Ovary

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Cortex

• Germinal epithelium - simple cuboidal epithelium with an underlying tunica albuginea

• Ovarian stroma

• Follicles of varying stages

(a) spheres of epithelial cells surrounding an oocyte

(b) multiple follicles progress through a series of stages until a single follicle ruptures to release the secondary oocyte at ovulation

(c) follicles secrete estrogen during first half of ovarian cycle

• Corpus luteum - formed from the wall of the ovulating follicle after the oocyte is ovulated

(a) secretes progesterone and estrogen and is present during the second half of the ovarian cycle.

• Atretic follicles - degenerating follicles that are not ovulated; 99%

• Corpus albicans - degenerating corpus luteum; a scar-like remnant that shrinks with time

Medulla - Inner region composed of CT, blood vessels, nerves

Stages of Follicular Development

1. Primordial follicle

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• Contains a primary oocyte

• Simple squamous epithelium, which has a basement membrane separating it from surrounding ovarian stroma

• Only stage present until puberty

• Organelles clustered around nucleus

• No zona pellucida

2. Primary follicle (defined by change to simple cuboidal epithelium)

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• contains a primary oocyte

• Begin as a simple cuboidal (unilaminar) -> stratified epithelium (multilaminar): granulosa

• zona pellucida - thick glycoprotein band surround the oocyte, is formed by both oocyte and adjaceent follicular cells

• theca folliculi - stromal cells orginize into region located outside the basement membrane of the follicular cells, formed by the differentiation of the surrounding multipotential stroma cells

• organelles scattered throughout cytoplasm

3. Secondary follicles (deinfed by the presence of fluid-filled spaces in follicular epithelium)

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• contains a primary oocyte

• multiple fuild-filled spaces eventually coalesce to form a single space: antrum

• granulosa layer: follicular cells surrounding the antrum-> convert androgrens (produced by theca interna) into estrogen

• cumulus oophorus: hillock of granulosa cells in which the primary oocyte is embedded (innermost layer surrounding the oocyte == corona radiata)

• theca folliculi develop into:

theca interna (outside the basement membrane): cells respond to LH and secrete androgrens

theca externa (multipotential CT cells): resembes a layer of flattened fibroblasts; serves as a reserve cell source for theca interna

•FSH (secreted by the pituitary gland) and estrogen (granulosa cells) influences follicular growth and maturation

4. Mature (Graafian) follicle: follicle that will rupture, releasing a secondary oocyte

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• present only the day before ovulation

• inc. in follicular liquid that increases antral and follicle size

• granulosa + theca interna cells -> corpus luteum

• bulges from ovarian surface, thinning the ovarian tissue covering the follicle and forming a stigma

• oocyte and surrounding cumulus oophorus detach from granulosa layer and lie free in the antral space

• Meiosis I is completed -> formation of secondary oocyte and first polar body; meiosis II arrests in metaphase

• Ovultation (Day 14 of ovarian cycle): Graafian follicle ruptures at stigma, releeasing haploid secondary oocyte, cumulus oophorus, follicular liquid, and blood

• Oocyte and surrounding cumulus are transported through the oviduct to the ampulla to await fertilization. Fertilization triggers the completion of meiosis II and formation of an ovum.

• Follicle wall continues its conversion to a corpus luteum

• ovulation is stimulated by a surge of LH from the pituitary gland

5. Atretic follicles

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•Of the 2 million primordial follicles and their primary oocytes present at birht, only 450,000 oocytes/follicles remain at puberty, and 450 of those will be ovulated. The remainder degerate, thereby producing more atretic than "normal" follicles

•Atresia can occur at any stage of follicular development and will begin in different layers of the follicle or oocyte depending on the follicle's stage of development. Therefore, many varieties of atertic follicles can be seen.

FSH (secreted by pituiary gland): influence follicular growth and maturation

LH (secreted by pituiary gland): stimulates the formation of the corpus luteum

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estrogen (aromatized by granulosa cells from androgen produced by the theca interna): influence follicular growth and maturation

progesterone: corpus leteum secretes this as well as estrogen during the second half of ovarian cycle (luteal phase); plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy; it also has the side effect of raising the woman's basal body temperature

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• Ovultation (Day 14 of ovarian cycle): Graafian follicle ruptures at stigma, releeasing haploid secondary oocyte, cumulus oophorus, follicular liquid, and blood

• Oocyte and surrounding cumulus are transported through the oviduct to the ampulla to await fertilization. Fertilization triggers the completion of meiosis II and formation of an ovum.

