Honors anatomy & physiology - PowerPoint Presentation

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Honors anatomy & physiologyThe reproductive systemPart 3

The Menstrual Cycle

&

Pregnancy

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Female Reproductive Cycle

2 parts:

Ovarian Cycle

series of events in ovaries occurring during & after maturation of

oocyte

Uterine (Endometrial) Cycle

concurrent with ovarian cycle

series of changes in

endometrium

to

repare

it for implantation of fertilized egg

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Hormonal Regulation

Hypothalamus secretes

GnRH

(

gonadotropin

-releasing hormone) that controls both the ovarian & uterine cycles

GnRH

stimulates release of FSH & LH from anterior pituitary

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FSH

LH

initiates follicle growthstimulates:follicles to release Egranulosa cells to turn androgens  E

stimulates :further development of folliclesrelease of E from folliclesrelease of androgens from theca cells@ midcycle LH surge triggers ovulationcorpus luteum  E, P, relaxin, inhibin

Effects on Ovaries

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Estrogens

3 of 6 different estrogens are present in significant amts:

ß

estradiol

Estrone

Estrial

m

ost abundant in non-pregnant female

made from cholesterol in ovaries

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Functions of Estrogens

promote development &maintenance of female reproductive structures, 2

◦ sex characteristics

increase protein anabolism working synergistically with

hGH

l

owers cholesterol (1 reason females <50

yo

have lower risk of CAD)

moderate levels inhibit release of

GnRH

, FSH, LH (negative feedback loop)

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Progesterone

secreted by corpus

luteum

with E prepares

endometrium

for implantation & breasts for lactation

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Relaxin

produced by corpus

luteum

i

nhibits contractions of

myometrium

during pregnancy, placenta secretes more

relaxin

…@ end of pregnancy it increases flexibility of pubic

symphysis

& may help dilate

cx

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Inhibin

secreted by

granulosa

cells of growing follicles & by corpus

luteum

after ovulation

action: inhibits secretion of FSH & to lesser extent LH

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Hormones of the Menstrual Cycle

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Phases of the Menstrual Cycle

Menstrual Phase

Preovulatory

Phase

in ovaries called follicular phase

in uterus: proliferative phase

Ovulation

Postovulatory Phase

in ovaries called

luteal

phase

in uterus:

secretory

phase

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Menstrual Phase

aka menstruation, menses

~1

st

5 d of cycle (d 1 of flow = day 1 of cycle)

Ovaries:

FSH causes several primordial follicles to develop

 1

◦

follicles  2

◦

follicles

Uterus:

declining E & P levels

 prostaglandins  constriction of uterine spiral arterioles  O deprived tissue  death & shedding 50 – 150

mL

of blood, tissue fluid, mucus, epithelial cells (entire stratum

functionalis

sloughs off)

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Preovulatory Phase

time between end of menses

 ovulation

most

v

ariable length in time (reason cycles vary in length)

Ovaries:

follicles secrete E &

inhibin

 d 16

one 2

◦

follicle in 1 of the 2 ovaries becomes the dominant follicle (secretes more E &

inhibin

 decreases FSH)

dominant follicle (

Graafian

) enlarges until ovulation:~2cm

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Preovulatory Phase (Proliferative)

Uterus:

E stimulates repair of

endometrium

producing new stratum

functionalis

new endometrial glands form

endometrium

thickens from ~4 to 10 mm

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Ovulation

d 14 in 28 d cycle

2

◦

oocyte

surrounded by

zona

pellucida

& corona

radiata

higher levels of E @ end of

preovulatory

phase have + effect on cells that secrete LH &

GnRH

: their increase leads to ovulation

OTC test for LH surge used to predict ovulation

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Mittleschmerz

pain noted @ time of ovulationcaused by small amt of blood that leaks into pelvic cavity from ruptured follicle

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Postovulatory Phase (Luteal)

time between ovulation & onset of next menses

Most constant part of cycle = 14 days (d15 – 28)

Ovary:

under influence of LH,

granulosa

cells transformed

 corpus

luteum

cellswhich

secrete E, P,

relaxin

,

inhibin

if

oocyte

not fertilized: corpus

luteum

lasts 2 wks  corpus

albicans

+ fertilization: corpus

luteum

persists until “rescued” by

hCG

(human chorionic

gonadotropin

) which is made by

chorion

of embryo @ ~ 8d after fertilization

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Postovulatory Phase (Secretory)

Uterus:

P & E made by corpus

luteum

promote: growth & coiling of endometrial glands

vascularization

of superficial

endometrium

thickening of

endometrium

(12 – 18 mm)

these changes peak 1 wk after ovulation

if no fertilization levels of P & E decline which eventually causes menstruation

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Homeostatic Imbalances

Dysmenorrhea

painful menses

Amenorrhea

absence of menses

#1 reason = pregnancy

Endometriosis

disorder in which

endometrium

grows outside uterus

+/- painful

can cause infertility due to scarring

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Embryonic Period

Fertilization:

Nuclei from sperm merges with nuclei from 2

◦

oocyte

forming a diploid nucleus

Fallopian tube normal site of fertilization w/in 12 -24 hrs after ovulation

sperm can remain viable up to 48 hrs after deposition in vagina

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Fertilization

sperm must penetrate 2 layers:

c

orona

radiata

g

ranulosa

cells that surround 2

◦

oocyte

zona

pellucida

clear glycoprotein layer between corona

radiata

&

oocyte’s

plasma membrane

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Fertilization

ZP3: 1 of glycoproteins acts as sperm receptoracrosomal reaction: occurs when ZP3 binds to specific membrane protein on sperm head plasma membrane  release of contents of acrosome

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Acrosomal Reaction

acrosomal

enzymes digest a path thru

zona

pellucida

lashing flagella of sperm pushes it forward

several sperm bind to ZP3 molecules but only 1

st

sperm to penetrate

zona

pellucida

& reach plasma membrane of

oocyte

“wins”

once diploid nucleus formed its called a

zygote

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Cleavage of the Zygote

rapid M phase but no growth

1

st

division begins ~24 hrs after fertilization taking 6 hrs to complete, following divisions take less time

~2 d after fertilization = 4 cells

~ 3 d after = 16 cells

cells get progressively smaller, & are called

blastomeres

morula

(mulberry) solid sphere of cells, still surrounded by

zona

pellucida

& still about size of original zygote

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Blastocyst Formation

~ end of 4

th

d: # of cells in

morula

increase as it is still moving thru fallopian tube

 enter uterine cavity on d 4-5

glycoprotein secretions

fromendometrial

glands enter

morula

providing nourishment

@ ~ 32 cell size, fluid enters

morula

& collects between

blastomeres

forming fluid-filled cavity =

blastocyst

cavity

(up to ~100 cells) & now called a

blastocyst

or

blastula

(still ~ same size as original zygote)

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Blastocyst Forms Layers

2 distinct structures form:

Inner cell mass

eventually becomes embryo

Trophoblast

u

ltimately forms fetal portion of placenta

5

th

d:

blastocyst

digests hole thru

zona

pellucida

& squeezes out

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Implantation

attachment of blastocyst to endometriumafter implantation endometrium becomes modified & is called decidua

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Trophoblast

develops into 2 layers (both part of chorion):SyncytiotrophoblastCytotrophoblast

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hCG is Produced

hCG

: human chorionic

gonadotropin

Produced by

trophoblast

starting on d 6

hCG

causes

endometrium

to grow & proliferate

hCGprevents

the menstrual cycle from

occuring

reason female misses her menses when she is pregnant

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Inner Cell Mass

differentiates into a bilaminar discHypoblastEpiblast

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Amnion

thin protective membranedevelops from cytotrophoblast

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Gastrulation

@ end of cleavage stage, cells making up the blastula move

surface proteins help cells recognize each other & help sort cells

3 layers of

gastrula

formed: called the 3

germ layers

Endoderm

Mesoderm

Ectoderm

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Extraembryonic Membranes

develop from the germ layers but are NOT part of the embryo (lost at birth)

lie outside embryo & provide protection & nourishment

4 components:

chorion

amnion

allantois

yolk sac

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Placentation

formation of the placenta

site of exchange of nutrients & wastes between the mother & fetus

also functions as protective barrier & produces several hormones to maintain pregnancy (

hCG

)

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Week 2

implantation continues until complete emersion into endometrium

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Weeks 3 - 4

development of nervous system & cardiovascular system evident

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Weeks 5 - 8

embryo will develop all structure that an adult has by end of week 8

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Embryonic Period

Fetal Period

1st thru 8th wkcharacterized by development of structures (organs)

begins @ 9th wk & goes until birth @ 38 wks (from fertilization)characterized by growth & development of structures formed in embryonic period

Embryo/ Fetus

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Maternal Changes in Pregnancy

uterus nearly fills abdominal cavity

GI tract compressed may cause heartburn, constipation

pressure on bladder causes frequency & urgency

compression of inferior vena cava may cause varicose veins, &/or edema in legs

compression on renal vessels may cause elevated BP (renal hypertension)

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Maternal Hormone Changes During Pregnancy

pregnancy maintained by

hCG

, E, & P

relaxin

increases flexibility of pubic

symphysis

hCS

(human chorionic

somatomammotropin

) contributes to:

breast development

protein anabolism

catabolism of glucose & fatty acids

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Labor

process by which fetus is expelled from uterus

true labor involves dilation & thinning of

cx

false labor may have painful contractions but there are no cervical changes

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Positive Feedback Loop

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Adjustments Infant Makes at Birth

Infant’s respiratory & cardiovascular systems undergo changes to enable them to become self-supporting

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Maternal Breast Changes

hormonal changes, increased blood flow, & changes in breast tissue cause breast to feel heavy, swollen, or sore

breast tenderness commonly starts w/in 4 wks

areolas enlarge & darken

Colostrum

the yellowish1

st

milk your baby gets may leak out any time after 3

rd

mo

contains

Ig

A antibodies, protein, fat-soluble vitamins, minerals

r

eplaced by milk after 2 – 4 days baby nursing

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Breastfeeding is Best

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Prolactin

Oxytocin

made in anterior pituitaryrelease controlled by dopamineaction: activates mammary glands to make milkseveral minutes of baby nursing stimulates release

made in hypothalamus & stored in posterior pituitarybaby nursing stimulates its releaseaction: milk let down

Lactation Hormones

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