Ch. 50/51: female reproduction

female development

XX chromosome required for differentiation of gonadal tissue into normal ovary

Absence of AMH - Mullein ducts develop as ovarian tubes

Absence of testosterone - Wolffian ducts degenerate

develop in absence of gonadal tissue

ovaries

paired female gonads on lateral walls of pelvic cavity and held in place by ligaments

produce ovum each month

secrete hormones - estrogen progesterone, inhibin, and relaxin

cortex of ovaries

outer region

Oogenesis occurs within saclike follicles

medulla of ovaries

inner region

Blood vessels, lymphatic vessels, and nerves

What occurs during ovulation?

A mature gamete (oocyte) is expelled from the ovary.

What role do fimbriae play in ovulation?

Fimbriae sweep the ovary surface and direct the oocyte into the uterine tube.

How is the oocyte moved along the uterine tube?

The oocyte is moved by smooth muscle peristaltic contractions and cilia.

What do conciliated cells produce in the uterine tube?

Conciliated cells produce nutritive secretion to support sperm cells and developing zygotes.

uterus

pear-shaped, hollow organ located in pelvis anterior to rectum and posterior to urinary bladder

uterus regions

Body: main region

Fundus: rounded region, superior to entrance to uterine tube

Cervix: narrow neck

uterine wall

3 layers: Perimetrium, Myometrium, and Endometrium

perimetrium

outermost - serous layer

myometrium

middle layer of smooth muscle

Thickens during pregnancy

Contract rhythmically during childbirth

Endometrium

Simple columnar epithelium and connective tissue

Endometriosis

occurs when issue similar to endometrium implants outside uterus

What are mammary glands?

Specialized organs of the integumentary system.

What are mammary glands composed of?

Lobes divided into secretory lobules.

What do ducts from lobules converge into?

Lactiferous duct.

What does the lactiferous duct enlarge to form?

Lactiferous sinus.

How many lactiferous ducts open at the base of the nipple?

15-20.

mammary gland activity

influenced by reproductive hormones and placental hormones

oogenesis

process in which female gametes are produced (ova)

oogenesis process

1. beings in utero, then suspended until reactivated in puberty

2. continues until menopause

take several monthly cycles before some go on to develop towards tertiary follicle - usually one dominates and is ovulated

oogenesis occurs

once per month as part of ovarian cycle

one oocyte

one mature ovum

oogonia

before birth female stem cells

complete mitotic division and undergo mitosis to produce primary oocytes

ovulation once a month

produces ~400-500 mature gametes

at best - only one tenth of one person of the total

Primordial follicle

first follicles formed in fetus contain one primary oocyte

Surrounded by single layer of squamous follicular cells

Follicular (preovulatory) phase

several primordial follicles hormonally stimulated [LH and FSH] to

develop into primary follicles

Oocyte develops

inside ovarian follicle located in cortex

clustered together in regions call egg nests

Granulosa (follicular) cells

organize into zona granulosa

squamous follicular cells divide and become cuboidal shaped

Secrete estrogen as it matures

stimulus changes in uterine lining

Zona pellucida

thin band of glycoproteins overtop plasma membrane that separates oocyte from follicular cells

Regulates sperm-egg interactions (has proteins to which sperm will bind)

Secondary follicle forms from primary follicle

pockets form in thick granulosa cell layer fill with fluid

Thecal cells

layer of cells formed outside granulosa

Produce androgens

Granulosa cells

Converts androgens to estrogen

Antral follicle (tertiary or Graafian follicle)

fluid filled pockets have merged not single antrum

Primary oocyte and its capsule of granolas cells project into antrum on stalk

Follicle continues to enlarge; creates bulge on ovary surface

primary oocyte

suspended in prophase I, completes meiosis I forms secondary oocyte and first polar body

secondary oocyte

arrests development in metaphase II completes second division if fertilized

Ovulation phase

releases secondary oocyte surrounded by zona pellucida and corona radiata

Luteal phase

Corpus luteum is the ruptured follicle that become endocrine gland

secretes progesterone and some estrogen

Persist ~ three months and then degrade if pregnancy does not occur

Corpus albicans

scar tissue remnants of previously active corpus luteum

Gonadotropin-releasing hormone (GnRH)

from hypothalamus

stimulates release of FSH and LH from anterior pituitary gland

FSH

initiates growth of follicle

initiates secretion of estrogen by developing follicle

LH

stimulates further development of follicle

stimulates maximum secretion of estrogen from developing follicle

eventually stimulates ovulation

stimulates formation of corpus luteum

corpus luteum

releases estrogen, progesterone, and inhibin

reproductive cycle

involves events happening concurrently in the ovary and the uterus

uterus phases

menstruation, proliferative phase, secretory phase

ovary phases

preovulatory phase (follicular), ovulation, postovulatory phase (luteal)

endometrium layers (strata)

stratum functionalis and stratum basalis

Stratum functionalis (functional layer)

is inner most of two layers and is site of implantation or is shed during menstruation

Cyclic change in response to fluctuating hormone levels

Stratum basalis (basal layer)

is the deeper, thinner, and mitotic layer

Does not thicken and not shed

Replaces stratum functionals at end of menstruation

uterine cycle

proceeds through three phases during average of 28 days

menstrual phase

days 1-5, uterus shed stratum functionalis

Proliferative (preovulatory phase)

days 6-14 overlaps with follicle growth

Secretory phase

days 15-28 progesterone and estrogen from corpus luteum stimulate functionalis

growth and recoiling of endometrial glands

Vascularization of superficial endometrium

Thickening of endometrium

estrogen

from developing follicles stimulates replacement of functionalism, endometrial glands, spiral arteries, and veins

