Female Reproductive System I

Female reproductive system

Ovaries Oviducts Uterus Vagina External genitalia

Ovary (female sex gland, female gonad)

Functions- female gamete production – ovogenesis

- female sex hormone secretion

⇓ estrogens

progesterone

Ovary is almond-shaped organ

is enclosed by the tunica albuginea is covered with the germinal epithelium

⇓

Ovary is subdivided into the cortex and medulla

Cortex

⇓- developing ovarian follicles

- atretic follicles and atretic bodies

- corpus luteum and corpus albicans

Medulla

⇓- loose connective tissue

- blood vessels and lymphatics

- nerves

Ovarian cortex contains ovarian follicles

Ovarian follicles include developing female germ cells

Ovogenesis is a process of the ovum development

Includes 3 stages- stage of proliferation

- stage of growth

- stage of maturation

Ovogenesis stage of proliferation

is represented by oogonia (2n, 2c) proliferating by mitotic divisions

⇑oogonia in the embryonic ovary

Oogonium proliferation occurs only in the fetal period

oogonia are converted to the primary oocytes before birth

⇔

Ovogenesis stage of growth

is represented by primary oocytes (2n, 4c) is subdivided into

- small growth

- large growth

Small growth begins in the embryogenesis

primary oocytes enter the prophase

of the first meiotic division prophase does not complete until puberty oocytes remain in suspended prophase

called the dictyotene for several years

Large growth begins at puberty

lasts for two weeks until before ovulation

oocytes considerably enlarge in size

⇓

from 30µm to 150 µm

oocytes synthesize and accumulate

⇓ - organelles

- cortical granules

- yolk granules

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Large growth is accompanied by folliculogenesis

⇒

⇒

0vogenesis stage of maturation includes meiosis

primary oocyte (2n, 4c)⇓

1st meiotic division

⇓

secondary oocyte (n, 2c)⇓

2nd meiotic division

⇓ ootida (n, c)

First meiotic division completes before ovulation

second meiotic division

⇓

- begins at ovulation

- is arrested at metaphase

- is completed in fertilization

Female meiotic division is unequal

only one cell receives almost all the cytoplasm polar bodies receive minimal cytoplasm and are nonfunctional cells

Ovarian follicle

is the oocyte surrounded by envelopes provides the microenvironment for developing oocyte

Folliculogenesis

Includes stages

⇓- primordial follicle

- primary follicle

- secondary follicle

- tertiary follicle

Primordial follicle

Consists of

- primary oocyte in the small growth

- a single layer of flat follicular cells

Primordial follicle primary oocyte

is arrested in the meiotic dictyotene

measures about 30 µm in diameter

Primordial follicles predominate in the ovary

are located in the cortex periphery just beneath the tunica albuginea

⇒

Primary follicle

Consists of

- primary oocyte

- zona pellucida

- a single layer of cuboidal follicular cells

Primary follicle oocyte

Primary oocyte- enters the large growth- becomes 50 to 80 µm in diameter

⇔

Zona pellucida

is homogeneous acidophilic gel-like layer consists of glycosaminoglycans and glycoproteins is secreted by oocyte and follicular cells

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Secondary (growing) follicle

Consists of

- primary oocyte in the large growth

- zona pellucida

- several layers of follicular cells

- connective tissue theca folliculi

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Membrana granulosa or stratum granulosum

is stratified follicular epithelium follicular cells are identified as the granulosa cells

Stratum granulosum results from cell proliferation

estrogens stimulate granulosa cell proliferation ⇒

Follicular fluid or liquor folliculi

appears when the stratum granulosum reaches

a thickness of 6 to 12-cell layers is secreted by the granulosa cells

FSH stimulates fluid secretion

Secondary antral follicles

fluid-containing cavities coalesce forming the antrum

⇔

Granulosa cell endocrine function

Granulosa cells

- convert androgens to estrogens under

FSH stimulation

- release estrogens to fluid and blood

Theca folliculi

Is subdivided into

- theca interna – loose connective tissue

- theca externa – more dense connective tissue

Theca interna

Contains

- rich network of small vessels

- theca cells

⇔

⇑theca cells arise from mesenchyme

Theca cells are typically steroid-producing cells

Are rich in

- sER

- Golgi apparatus

- vesicular mitochondria

- lipid droplets

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LH stimulates cell activity

Theca cells produce androgens under LH stimulation

Androgens

are transported to the stratum granulosum Granulosa cells

- convert androgens into estrogens

- release estrogens into the fluid and blood

⇑

⇑

Growing follicles are estrogen-producing structures

Estrogen blood level ⇒- increases as the follicles grow

- attains the maximal size before ovulation

Hormonal regulation of ovarian follicle endocrine function

LH stimulates the theca cells

- to produce androgens FSH stimulates the granulosa cells

- to convert androgens to estrogens

- to release estrogens into the blood

Estrogens through feed-back loop

- inhibit FSH release

- activate LH production

Tertiary follicle (mature follicle or Graafian vesicle)

represents the final stage of folliculogenesis is preovulatory follicle measures 10 mm and more in diameter extends through the full cortex thickness bulges on the ovarian surface

