the theca folliculi, just external to the basal lamina. eca folliculi fu her di erentiates into two layers: theca interna: inner, highly vascularized layer of cuboidal secreto cells, possesses Luteinizing hormone (LH) receptors theca externa is the outer layer of connective tissue cells, contains mainly smooth muscle cells and bundles of collagen bers Maturation of the oocyte occurs in the prima follicle.  e seconda follicle is characterized by a uid-containing antrum. Several factors are required for oocyte and follicular growth: Follicle-stimulating hormone (FSH) Growth factors (e.g., epidermal growth factor [EGF], insulin- like growth factor I [IGF-I]) Calcium ions (Ca2) Fluid lled cavities appear among the granulosa cells. As the hyaluronan-rich uid called liquor folliculi continues to accumulate among the granulosa cells, the cavities begin to coalesce, eventually forming a single, crescent shaped cavity called the antrum.  e mature or Graa an follicle contains the mature seconda oocyte. Due to lack of the enzyme aromatase, the theca interna cells are not able to produce estrogen. In contrast, granulosa cells are equipped with aromatase. Ovulation is a hormone-mediated process resulting in the release of the seconda oocyte. Ovulation is the process by which a seconda oocyte is released from the Graa an follicle. release of the seconda oocyte in the middle of the menstrual cycle (i.e., on the 14th day of a 28-day cycle). Factors for the actual release of seconda oocyte include: increase in the volume and pressure of the follicular uid enzymatic proteolysis of the follicular wall by activated plasminogen hormonally directed deposition of glycosaminoglycans between the oocyte–cumulus complex and the stratum granulosum contraction of the smooth muscle bers in the theca externa layer, triggered by prostaglandins  Just before ovulation, blood ow stops in a small area of the ovarian su ace overlying the bulging follicle. ese area of the germinal epithelium, known as macula pellucida or follicular stigma, becomes elevated and then ruptures. e oocyte, surrounded by the corona radiata and cells of the cumulus oophorus, is released from the ruptured follicle. At the time of ovulation, the mbriae of the uterine tube become closely apposed to the su ace of the ova , and the cumulus mass containing the oocyte is then gently swept by the mbriae into the abdominal ostium of the uterine tube.  After ovulation, the seconda oocyte remains viable for approximately 24 hours. If fe ilization does not occur this period, the seconda oocyte degenerates as it passes through the uterine tube.  e collapsed follicle undergoes reorganization into the corpus luteum after ovulation. Cells of the granulosa and theca interna layers then di erentiate into granulosa luteal and theca luteal cells in the process called luteinization. ese luteal cells undergo dramatic morphologic changes, increasing in size and lling with lipid droplets. A lipid-soluble pigment, lipochrome, in the cytoplasm of cells gives them a yellow appearance in fresh preparations. Two types of luteal cells are identi ed: Granulosa lutein cells (80%): centrally located cells, synthesize estrogens, progesterone, and inhibin Inhibin: regulates production and secretion of FSH from the anterior lobe of the pituita gland. eca lutein cells (20%): peripherally located, secrete androgens and progesterone  e corpus luteum of menstruation is formed in the absence of fe ilization. e corpus luteum is a transient endocrine gland in the adult ova that di erentiates from the follicle wall after ovulation. It is vital to mammalian reproduction as it produces the steroid hormone, progesterone, which acts on the reproductive tract to permit emb o implantation and to suppo a maternal environment that sustains intrauterine pregnancy. If the egg is not fe ilized, the corpus luteum stops secreting progesterone and decays (after approximately 10 to 12 days in humans). It then degenerates into a corpus albicans, which is a mass of brous scar tissue. During capacitation, the mature spermatozoa acquire the ability to fe ilize the oocyte Capacitation: spermatozoa must be activated within the female reproductive tract Successful capacitation is con rmed by hyperactivation of the spermatozoa, which manifests as a vigorous, whiplash-like beating pattern of their agella. Fe ilization normally occurs in the ampulla of the uterine tube. Spermatozoa must penetrate the corona radiata to gain access to the zona pellucida. Capacitation is complete when spermatozoa are able to bind to the zona pellucida receptors. Penetration is accomplished by limited proteolysis of the zona pellucida. Before