embryology Flashcards

1
Q

sonic hedgehog gene

A

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

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2
Q

Wnt-7 gene

A

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

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3
Q

FGF gene

A

made at apical ectodermal ridge; stimulates mitosis for limb lengthening

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4
Q

Hox (homeobox) genes

A

segmental organization of embryp in a craniocaudal fashion

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5
Q

hox mutation causes…

A

appendage in wrong place

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6
Q

10 weeks of early fetal development

A

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

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7
Q

gastrulation

A

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

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8
Q

what forms the CNS? PNS?

A

cns = neuroectoderm pns = neural crest

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9
Q

mesodermal defects

A

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

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10
Q

what is derived from surface ectoderm?

A

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

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11
Q

what is derived from the neuroectoderm?

A

CNS brain, retina, optic nerves, spinal cord

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12
Q

what is derived from neural crest?

A

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

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13
Q

what is derived from the mesoderm?

A

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

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14
Q

endoderm forms the…

A

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

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15
Q

agenesis

A

absent organ due to absent primordial tissue

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16
Q

aplasia

A

absent organ despite present primordial tissue

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17
Q

hypoplasia

A

incomplete organ development

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18
Q

disruption

A

secondary breakdown of a previously normal structure

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19
Q

malformation vs deformation

A

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

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20
Q

sequence error

A

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

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21
Q

when is embryo most susceptible to teratogens?

A

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

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22
Q

fetal alcohol syndrome

A

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

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23
Q

dizygotic twins

A

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

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24
Q

monozygotic twins

A

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

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25
Q

what determines degree of separation of monozygotic twins?

A

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

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26
Q

amnion vs chorion

A

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

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27
Q

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

A

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

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28
Q

where are nutrient and gas exchanged between mother and fetus?

A

placenta

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29
Q

three components forming the placenta?

A

cytotrophoblast, syncytiotrophoblast, and decidua basalis

30
Q

cytotrophoblast

A

inner layer of chorionic villi of placenta (fetal component)

31
Q

syncytiotrophoblast

A

outer layer of chorionic villi; secretes hCG; fetal component of placenta

32
Q

hCG stimulates what?

A

stimulates the corpus luteum to secrete progesterone during first trimester

33
Q

decidua basalis

A

derived from the endometrium; maternal blood in lacunae; layer on outside of placenta where maternal veins and arteries pass through into placenta

34
Q
A
35
Q

umbilical cord contains…

A

2 unbilical arteries, 1 umbilical vein, allantoic duct, wharton jelly, and amniotic epithelium

36
Q

what do umbilical arteries do?

A

returns deoxy blood from fetal internal iliac arteries to placenta

37
Q

what does umbilical vein do?

A

supplies oxy blood from placenta to fetus; drains IVC via liver or ductus venosus

38
Q

what are umbilical arteries and veins derived from?

A

the allantois

39
Q

allantois

A

made from yolk sac in 3rd week, and becomes the urachus

40
Q

urachus

A

formed from the allantois

the urachus is a duct between fetal bladder and yolk sac

41
Q

failure of urachus to obliterate can result in three conditions–>

A

1 - patent urachus (urine comes out umbilicus)

2 - urachal cyst (fluid filled cavity between umbilicus and bladder, can cause infection or adenocarcinoma)

3 - vesicourachal diverticulum (bladder outpouching)

42
Q

vitelline duct

A

connects yolk sac to midgut lumen

obliterates in week 7

43
Q

failure of vitelline duct to obliterate can cause these 2 conditions…

A

vitelline fistula - meconium comes out the umbilicus

meckel diverticulum – partial closue, with patent portion attached to ileum (TRUE diverticulum)

44
Q

1st-6th branchial arches

A

1 = Ms to CHEW (meckel cartilage, mandible, malleus, mandibular ligament, muscles of mastication, massetter, medial pterygoid, mylohyoid) — CNV2 and V3

2 = S/SMILE (stapes, styloid process, stylohyoid ligament, muscles of facial expression, stapedius, stylohyoid, platySma) —CN7

3 = SWALLOW STYLishly/CN9 ( stylopharyngeus/glossopharyngeal nerve)

4= CNX superior laryngeal (swallow) - cricothyriod, pharyngeal constrictors, levator veli palatini

6 = CNX recurrent laryngeal branch (talk) - intrinsic muscles of larynx

45
Q

treacher collins syndrome

A

1st arch neural crest fails to migrate –> mandibular hypoplasia, facial abnormalities