• Follicle wall continues its conversion to a corpus luteum

• Ovulation is stimulated by a surge of LH from the pituitary gland

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corpus luteum: continues to grow for some time after ovulation and produces significant amounts of progesterone and estrogen, which make implantation possible in the endometrium.

corpus luteum (yellow body) - a large, infolded body that is functional during the second half of the ovarian cycle

Functional stage - the corpus luteum is formed by differentiation of the granulosa and theca interna cells in the graafian follicle before and after ovulation.

Formation is stimulated by LH (secreted by pituitary gland).

SECRETE progesterone and estrogen

If pregnancy occurs, placental hormones maintain the corpus luteum, and it is known as the corpus luteum of pregnancy. This structure is functional for the first trimester of pregnancy.

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Composed of:

Granulosa lutein cells: form from cells in the granulosa layer; typical steroid-secreting cells; major component of the corpus luteum;

Theca lutein cells: form from theca interna cells; typical steroid secreting cells but smaller than granulosa lutein cells; remain at the outer boundary of the corpus luteum surrounding the granulosa lutein cells; form a peripheral layer and the infoldings of the corpus luteum

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Corpus albicans (white body) = degenerating stage

consists of a white mass of scar tissue composed of type I collagen and scattered fibroblasts; resulting from the degeneration of the corpus luteum

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Oviduct

Subdivisions:

Infundibulum - funnel-shaped, free end with finger-like fimbria embracing the ovary

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Ampulla (above) - thin walled, lateral two-thirds; fertilization occurs here near its junction with the isthmus

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Isthmus (above) - thicker walled, medial one-third

intramural (interstitial) - within uterine wall; lumen is continuous with uterine lumen

mucosal changes: complex mucosal folds most elaborate in infundibulum and are sparse in the intramural subdivision

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epithelium (above)- simple columnar:

(I) ciliated cells: most abundant in the infundibulum

(II) non-ciliated secretory cells: most abundant in the intramural portion

muscularis mucosae is lacking

submucosa - continuous with lamina propria, forming a continuous CT layer

muscularis externa - poorly defined inner circular and outer longitudinal smooth muscle layers, which are thinnest in the infundibulum and thickest in the intramural portion

serosa: covers the outer surface except the intramural portion

Uterus

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perimetrium: outermost layer of serosa, covering hte upper and posterior regions only; an adventitia surrounds the remaining portions that lie adjacent to the urinary bladder

myometrium: a thick, well-vascularized band of smooth muscle that is arranged in ill-defined layers. the myometrium forms the major portion of the uterus and is equivalent to a muscularis externa.

endometrium = mucosa: simple tubular glands; epithelium is simple columnar, some with cilia. lamina propria (endometrial stroma) contains multipotential stromal cells and abundant ground substance.

zonation of endometrium -

functional zone (stratum functionalis): luminal 2/3 that is slughed during menstruation

basal zone (stratum basalis): firmly attached to the myometrium and retained during menstruation; cell growth from this zone restores functional zone following menstruation.

Phases of the menstrual cycle:

Menstrual Phase (Days 1-4): clinical beginning of cycle; though this actually marks the end of the cycle; at the end of menstruation the functional zone has been sloughed and only the basal zone remains.

Proliferative phase - estrogenic (Days 5-14):

• ovarian follicles are growing and secreting estrogen

• the functional zone proliferates and regernates from the basal zone.

• glands are initially straight but become slightly wavy toward the end of the phase

• spiral arteries grow with endometrium but are difficult to see because they are not yet coiled (i.e., are straight)

Secretory phase - luteal (Days 15-26):

• Corpus luteum is present and functional

• Uterine glands are actively secreting glycogen and glycoproteins by day 20 or 21 when implantation could occur

• Endometrial changes leading up to day of implantation

(a) Glands enlarge and become tortuous, coiled, and secretory.

(b) Spiral arteries lengthen, are highly coiled, and readily visible.

(c) Stromal cells become (pre)decidual cells (about day 24).

(i) Large, pale cells, with glycogen and lipid, located under the surface epithelium and around spiral arteries

(ii) If pregnancy occurs, these cells are called decidual cells and form the decidua, the maternal placenta.