spermatozoa can fe ilize the seconda oocyte, they must acquire more thrust to penetrate the corona radiata and zona pellucida Impregnation of the oocyte allows structures lying inside the spermatozoon to enter the cytoplasm of the oocyte. Several spermatozoa may penetrate the zona pellucida, but only one spermatozoon completes the fe ilization process. ree types of postfusion reaction occur to prevent other spermatozoa from entering the seconda oocyte. Fast block to polyspermy. A large and long-lasting (up to 1 minute) depolarization of the oolemma creates a transient electrical block to polyspermy. Co ical reaction. Changes in the polarity of the oolemma then trigger release of Ca2 from the ooplasmic stores. Zona reaction. e released enzymes (proteases) of the co ical granules not only degrade the glycoprotein oocyte plasma membrane receptors for sperm binding but also form the perivitelline barrier by cross-linking proteins on the su ace of the zona pellucida.  e corpus luteum of pregnancy is formed after fe ilization and implantation. e existence and function of the corpus luteum depends on a combination of paracrine and endocrine secretions, collectively described as luteotropins. Paracrine Estrogens IGF-I and IGF-II Endocrine hCG, LH and prolactin, Insulin  High levels of progesterone, produced from cholesterol by the corpus luteum, block the cyclic development of ovarian follicles. Human chorionic gondatropin (hCG) can be detected in the serum as early as 6 days after conception and in the urine as early as 10 to 14 days of pregnancy. UTERINE TUBES e uterine tubes are paired tubes that extend bilaterally from the uterus towards the ovaries. Also commonly called the fallopian tubes. Each tube is 10 to 12 cm long and can be divided into four segments by gross inspection: Infundibulum: funnel-shaped segment Fringed extensions, or mbriae Ampulla: longest segment Site of fe ilization Isthmus: narrow, medial segment Uterine or intramural pa lies within the uterine wall and opens into the cavity of the uterus.  e wall of the uterine tube is composed of three layers. e serosa or peritoneum is the outermost layer and is composed of mesothelium and a thin layer of connective tissue Muscularis: inner circular and outer thinner longitudinal layer Mucosa: inner lining e mucosal lining is simple columnar epithelium composed of two kinds of cells—ciliated and nonciliated. Ciliated cells: most numerous Nonciliated cells or peg cells: secreto cells Bidirectional transpo occurs in the uterine tube. Several conditions that may alter the integrity of the tubal transpo system (e.g., in ammation, use of intrauterine devices, surgical manipulation, tubal ligation) may cause ectopic pregnancy. Majority of ectopic pregnancies (98%) occur in the uterine tube. Uterus e human uterus is a hollow, pear-shaped organ located in the pelvis between the bladder and rectum. Anatomically, the uterus is divided into two regions: Body: large upper po ion, anterior su ace is almost at; the posterior su ace is convex Ce ix: lower, barrel-shaped, separated from the body by isthmus. e lumen of the ce ix, the ce ical canal, has a constricted opening at each end. e internal os communicates with the cavity of the uterus; the external os with the vagina. Uterine wall is composed of three layers. Endometrium: mucosa Myometrium: thick muscular layer Perimetrium: outer serous layer or visceral peritoneal covering of the uterus. e perimetrium covers the entire posterior su ace of the uterus but only pa of the anterior su ace. e remaining pa of the anterior su ace consists of connective tissue or adventitia. Both myometrium and endometrium undergo cyclic changes each month to prepare the uterus for implantation of an emb o.  e myometrium forms a structural and functional syncytium. e myometrium is the thickest layer of the uterine wall. It is composed of three indistinctly de ned layers of smooth muscle. e middle muscle layer contains numerous large blood vessels (venous plexuses) and lymphatics and is called the stratum vasculare. e smooth muscle bundles in the inner and outer layers are predominantly oriented parallel to the long axis of the uterus.  e endometrium proliferates and then degenerates during a menstrual cycle. During reproductive life, the endometrium consists of two layers or zones that di er in structure and function: e stratum functionale or functional layer is the thick pa of the endometrium, which is sloughed o at menstruation. e stratum basale or basal layer is retained during menstruation and se es as the source for the regeneration of the stratum functionale.  