Tertiary follicle oocyte

reaches its final size – about 150 µm in diameter resumes the first meiotic division becomes secondary oocyte

Tertiary follicle oocyte is acentrically positioned

on the cumulus oophorus

is surrounded by envelopes

- zona pellucida

- corona radiata

cumulus oophorus ⇑

Tertiary follicle envelopes

Stratum granulosum

- becomes thin

- forms the cumulus oophorus Antrum

- increases in size Theca folliculi

- is more prominent

Ovulation

is the release of the secondary oocyte

with zona pellucida and corona radiata

from the Graafian follicle ⇒

occurs on the 14th day of the large growth

Ovulating oocyte

begins the second meiotic division progresses only to the metaphase division is arrested at the metaphase II

secondary oocyte at the metaphase II

leaves the ovary in ovulation ⇒

Stigma formation Stigma ruptures, forming a small gap in

- germinal epithelium

- ovarian capsule

- wall of the Graafian follicle

⇓secondary oocyte with envelopes leaves the ovary

Ovulation mechanisms

follicular fluid increases in volume and pressure proteolytic enzymes

- lyse the stigma and follicular wall

- separate the oocyte-cumulus complex theca externa myofibroblasts contract

the oocyte leaves the ovary ⇒

Ovulation is hormonal-mediated process

is induced by the gonadotropin maximal

blood concentration ⇒⇓

LH peak (surge) – 12 hours before ovulation

FSH peak (surge) – 36 hours before ovulation

Ovulated oocyte enters the oviduct

Oviduct infundibulum fimbriae cover the ovarian surface direct the oocyte into the oviduct prevent it to enter the peritoneal cavity

Corpus luteum or yellow body

develops in the place of collapsed follicle

after ovulation

Bleeding from the capillaries into the follicular lumen

leads to the corpus hemorrhagicum formation with a central clot connective tissue invades the former follicular cavity

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Corpus luteum formation – luteinization

Stages of vascularization and proliferation glandular metamorphosis secretion involution

Stage of vascularization and proliferation

granulosa basement membrane is destroyed capillaries enter the stratum granulosum and form a rich vascular network granulosa cells and theca cells proliferate

Stage of glandular metamorphosis

granulosa cells and theca-cells differentiate and become the lutein cells increase in size and accumulate

- sER- mitochondria with vesicular cristae- Golgi apparatus- lipid droplets- pigment lipochrome

lipochrome imparts to lutein cells a yellow appearance in fresh preparation

Granulosa lutein cells

are derived from the granulosa cells are pale and large – 30 µm in diameter are centrally located

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Theca lutein cells

are derived from the theca-cells are darker and smaller – 15 µm in diameter are peripherally located

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Corpus luteum development

lasts from 2 to 3 days after ovulation is controlled by LH

Stage of secretion

Corpus luteum secretes progesterone

⇓- prepares female organs (the endometrium, mammary glands) for pregnancy

- inhibits ovarian follicle development

secretion is regulated by LTH (prolactin)

Corpus luteum types

Corpus luteum of pregnancy develops if fertilization and implantation occur attains a size of 2 to 3 cm exists about 6 months

Corpus luteum of menstruation develops if fertilization do not occur is small in size exists about 12 days

Stage of involution occurs after pregnancy or menstruation

lutein cells die by apoptosis cell remnants are phagocytosed by macrophages connective tissue corpus albicans is formed

⇔

Atresia is a process of ovarian follicle degeneration

primordial and primary follicles degenerate and disappear,

leaving no trace of their existence

Atresia of secondary and tertiary follicles

results in the atretic body formation

⇒ ⇒ ⇒⇑

Stratum granulosum changes appear in the first place

granulosa is infiltrated by neutrophils and macrophages granulosa cells are sloughed into the antrum connective tissue and blood vessels invade

the granulosa and antrum

Oocyte degeneration occurs for the second time

oocyte undergoes apoptosis zona pellucida becomes folded and is broken down their remnants are phagocytozed by macrophages

Theca-cells proliferate and differentiate

become the atretic body cells produce steroid hormones, mainly estrogens

⇔

⇑atretic body contains rich capillary network

Glassy membrane is a characteristic feature of the atretic bodies

is the former granulosa basal membrane separates from follicular cells increases in thickness and becomes folded

the glassy membrane in an atretic follicle ⇒

The End

Thank you for attention!