46
Q

congenital pharyngocutaneous fistula

A

persistence of cleft and pouch –> fistula between tonsillar area and lateral neck (2nd arch abnormality)

47
Q

digeorge syndrome

A

aberrant development of 3rd and 4th pouches –> T cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development)

associated with cardiac defects (conotruncal abnormalities)

48
Q

MEN 2a

A

mutation of RET (neural crest cells) that causes:

pheochromocytoma (adrenal medulla)

parathyroid tumor (3/4 pharyngeal pouch)

parafollicular cells/medullary thyroid cancer (4/5 pharyngeal pouches)

49
Q

cleft lip

A

failure of fusion of the maxillary and medial nasal processes (formation of the primary palate)

50
Q

cleft palate

A

failure of fusion of the two lateral palatine processes or failure of fusion of lateral palatine processes with the nasal septum and or median palatine process (formation of the secondary palate)

51
Q

cleft lip and cleft palate…..

A

often occur together but have different etiologies

52
Q

default genital development

A

is the female form

–mesonephric duct degenerates and paramesonephric duct develops

53
Q

male genital development

A

SRY gene on ch. Y produces testis-determining factor –> testes development

Sertoli cells secrete Mullerian inhibitory factor (MIF) that suppresses development of paramesonephric ducts

Leydig cells secrete androgens that stimulate the development of the mesonephric ducts

54
Q

mullerian duct

A

aka the paramesonephric duct

default; develops into female structures –> fallopian tubes, uterus, and upper vagina

55
Q

mullerian duct abnormalities results in…

A

presents as primary amenorrhea in females with fully developed secondary sex characteristics (indicates functional ovaries)

56
Q

wolfian duct

A

aka the mesonephric duct

develops into male internal structures (except prostate) –> Seminal vesicales, Epididymis, Ejaculatory duct, and Ductus deferens (SEED)

57
Q

bicornuate uterus

A

results from incomplete fusion of the paramesonephric ducts

can cause anatomical defects –> recurrent miscarriages

58
Q

complete failure of paramesonephric ducts fusion causes –?

incomplete fusion…?

A

complete failure –> double uterus and vagina

incomplete failure –> bicornuate uterus

59
Q

where do you find sertoli and leydig cells?

A

testes

60
Q

what produces testis determining factor (TDF)?

A

SRY gene on Y ch.

61
Q

sertoli cells produce?

leydig cells produce?

A

Sertoli –> MIF (mullerian inhibitory factor)

leydig –> testosterone

62
Q

MIF causes…

A

degeneration of the paramesonephric duct (so no female genitalia)

63
Q

if there are not sertoli cells or MIF –>

A

develop both male and female internal genitalia and male external genitalia

64
Q

5alpha reductase deficiency

A

inability to convert testosterone to DHT –> has male internal genitalia, ambiguous external genitalia until puberty (when increased testosterone causes masculinization)

65
Q

gubernaculum

1) male remnant
2) female remnant

A

1 - anchors testes within scrotum

2 - ovarian ligament + round ligament of uterus

66
Q

processus vaginalis

1) male remnant?
2) female remnant?

A

1 - forms tunica vaginalis

2 - obliterated

67
Q

hypospadias

vs

epispadias

A

H - abnormal opening of urethra on INFERIOR/VENTRAL side of penis due to failure of urethral folds to close

E - abnormal opening of urethra on SUPERIOR/DORSAL side of penis due to faulty positioning of genital tubercle; associated with exstrophy of bladder ( Epispadias hits your EYE when you pEE)

68
Q

genital tubercle becomes what…

1) with DHT (dihydrotestosterone)
2) with estrogen

A

1) glans penis, corpus cavernosum, and songiosum
2) glans clitoris and vestibular bulbs

69
Q

urogenital sinus becomes what…

1) with DHT (dihydrotestosterone)
2) with estrogen

A

1 - bulbourethral glands and prostate gland

2 - greater vestibular glands of bartholin and urethral and paraurethral glands of skene

70
Q

urogenital folds becomes what…

1) with DHT (dihydrotestosterone)
2) with estrogen

A

1 - ventral shaft of penis (penile urethra)

2 - labia minora

71
Q

labioscrotal swelling becomes what…

1) with DHT (dihydrotestosterone)
2) with estrogen

A

1 - scrotum

2 - labia majora

72
Q
A