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*USMLE* > Embryo > Flashcards

Embryo Flashcards

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USMLE® Step 1 flashcards
1
Q

Lens, cornea

Inner ear sensory organs

Olfactory epithelium

all DERIVED FROM WHAT?

A

surface ectoderm

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2
Q

Neural ganglia, adrenal medulla

Schwann cells, pia + arachnoid mater

all derived from WHAT?

A

Neural crest cells (part of ectoderm)

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3
Q

Brain + SC

Posterior pituitary, pineal gland

Retina

all derived from WHAT?

A

Neural tube (part of ectoderm)

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4
Q

Muscles (all 3 types)

CT, bone + cartilage

Spleen + HSCs

all derived from WHAT?

A

mesoderm

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5
Q

GI tract, liver, pancreas

Lungs

Bladder and urethra

All derived from WHAT?

A

endoderm

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6
Q

Middle ear + auditory tube

Thymus, parathyroids, thyroid follicular cells

Parafollicular C cells

all derived from what?

A

endoderm

specifically endoderm of pharyngeal pouches

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7
Q

Serosal linings

CV and lymphatic system

Adrenal cortex

all derived from what?

A

mesoderm

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8
Q

Kidneys, ureters and internal genitalia

all derived from what?

A

mesoderm

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9
Q

Anterior pituitary

Nasal + oral epithelium, salivary glands

Epidermis, sweat + mammary glands

All derived from what?

A

surface ectoderm

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10
Q

Aorticopulmonary septum + endocardial cushions

derived from what?

A

Neural crest cells (part of ectoderm)

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11
Q

Branchial arches (their bones + cartilage)

Skull bones

derived from what?

A

Neural crest cells (part of ectoderm)

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12
Q

Melanocytes

derived from what?

A

Neural crest cells (part of ectoderm)

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13
Q

musculoskeletal + nerve derivatives of pharyngeal arch 1

A

Meckel’s cartilage - CN V3 (mandibular)

muscles of mastication
maxilla + mandible
malleus + incus
sphenoMandibular ligament
Mylohyoid

(ant. belly digastric, tensor tympani + veli palatini, ant 2/3 of tongue)

(related to Pierre-Robin sequence - micrognathia, glossoptosis, cleft palate + airway obstruction)

(remember incus and the Ms … Meckel’s, mastication muscles, maxilla, mandible + malleus … plus incus)

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14
Q

musculoskeletal + nerve derivatives of pharyngeal arch 2

A

Reichert’s cartilage - CN VII facial n.

Facial expression mm. (“Smile”)
Stapes + Stapedius m.
PlatySma
PoSt. belly digaStric

Styloid proc. > Stylohyoid lig. and muscle > leSSer horn hyoid

Remember R, S (Reicherts, stapes, styloid stylohyoid > hyoid) and RiSorius (facial expression)

(assoc. with Treacher Collins syndrome)

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15
Q

musculoskeletal + nerve derivatives of pharyngeal arch 3

A
  • StyloPHARYNGEUS muscle + glossoPHARYNGEAL nerve (CN IX)
  • Greater horn hyoid (greater number 3 = greater horn)

(“stylishly swallow”)

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16
Q

msk and nerve derivatives of pharyngeal arch 4 + 6

A
  • thyroid cartilage (4)
  • cricoid cartilage (6)
  • arytenoids, corniculate + cuneiform cartilages
  • muscles of pharynx and larynx
  • post 1/3 tongue

4th - SUPERIOR LARYNGEAL BRANCH of Vagus (“simply swallow”)

5th - RECURRENT/INF. LARYNGEAL BRANCHES of Vagus

(remember that the ant 2/3 tongue is from the 1st arch and the post 1/3 is from the last arches)

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17
Q

Treacher Collins syndrome

dev. abnormality of what?
affecting what?

A

abnormal 1ST / 2ND PHARYNGEAL ARCH DEV. due to NEURAL CREST issue

craniofacial issues (maxilla, mandible, zygomatic hypoplasia) > AIRWAY + FEEDING ISSUES

ossicle issues > CONDUCTIVE HEARING LOSS

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18
Q

Germ layer embryonic kidney is from?

this germ layer forms what which then gives what?

