Embryology (Endo and Repro) Flashcards

1
Q

Thyroid development

A
  1. ) Thyroid diverticulum arises from floor of primitive pharynx and DESCENDS into neck
  2. ) Connected to tongue by thyroglossal duct –>may persist as pyramidal lobe
  3. ) Most common ectopic thyroid site is tongue (lingual thyroid)
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2
Q

Thyroglossal duct

A
  1. ) Foramen cecum is normal remnant of thyroglossal duct

2. ) May persist as thyroglossal duct cyst – anterior midline neck mass that moves with swallowing

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3
Q

Fetal adrenal gland

A

Inner active fetal zone
Outer adult zone - secretes cortisol (lung maturation, surfactant production) during late gestation under control of fetal pituitary and placenta (ACTH, CRH)

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4
Q

Sonic hedgehog

A
  1. ) A/P axis patterning; produced at base of limbs in ZPA

2. ) Involved in CNS development; mutation can cause holoprosencephaly (forebrain does not form 2 hemispheres)

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5
Q

Wnt-7

A

D/V axis patterning; produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)

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6
Q

FGF gene

A

Produced at apical ectodermal ridge; stimulates mitosis of underlying mesoderm –>limb elongation

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7
Q

Hox genes

A

DNA-binding TFs that regulate morphogenesis; involved in segmental organization of embryo in craniocaudad direction; mutation –>appendages in wrong locations

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8
Q

Fetal development: day 0

A

Fertilization by sperm forming zygote, initiating embryogenesis

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9
Q

Fetal development: within week 1

A

hCG secretion begins after implantation of blastocyst

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10
Q

Fetal development: within week 2

A

Bilaminar disc (epiblast, hypoblast) **2 weeks = 2 layers

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11
Q

Fetal development: within week 3

A

Gastrulation –>trilaminar disk **3 weeks = 3 layers

Epiblast invaginates to from primitive streak, notochord, mesoderm + organization, neural plate

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12
Q

Fetal development: weeks 3-8

A

Neural tube formed by neuroectoderm and closes
Organogenesis
Extremely susceptible to teratogens

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13
Q

Fetal development: within week 4

A

Heart begins to beat

Upper and lower limb buds begin to form **4weeks = 4 limbs

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14
Q

Fetal development: week 8 (start of fetal period)

A

Fetal movement, fetus looks like a baby

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15
Q

Fetal development: week 10

A

Genitalia have male/female characteristics

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16
Q

Surface ectoderm derivatives

A
Epidermis
Rathke's pouch (ant. pit)
Lens and cornea
Inner ear sensory organs
Nasal, oral, and olfactory epithelium
Salivary, sweat, mammary glands
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17
Q

Neuroectoderm (neural tube) derivatives

A

Brain and spinal cord
Posterior pituitary
Pineal gland
Retina

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18
Q

Neural crest derivatives

A
Autonomic, sensory, and celiac ganglia
Adrenal medulla
Pia and arachnoid mater
Melanocytes
Schwann cells
Aorticopulmonary septum
Endocardial cushions
Branchial arches (bones & cartilage)
Skull bones
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19
Q

Mesoderm derivatives

A
Paraxial mesoderm
Muscles (skeletal, cardiac, smooth)
Bones & cartilage
Connective tissue
Cardiovascular system and blood
Lymphatics
Serosal linings
Spleen (foregut mesentery)
Wall of gut tube
Adrenal cortex

Intermediate mesoderm
Kidney & ureters
Internal genitalia

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20
Q

Endoderm derivatives

A
Middle ear
Lung
Thymus
Thyroid follicular cells
Parathyroids
GI tract
Liver
Pancreas
Bladder and urethra
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21
Q

Errors: agenesis

A

Absent organ due to absent primordial tissue

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22
Q

Errors: aplasia

A

Absent organ despite primordial tissue

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23
Q

Errors: deformation

A

Extrinsic disruption; occurs after the embryonic period

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24
Q

Errors: hypoplasia

A

Incomplete organ development; primordial tissue present

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25
Q

Errors: malformation

A

Intrinsic disruption; occurs during the embryonic period (weeks 3-8)

