Female-Reproductive-System PDF

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Female Reproductive SystemIntroduction The organs that comprise the female reproductive system are group: Internal & External Genitalia (vulva)  Internal Genitalia: Ovaries,Oviducts, Uterus and Vagina  External Genitalia (vulva): Clitoris ,Labia majora, Labia minora, Some glands whose duct...

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Female Reproductive System

Introduction The organs that comprise the female reproductive system are group: Internal & External Genitalia (vulva)  Internal Genitalia: Ovaries,Oviducts, Uterus and Vagina  External Genitalia (vulva): Clitoris ,Labia majora, Labia minora, Some glands whose ducts open into the vestibule Menstrual cycle  Ensure that an ovum is periodically available for fertilization, and in successful implantation and pregnancy  Average: 28days  Manifestation: Menstruation or Menstrual flow- vaginal bleeding for 3 to 5 days  The reproductive life of females is considered shorter than that of Males.  Starts: puberty and is heralded by menarche (first menstruation) occurs when a girls is between 11 to 14 years of age  Ends: menopause (cessation of menstruation) average of age 52. Developmental development of the Female Gamete  Primordial cells: earliest recognizable stem cell of both male and female gametes  2nd to the 8th week of intrauterine life: arise from the endoderm of the yolk sac  4th week of intrauterine life: begin to migrate to the developing gonads; undergoing mitosis  5th week of intrauterine life: reach the developing ovaries, differentiate into the precursor cells (oogonia) of the female gamete or ova  oogonia undergo further mitosis before the daughter cell start the process of Oogenesis that will transform them into ova. Oogenesis  Differentiation of the oogonia into ova in ovaries

 initial stage: differentiation of oogonia into a bigger cells called Primary oocytes, that are no longer capable of mitosis.  End of 3rd month of IUL: oogonia starts to transform into primary oocyte  7TH Month of IUL: all the oogonia in the ovaries of a female fetus have transformed into primary oocytes. 

undergo SUCCESSIVE MEIOTIC DIVISIONS (MEIOSIS 1 & 2) Meiosis I  Primary oocyte replicate their chromosomes, then start the first meiotic division.  similar to meiosis I in Spermatogenesis, EXCEPT in oogenesis the process is suspended in the diplotene stage of prophase and not completed by any of the cells until the female has reached sexual maturity.  DICTYOTENE PHASE: The Primary oocyte go into a meiotic resting period that last for many years.  At birth: 2 million primary oocytes in ovaries that are in DICTYOTENE PHASE  Rule: only one primary oocyte is allowed to resume and complete meiosis I every mens. cycle  produces 2 haploid daughter cells (not identical and not bound to each other by cytoplasmic bridges) 1 daughter cell (Secondary oocytes or ovum) : all cytoplasm from the mother cell goes to  1 daughter cell (First polar body): ends up with nuclear material but without or with minimal cytoplasm  Ovum: capable of further development while first polar body is not, and is later extruded  Some lower forms of animals: First polar body has been observed to undergo meiosis II

Meiosis II  Secondary oocytes or ovum: starts meiosis II  similar also to meiosis II in spermatogenesis , EXCEPT in oogenesis the process is suspended at the metaphase stage and resume only if the cells is fertilized.  NOT FERTILIZED by a spermatozoon: the ovum undergoes no further development and degenerates.  FERTILIZED it hastily completed meiosis II to produce 2 very unequal daughter cells called:  SECOND POLAR BODY : same to the first polar body but later extruded  FERTILIZED OVUM (ZYGOTE); receives all the cytoplasm -It is diploid because its nucleus contains not only 23 but 46 chromosomes since it was formed by the fusion of the male pronucleus (i.e.. nuclear material of the spermatozoon that fertilized ovum) and female pronucleus (i.e. nuclear material of the ovum)

1. OVARY  pair (left and right) of slightly flattened, ovoid organs  About 3cm x 1.5 cm x 1cm in size  sites of oogenesis and produce few hormones.  enveloped by a simple squamous or cuboidal epithelium called germinal epithelium because early histologic thoughts it is the source of the female germ cells.  beneath the epithelium:  tunica albuginea: layer of dense irregular connective tissue which forms a Capsule  Cortex: a thick peripheral zone in the substances of the ovary, that surrounds the medulla.  contains numerous ovarian follicles that are supported by a stroma of collagenous connective tissue  Medulla: a very vascular inner zone; consist of loose connective tissue that is richly supplied with blood vessel.  ovarian follicle: consist of developing female gametes and the cells and other tissue elements that encase it.