A

Intermediated MESODERM forms the UROGENITAL RIDGE which then forms the NEPHROGENIC CORD

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19
Q

Primitive structure that arises from cephalic part of nephrogenic cord?

what does it become?

A

PRONEPHROS

completely regresses

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20
Q

after the pronephros, what forms from the midportion of the nephrogenic cord?

what persists from it?

A

MESONEPHROS

Wolffian ducts - gives vas deferens + epididymis

regresses in females (> vestigial Gartner’s ducts)

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21
Q

after the mesonephros, how does the actual kidney begin to form?

A

METANEPHROS formation starts with URETERIC BUD (aka metanephric diverticulum; sprouts off caudal mesonephric duct)

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22
Q

how does the ureteric bud induce continuation of renal development?

A

ureteric bud penetrates sacral intermediate mesoderm to induce formation of the METANEPHRIC MESODERM (aka metanephric blastema)

the metanephric mesoderm + ureteric bud then exchange inductive signals to promote each other’s growth

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23
Q

what structures come from the ureteric bud?

from the metanephric mesoderm?

A

bud - collecting tubules + ducts, calyces, pelvis + ureters

metanephric mesoderm - glomeruli, Bowman’s space, PCT, loop, DCT

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24
Q

gene that controls differentiation of the gonads into testes or ovaries

what does it code for?

A

SRY gene on Y chromosome

codes for “testes determining factor” which allows XY embryos to develop testes

(absence of SRY > ovaries develop)

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25
Q

What do the two special cell types within testes stimulate in male reproductive development?

A

Sertoli cells - suppress female internal organ development via ANTI-MULLERIAN HORMONE; (also make androgen-binding protein that concentrates testosterone in the seminiferous tubules)

Leydig cells - secrete testosterone which STIMULATES WOLFFIAN DUCT formation + its derivatives (epididymis, vas deferens, ejaculatory ducts, seminal vesicles)

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26
Q

Heart embryo: these give rise to what?

Truncus arteriosus…
Bulbus cordis…
Endocardial cushion…

A

TA - asc. aorta + pulmonary trunk

BC - smooth parts of ventricles (outflow tracts)

EC - atrial septum; membranous IV septum; valves (all 4) … from endothelial cells that undergo EMT

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27
Q

Heart embryo: these give rise to what?

Primitive atrium
Primitive ventricle
Primitive pulmonary vein

A

A - trabeculated part of both atria

V - trabeculated part of both ventricles

PV - SMOOTH part of left atrium

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28
Q

Heart embryo:

L and R horns of SINUS VENOSUS give what?

A

Left horn - coronary sinus

Right horn - “sinus venarum” smooth part of RA

29
Q

Heart embryo:

what gives the SVC?

A

R common cardinal v.

R anterior cardinal v.

30
Q

What forms the VALVE of FORAMEN OVALE?

A

inferior remnant of SEPTUM PRIMUM

after septum secundum forms to the right of the remnant; higher RA pressure in utero pushes blood through, higher LA pressure postpartum presses it shut > FO closes + fossa ovale remains

31
Q

What cells give rise to the AORTICOPULMONARY SEPTUM?

A

ectodermal NEURAL CREST cells

failure > persistent truncus arteriosus + VSD

32
Q

What is the most common external opening site for a BRANCHIAL CYST?

what causes it?

