1: Embryology, The First Two Weeks

Front 1

what is the incidence of birth defects?

Back 1

6/100

Front 2

what is the peak risk period for developmental defects?

Back 2

3-8 weeks

Front 3

briefly define mitosis

Back 3

somatic cell division forming 2 genetically identical daughter cells

Front 4

briefly define meiosis

Back 4

germ cell division forming male and female gametes

Front 5

what is the frequency of a meiotic cross over event?

Back 5

dozen per event, 1 per chromosome (roughly)

Front 6

Roughly estimate the number of oocytes in a newly pubescent woman

Back 6

40-50k

Front 7

what is the zona pellucida?

Back 7

protein coat surrounding egg

Front 8

define the cumulus oophorus

Back 8

loose protecting cells surrounding oocyte distantly

Front 9

define the corona radiata

Back 9

dense protecting cells surrounding oocyte nearby

Front 10

what is an oocyte?

Back 10

egg in suspended animation

Front 11

define fimbriae

Back 11

fingerlike appendiges of oviduct used to grab ovary

Front 12

define acrosome

Back 12

in head of sperm cells, holds enzymes for penetration

Front 13

define trisomy

Back 13

extra chromosome present

Front 14

define monosomy

Back 14

a chromosome is missing

Front 15

what are the most frequent trisomy chromosomes and why?

Back 15

13, 18, 21 (down) (more susceptible? less lethal?)

Front 16

define translocation and give an example

Back 16

chunk of another chromosome moved to different chromosome, chromosome 21 chunk moved to 14 also causes down syndrome

Front 17

what percentage of infant death is roughly due to genetic error

Back 17

20-30%

Front 18

what are the characteristics of down syndrome as well as clinical aspects and prevalence in pregnancies

Back 18

mental retardation, craniofacial abnormalities (slant eyes, flat face, protruding tongue, small ears etc.) prevalence of cardiac defects, thyroid issues, leukemia and premature aging. 1/2000 (under age 25), 1/100 (age 40)

Front 19

what are the characterstics of angelman syndrome

Back 19

microdeletion on long arm of maternal chromosome 15, mental retardation, cannot speak, craniofacial defects, poor motor development

Front 20

what are the characteristics of prader-willi syndrome

Back 20

microdeletion on long arm of paternal chromosome 15, mental retardation, craniofacial defects, obesity, hypogonadism

Front 21

define capacitation

Back 21

conditioning of sperm, removal of glycoprotein coats from plasma membrane over acrosomal region of sperm (~7hrs)

Front 22

describe phase 1- fertilization

Back 22

penetration of corona radiata (must be capacitated)

Front 23

describe phase 2- fertilization

Back 23

penetration of zona pellucida at ZP3 receptor, induces acrosomal region, release acrosin enzyme (need 200-300 sperm releasing acrosin to penetrate, only 1 gets through)

Front 24

describe phase 3- fertilization

Back 24

sperm and oocyte fuse, calcium wave triggers release of oocyte granules and changes membrane (makes a gap), makes it impermeable. resume meiotic division, activate egg

Front 25

define the pronucleus

Back 25

female and male formed from egg and sperm, join to become first diploid cell

Front 26

define blastomere

Back 26

each cell in the 4 cell stage

Front 27

define the morula

Back 27

8-16 cell stage

Front 28

describe compaction

Back 28

blastomeres flatten and compact, increase cell to cell contacts, formation of morula

Front 29

what does the inner cell mass become

Back 29

forms embryo (embryoblast)

Front 30

what does the outer cell mass become

Back 30

will form trophoblast

Front 31

when does the blastocyst form

Back 31

fluid accumulation in morula, forms blastocyst cavity

Front 32

what is the function L-selectin in fertilization

Back 32

carbohydrate binding protein allows capture of blastocyst to uterine lining

Front 33

describe an ectopic pregnancy

Back 33

implantation event occurred in the wrong location (probably in oviduct). cannot be carried to term

Front 34

define epiblast cells and what they do

Back 34

cells split from embryoblast which in turn separate and create the amniotic cavity

Front 35

what does bilaminar embryo describe

Back 35

epiblast and hypoblast layer on each side

Front 36

describe Heuser's membrane

Back 36

layer of hypoblast cells which have migrated around the inner cavity of the blastocyste, forms primative yolk sac

Front 37

what is the chorionic cavity

Back 37

continued spreading and proliferation of hypoblast cells forms another cavity around the yolk sac

Front 38

describe the definitive yolk sac

Back 38

primary yolk sac is pinched and budded off and removed

Front 39

define extracoelomic cysts

Back 39

budded off yolk sacs, not important

Front 40

describe fraternal twins

Back 40

dizygotic, non-identical, 90% of twins, roughly 30/1000 births (premature delivery, low birth weight risks), 2 placentas

Front 41

describe identical twins

Back 41

monozygotic, identical, 10% of twins, 3/1000 births (premature delivery, low birth weight, twin-twin transfusion risks), 1 placenta (usually)