Begins to thicken

Gland enlarge and veins and arteries increase in number

functionalis is converted

into secretory mucosa as glands secrete glycogen-rich fluid (uterine milk)

[sustains embryo]

no pregnancy

functionalis dies

Menstrual phase begins

pregnancy

secretory phase continues

Uterus continues to develop in preparation for embryos

hormonal control of uterine cycle

beginning: ovarian hormones low, FSH and LH start to rise

by day 5: ovarian follicles increase estrogen production

hormonal control of uterine cycle: proliferation phase

estrogen levels rise

LH and FSH surges - triggers ovulation

ovulation produces corpus luteum (progesterone)

hormonal control of uterine cycle: secretory phase

progesterone levels rise and estrogen levels decrease resulting in inhibition of LH secretion

ovarian cycle

averages about 28 days overall

Follicular phase days 1-14 [variable]

a group of primordial follicles stimulated to develop and may take several cycles before tertiary follicle

develops, and ovulation occurs in a specific follicle occur

What is the duration of the follicular phase?

Days 1-14 [variable]

What hormone's secretion increases during the follicular phase?

GnRH

What hormones are stimulated by GnRH during the follicular phase?

FSH and LH

What does FSH stimulate during the follicular phase?

Initial development of follicles and estrogen production by developing follicles

What role does LH play in the follicular phase?

Stimulates full follicle development and more estrogen production

What happens to the follicles after about one week in the follicular phase?

One follicle becomes dominant and secretes estrogen and inhibin

What effect does inhibin have on FSH secretion?

Causes a decrease in FSH secretion

What do granulosa cells secrete that decreases follicle sensitivity to FSH?

AMH (Anti-Müllerian Hormone)

ovulation occurs

34-48 hrs. after LH surge begins (~9 hrs. after LH peak)

ovulation is triggered by

sudden surge in LH

Primary oocyte completes meiosis I

Zona pellucida and corona radiata surround oocyte

What days does the luteal phase of the ovarian cycle occur?

Day 14 to 28

What hormone maintains the structure and secretory function of the corpus luteum?

LH (Luteinizing Hormone)

What happens to the corpus luteum if there is no pregnancy?

It lasts for 2 weeks before degenerating.

What happens to progesterone and estrogen levels if there is no pregnancy?

They drop.

What triggers the formation of the corpus luteum?

High LH levels that occur after ovulation.

Is the luteal phase relatively constant or variable?

Relatively constant.

estrogen stimulates

Dominate follicle to develop int vesicular follicles -estrogen production positive feedback

Elevated estrogen eventually triggers LH surge that induces ovulation

estrogen inhibits

Regulates GnRH and FSH secretions

Early follicles development while in an active cycle

progesterone

Maintenance of pregnancy once fertilization has occurred with estrogen

other effects of estrogen

increase bone density

increasing HDL cholesterol level

promotes blood coagulation

maintenance of female characteristics

pre-ovulatory phase: Ovary summary

oocyte and follicle develop into tertiary follicle

stimulated by estrogen produced by granulosa cells utilized androgens produced by theca cells

estrogen inhibits FSH and LH

pre-ovulatory phase: uterus summary

menstruation - shed functionalis

replace functionalis

develop blood vessels and glands

ovulation summary

ovary specific event

LH surge - triggered by high estrogen levels - stimulates ovulation

FSH surge - involved in stimulation ovulation, prepare other follicles for future development

post-ovulatory phase: ovary summary

empty follicle transitions to corpus luteum: produces estrogen and progesterone, and inhibin that affect FSH secretion

corpus luteum degenerates into corpus albicans

post-ovulatory phase: uterus summary

functionalis thickens

blood supply increases

glands become active and secrete nutrients

glands become active and secrete nutrients

if no pregnancy - blood vessels constrict starting menstration

Fertilization

events normally occur in upper third of uterine tube

Acrosome reaction

required for fertilization to occur

Releases enzymes from head of sperm - multiple sperm at different times

Hyaluronidase enzyme

allows sperm to break down extracellular matrix of corona radiata [granulosa cell

layer]

Sperm head can now meet oocyte membrane

fertilization events: sperm

receptors bin sperm tip

sperm intracellular Ca rises and stimulated releases of acrosomal enzyme (penetrate zona pellucida) and extension of acrosomal process (binding of oocyte membrane)

sperm and oocyte membranes fuse

sperm DNA enters ovum

nuclei fuse restoring 2N

zona pellucida

layer of extracellular glycoprotein-rich matrix secreted by granulosa cells

beneath corona radiata and just outside plasma membrane

zona pellucida contains

glycoproteins (ZP 1-4) - act as receptors for sperm and facilitate acrosome reaction and fertilization

acrosomal reaction

human oocyte showing surrounding corona radiata and sperm cells

fertilization events: ovum

intracellular Ca rises

polar body formed

cortical vesicles bind oocyte membrane

release enzymes causing ZP to harden and receptor breakdown

prevents sperm binding

human fertilization

is monospermic

polyspermy

around 1-2% if fertilization occurs near ovulation

hatching

Around 5 days blastocyst hatches out of zona pellucida

Allows better access to uterine secretions (nutrients)

Increased growth

Blastocyst adhere to uterine layer

gastrulation

blastula becomes a three layered embryo

ectoderm - skin epidermis

mesoderm - muscle, bone, kidneys, blood, gonads, connective tissue

endoderm - lining of gut, parts of respiratory tract and urinary tract, several internal organs