A

anterior to SCM

painless, slowly enlarging mass on side of neck; freely mobile and soft

incomplete fusion SECOND + THIRD BRANCHIAL ARCHES to obliterate the 2nd branchial cleft

33
Q

Dandy-Walker malformation

2 main features (visible on CT)

A
  1. VERMIS ABSENCE - no cerebellar vermis

2. 4TH VENTRICLE DILATION - cystic dilation causes enlargement of posterior fossa

34
Q

Dandy-Walker malformation

associated features (3)

A
  1. CORPUS CALLOSUM agenesis
  2. MALFORMATIONS - face, heart, limbs
  3. SPINA BIFIDA
35
Q

Dandy-Walker malformation

presentation (3) + complications (1)

A

infant with a) dev delay and b) large skull

c) unsteadiness + malcoordination (cerebellar)

complication - high ICP w/ lethargy/vomit (atresia of 4th ventricle foramina with NON-COM HYDROCEPHALUS)

36
Q

Arnold-Chiari malformation ( aka Chiari II )

structural abnormality + consequence

A

herniation of low lying VERMIS and TONSILS thru f. magnum (Chiari II = 2 structures)

aqueductal stenosis > HYDROCEPHALUS

37
Q

Arnold-Chiari malformation ( aka Chiari II )

associated abnormality far from brain

A

LUMBOSACRAL myelomeningocele - presents as paralysis/sensory loss below lesion

38
Q

Chiari I malformation

structural issue? when presents?

assoc?

A

ECTOPIA of the cerebellar TONSILS (Chiari I = 1 structure)

presents in ADULTHOOD (asymp. in kids) with HA and ATAXIA

assoc. with SYRINGOMYELIA

39
Q

Urogenital folds

give what in females?
in males?

A

labia minora

ventral penis + penile raphe

40
Q

Failure of fusion of urogenital folds

causes what?

A

HYPOSPADIAS in males

normal in females - forms labia minora

41
Q

Genital tubercle

becomes what in males? females?

A

glans penis + clitoris

42
Q

Malpositioning of the genital tubercle causes what?

A

epispadias

presents as a small bifid penis with urethra on top

43
Q

Failure of fusion of labioscrotal folds causes what in males

A

bifid scrotum

don’t fuse in females > labia majora

44
Q

What are the derivatives of the FIRST and SECOND aortic arches?

A

1st - part of maxillary artery

2nd - stapedial + hyoid arteries

(1st is “MAXimal” and Second is Stapedial)

45
Q

What are the derivatives of the 3rd aortic arch?

A

CCA and proximal ICA

C is the 3rd letter of the alphabet

46
Q

What are the derivatives of the 4th aortic arch?

A

on left - AORTIC ARCH
on right - proximal R SUBCLAVIAN

(4th arch supplies the 4 limbs)

47
Q

What are the derivatives of the 6th aortic arch?

A

Proximal pulmonary arteries

Ductus arteriosus

48
Q

What is the Pierre Robin Sequence?

4 issues, due to what

A

1st pharyngeal arch derivative issues

  1. Micrognathia
  2. Glossoptosis
  3. Airway obstruction
  4. Cleft palate
49
Q

inheritance of cleft lip / palate issues?

A

multifactorial

50
Q

When and where are the two “meiotic arrests” in oogenesis?

A
  1. All PRIMARY oocytes in the ovary are arrested in PROphase (“diplotene”) of Meiosis I by MONTH 5 of FETAL LIFE

(at puberty, a primary oocyte becomes unarrested and undergoes meiosis I to form a secondary oocyte + polar body)

  1. SECONDARY OOCYTE is arrested at METAphase of Meiosis II and then ovulated

(it only continues meiosis II to form mature oocyte + polar body if fertilized)

(remember PRIMARY = PROphase of meio I …. SECONDARY = METAphase of meio II)

51
Q

Over the first ~6 days after fertilization, the zygote (46, 2N) undergoes MITOSIS within the Fallopian tube…

what are the names of the THREE STRUCTURES that form as mitosis continues before implantation?

A
  1. BLASTULA - about days 1-4
  2. MORULA - once blastula reaches 32-cell size (day 4)
  3. BLASTOCYST - formed of embryoblast + trophoblast with cavity
52
Q

Implantation

what degenerates first to allow it?

where does it implant? (part of uterus and layer of wall)

what part implants first?

A

ZONA PELLUCIDA degenerates, then

EMBRYONIC POLE implants into the POSTERIOR UTERINE WALL in the FUNCTIONAL LAYER of the endometrium

53
Q

What embryonic process is occuring in WEEK TWO after fertilization?