OVARIAN CYCLE  refers to the structural and physiological changes that some ovarian follicle undergo during the menstrual cycle in response to the gonadal hormones (FSH and LH) from the pituitary gland.  has 2 phases: Follicular, Luteal  Follicular phase: 1st two weeks of cycle , which ends with ovulation  governed by FSH  Several ovarian follicles undergo varying levels of development  Luteal phase: last 2 weeks which starts the ovulation  Governed by LH  corpus luteum develops and becomes functional OVARIAN FOLLICLE  3 types of ovarian follicles may be seen in the cortex of the ovaries of the sexually mature females: Primodial, Primary & Secondary 1. PRIMORDIAL FOLLICLE : 40 μm  In the ovaries, all primary oocyes get enveloped by a single layer of flattened epithelial cells (Granoulousa cells, squamous epithelial cells, follicular epithelial cells) that rest on a thin basal lamina.  granulosa cells and the basal lamina on which the granulosa cells rest comprise a primordial follicle.  Granulosa cells: flattened cells that resemble ordinary connective tisssue cells  supporting cells that provide developing gamete with nutrients and oxygen.  A primordial follicle that is destined to produce an ovum becomes initially, a primary follicle and later a secondary follicle.

2. PRIMARY FOLLICLE  granulosa cells initially becomes Cuboidal then Columnar and finally as a consequence of repeated mitosis,they stratify.  follicular fluid; liquor folliculi: a fluid that starts to appear between the cells when there are already several layers of granulosa cells

 Primary oocyte gradually increases in size.  When about twice its original diameter: a thick, deeply-staining, glycoprotein membrain-the zona pellucida develops around it.  While the oocyte and the granulosa cells are undergoing the changes…  theca folliculi: the stroma that immediately surrounds the ovarian follicle becomes organized to form a sheath that envelops and becomes part of the follicle.  differentiate into 2 layers: Inner and Vascular Layer (theca interna) and Outer fibrous layer (theca externa)  Theca interna: richly supply with capillaries.  Its cells are large and loaded with lipid.  Under the influence of LH Luteinizing hormone, they secrete androstenedione (a precursor of testosterone), which seeps into the granulosa cell area where it is transformed into estrogen through the help of aromatase, an enzyme that is activated by the granulosa cells under the influence of FSH Follicle-stimulating hormone.  Then the estrogen diffuses into capillaries of the theca interna to carried by blood to its target organs (i.e uterus and other organs of the female reproductive system).  Theca externa: a CT layer that can be regarded as a capsule that envelops and separates the follicle from ovarian stroma.

(Early Prim. Follicle)

(Late Prim. Follicle)

3. SECONDARY FOLLICLE (ANTRAL FOLLICLE)  As the liqour follicle in the primary folliculi increase amount, the irregular spaces between the granulosa cells, which contain liqour folliculi becomes fluent to form a single cresentic fluid cavity called antrum.Once antrum developed, the ovarian follicle has transformed into antral follicle or secondary follicle.  oval shape  stratified epithelium consisting of granulosa cells that displays the thickening (cumulus oophorus) on one pole.  cumulus oophorus protrudes into the fluid-filled antrum and its central area is ocupied by the oocyte, which incidentally stays a primary oocyte until shortly before ovulation.

4. GRAAFIAN FOLLICLE (MATURE FOLLICLE)  as the ovulation approaches, the connection of the ovum and the granulosa cells is loosened by the development of new liquor-filled intercellular spaces.  A FULLY DEVELOPED OR MATURE OVARIAN FOLLICLE IS CALLED GRAAFIAN FOLLICLE.  Final stage in the differentiation of ovarian follicle. Expel ovum and sec. Oocyte  Takes 14 DAYS FOR AN OVARIAN FOLLICLE TO MATURE.  Only one, a dominant follicle, reaches maturity as most of them degenerate at various stages  elaborates follicular regulatory protein: prevents other follicle from getting stimulated by FSH.

OVULATION  LH surge that triggers completion of meiosis I by the primary oocyte also causes the Graafian follicle to burst a few hours later and release its ovum into into the abdominal cavity. (ovulation-release of ovum)  aided by the ciliary action of the oviductal mucosa, the ovum finds its way into the oviduct.  occurs on or about 14th day of an ideal 28 day ovarian cycle.  carries with it the zona pellucida and one to several layers of granulosa cells that cling to the zona pellucida. These granulosa cells are our collectively referred to as corona radiata. FERTILIZATION  An ovum is viable only for about 24 hours after being ovulated, but it takes three to four days for it to travel from the abdominal cavity into the uterus via an oviduct. 

