Germ Layer Derivatives

Overview

• Germ layers: ectoderm, mesoderm, endoderm
• Importance in embryology and medical exams (USMLE, COMLEX)
• Focus on derivatives of each layer

Ectoderm Derivatives

1. Surface Ectoderm

   • Mnemonic: "You clean the surface with soap"
   • CLEAN
     • C: Canal (anal canal below pectinate line)
     • L: Lens
     • E: Epidermis
     • A: Adenohypophysis
     • N: Nipple (mammary gland)
   • SOAP
     • S: Sweat gland
     • O: Olfactory epithelium
     • A: Auditory organs
     • P: Parotid glands

2. Neural Tube

   • Mnemonic: "Tube of Neosporin"
   • NEASPOREN
     • N: Neural tube
     • E: Ependymal cells
     • A: Astrocytes
     • S: Spinal cord
     • P: Pineal gland
     • O: Oligodendrocytes
     • R: Retina
     • E: Ependymal cells
     • N: Neurohypophysis

3. Neural Crest

   • Mnemonic: "Motels get spammed with Crest toothpaste"
   • SPAMS
     • S: Schwann cells
     • P: Peripheral nervous system
     • A: Adrenal medulla
     • M: Myenteric plexus
     • S: Spiral membrane
   • MOTEL
     • M: Melanocytes
     • O: Odontoblasts
     • T: Thyroid C cells
     • E: Endocardial cushion
     • L: Laryngeal cartilage

Mesoderm and Endoderm

• General rule of thumb:
  • Mesoderm: Musculoskeletal structures ("Mezzo" = middle)
  • Endoderm: GI organs and viscera ("Endo" = inside)

Mesoderm Abnormalities

• Mnemonic: "Clear TV with Malcolm in the Middle"
  • CLEAR TV
    • C: Cardiac abnormalities
    • L: Limb abnormalities
    • E: Esophageal abnormalities
    • A: Anal abnormalities
    • R: Renal abnormalities
    • T: Tracheal abnormalities
    • V: Vertebral abnormalities

Summary

• Key to remember derivatives, especially ectoderm
• Memorize mnemonics to aid recall
• Understand abnormalities associated with mesoderm formation
• High-yield takeaway: Especially know ectoderm derivatives and mesoderm errors