Human Embryology test #2 Doroski Pt. 1

placenta

organ that nourishes the embryo & allows exchange between maternal and fetal circulation, major functions include: gas and nutrient exchange & antibody exchange

chorion

fetal part of placenta, forms from the trophoblast

chorionic villi

extensions of chorion, where exchanges occur between fetal and maternal blood

decidua

maternal part of placenta, forms from the endometrium

decidual reaction

endometrial changes due to implantation, provides an area safe from the mother's immune system

Gas and nutrient exchange

O2 and nutrient exchange-

Travels from maternal blood to fetal blood

Umbilical cord receives O2 and nutrients

CO2 and waste exchange-

travels from fetal blood to maternal blood

umbilical cord is emptied of wastes/CO2

Antibody exchange

maternal antibodies cross placenta and protect the fetus

basic cause of ectopic pregnancy

slowed transport, zona pellucida normally prevents attachment, premature hatching promotes implantation

causes of slowed transport

cilia problems, sexually transmitted diseases, endometriosis

cilia problems

Slows transport

Hatching may occur before transport is complete

Smoking slows cilia

Increased age can lower the number of cilia

endometriosis

endometrium like tissue in abnormal area, can promote uterine tube scarring, provides abnormal areas of easy implantation

human chorionic gonadotropin (hCG)

hormone produced by developing placenta, detected in pregnancy tests

sexually transmitted diseases

can scar uterine tubes, creates obstacles in uterine tubes

expectant management

close observation with interventions only when symptoms manifest,

many cases result in natural death of the embryo, all other treatments are licit afterwards

salpingectomy

removal of uterine tube containing embryo, licit under the principle of double effect

implantation

embedding of embryo in the uterine lining

ectopic pregnancy

an implantation in an abnormal area, most commonly the uterine tubes

salpingostomy

removal of the embryo, leaving the uterine tube intact,

disagreement on whether it is licit, kills the conceptus

methotrexate

a drug that prevents cell division and growth,

prevents growth of trophoblast (makes placenta) causes embryo to die from lack of nutrition, disagreement on whether it is licit

embryo transfer

transfer of embryo to womb, occurred successfully in 1915 and 1980

regulative development

ability to produce normal structures if cells are removed or added

blastomere isolation

Single blastomeres can form normal embryos - up to the 4-cell stage

chimera

an organism with a mixture of cells from two individuals

ex. add a blastomere to a blastocyst, blastomere integrates with host blastocyst

tetraparental embryo

embryo with 4 genetic parents,

blastomeres of 2 early embryos are mixed, a single embryo forms, a normal embryo can result

fetal microchimerism

the presence of fetal cells in mother's body, found in multiple organs, may protect from diseases

fertility cycle

the cycle of physiological preparations for a possible pregnancy

produces oocytes (fertility cycle function)

new oocyte needed after previous oocyte degenerates

conserves energy (function of fertility cycle)

maintenance of endometrium requires a lot of energy

protects against pathogens (function of fertility cycle)

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

typical cycle length

28 days,

varies between women and cycle, most are not 28 days

pre-ovulatory phase

from menstruation to ovulation,

can be variable,

ovulation cannot be predicted

post-ovulatory phase

ovulation to beginning of menstruation,

relatively constant (if a cycle lengthens it is in the pre-ovulatory phase), menstruation can be predicted based on ovulation

menstrual phase

first phase of fertility cycle, bleeding occurs (indicates day 1 of cycle), surface layer of endometrium is lost

proliferative phase

second phase of fertility cycle,

FSH (follicle stimulating hormone) peaks,

estrogen levels rise, Luteinizing hormone surges

LH surge

peak in Luteinizing hormone that causes ovulation, causes follicle to become corpus luteum

corpus luteum

follicle cells left in ovary after ovulation, produces estrogen and progesterone

secretory phase

last phase of fertility cycle,

ovulation occurs, corpus luteum is created, progesterone rises

pregnancy

not a phase of the fertility cycle, interrupts the fertility cycle, new hormonal patterns develop

HCG

produced by placenta, maintains corpus luteum

Estrogens during pregnancy

produced by placenta, rises throughout pregnancy, increases muscle tissue (needed to push baby out, allows uterus to grow as baby grows)

progesterone during pregnancy

produced by placenta, rises throughout pregnancy, prevents uterine contractions (prevents premature birth, helps maintain pregnancy)

Fertility suppression

methods/devices designed to make a fertile act infertile

contraceptive

an agent that prevents conception (fertilization)

interceptive

an agent that impedes implantation

contragestive

an agent that disrupts pregnancy after implantation

barrier methods

ex. condoms,

prevents sperm from entering female body, prevents sampling of sperm DNA, prevents vaginal absorption of seminal fluid

surgical sterilization

cutting and sealing off ducts that transport gametes, prevents fertilization

vasesctomy

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

tubal ligation

sealing uterine tubes, makes a woman sterile

hormonal methods

fertility hormones are used to promote infertility, mimics hormones of pregnancy- ovulation doesn't occur during pregnancy

ex. the pill, hormonal IUD

AIDS prevention - condom distribution- theory

-usage of condoms prevents exposure to bodily fluids during sexual intercourse

-artificial barriers prevent HIV transmission, thus decreasing infections

AIDS prevention- condom distribution- results

-appear ineffective

-infection rates do not decline and may even increase

-may fail due to risk compensation

risk compensation

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

ABC approach to prevent AIDS

abstinence, be faithful, condoms as last resort

used effectively in Uganda,

reduced HIV rate dramatically

fertility awareness

methods for determining periods of fertility and infertility, monitor natural biomarkers of fertility

fertile phase

day of ovulation + ~5 days before

infertile phase

times not in fertile phase

calendar methods

uses length of typical cycle to estimate fertility

Least accurate method

Pre-ovulatory phase inconsistency hinders effectiveness

cervical mucus

mucus changes over cycle time

changes produced by estrogen/progesterone levels

clearness = more fertile

stretchiness = more fertile

basal body temperature

body temperature at rest, rise indicates ovulation has occurred, caused by progesterone increase,

predicts postovulatory infertile phase

hormone monitor

-detects the estrogen rise and LH surge.

-estrogen rise indicates when ovulation may be occurring in the next few days, a potentially fertile time

-LH surge predicts ovulation will occur soon and predicts post ovulatory infertile phase

Fertility awareness method effectiveness

-similar method effectiveness to condoms

-lower method effectiveness than the pill and other highly effective fertility control methods