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26
Q

Teratogen timing of effect

A

Before week 3: all or nothing effects
Weeks 3-8: most susceptible
After week 8: growth and function affected

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27
Q

Teratogen: ACEi

A

Renal damage

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28
Q

Teratogen: Alkylating agents

A

Absence of digits, multiple anomalies

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29
Q

Teratogen: Aminoglycosides

A

CN VIII toxicity (ototoxicity)

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30
Q

Teratogen: Carbamazepine

A

NTDs, craniofacial defects, fingernail hypoplasia, developmental delay, IUGR

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31
Q

Teratogen: DES

A

Vaginal clear cell adenocarcinoma, congenital Mullerian anomalies

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32
Q

Teratogen: Folate antagonists

A

NTDs

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33
Q

Teratogen: Lithium

A

Ebstein’s anomal (atrialized RV)

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34
Q

Teratogen: Phenytoin

A

Fetal hydantoin syndrome: microcephaly, dysmorphic craniofacial features, hypoplastic nails and distal phalanges, cardiac defects, IUGR, mental retardation

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35
Q

Teratogen: Tetracyclines

A

Discolored teeth

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36
Q

Teratogen: Thalidomide

A

Limb defects (flipper limbs)

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37
Q

Teratogen: Valproate

A

Inhibition of maternal folate absorption –>NTDs

38
Q

Teratogen: Warfarin

A

Bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities

39
Q

Substance abuse: alcohol

A

Birth defects, mental retardation, fetal alcohol syndrome

40
Q

Substance abuse: cocaine

A

Abnormal fetal development and fetal addiction; placental abruption –>prematurity

41
Q

Substance abuse: smoking (nicotine, CO)

A

Preterm labor, placental problems, IUGR, ADHD

42
Q

Iodide imbalance

A

Congenital goiter or hypothyroidism (cretinism)

43
Q

Maternal diabetes

A

Caudal regression syndrome (anal atresia to sirenomelia; agenesis of lower spine/sacrum), congenital heart defects, NTDs

44
Q

X rays

A

Microcephaly, mental retardation

45
Q

Fetal alcohol syndrome

A

Congenital abnormalities, mental retardation, pre- and post-natal developmental retardation, microcephaly, holoprosencephaly, facial abnormalities, limb dislocation, heart and lung fistulas

46
Q

Twinning: monozygotic

A

Dichorionic diamniotic, fused or separate placenta (0-4d, 25%)
Monochorionic diamniotic (4-8d, after morula, 75%)
Monochorionic, monoamniotic (8-12d, after blastocyst, 13d)

47
Q

Twinning: dizygotic

A

Always dichorionic, dizygotic

48
Q

Cytotrophoblast

A

Inner layer of chorionic villi; makes cells

49
Q

Syncytotrophoblast

A

Outer layer of chorionic villi; secretes hCG (similar to LH; stim of CL to make progesterone during 1st trimester)

50
Q

Decidua basalis

A

Derived from endometrium; maternal blood in lacunae

51
Q

Umbilical cord

A

2 umbilical arteries (deox blood from fetal internal iliac aa.), 1 umbilical vein (ox blood from placenta); derived from allantois, surrounded by Wharton jelly

52
Q

Urachal duct

A

3rd week - yolk sac forms allantois which becomes urachus – connects bladder and yolk sac

53
Q

Patent urachus

A

Urine discharge from umbilicus

54
Q

Vesicourachal diverticulum

A

Outpouching of bladder

55
Q

Vitelline duct

A

7th week - obliteration of vitelline duct which connects yolk sac to midgut lumen

56
Q

Vitelline fistula

A

Meconium discharge from umbilicus

57
Q

Meckel’s diverticulum

A

Partial closure, with patent portion attached to ileum. May have ectopic gastric mucosa –>melena, periumbilical pain, and ulcer

58
Q

1st aortic arch derivative

A

Maxillary artery

59
Q

2nd aortic arch derivative

A

Stapedial artery

60
Q

3rd aortic arch derivative

A

Common carotid and proximal part of internal carotid artery

61
Q

4th aortic arch derivative

A

(L) Aortic arch and (R) right subclavian artery

62
Q

6th aortic arch derivative

A

Proximal part of pulmonary artery and (L) ductus arteriosus

63
Q

Branchial cleft derivatives

A

1st cleft becomes external auditory meatus; the remaining clefts make temporary cervical sinuses which obliterate with development of 2nd arch mesenchyme

