Updated: 2/8/2019

Germ Layer Derivatives

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 germ layers 
 
Ectoderm
  • Surface ectoderm
    • adenohypophysis 
    • lens of the eye
    • sensory organs 
      • ear
      • olfactory epithelium
    • epithelial linings
      • oral cavity
      • lower anal canal
      • external auditory meatus
    • epidermis, hair, and nails
    • mammary, sweat, and salivary glands
  •  Neuroectoderm - CNS and brain
    • brain - all neurons within brain and spinal cord/CNS
      • neurohypophysis
      • oligodendrocytes
      • astrocytes
      • ependymal cells
      • pineal gland
    • retina
  • Neural Crest - PNS and nearby non-neural structures
    • ANS
    • enteric nervous system 
    • ganglia (dorsal root, cranial, and autonomic)
    • cranial nerves
    • celiac ganglion
    • melanocytes  
    • chromaffin cells of adrenal medulla
    • enterochromaffin cells
    • Schwann cells
    • pia and arachnoid
    • bones of the skull
    • odontoblasts
    • aorticopulmonary septum
Endoderm
  • Epithelium lining of
    • respiratory: trachea, bronchi, and lungs
    • urinary: urinary bladder, female urethra, and majority of male urethra
    • GI tract
    • biliary system
    • lower 2/3 of vagina
    • middle ear cavity and auditory tube
  • Liver
  • Parathyroid
  • Thyroid follicular cells
  • Thymus
  • Pancreas
  • Parafollicular (C) cells of thyroid
Mesoderm
  • Muscle (smooth, cardiac, and skeletal)
  • Dermis and subcutaneous layers of skin
  • Bone, cartilage, and connective tissue
  • Dura mater
  • Serous linings of body cavities
    • peritoneum
  • Spleen
  • Cardiovascular structures
  • Lymphatics
  • Laryngeal cartilage
  • Blood: RBCs, WBCs, Kupffer cells, and microglia
  • Urogenital structures
    • male: testes, epididymis, ductus deferens, seminal vesicle, and ejaculatory duct
    • female: ovaries, uterus, uterine tubes, and upper 1/3 of vagina
  • Kidneys
  • Adrenal cortex
Defects
  • Types of errors
    • malformation vs. deformation 
      • malformation is intrinsic embryological disruption during the embryonic period
      • deformation is extrinsic disruption, occurs after embryonic period
    • agenesis vs. hypoplasia vs. aplasia
      • agenesis = organ is absent because of absent primordial tissue
        • e.g., renal agenesis - failure of one or both kidneys to develop
      • hypoplasia = organ develops incompletely with remnant primordial tissue
        • e.g., microorchidism in Klinefelter syndrome
      • aplasia = organ absent but primordial tissue present
        • e.g., thymic aplasia in DiGeorge syndrome
  • Craniopharyngioma
    • benign Rathke's pouch tumor containing cholesterol crystals and calcifications, tends to compress the optic chiasm 
  • Mesodermal defects VACTERL 
    • Vertebral defects: usually small hypoplastic vertebrae or hemivertebrae, only half of the bone is formed
    • Anal atresia/imperforate anus 
    • Cardiac defects: ventricular septal defect, atrial septal defect, and Tetralogy of Fallot
    • Tracheo-Esophageal fistula
    • Renal defects: incomplete formation of one or both kidneys
    • Limb defects: absent or displaced thumbs, polydactyly, and syndactyly
 

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Questions (8)
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
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(M1.EB.28) A 75-year-old patient presents to the dermatologist with a 4 cm brown lesion on the right cheek (Figure A). The patient states that the lesion has been there for years but just recently began to change in appearance. She has noticed cracking and oozing from the lesion over the past few months. Which cell line most directly gives rise to the pathologic cell in this patient? Review Topic

QID: 101922
FIGURES:
1

Notochord

0%

(0/175)

2

Endoderm

0%

(0/175)

3

Neural crest cells

80%

(140/175)

4

Mesoderm

2%

(4/175)

5

Ectoderm

17%

(29/175)

M1

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PREFERRED RESPONSE 3
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(M1.EB.28) A 52-year-old woman sees you in her office with a complaint of new-onset headaches over the past few weeks. On exam, you find a 2 x 2 cm dark, irregularly shaped, pigmented lesion on her back. She is concerned because her father recently passed away from skin cancer. What tissue type most directly gives rise to the lesion this patient is experiencing? Review Topic

QID: 101046
1

Ectoderm

19%

(15/81)

2

Neuroectoderm

14%

(11/81)

3

Mesoderm

1%

(1/81)

4

Neural crest cells

64%

(52/81)

5

Endoderm

0%

(0/81)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(M1.EB.63) Twenty-four hours after birth, a male newborn has not passed meconium. The newborn's abdomen is distended and he has had two episodes of bilious vomiting. Based on findings during physical exam of the patient (Figure A), for which other abnormalities should this patient also be evaluated? Review Topic

QID: 106457
FIGURES:
1

Vision defects

2%

(3/137)

2

Hearing defects

5%

(7/137)

3

Arteriovenous malformation

26%

(35/137)

4

Urogenital tract anomalies

66%

(90/137)

5

Bleeding disorder

1%

(1/137)

M1

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PREFERRED RESPONSE 4
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