(2 cell types, 2 cavities, 1 important future structure)

A

formation of the BILAMINAR DISC

  • Epiblast - just below amniotic cavity
  • Hypoblast - just above yolk sac
  • fusion of epi-/hypoblast cells at one end forms the PRECHORDAL PLATE (future mouth)
    (all projecting out into chorionic cavity)
54
Q

Hematopoiesis

Where does it FIRST occur in the embryo (during what time period)?

Then what 3 places does it occur next (during what time period)?

A
  1. YOLK SAC - in mesoderm around yolk sac up to 6 weeks

2. LIVER, SPLEEN + THYMUS of fetus from 6 weeks to 3rd trimester

55
Q

low hCG vs. high hCG

A

low - can mean MISCARRIAGE or ECTOPIA

high - can mean TWINS, MOLE, or gestational trophoblastic disease

56
Q

What is GASTRULATION?

A

the process that produces the 3 primary germ layers: endoderm, ectoderm and mesoderm

begins with formation of PRIMITIVE STREAK in

57
Q

What occurs in the embryo during the THIRD WEEK?

1 fundamental embryonic dev. process
2 organ systems begin development

A
  1. GASTRULATION - formation of germ layers
  2. NERVOUS and CV systems begin development
    a. ectoderm forms neuroectoderm + NC cells
    b. mesoderm forms PARAXIAL somites (35 pair),
    plus int./lat. mesoderm
58
Q

What tumor arises from remnants of the primitive streak?

where is it and what’s its morpho like?

A

SACROCOCCYGEAL teratoma

various types of tissue: bone, nerve, hair etc.

59
Q

What kind of tumor arises from the notochord remnants?

found in what 2 places?

A

CHORDOMA

either INTRACRANIAL or SACRAL

60
Q

What is the state of the embryonic nervous system at the ABOUT 20 DAYS of development?

A

NEURAL PLATE is present, but the neural tube is not yet complete

61
Q

What structure within the embryonic mesoderm induces formation of the neural plate?

And what does it later become?

A

NOTOCHORD induces neural plate formation (day 18) and later becomes NUCLEUS PULPOSUS of IV discs

62
Q

When is NEURAL TUBE formation complete?

A

day 21

and NC cells have pinched off the neural folds as they close, coming to rest in mesoderm on either side of neural tube

63
Q

What are the two “plates” of the neural tube and how do they correspond to later CNS structures?

A

ALAR plate - dorsal, corresponds to dorsal horns (sensory)

BASAL plate - ventral, corresponds to anterior/ventral horns (motor)

64
Q

What is HOLOPROSENCEPHALY?

mutations involved, structurally what happens, moderate vs. severe forms

A

FAILED SEPARATION of L/R hemispheres of brain, usually during WEEK 5 or 6, prob due to SHH signaling issue

moderate = cleft lip/palate
severe = cyclopia
65
Q

Holoprosencephaly

assoc. with what? (2)

MRI shows what? (2)

A

assoc. with 1) PATAU, trisomy 13 and 2) fetal alcohol syndrome

MRI shows 1) “MONOVENTRICLE” and 2) basal ganglia fusion

66
Q

1st pharyngeal pouch, membrane + groove derivatives

remember pouch = internal, groove = external

A

pouch = middle ear + auditory tube epithelium

membrane = tympanic membrane

groove = ext. auditory canal epithelium

67
Q

2nd pharyngeal pouch derivative

A

palatine tonsil crypt epithelium

groove and membrane obliterate + contribute to cervical sinus

68
Q

3rd pharyngeal pouch derivatives

A

INFERIOR parathyroid glands and THYMUS

groove and membrane obliterate + contribute to cervical sinus

69
Q

4th pharyngeal pouch derivatives

A

SUPERIOR parathyroid glands and “ultimobranchial body” which gives the PARAFOLLICULAR C CELLS of thyroid medulla

(groove and membrane obliterate + contribute to cervical sinus)

*USMLE* (28 decks)

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