e stratum functionale is the layer that proliferates and degenerates during the menstrual cycle. e vasculature of the endometrium also proliferates and degenerates during each menstrual cycle. Cyclic changes of the endometrium during the menstrual cycle are represented by the proliferative, secreto , and menstrual phases. e menstrual cycle is a continuum of developmental stages in the functional layer of the endometrium. It is ultimately controlled by gonadotropins secreted by the pars distalis of the pituita gland that regulate secretion of the ova. e cycle normally repeats eve 28 days.  ree successive phases of menstrual cycle: Proliferative phase: occurs concurrently with follicular maturation and is in uenced by ovarian estrogen secretion. Secreto phase: coincides with the functional activity of the corpus luteum and is primarily in uenced by progesterone secretion. Menstrual phase: commences as hormone production by the ova declines with the degeneration of the corpus luteum. e proliferative phase of the menstrual cycle is regulated by estrogens. continues after day 1 after ovulation, which occur about day 14 of a 28-day cycle e secreto phase of the menstrual cycle is regulated by progesterone. beginning a day or two after ovulation  e menstrual phase results from a decline in the ovarian secretion of progesterone and estrogen. e corpus luteum actively produces hormones for about 10 days if fe ilization does not occur. As hormone levels decline, changes occur in the blood supply to the stratum functionale. -> eventual ischemic -> sloughing o e menstrual ow normally lasts about 5 days. e average blood loss in the menstrual phase is 35 to 50 ml.  In the absence of ovulation (a cycle referred to as an anovulato cycle), a corpus luteum does not form, and progesterone is not produced. If fe ilization and implantation occur, a gravid phase replaces the menstrual phase of the cycle. Implantation is the process by which the blastocyst settles into the endometrium. e cell mass resulting from the series of mitotic divisions is known as morula, and the individual cells are known as blastomeres. e early emb o gives rise to a blastocyst, a hollow sphere of cell with a centrally located clump of cells. is inner cell mass will give rise to the tissues of the emb o proper; the surrounding placenta. layer of cells, the outer cell mass, will form the trophoblast and the  Fluid passes inward through the zona pellucida during this process, forming a uid- lled cavity, the blastocyst cavity. is event de nes the beginning of the blastocyst. e outer cell mass is now called the trophoblast, and the inner cell mass is referred to as the emb oblast. Implantation occurs during a sho period known as the implantation window. In humans, the implantation window begins on day 6 after the LH surge and is completed by day 10. e invading trophoblast di erentiates into the syncytiotrophoblast and the cytotrophoblast. e cytotrophoblast is a mitotically active inner cell layer producing cells that fuse with the syncytiotrophoblast, the outer erosive layer. e syncytiotrophoblast is not mitotically active and consists of a multinucleate cytoplasmic mass; it actively invades the epithelium and underlying stroma of the endometrium. rough the activity of the trophoblast, the blastocyst is entirely embedded within the endometrium on about 11 day of development. th After implantation, the endometrium undergoes decidualization. During pregnancy, the po ion of the endometrium that undergoes morphologic changes is called the decidua or decidua graviditas. ree di erent regions of the decidua: decidua basalis is the po ion of the endometrium that underlies the implantation site decidua capsularis is a thin po ion of endometrium that lies between the implantation site and the uterine lumen decidua parietalis includes the remaining endometrium of the uterus By the 13th day of development, an extraemb onic space, the chorionic cavity, has been established. e cell layers that from the outer bounda of this cavity (i.e., the syncytiotrophoblast, cytotrophoblast, and extraemb onic somatic mesoderm) are collectively referred to as the chorion. e innermost membranes enveloping the emb o are called the amnion.  e endometrium of the ce ix di ers from the rest of the uterus. e transformation zone is the site of transition between vaginal strati ed squamous epithelium and ce ical simple columnar epithelium. e po ion of the ce ix that projects into the vagina, the vaginal pa or ectoce ix, is covered with a strati ed squamous epithelium. Columnar epithelium of the ce ical canal, the endoce ix, occurs in the transformation zone.  e developing fetus is maintained by the placenta, which develops from fetal and maternal tissues. e placenta consists of a fetal po ion, formed by the chorion, and a maternal po ion, formed by the decidua basalis. e uteroplacental circulato system begins to develop around day 9, with the development of vascular spaces called trophoblastic lacunae within the syncytiotrophoblast. Maternal sinusoids, which develop from capillaries of the maternal side, anastomose with the trophoblastic lacunae.  