Fertilization: has to take place in the abdominal cavity or the initial part of the oviduct- usually occurs in the distal 3rd of the oviduct.

 spermatozoa still need to undergo capacitation within the female genital tract.  Capacitation: (see male RS) completed by the spermatozoa on a staggered basis some soon after getting deposited in the female genital tract while other as long as five to six hours later; to keep

the chance for fertilization alive over a relatively long time inasmuch as the exact moment that the oocyte and spermatozoon will meet cannot be determined ahead of time.  During Fertilization:  Capacitated spermatozoa undergo acrosomal reaction: breakdown of acrosome; and releases it's hydrolytic enzymes. These enzymes enable a sperm cell to digest and penetrate the zona pellucida.  Once a sperm cell has penetrated the zona pallucida, the zona becomes impermeable to any other sperm cell. This ensures but only one sperm cell fertilizes the ovum.  entry of the spermatozoon into an ovum triggers the completion of meosis II by the secondary oocyte that results in the formation of a diploid fertilized ovum or zygote and second polar body, which, like the first polar body, is consigned to the perivitelline space prior to this extruction.  Aside from restoring the normal (diploid) number of chromosomes in the zygote, fertilization also determines the sex of the fetus and initiates cleavage (i.e., mitotic division of the zygote). Corpus Luteum  granulosa cell layer and theca interna: under the influence of LH, enlarge, become plump, pale staining and polygonal, and they accumulate lipids called lutein cells and what used to be the ovarian follicle is now the corpus luteum.  granulosa lutein cells: cells derived from the granulosa layer  80% of the substance of C. luteum  lighter-staining and larger than the theca lutein cells  produce, and are the main source of progesterone: a hormone that is necessary for preparing the mucosa of the uterus or endometrium for reception of the conceptus (i.e., the product of conception after fertilization)  necessary for the conduct of a successful pregnancy.  theca lutein cells: cells derived from the theca interna  like the theca interna cells, secrete testosterone precursors, which transformed into estrogen.  secrete some amount of progesterone.  Towards the end of the menstrual cycle, corpus luteum, which is maintained by LH, degenerates as LH levels decrease (unless implantation occurs)  IF NOT PREGNANT, the corpus luteum lasts for only about 10 to 14 days and is called corpus luteum of menstruation.  If IMPLANTATION AND PREGNANCY OCCUR, corpus luteum becomes considerably bigger and remains functional for about six more months and becomes known as corpus luteum of pregnancy.  This is because of hormone, human chorionic gonadotropin (hCG), which is secreted initially by the embryo and later by the developing placenta, takes over from LH in maintaining and further developing the corpus luteum.  In addition to estrogen and progesterone, also elaborates Relaxin: secreted by the granulosa lutein cells. It helps maintain pregnancy by inhibiting the contractions of the myometrial muscle fibers. It also aids during delivery by relaxing the pelvic ligaments and cervix.

(Corpus Luteum)

(Lutein cells) Corpus Albicans  the corpus luteum is reduced to a white scar in the ovarian cortex called corpus albicans.  Over a period of months or years, gradually involutes until it finally disappears.

(Corpus Albicans)

Atresia of Follicles 

More than 99.9% of ovarian follicles do not reach maturity. They instead undergo degenerative processes at various stages of development.  Out of 2M, less than 500 are ovulated throughout lifetime

 ATRESIA: The process of degeneration of ovarian follicle. It occurs continuously throughout a woman's lifetime. This is followed by degeneration of the granulosa cells.  small secondary follicles: first sign of abnormality is the eccentric location of the egg nucleus.  bigger secondary follicles, the process is appreciated in the wall of the follicle before changes in the oocyte are noted.  Glassy membrane: the cells of the theca interna become bigger while the basal lamina between the theca interna and the granulosa cells thickens

(Atresia of follicles)

Interstitial Gland of the Ovary  epithelioid cells in the stroma of the ovary that cytologically resemble theca lutein cells.  Numerous during the first years but hardly seen in adults  secrete estrogen and are collectively referred to as interstitial gland of the ovary.

2. OVIDUCTS (UTERINE TUBES; FALLOPIAN TUBES)  pair (left and right) of muscular tubes (about 12 cm long) that serve as passageways for the ovum or the conceptus on its way to the uterus, and for the sperms on their way to fertilizing the ovum.  has four segments: 1. Infundibulum-the funnel-shaped area that is related to the ovary and that opens into the peritoneal cavity and whose margins are provided with numerous processes called fimbriae; 2. ampulla- expanded intermediate portion that comprises 2/3 of the length of the tube; 3. isthmus-the narrow and slender part that connects the Fallopian tube to the uterus; 4. pars interstitialis-the part of the tube within the uterine wall.  Histologic Layers of the Oviducts: 3 layers (mucosa, muscularis and serosa) 1. oviductal mucosa: consists of an epithelium and lamina propria,  forms numerous folds in the ampullary area  Epithelium: simple columnar. The cells are tall in the ampulla but diminish in height towards the uterus.  ciliated cells: play an important role in transporting the ovum or conceptus to the uterus  peg cell: nonciliated but secretory and its secretion provides the conceptus with nutritive material as it traverses the length of the oviduct on its way to the uterus.