64
Q

1st branchial arch

A

Mandible, Malleus, incus, Mandibular ligament, muscles of mastication, CN V2 and V3

65
Q

1st branchial arch abnormality

A

Treacher Collins syndrome: neural crest of 1st arch fails to migrate –>mandibular hypoplasia, micrognathia, facial abnormalities

66
Q

2nd branchial arch

A

Stapes, Styloid process, Stylohyoid ligament, less horn of hyoid, Stapedius, Stylohyoid, posterior belly of digastric, CN VII

67
Q

3rd branchial arch

A

Greater horn of hyoid, stylopharyngeus, CN IX

68
Q

3rd branchial arch abnormality

A

Congenital pharyngo-cutaneous fistula: persistence of cleft and pouch –>fistula between tonsillar area, cleft in lateral neck

69
Q

4th-6th branchial arches

A

Thyroid, cricoid, arytenoids, corniculate, cuneiform cartilages
4th arch - pharyngeal constrictors, cricothyoid, levator veli palatini, CN X (superior laryngeal branch)
6th arch - all intrinsic muscles of larynx except cricothyroid, CN X (recurrent laryngeal branch)

70
Q

1st branchial pouch

A

Middle ear cavity, eustachian tubes, mastoid air cells

71
Q

2nd branchial pouch

A

Develops into epithelial lining of palatine tonsil

72
Q

3rd branchial pouch

A

Dorsal wings –>inferior parathyroids

Ventral wings –>thymus

73
Q

4th branchial pouch

A

Dorsal wings –>superior parathyroids

74
Q

DiGeorge syndrome

A

Aberrant development of 3rd and 4th branchial pouches –>T cell deficiency (thymic aplasia), hypocalcemia (absent parathyroids)

75
Q

MEN2a syndrome

A

Mutation of germline RET (neural crest):
Adrenal medulla (pheo)
Parathyroid tumor: 3rd-4th pharyngeal pouches
Parafollicular cells (MTC): 4th-5th pharyngeal pouches

76
Q

Cleft lip

A

Failure of fusion of the maxillary and medial nasal processes (formation of 1st palate)

77
Q

Cleft palate

A

Failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process (formation of the 2nd palate)

78
Q

Female genital development

A

Default development; mesonephric duct degenerates and paramesonephric duct develops

79
Q

Male genital development

A

SRY gene on Y chromosome produces testes determining factor –>testes
Sertoli cells secrete MIF –>suppresses development of paramesonephric ducts
Leydig cells secrete androgens –>promotes development of mesonephric ducts

80
Q

Paramesonephric duct

A

Develops into female internal structures

81
Q

Mullerian duct abnormalities

A

Result in primary amenorrhea with secondary sex characteristics (Mullerian agenesis/imperforate hymen)

82
Q

Bicornuate uterus

A

Failure of fusion of paramesonephric ducts

Assoc. with urinary tract abnormalities and miscarriages

83
Q

Mesonephric duct

A

Develops into male internal structures except prostate

Ductules differentiate to form efferent ductules

84
Q

Absent Sertoli cells/no MIF

A

Develop both male and female internal genitalia, male external genitalia

85
Q

5a-reductase deficiency

A

Male internal genitalia, ambiguous external genitalia until puberty (small phallus, hypospadias), no electrolyte abnormalities

86
Q

Genital tubercle (structure)

A

DHT –>glans penis, corpus cavernosum and spongiosum

Estrogen –>glans clitoris, vestibular bulbs

87
Q

Urogenital sinus

A

DHT –> Cowper’s glands, prostate gland

Estrogen –>Bartholin’s glands, Skene’s glands

88
Q

Urogenital folds

A

DHT –>penile urethra

Estrogen –>labia minora

89
Q

Labioscrotal swelling

A

DHT –>scrotum

Estrogen –>labia majora

90
Q

Hypospadias

A

Opening of penile urethra on inferior side of penis due to failure of urethral fold closure

91
Q

Epispadias

A

Opening of penile urethra on superior side of penis due to faulty positioning of genital tubercle