Fetal and maternal blood are separated by the placental barrier. e placenta is the site of exchange of gases and metabolites between the maternal and fetal circulation.  e placenta is a major endocrine organ producing steroid and protein hormones e placenta produces steroids and peptide hormones as well prostaglandins that play an impo ant role in the onset of labor. e following peptide hormones are secreted by the placenta: HCG: trophoblasts Human chorionic somatomammotropin (hCS), also known as human placental lactogen (hPL): syncytiotrophoblast IGF-I and IGF-II: cytotrophoblast Endothelial growth factor (EGF) Relaxin: softening of the ce ix Leptin: syncytiotrophoblast Other growth factors stimulate cytotrophoblastic growth (e.g., broblast growth factor, colony-stimulating factor [CSF-1], platelet-derived growth factor, and interleukins [IL-1 and IL-3]) or inhibit trophoblast growth and proliferation (e.g., tumor necrosis factor).  e vagina is a bromuscular tube that joins internal reproductive organs to the external environment. e vaginal wall consists of the following: An inner mucosal layer has numerous transverse folds or rugae and is lined with strati ed squamous epithelium. An intermediate muscular layer; outer longitudinal layer and an inner circular layer. An outer adventitial layer; inner dense connective tissue layer adjacent to the muscularis and an outer loose connective tissue layer. e vagina possesses a strati ed, squamous nonkeratinized epithelium and lacks glands. EXTERNAL GENITALIA e female external genitalia consists of the following pa s, which are collectively referred to as the vulva and have a strati ed squamous epithelium as follows: e mons pubis is the rounded prominence over the pubic symphysis formed by subcutaneous adipose tissue. e labia majora are two large longitudinal folds of skin, homologous to the skin of the scrotum. e labia minora are paired, hairless folds of skin that border the vestibule and are homologous to the skin of the penis. e clitoris is an erectile structure that is homologous to the penis. Its body is composed of two small erectile bodies, the corpora cavernosa. Contains numerous senso ne e endings. Vestibule. Lined with strati ed squamous epithelium. the lesser vestibular glands (also called Skene’s glands) – present near the clitoris the greater vestibular glands (also called Ba holin’s glands) – are homologous to the male bulbourethral glands Numerous senso ne e endings are present in the external genitalia: Meissner’s corpuscles: mons pubis and labia majora Pacinian corpuscles: labia majora and clitoris Free ne e endings: external genitalia In females, mamma glands develop under the in uence of sex hormones. Mamma glands are modi ed tubuloalveolar apocrine sweat glands. e areola contains sebaceous glands, sweat glands, and modi ed mamma glands (glands of Montgome ). -> produce a lubricating and protective secretion that changes the skin’s pH and discourages microbial growth. Terminal duct lobular unit (TDLU) of the mamma gland represents a cluster of small secreto alveoli (in lactating gland) or terminal ductules (in inactive gland) surrounded by intralobular stroma. TDLU Each TDLU represents a grape-like cluster of small secreto alveoli that forms a lobule and consists of the following: Terminal ductules are present in the inactive gland intralobular collecting duct carries alveolar secretions into the lactiferous duct. intralobular stroma is specialized hormonally sensitive loose connective tissue Glandular epithelial cells and myoepithelial cells are the most impo ant cells associated with mamma ducts and lobules. e morphology of the secreto po ion of the mamma gland varies with the menstrual cycle. Mamma glands undergo dramatic proliferation and development during pregnancy. First trimester is characterized by elongation and branching of the terminal ductules. Second trimester is characterized by di erentiation of alveoli from the growing ends of the terminal ductules. ird trimester commences maturation of the alveoli. Both merocrine and apocrine secretion are involved in production of milk e secretion released in the rst few days after childbi h is known as colostrum Lactation is under the neurohormonal control of the adenohypophysis and hypothalamus.