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USMLE 1 > Reproductive- Embryology > Flashcards

Reproductive- Embryology Flashcards

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USMLE® Step 1 flashcards
1
Q

Important genes of embryogenesis

- Sonic hedgehog gene

A

Produced at base of limbs in zone of polarizing activity. Involved in patterning along anteroposterior axis and CNS development;

mutation can cause holoprosencephaly

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2
Q

Important genes of embryogenesis

- Wnt-7 gene

A

Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb).

Necessary for proper organization along dorsal-ventral axis.

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3
Q

Important genes of embryogenesis

- Fibroblast growth factor (FGF) gene

A

Produced at apical ectodermal ridge.

Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.

“Look at that Fetus, Growing Fingers.”

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4
Q

Important genes of embryogenesis

- Homeobox (Hox) genes

A

Involved in segmental organization of embryo in a craniocaudal direction. Code for transcription factors.

Hox mutations Ž appendages in wrong locations.

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5
Q

Early fetal development

  • Within week 1
  • Within week 2
  • Within week 3
A

hCG secretion begins around the time of implantation of blastocyst

Bilaminar disc (epiblast, hypoblast).

Gastrulation forms trilaminar embryonic disc. Notochord arises from midline mesoderm; overlying ectoderm becomes neural plate.

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6
Q

Early fetal development

- Weeks 3–8 (embryonic period)

A

Neural tube formed by neuroectoderm and closes by week 4. Organogenesis.

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7
Q

Early fetal development

  • Week 4
  • Week 6
  • Week 8
  • Week 10
A

Heart begins to beat. Upper and lower limb buds begin to form.

Fetal cardiac activity visible by transvaginal ultrasound

Fetal movements start.

Genitalia have male/female characteristics

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8
Q

Mesodermal defects = VACTERL

A 
Vertebral defects
Anal atresia
Cardiac defects
Tracheo-Esophageal fistula
Renal defects
Limb defects (bone and muscle)
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9
Q

Embryologic derivatives

A

Pag. 595

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10
Q

Types of errors in morphogenesis

  • Agenesis
  • Aplasia
  • Hypoplasia
  • Deformation
A

Absent organ due to absent primordial tissue.

Absent organ despite presence of primordial tissue

Incomplete organ development; primordial tissue present.

Extrinsic disruption; occurs after embryonic period.

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11
Q

Types of errors in morphogenesis

  • Disruption
  • Malformation
  • Sequence
A

2° breakdown of previously normal tissue or structure (eg, amniotic band syndrome).

Intrinsic disruption; occurs during embryonic period (weeks 3–8).

Abnormalities result from a single 1° embryologic event (eg, oligohydramnios Ž Potter sequence).

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12
Q

Teratogens

A

Most susceptible in 3rd–8th weeks of pregnancy.

Before week 3, “all-or-none” effects. After week 8, growth and function affected.

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13
Q 
Teratogens medications
- ACE inhibitors
- Alkylating agents
- Aminoglycosides
- Folate antagonists (trimethoprim, methotrexate,
antiepileptic)
A

Renal damage

Absence of digits, multiple anomalies

Ototoxicity

Neural tube defects

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14
Q

Teratogens medications

  • Antiepileptic drugs
  • Diethylstilbestrol
A

Neural tube defects, cardiac defects, cleft palate, skeletal abnormalities. (valproate, carbamazepine, phenytoin, phenobarbital)

Vaginal clear cell adenocarcinoma, congenital Müllerian anomalies

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15
Q

Teratogens medications

  • Isotretinoin
  • Lithium
  • Methimazole
  • Tetracyclines
A

Multiple severe birth defects (Contraception mandatory)

Ebstein anomaly

Aplasia cutis congenita

Discolored teeth, inhibited bone growth

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16
Q

Teratogens medications

  • Thalidomide
  • Warfarin
A

Liimb defects

Bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities

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17
Q

Teratogens Substance abuse

  • Alcohol
  • Cocaine
  • Smoking (nicotine, CO)
A

birth defects and intellectual disability; fetal alcohol syndrome

Low birth weight, preterm birth, IUGR, placental abruption

Low birth weight, preterm labor, placental problems,
IUGR, SIDS, ADHD

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18
Q

Teratogens Others

  • Iodine (lack or excess)
  • Methylmercury
  • Vitamin A excess
  • X- rays
A

Congenital goiter or hypothyroidism (cretinism)

Neurotoxicity

Extremely high risk for spontaneous abortions and birth defects

Microcephaly, intellectual disability

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19
Q

Teratogens Others

- Maternal diabetes

A

Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects, macrosomia, neonatal hypoglycemia, polycythemia

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20
Q

Fetal alcohol syndrome

  • Epidemiology
  • CLinical manifestations
  • Mechanism
A

Leading cause of intellectual disability in the US.

microcephaly, facial abnormalities, limb dislocation, heart defects. Heart-lung fistulas and holoprosencephaly in most severe form

Mechanism is failure of cell migration.

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21
Q

Neonatal abstinence syndrome

A

Secondary to maternal opiate use/abuse.

Newborns may present with uncoordinated sucking reflexes, irritability, high-pitched crying, tremors, tachypnea, sneezing, diarrhea, and possibly seizures.

22
Q

Twinning Monozygotic

- timing of cleavage

A

(SCAB):
ƒƒ Cleavage 0–4 days: Separate chorion and amnion
ƒƒ Cleavage 4–8 days: shared Chorion
ƒƒ Cleavage 8–12 days: shared Amnion
ƒƒ Cleavage 13+ days: shared Body (conjoined)

23
Q

Placenta Fetal component

  • Cytotrophoblast
  • Syncytiotrophoblast
A

Inner layer of chorionic villi. Cytotrophoblast makes Cells.

