ch. 12 conception & fetal development Flashcards
what does healthy people 2030 recommend for childbearing women of age
daily intake of atleast 400 mcg of folic acid from fortified foods or dietary supplements
TIP: b vitamin complex prevents spina bifida in babies
where does fertilization occur in the uterus (6)
outer 1/3 of the fallopian tubes
- ovary is an extension of the uterus
- uterine fundus: top of the uterus
- endometrium: inner layer of uterus
- myometrium: middle layer of uterus
- perimetrium: outer layer of uterus
fertilization (occurs where, most fertile, survive, avg. male will deposit __ before reaching ___)
- takes place in the ampulla (out 1/3 of fallopian tubes)
- ova MOST FERTILE 12-24 hours after ovulation (sometimes releases from both ovaries which indicates TWINS)
- sperm can survive 48-72 hours
- average male will deposit 200-500 million sperm in the vagina about 1000 reaching the ampulla
embryo and fetus: pregnancy lasts how many days? embryo develops? most critical time)
280 days from first day of last menstrual period (LMP)
- embryo develops day 15 until 8 weeks after conception (2-8 weeks)
- MOST CRITICAL TIME for development of the organ systems and main external features (have to keep embryo safe during this time)
teratogens
substances or exposure that causes abnormal development
fertilization pre-fetal stages
zygote -> morula -> blastocyst -> trophoblast -> implantation (nidation) -> embryo -> fetus
zygote
fertilized ova that goes through rapid cell division
- referred to as blastomeres
morula
blastomeres form a solid ball of 12-32 cells
blastocyst (3)
(day 5-7 with implantation day 9)
- inner solid mass of cells inside a central cavity (middle layer of placenta)
- later develops into a double layer of cells (embryonic disk) from which the embryo & amnion (inner amniotic sac membrane) will develop
- AKA AMNION
trophoblast (3)
outer later of cells that surrounds the cavity
- develops into one of the embryonic amniotic membranes
- AKA CHORION
implantation
occurs 7-9 days after fertilization
embryo
2-8 week development
fetus
9 week -> birth
chorioamnionitis
infection of both layers
membranes (2)
two fetal membranes that surround the developing embryo
- chorion (trophoblast)
- amnion (blastocyst)
amniotic fluid (98-99% ____, 6)
98-99% water
- thermoregulation for fetus
- source of oral fluid/repository for waste (drink/urinate)
- assists with fluid/electrolyte homeostasis
- provides for fetal cushioning, musculoskeletal development (protects)
- antibacterial factors
- provides for auditory stimulation (can start hearing at early age)
polyhydramnios (hydramnios)
> 2 Liters volume (too much volume)
- connected with congenital defects
oligohydramnios
< 300mL (not enough volume)
- baby can’t grow, vasoconstriction
development of the embryo (2)
1) yolk sac
- cavity on the other side of the developing embryonic disk
- aids in transferring maternal nutrients and oxygen for the first 5-6 weeks
2) umbilical cord
- located centrally on placenta
- vessels: 2 arteries, 1 veins (smaller)
- wharton’s jelly: surrounds vessels to prevent compression
TIP:
- vein carries good nutrients
- arteries: carries toxins and waste products from umbilical cord
placenta (structure, function - endocrine, function - metabolic, circulatory effect) (4)
1) structure:
- complete by 12th week (fully functional by 4th week)
2) function (endocrine gland function):
- produces 4 hormones: human chorionic gonadotropin (HcG), human placental lactogen (hPL), progesterone (maintain pregnancy), estriol (one of the main estrogens produced by placenta)
3) function (metabolic):
- respiration
- nutrition
- excretion
- storage
4) circulatory effects on placental function -> dependent on maternal blood pressure supplying circulation
fetal maturation
stage of the fetus begins at 9 weeks (when fetus becomes recognizable as a human being and lasts until pregnancy ends)
viability (what, how long)
the capability of the fetus to survive outside the uterus
- 20 weeks (22-23 weeks)
fetal circulatory system (3)
1) ductus arteriosus: shunt blood R -> L atrium (closes at birth)
2) ductus venosus: feeds liver, shunts liver
3) foramen ovale: shunts within the heart (tunnel like opening that allows blood to flow from the right atrium to the left atrium during fetal development)
hematopoietic system (2)
- fetal hemoglobin: has a high affinity for oxygen and carries 20% - 30% more oxygen than maternal hemoglobin (HgbF -> 3rd week pregnancy develops)
- hematopoiesis: the formation of blood and begins in the 3rd week
respiratory system (2)
- pulmonary surfactants: present by 36 weeks
- L/S ratio: used to determine fetal lung maturity (eg. preeclampsia, uncontrolled DM can lead to early birth, done via amniocentesis)
TIP:
- fetus can’t breathe on own at 28 weeks
- amniocentesis: extract amniotic fluid to look for ratio -> see how well fetus will do outside uterus
gastrointestinal system(2)
- meconium: first fetal/newborn stool
- EXAM: sign of distress!!!
hepatic system (2)
- develops from the foregut around 4 weeks gestation
- glycogen stored in fetal liver (helps fetus to survive)
renal system (2)
- kidneys form at week 5
- function at week 9n
neurological system (2)
- originates from ectoderm
- fetal senses: taste (16 wks), sound (24 wks), sight (26 wks)
endocrine system: (3)
thyroid
adrenal cortex
pancreas
reproductive system
sex differentiation begins during the 7th week (1 1/2 months)
integumentary system (2)
- vernix caseosa: thick cheese substance over baby, functions as moisturizer
- lanugo: fine, downy hair gives skin protection
immunologic system (2)
- IgG crosses placenta (mom -> fetus)
- fetus produces IgM (own antibodies)
TIP:
- receives immunity from mother
dizygotic (4)
multiple mature ova results in 2 zygotes
- occurs in approximately 1/3 births in the US accoutning for 70% of all twin gestations
- considered FRATERNAL
- increases in frequency with: maternal age (peaking at 37 years) with parity (more pregnancies increases chances of having twins again), use of ART
monozygotic (5)
one ova that divides
- same sex, often referred to as IDENTICAL
- 0.4% of all pregnancies
- mono-di: each twin has own amnion, but one chorion
- mono-mono: most dangerous, one amnion, one chorion, twins (one sac)
conjoined
cleavage is incomplete and occurs late (cellular division)
factors influencing fetal growth and development (3)
- influenced by complex interactions between genetic and environmental factors (genetic/lifestyle)
- fetal and parental genetics play a major role (sperm donor: may not know genetic history - many CONGENITAL ANOMALIES d/t teratogens)
- environmental influences on fetal development: health of placenta, maternal health (nutritional status, maternal age, drugs, chemicals, hormones, viruses in maternal system), teratogens (effects depends on timing of exposure in pregnancy)
TIP: first 3 MONTHS of pregnancy are recognized as the MOST CRITICAL PERIOD of embryonic and fetal development
what is a major cause for the increase in multiple births in the US?
increased use of assisted reproductive technology
