Updated: 2/8/2019

Genital Embryology

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Overview
  • Week 1-6
    • embryo is sexually indifferent
    • genetically male and female embryos are phenotypically the same
    • both male and female have mesonephric (Wolffian) ducts at this stage
  • Week 7
    • sexual differentiation occurs
  • Week 12
    • sex of embryo can be distinguished based on external genitalia 
  • Week 20
    • phenotypical differentiation is complete
Male vs. Female Differentiation
  • Mesonephric (wolffian) duct
    • needs to be induced to develop
      • by testosterone from the Leydig cells of testes
    • forms male internal sexual organs: Seminal vesicles, Epididymis, Ejaculatory duct, Ductus deferens
  • Paramesonephric (müllerian) duct
    • default development but can be suppressed
    • forms female internal sexual organs: fallopian tube, uterus, upper 1/3 of vagina (lower 2/3 from urogenital sinus
  • Female 
    • default phenotypic differentiation
    • mesonephric duct degenerates and paramesonephric duct develops
  • Male 
    • SRY gene (Y chromosome) produces testis-determining factor which is necessary for testes development
    • testes gives rise to
      • sertoli cells: produces Müllerian inhibitory factor suppressing the development of paramesonephric ducts
      • leydig cells: produces androgens stimulating development of mesonephric ducts 
 
Male/Female Genital Homologues
 
Dihydrotestosterone Results in Development
Common Precursor
Estrogen Results in Development
Glans penis
  • Genital tubercle
  • Glans clitoris
Corpus cavernosum and spongiosum
  • Vestibular bulbs
Bulbourethral glands (of Cowper)
  • Urogenital sinus
  • Greater vestibular glands (of Bartholin)
Prostate gland
  • Urethral and paraurethral glands (of Skene)
Ventral shaft of penis (penile urethra)
  • Urogenital folds
  • Labia minora
Scrotum
  • Labioscrotal swelling 
  • Labia majora

 

Female Genital Abnormalities

 


  • Unicornate Uterus
    • one paramesonephric fails to develop
  • Bicornuate Uterus
    • due to incomplete/partial fusion of the paramesonephric ducts
    • associated with urinary tract abnormalities and infertility
  • Uterus didelphys
    • no fusion between the two paramesonephric ducts resulting in a "double uterus"
  • Müllerian agenesis 
    • failure of paramesonephric ducts to develop resulting in abnormalities of the upper portion of the vagina, cervix, uterus, and fallopian tubes
Male Genital Abnormalities
  • Hypospadias
    • failure of urethral folds to fuse
    • resulting in opening of penile urethra on inferior side of penis
    • susceptible to UTI's
    • surgery is recommended for treatment
  • Epispadias
    • faulty positioning of genital tubercle
    • resulting in penile urethra opening on superior side of penis
    • associated with exstrophy of the bladder
  • Cryptochidism
    • failure of testes to descend into scrotum (undescended testes)
    • testes can be found in inguinal canal or abdominal canal
    • can lead to infertility if both are undescended
    • observable within 3 months of birth
  • Hydrocele
    • processus vaginalis remains patent allowing fluid to flow in
    • resulting in a fluid filled sac in the scrotum
    • can differentiate from tumor by shining light through testes
    • hydrocele allows light to flow through whereas a tumor does not
 

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Questions (7)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M1.EB.36) A 22-year-old G2P1 female presents to the clinic at the beginning of her third trimester for a fetal ultrasound. The sonographer is unable to visualize any of the structures arising from the mesonephric duct. This infant is at risk for malformation of which of the following? Review Topic

QID: 101930
1

Fallopian tubes

8%

(20/241)

2

Uterus

11%

(26/241)

3

Upper 1/3 of vagina

18%

(43/241)

4

Lower 2/3 of vagina

9%

(22/241)

5

No malformation would be expected

53%

(128/241)

M1

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PREFERRED RESPONSE 5

(M1.RP.4753) A 35-year-old female presents to her gynecologist complaining of vaginal discomfort. She reports that over the past two weeks, she has developed dyspareunia and feels as if there is a mass on the external aspect of her vagina. She is sexually active in a monogamous relationship. On physical examination, there is a 2 cm unilateral erythematous swelling on the right side of the posterolateral labia minora. Which of the following embryologic precursors gives rise to the affected tissue in this patient? Review Topic

QID: 108748
1

Paramesonephric duct

14%

(29/202)

2

Genital tubercle

14%

(28/202)

3

Urogenital sinus

19%

(39/202)

4

Urogenital fold

32%

(65/202)

5

Labioscrotal swelling

15%

(31/202)

M1

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PREFERRED RESPONSE 3
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(M1.EB.11) A 4-day-old healthy male infant is born with normal internal and external male reproductive organs. Karyotype analysis reveals a 46XY genotype. Production of what substance by which cell type is responsible for the development of the normal male seminal vesicles, epididymides, ejaculatory ducts, and ductus deferens? Review Topic

QID: 101905
1

Testis-determining factor; Sertoli cells

11%

(20/178)

2

Testis-determining factor; Leydig cells

15%

(26/178)

3

Testosterone; Sertoli cells

9%

(16/178)

4

Testosterone; Leydig cells

37%

(65/178)

5

Mullerian inhibitory factor; Sertoli cells

26%

(46/178)

M1

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(M1.EB.35) A newborn infant with karyotype 46, XY has male internal and external reproductive structures. The lack of a uterus in this infant can be attributed to the actions of which of the following cell types? Review Topic

QID: 101929
1

Leydig

30%

(46/152)

2

Sertoli

62%

(94/152)

3

Theca

4%

(6/152)

4

Granulosa

3%

(4/152)

5

Reticularis

0%

(0/152)

M1

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PREFERRED RESPONSE 2
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