Embryology, Conception, & Fetal Development Flashcards
Phases of the endometrial cycle
- menstrual phase (days 1-5/7)
- proliferative phase (day 5 to ovulation/15))
- secretory phase (days 15-28)
- ischemic phase (days 28-30ish)
Phases of the ovarian cycle
- follicular phase (days 1-14)
- ovulation (day 15/18)
- luteal phase (days 15-28)
graafian follicle
fluid-filled structure where the ovum develops into a mature oocyte that ruptures to release the ovum during ovulation
what does the heightened estrogen and progesterone levels during the secretory phase do to the uterine lining?
it prepares the uterine lining for implantation
When does ovulation occur in relation to menses?
14 days prior to menstruation
When is a woman most fertile?
during ovulation
How many days does the sperm last?
3-5 days
How many days does an ovum survive?
12-24 hours
What is cervical mucus like when not ovulating?
dry or sticky
What is cervical mucus like when ovulating/fertile?
wet and sticky- resembles raw egg whites
When is sex determined?
At fertilization as the chromosomes combine to be XX or XY
Not known until 18-21 weeks
Oogenesis
- primordial germinal cells divide repeatedly to form the oogonia
- oogonia go through mitotic division to form the primary oocyte
- in the growth phase the size of the primary oocyte increases enormously and then goes through two phases of meiosis to form a haploid egg cell
Spermatogenesis
- spermatogonia
- primary spermatocytes
- secondary spermatocytes
- spermatids
- spermatozoa
Mitosis and meiosis differences
mitosis
- maintenance of chromosome number (diploid)
- takes place in somatic cells
- no crossing over
meiosis
- reduction of chromosome number (haploid)
- takes place in reproductive cells
- crossing over occurs
Stages of prenatal development
- germinal stage= the two weeks from formation of the zygote to implantation
- embryonic period= the third through eighth week where the embryo forms its basic organs, CNS, and PNS
- fetal period= ninth week through birth
Morula
a mass of 16 blastomeres formed by cleavage of the zygote that forms before a blastocyst on day 4
Blastocyst
32+ rapidly dividing cells whos inner group will become the emrbyo and outer group will become to amnion
When does implantation occur?
6-12 days after ovulation when the blastocyst implants after shedding the zona pellucida
Ectoderm
outer germ cell layer that forms the skin, hair, nails, glands, and PNS
Mesoderm
middle germ cell layer that becomes the dermis, heart, muscles, urinary system, etc
Endoderm
inner germ cell later that becomes the inner lining and other organs
What are the purposes of the placenta?
- serves as fetal lungs, liver, and kidney until birth
- upkeeps healthy growth environment (immune attack, remove waste products, etc)
What hormones does the placenta produce?
- human chorionic gonadotropin hormone= tells the uterus to stop shedding its lining and thickens it for the growing embryos
- human lactogen= provides nutrition to the fetus and stimulates the mother’s milk glands
- estrogen
- progesterone
Ductus arteriosus
connects the aorta to the pulmonary artery which shunts blood away from the lungs
Foramen ovale
allows oxygenated blood into the right atrium so it can enter the left atrium to bypass going through the lungs for gas exchnage
Ductus venosus
connects the umbillical vein to the vena cava shunting the deoxygenated blood away from the liver
Why are the 3 structures of the fetal heart not in the newborn heart?
Because the fetus does not have working lungs or a liver
How many cord vessels and which carries oxygenated blood to and from where?
- 1 umbillical vein carries oxygenated blood from the placenta
- 2 umbillical arteries carry deoxygeated blood to the placenta
Wharton’s jelly
surrounds the vessels to prevent compression of the umbillical cord
When does FSH peak?
the 1st week of the menstrual cycle
When does gonadotropin-releasing hormone peak?
at the beginning of the ovarian cycle
When does luteinizing hormone peak?
12-24 hrs before follicle rupture/ovulation
When is estrogen at its peak?
right before ovulation
When is progesterone at its peak?
5-7 days after ovulation