 lamina propria: very cellular connective tissue that is richly supplied with blood and lymphatic vessels. It is devoid of true glands. 2. Muscularis- smooth muscle cells that gather in bundles; in between the muscle bundles is an abundant amount of loose connective tissue  outer layer: longitudinally arranged  inner layer: circularly or spirally arranged smooth muscle cells that gather in bundles. In . 3. Serosa: contains a plexus of nerves from where fibers pass inward to supply the muscle and mucosal layers  Is also richly supplied with blood and lymphatic vessels.

(Histologic Layers)

Effects of Ovarian Hormones on the Oviducts  first half of the menstrual cycle:  ciliated cells increase in number and height in response to the estrogen that comes from the ovarian follicles  mid-menstrual cycle (just about the time of ovulation)  ciliated cells are at their tallest and their ciliary beat at their fastest while the peg cells become secretory.  Later in the cycle: progesterone favors the loss of cilia and a decrease in the secretory activity of the epithelial cells.  During the last few days of the cycle, very few cells of the oviductal epithelium are still ciliated and many of the secretory cells are already atrophic. 3. UTERUS  pear-shaped, dorsoventrally flattened, hollow, pelvic organ  receives the conceptus a few days after fertilization and nourishes and nurtures it throughout its development.  non-pregnant adult female: it is about 6.5 cm long, 3.5 cm wide, and 2.5 cm thick. 

two regions: demarcated from each other by a constricted area, the isthmus

1. Body or corpus uteri: expanded upper region comprising much of the organ  Cavity: uterine cavity 2. Cervix: cylindrical inferior region  Cavity: cervical canal (endocervical canal). The two regions are demarcated from each other by a constricted area, the isthmus. Corpus Uteri  3 histologic layers 1. Endometrium: innermost layer is a mucosa.

2. Myometrium: middle layer; the thickest of the three layers and it consists mainly of smooth muscle cells 3. Perimetrium: outermost layer, is serosa/adventitia.

1. Endometrium  where the conceptus implants and develops initially into an embryo and later into a fetus  consists of an epithelium and an underlying lamina propria  simple columnar epithelium and some of the cells are ciliated  simple tubular glands (endometrial glands) invaginate into the entire thickness of the lamina propria  The cells in the lamina propria are mainly fibroblasts but lymphocytes and other types of leukocytes are also present.  superficial portion: 2/3; when it is at its thickest, is shed during menstruation and is aptly referred to as functional layer  Deeper portion: 1/3, which is responsible for regenerating the functional layer after menstruation is referred to as basal layer.  blood supply of the endometrium comes from branches of the uterine arteries called arcuate arteries.  In the functional layer, the branches of the arcuate arteries are very tortuous and are called coiled or helicine arteries. Endometrial Cycle  recurring morphological and physiological changes that the endometrium undergoes during the menstrual cycle in response to the ovarian hormones.  changes are designed to ensure that the endometrium is prepared for implantation of the conceptus in the event of a successful fertilization.  three stages: proliferative or follicular phase, secretory or luteal phase, and menstrual phase.

1. proliferative phase: governed by estrogen that is secreted by the ovarian follicles. In relation to the ovarian cycle, it coincides with the growth of the ovarian follicle.  Starts at the end of menstruation and ends at ovulation.  The functional layer of the endotrium is restores in this phase 2. secretory phase: starts after ovulation and is governed by progesterone that is produced by the corpus luteum in the ovary  Starts immediately after ovulation and lasts until the start of the menstrual phase of the next menstruation. 3. menstrual phase: results from the withdrawal of the ovarian hormones during the latter part of the menstrual cycle.  It's when you get your period. This phase starts when an egg from the previous cycle isn't fertilized and because pregnancy hasn't taken place, levels of the hormones estrogen and progesterone drop.  Average blood loss per menstrual flow is only about 35-50 ml.

2. Myometrium  thickest layer of the corpus uteri, is made up of bundles of large and long (40 um to 90 µm) smooth muscle fibers. The muscle bundles are separated by connective tissue and form four ill-defined layers.

 myometrial muscle fibers increase in size in the presence of estrogen and are smallest immediately after menstruation.  In pregnancy, as uterus increases ...