Conception & Prenatal Development Flashcards
Oogenesis
- Formation, maturation of an egg (ovum)
- By 30th week of gestation, female fetus has developed all of the ova she’ll ever have
- Eggs aren’t released by ovary until after puberty has occurred
- Mature ovum released from ovary during ovulation
> Occurs 14 days before next menstrual period would begin
Sperm
- Head - penetrates through wall of ovum; enters cell & joins nucleus of ovum; starts formation of zygote
- Middle
- Tail - provides mobility (all the way to the distal 3rd of the fallopian tube)
Female (XX) - gives X chromosome
Male (XY) - gives X or Y chromosome
Ability to conceive, implant, grow, & birth
Females need ___ & ___ hormones
Male sperm undergoes physiologic changes to penetrate the egg
estrogen; progesterone
___-___ Period
Fusion of egg & sperm
First 2 weeks after conception
Zygote undergoes cellular division
Zygote enters & implants in the uterus
> 3-4 days -> ___
> implantation 6-7 days post conception (can be mistaken for start of period)
Production of ___
Pre-Embryonic
decidua
human chorionic gonadotropin (hCG)
?
Best implantation site
uterine fundus
?
___ cells develop into the placenta & fetal membranes
___ cells develop into the fetus
Outer
Inner
hCG keeps estrogen & progesterone levels increased to support pregnancy
___ Period
Beginning of the 3rd week through the 8th week post-conception
Basic structures of all major body organs are completed during this period
Organs are especially vulnerable to ___ (environmental agents that may cause damage); can also be due to a lack of “something” (e.g. folic acid)
Embryonic
teratogens
By 4 weeks, ___ closes
By 8 weeks, ___ has developed
Ears & kidneys develop at the same time
neural tube
spinal cord
Which developmental week is this?
Period is missed
Early heartbeat at 21-22 days post-conception
Week 3
Which developmental week is this?
Heart is beating
Rapid brain growth
Paddle-shaped limb development
Week 5
Which developmental week is this?
Embryo shape changes
Neural tube closure
Heart partitions into 4 chambers
Respiratory & early digestive tracts develop
Trachea & esophagus separate completely
Week 4
Which developmental week is this?
Heart completes its final 4 chamber formation
Ears & facial features begin to develop
Week 6
Which developmental week is this?
Embryo takes on a more human-like form
Refinements to all systems continue
Eyes pigmented but not covered by eyelids yet
Fingers & toes defined
External genitalia begin to differentiate but not fully distinguished until week 10
Week 8
Which developmental week is this?
Growth & refinement of all systems
Intestines grow faster than abdominal cavity; contained in umbilical cord
Week 7
___ Period
Begins at 9 weeks post-conception until birth
Fetal
Weeks 9-12
Large head that is 1/2 total length of fetus
Body catching up to grow w/the embryonic period
Fetal movement begins but detection by mother is too light
Eyes close & won’t reopen until about 26 weeks
Intestines move from umbilical cord into abdomen
Fetus produces urine which is excreted into amniotic sac; is 1 of the main components of amniotic fluid
By end of 12th week, fetal sex can be determined by appearance of external genitalia on ultrasound
Weeks 13-16
Fetal body grows rapidly
Fetal movements strengthen
Multiparous women can detect those movements
Experience of fetal movements - quickening
Primiparous women don’t pick up on these sensations as fetal movements; e.g. “butterflies”
Eyes & ears reach final position, appearing more “human-like”
Weeks 17-20
Whether primiparous or multiparous, experience fetal movement
___ begins to cover the skin to protect it from amniotic fluid
___ covers the entire body & helps ↑ attach to the fetus
Minimal amounts of ↑ & ↑ at birth
___ builds up on back of neck, behind sternum, & around kidneys
* Important in thermoregulation of neonate
Vernix caseosa
Lanugo
vernix caseosa; lanugo
Brown fat
Weeks 21-24
Growth & weight gain continue
Little subcutaneous fat
Lungs produce ___ (important for breathing)
> is a surface-active lipid that makes it easier for baby to breath after birth by reducing surface tension in the alveoli & preventing alveolar collapse w/each breath
Complications here can cause permanent disability & death
surfactant
Weeks 25-28
24 weeks & beyond = viability
Subcutaneous fat develops under skin, assisting thermoregulation
Surfactant production up until delivery
Eyes reopen
Blood produced in ___ instead of liver & spleen
Fetus in head down position (___)
bone marrow
vertex
Weeks 29-32
Skin pigments
Toenails & fingernails present
Increase in subcutaneous fat = contour shape
If born now = NICU support
Weeks 33-38
Pulmonary system continues to mature
Abundant subcutaneous fat
Lanugo may still be present (it will fall out)
Vernix caseosa remains in folds & creases (in ears, groin, armpits)
Testes descend into scrotum
Breast tissue present on male & female babies (a baby girl can lactate & “pseduo-menstruate”; this is normal!)
? age is about 2 weeks longer than fertilization age
Consider 38-42 weeks of development
If fertilization age is 2 weeks, this age is 4 weeks
* Pulls into account from date of menstrual period to ovulation
Gestational
