Embryology Test 2: fertility cycle/control

fertility cycle

the cycle of physiological preparations for a possible pregnancy

functions of fertility cycle

produce oocytes
conserve energy
protection from pathogens

protection against pathogens

shedding of uterine lining cleans tissue of pathogens
cervical mucus prevents pathogen entrance for most of cycle

effects of fertility cycle

short-term partner preferences change throughout cycle
long-term preferences do not change
fluctuations in attraction to partner
stronger preferences for symmetrical male scents at mid-cycle

average cycle length

28 days

what can change cycle length?

high stress and change in diet

phase organization

ovulation-based phases
standard phases

ovulation-based phases

Pre-ovulatory phase
Post-ovulatory phase

Preovulatory phase

from menstruation to ovulation
-can be variable
-ovulation cannot be predicted based of menstruation

Post-ovulatory phase

ovulation to beginning of menstruation
-relatively constant
-menstruation can be predicted based on ovulation

Standard phases

Menstrual phase
Proliferative phase
Secretory phase

Menstrual phase

first phase of fertility cycle
-bleeding occurs - indicating day 1 of cycle
-surface layer of endometrium is lost
-deep layer remains

Menarche

the onset of menstruation
-occurs earlier than in previous centuries - mainly due to better nutrition

Menopause

cessation of menstruation - due to lack of follicles - estrogen decreases

Proliferative phase

second phase of fertility cycle
-Follicle stimulating hormone (FSH)
-Estrogen
-Luteinizing hormone (LH)

when does FSH peak?

Shortly before ovulation
Stimulates follicle developmet

Estrogen in proliferative phase

levels rise - produced by cells of the mature follicle
increases sensitivity to progesterone
thickens endometrium - aids implantation
promotes cilia growth in uterine tube - fimbriae approach ovary
creates fertile (E) cervical mucus

Luteinizing hormone in proliferative phase

LH surge occurs - peak in LH that causes ovulation
LH surge causes follicle to become a corpus luteum

Corpus luteum

follicle cells left in ovary after ovulation

Secretory phase

last phase of fertility cycle
-ovulation occurs
-corpus luteum is created
-corpus luteum produces estrogen and progesterone

progesterone in the secretory phase

rises
-thickens cervical mucus
-prevents pathogen and sperm penetration
-promotes nutrient secretion in uterine tubes - provides nutrition for possible conceptus
-prevents new follicle development
-blocks FSH and LH
-increases body temperature

Is pregnancy a phase of the fertility cycle?

no.
-interrupts the fertility cycle
-new hormonal patterns develop

HCG

produced by placenta
maintains corpus luteum

estrogens in pregnancy

produced by the placenta
rises throughout pregnancy
increases muscle tissue - needed to push baby out and allows uterus to grow with the baby

Corpus luteum

-corpus luteum produces estrogen/progesterone

progesterone in pregnancy

-progesterone prevents menstruation
-progesterone maintains endometrium
-produced by placenta
-rises throughout pregnancy
-prevents uterine contractions - prevents premature birth, helps maintain pregnancy

fertility control

methods/devices designed to make a fertile act infertile
-prevent proper function of the reproductive system

Methods of action regarding fertility control

contraceptive
interceptive
contragestive

contraceptive

an agent that prevents conception (fertilization)

interceptive

an agent that impedes implantation

contragestive

an agent that disrupts pregnancy after implantation

fertility control vs church teaching

-use of methods is against church teaching - separate unitive and procreative aspects of conjugal union
-breaks the healthy function of the body
-condemned by all christians (including protestants) up to 1930
*could be used for appropriate medical reasons

Methods of fertility control

barrier methods
surgical
hormonal

barrier method of fertility control

Ex: condoms
-prevents sperm from entering female body- prevents sampling of sperm DNA
-prevents vaginal absorption of seminal fluid

Side effects to barrier method

depression
preeclampsia: pregnancy complication with high blood pressure
less frequent conjugal union

preeclampsia

pregnancy complication with high blood pressure

surgical sterilization

cutting and sealing off ducts that transport gametes

Aspects of surgical sterilization

prevents fertilization
can be reversed, but is difficult

kinds of surgical sterilization

vasectomy
tubal ligation

vasectomy

sealing the vas deferns
-makes a man sterile
-sperm die in duct and are consumed by immune cells

side effects of vasectomy

chronic scrotal pain
bleeding
infection

tubal ligation

sealing uterine tubes
-makes a woman sterile

side effects of tubal ligation

painful intercourse
severe hormonal imbalance
osteoporosis
heart disease

hormonal fertility control

fertility hormones are used to promote infertility
-mimics hormones of pregnancy - ovulation doesn't occur during pregnancy
Ex: the pill, hormonal IUDs

Hormonal control generally contains

a progestin and xenoestrogens
-some only contain a progestin

progestogen

a group of hormones with a similar chemical structure

progestin

a synthetic progestogen

progesterone

a natural progestogen

xenoestrogen

a molecule that acts similar to human estrogen
-not found naturally in the human body-can by synthetically created
those in hormonal fertility control are a synthetic type of estrogen

Hormonal methods of action

block hormonal signals for ovulation
create hormonal signals that thicken cervical mucus
prevent full growth of endometrial lining
-impedes implantation
-could promote miscarriage

hormonal control during breastfeeding

hormones enter breast milk and affect baby
reduces the amount of milk produced (if contains xenoestrogens)
negatively alters nutritional composition (if high dose)
may inhibit endometrial gland formation as child grows

Hormonal endometrial effect

long-term use may cause permanent thinning
may impair fertility

Cycles after cessation of hormonal fertility control

may return immediately
may require multiple months for cycle to return to normal

risks to developing child when using hormonal fertility control

increased risk of miscarriage
increased ectopic pregnancy risk
can cause developmental defects if taken during pregnancy
pregnancy may not be recognized

Results of increased fertility control

most abortions (54%) occur after fertility control failure
most unintended pregnancies (80%) result from fertility control failure
divorces rose 50% from 1960 to mid 1970s - attributed to increased use of artificial birth control

condom distribution theoretical basis

usage of condoms prevents exposure to body fluids during sexual intercourse
artificial barriers prevent HIV transmission, thus decreasing infections

results of condom distribution

ineffective
infection rates do not decline and may even increase
may fail due to risk compensation
risky behavior encouraged

risk compensation

the increase of risky behavior to a greater extent than the decrease in risk from an intervention