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Flashcards in embryology Deck (72)
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1

sonic hedgehog gene

made in base of limbs in the zone of polarizing activity ---anterior/posterior patterning; involved in CNS development

2

Wnt-7 gene

made at apical ectodermal ridge (distal end of growing limbs); for dorsal/ventral organization

3

FGF gene

made at apical ectodermal ridge; stimulates mitosis for limb lengthening

4

Hox (homeobox) genes

segmental organization of embryp in a craniocaudal fashion

5

hox mutation causes...

appendage in wrong place

6

10 weeks of early fetal development

day 0 - fertilization forms a zygote; embryogenesis initiated week 1 - hCG secretion and implantation of blastocyst week 2 - 2 wks = 2 layers --> bilaminar disc (epiblast and hypoblast) week 3 - 3 wks = 3 layers --> trilaminar disc; gastrulation; primitive streak, notochord, mesoderm, and neural plate begin to form weeks 3-8 - extremely susceptible to teratogens week 4 - heart begins to beat; limb buds begin to form (4wks = 4 limbs) week 6 - fetal cardiac activity visible by transvaginal ultrasound week 10 - sex specific genitalia

7

gastrulation

process that forms the trilaminar disc (ectoderm, mesoderm, and endoderm germ layers) starts with the epiblast invaginating to form the primitive streak

8

what forms the CNS? PNS?

cns = neuroectoderm pns = neural crest

9

mesodermal defects

VACTERL vertebral anal atresia cardiac trachea-esophageal fistula renal limb (bone and muscle)

10

what is derived from surface ectoderm?

eye lens, oral cavity linings, ear sensory organs and olfactory epithelium, anal canal below pectinate line, parotid/sweat/mammary glands

11

what is derived from the neuroectoderm?

CNS brain, retina, optic nerves, spinal cord

12

what is derived from neural crest?

pns dorsal root ganglia, schwann cells, melanocytes, bones of skull, odontoblasts, aorticopulmonary septum, chromaffin and parafollicular cells

13

what is derived from the mesoderm?

muscle, bone, CT, serous linings of cavties (peritoneum), spleen, CV structures, lymphatics, blood, wall of gut tube, vagina, kidneys, dermis, testes, ovaries,

14

endoderm forms the...

gut tube epithelium, anal canal above pectinate line, urethra and luminal epithelium derivatives (lungs, liver, gallbladder, Eustachian tube, thymus, etc)

15

agenesis

absent organ due to absent primordial tissue

16

aplasia

absent organ despite present primordial tissue

17

hypoplasia

incomplete organ development

18

disruption

secondary breakdown of a previously normal structure

19

malformation vs deformation

M = intrinsic disruption; during the embryonic period (wks 3 - 8) D = extrinsic disruption; after the embryonic period

20

sequence error

abnormalities result from a single embryological event ex: oligohydramnios --> potter sequence

21

when is embryo most susceptible to teratogens?

weeks 3-8 (embryonic period) during organogenesis before week 3 --> all or none effect after week 8 --> growth and function affected

22

fetal alcohol syndrome

mothers consume a lot of alcohol during pregnancy --> increased risk for congenital malformations ---intellectual disability, retardation, microcephaly, holopresencephaly, facial abnormalities, limb dislocation, and heart defects

23

dizygotic twins

arises from 2 eggs that are separately fertilized by 2 different sperm (always 2 zygotes) --2 different amniotic sacs and 2 separate placentas (chorions)

24

monozygotic twins

from 1 fertilized egg (1 egg + 1 sperm) that splits into 2 zygotes in early pregnancy

25

what determines degree of separation of monozygotic twins?

depends on when the fertilized egg splits into 2 zygotes --timing determines the number of chorions and amnions

26

amnion vs chorion

Amnion is the inner layer that surrounds the amniotic cavity while chorion is the outer layer that covers amnion, yolk sac and the allantois amnion does not contain any vessels or nerves

27

early separation of monozygotic twins? middle latest separation of monozygotic twins?

before morula (0-4 days) --> dichorionic diamniotic after morula, before blastocyst (4-8 days) --> monochorionic diamniotic after blastocyst stage (8+ days) --> monochorionic monoamniotic

28

where are nutrient and gas exchanged between mother and fetus?

placenta

29

three components forming the placenta?

cytotrophoblast, syncytiotrophoblast, and decidua basalis

30

cytotrophoblast

inner layer of chorionic villi of placenta (fetal component)