questions 7

Germ Layer Derivatives

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Topic updated on 09/16/17 9:42am

 
 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
    • ganglia (dorsal root, cranial, and autonomic)
    • cranial nerves
    • celiac ganglion
    • melanocytes  
    • chromaffin cells of adrenal medulla
    • enterochromaffin cells
    • parafollicular (C) cells of thyroid
    • Schwann cells
    • pia and arachnoid
    • bones of the skull
    • odontoblasts
    • laryngeal cartilage
    • 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
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
  • 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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Qbank (3 Questions)

TAG
(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. The lesion most likely originated from a cell derived from which germ cell line? Topic Review Topic
FIGURES: A          

1. Notochord
2. Endoderm
3. Neural crest cells
4. Mesoderm
5. Ectoderm

PREFERRED RESPONSE ▶
TAG
(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? Topic Review Topic

1. Ectoderm
2. Neuroectoderm
3. Mesoderm
4. Neural crest cells
5. Endoderm

PREFERRED RESPONSE ▶
TAG
(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? Topic Review Topic
FIGURES: A          

1. Vision defects
2. Hearing defects
3. Arteriovenous malformation
4. Urogenital tract anomalies
5. Bleeding disorder

PREFERRED RESPONSE ▶
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