Outer layer of chorionic villi; synthesizes and secretes hormones (Lacks MHC-I expression).

24
Q

Placenta Maternal component

- Desidua basalis

A

Derived from endometrium. Maternal blood in lacunae.

Pag. 599

25
Q

Umbilical cord

  • Umbilical arteries (2)
  • Umbilical vein (1)
  • Both derived from allantois.
A

return deoxygenated blood from fetal internal iliac arteries to placenta

supplies oxygenated blood from placenta to fetus; drains into IVC via liver or via ductus venosus.

*Single umbilical artery (2-vessel cord) is associated with congenital and chromosomal anomalies

26
Q

Urachus

A

In the 3rd week the yolk sac forms the allantois, which extends into urogenital sinus. Allantois becomes the urachus, a duct between fetal bladder and umbilicus

Obliterated urachus is represented by the median umbilical ligament after birth

27
Q

Urachus

  • Patent urachus
  • Vesicourachal diverticulum
A

Total failure of urachus to obliterate Ž urine discharge from umbilicus

Slight failure of urachus to obliterate Ž outpouching of bladder.

28
Q

Urachus

- Urachal cyst

A

Partial failure of urachus to obliterate; fluid-filled cavity lined with uroepithelium, between umbilicus and bladder.

Cyst can become infected and present as painful mass below umbilicus

29
Q

Vitelline duct

A

7th week—obliteration of vitelline duct (omphalomesenteric duct), which connects yolk sac to
midgut lumen.

30
Q

Vitelline duct

  • Vitelline fistula
  • Meckel diverticulum
A

Vitelline duct fails to close Ž meconium discharge from umbilicus.

Partial closure of vitelline duct, with patent portion attached to ileum (true diverticulum). Melena, hematochezia, abdominal pain.

31
Q

Aortic arch derivatives

  • 1st
  • 2nd
  • 3rd
A

Part of maxillary artery

Stapedial artery and hyoid artery

Common Carotid artery and proximal part of internal Carotid artery.

32
Q

Aortic arch derivatives

  • 4th
  • 6th
A

On left, aortic arch; on right, proximal part of right subclavian artery

Proximal part of pulmonary arteries and (on left only) ductus arteriosus

33
Q

Branchial apparatus

A

CAP covers outside to inside:
Clefts = ectoderm
Arches = mesoderm + neural crest
Pouches = endoderm

34
Q

Branchial arch derivatives

Branchial pouch derivatives

A

Pag. 602

Pag. 603

35
Q

Pierre Robin sequence

A

micrognathia, glossoptosis, cleft palate, airway obstruction

36
Q

Treacher Collins syndrome

A

neural crest dysfunction Ž mandibular hypoplasia, facial abnormalities

37
Q

DiGeorge syndrome

A

Chromosome 22q11 deletion. Aberrant development of 3rd and 4th pouches Ž thymic aplasia and failure of parathyroid development. Associated with cardiac
defects (conotruncal anomalies)

38
Q

Cleft lip

Cleft palate

A

Failure of fusion of the maxillary and merged medial nasal processes (formation of 1° palate).

failure of fusion of the two lateral palatine shelves or failure of fusion of lateral palatine shelves with the nasal septum and/or median palatine shelf (formation of 2° palate).

39
Q

Genital embryology

- Male

A

SRY gene on Y chromosome—produces testisdetermining factor Ž testes development.

Sertoli cells secrete MIF that suppresses development of paramesonephric ducts.

Leydig cells secrete androgens that stimulate development of mesonephric ducts.

40
Q

Genital embryology

- Female

A

Mesonephric duct degenerates and paramesonephric duct develops

41
Q

Müllerian agenesis (Mayer-Rokitansky- Küster-Hauser syndrom)

A

1° amenorrhea (due to a lack of uterine development) in females with fully developed 2° sexual characteristics (functional ovaries).

42
Q

Mesonephric (Wolffian) duct

A

Develops into male internal structures (except prostate) Seminal vesicles, Epididymis, Ejaculatory duct, Ductus deferens (SEED).

*Female remnant is Gartner duct

43
Q

Paramesonephric (Müllerian) duct

A

Develops into female internal structures— fallopian tubes, uterus, upper portion of vagina (lower portion from urogenital sinus).

*Male remnant is appendix testis.

44
Q

No Sertoli cells or lack of Müllerian inhibitory factor

A

develop both male and female internal genitalia and male external genitalia

45
Q

5α-reductase deficiency

A

inability to convert testosterone into DHT Ž male internal genitalia, ambiguous external genitalia until
puberty (when  testosterone levels cause masculinization)

46
Q

Uterine (Müllerian duct) anomalies

  • Septate uterus
  • Uterus didelphys
A

Incomplete resorption of septum. low fertility and early
miscarriage/pregnancy loss. Treat with septoplasty

Complete failure of fusion Ž double uterus, cervix, vagina. Pregnancy possible.

47
Q

Uterine (Müllerian duct) anomalies

- Bicornuate uterus

A

Incomplete fusion of Müllerian ducts. risk of complicated pregnancy, early pregnancy loss, malpresentation, prematurity

48
Q

Male/female genital homologs

A

Pag. 605

49
Q

Congenital penile abnormalities

A

Hypospadias: Associated with inguinal hernia and
cryptorchidism

Epispadias: Exstrophy of the bladder is associated with
Epispadias.

50
Q

Descent of testes and ovaries

  • Gubernaculum
  • Processus vaginalis
A

Band of fibrous tissue. Anchors testes within scrotum. Ovarian ligament + round ligament of uterus.

Evagination of peritoneum. Forms tunica vaginalis (male). Obliterated (female)

USMLE 1 (73 decks)

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