(iii)If pregnancy does not occur, these same cells are called pre-decidual cells and they are sloughed with menses.

Premenstrual phase = (ischemic portion of secretory phase) = Days 26-28

(1) Estrogen and progesterone secretion from the ovarian corpus luteum decreases, resulting in:

(2) periodic constriction of spiral ischemia in the overlying tissue in the functional zone =>

(3) the endometrium becomes necrotic and disrupted

(4) Spiral arteries reopen and blood flows into the ischemic tissue, resulting in bleeding from the spiral arteries into the stroma

(5) Cycles of constriction and reopening of the arteries leads to degeneration of the functional zone and menstruation.

Menstrual phase (Days 1-4):

(1) The functional zone becomes necrotic and is sloughed as menses

(2) Menstrual flow contains blood, tissue frgaments, and uterine fluids.

(3) Only the basal zone remains, from which the functional zone will be regenerated

Cervix - the lowest portion of the uterus, beginning above and extending into the vagina

Endocervix: surrounds the (endo)cervical canal

Mucosa: simple columnar epithelium with cilia  and many mucus secreting cells; lamina propria is fille dwith epithelial folds, the plica palmatae, that are lined with mucus secreting cells; nabothian cysts occur when a fold becomes occluded

Cyclic changes and functions of the cervix:

Mucosa is not sloughed during menstruation. Spiral arteries are absent.

Cyclic changes in the cervical mucus

•At mid-cycle, secretions are abundant and more fluid, facilitating the movement of sperm through the cervix. The alkalinity of the cervical mucus neutralizes the low vaginal pH, providing a more favorable environment for spermatozoa.

• At other times cervical mucus is more viscous, making sperm penetration difficult.

Ectocervix: portion of cervix that protrudes into the vagina

•simple stratifed squamous epithelium

•The junction of this epithelium with the simple columnar epithelium of the endocervical canal is abrupt and called the transitional zone; occurs at the external os; the transition zone is where squamous metaplasia of the endoervix is most likely to occur & is the site where cervical cancers most frequently arise.

Vagina

Mucosa: Epithelium - stratified squamous nonkeraitinized that synthesizes and accumulates glycogen; no glands

lamina propria: rich with numerous erectile-type blood vessels and elastic fibers

muscularis mucosae: lacking

submucosa: continuous with the lamina propria, forming a single CT layer

muscle layer: inner circular and outer longitudinal smooth muscle layers intertwine; skeletal muscle surrounds the vaginal orifice

Adventitia of loose CT:

Chorion (fetal placenta) - composed of extraembryonic CT and 2 cell layers derived from the trophobalst, called the cytotrophoblast and the syncytiotrophoblast

Formation of fetal placenta - forms within the 23 days following ovulation

Trophoblast erodes into the maternal endometrium and immediately differentiates into

(1) cytotrophoblast: inner (towrad embryo) single layer that gives rise to the syncytiotrophoblast

(2) synctyiotrophoblast: multinucleated, outer syncytium formed from the cytotrophoblast; aggressively invades the uterine endometrium

Lucunae: separated by columns of syncytiotrophoblast, develop in the syncytiotrophoblast and coalesce, becoming filled with maternal blood from the spiral arteries. After the formation of villi, lacunae are called intervillous spaces

Tertiary (definitive) chorionic villi: the final in a series of villi that protrude from the syncytiotrophoblast colums into the lacunae, increasing the surface area of the placenta that is exposed to maternal blood

Formed by invasion of syncytiotrophoblast columns by cytotrophoblastic cells and then by fetal connective tissue. Finally, fetal blood vessels invade into and form within the fetal connective tissue.

Ovarian Cycle

(1) Follicular phase (days 1-13): follicles are differentiating and secreting estrogen. Follicles are developing while menstruation (days 1-4) is occuring

(2) Ovulation (day 14): Graafian follicle ruptures, releasing secondary occyte.

(3) Luteal phase (days 15-28): Corpus luteum is the functional ovarian structure, secreting progesterone and estrogen. Hormone secretion dimishes after day 26.

(4) The fall in estrogen triggers FSH release.

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basal (straight) arteries: remain in and supply basal zone

spiral arteries: arise in the basal and extend into and supply the functional zone and a capillary plexus beneath its surface epithelium. Early in the menstrual cycle, spiral arteries are nearly straight, but they become highly coiled later in the cycle.