Test Bank for LANGMAN’S Medical Embryology (Twelfth
Edition) by T. W. Sadler. National Board–Style MCQs
with 100% Correct Answers and Explanations Top
Rated
,Table of Contents
Part 1: General Embryology
● Introduction: Clinical Relevance and Historical Perspective
● Chapter 1: Introduction to Molecular Regulation and Signaling
● Chapter 2: Gametogenesis: Conversion of Germ Cells into Male and Female
Gametes
● Chapter 3: First Week of Development: Ovulation to Implantation
● Chapter 4: Second Week of Development: Bilaminar Germ Disc
● Chapter 5: Third Week of Development: Trilaminar Germ Disc
● Chapter 6: Third to Eighth Weeks: The Embryonic Period
● Chapter 7: The Gut Tube and the Body Cavities
● Chapter 8: Third Month to Birth: The Fetus and Placenta
● Chapter 9: Birth Defects and Prenatal Diagnosis
Part 2: Systems-Based Embryology
● Chapter 10: The Axial Skeleton
● Chapter 11: Muscular System
● Chapter 12: Limbs: Growth, development, and musculature
● Chapter 13: Cardiovascular System
● Chapter 14: Respiratory System
● Chapter 15: Digestive System
● Chapter 16: Urogenital System
● Chapter 17: Head and Neck
● Chapter 18: Central Nervous System
● Chapter 19: Ear:
● Chapter 20: Eye
● Chapter 21: Integumentary System
,Topic 1: Introduction to Molecular Regulation and Signaling
1. A child is born with holoprosencephaly, a severe midline defect of the brain and face.
The underlying molecular cause is a "haploinsufficiency" of a signaling molecule that
normally establishes the midline. Which pathway is most likely affected?
A. Wnt pathway
B. Fibroblast Growth Factor (FGF) pathway
C. Notch pathway
D. Sonic Hedgehog (Shh) pathway
E. Transforming Growth Factor-beta (TGF-β) pathway
Answer>>D
Explanation: Sonic Hedgehog (Shh) is the "master gene" for midline paflerning in the
CNS. Loss of one Shh allele (haploinsufficiency) or interference with its signaling (e.g., by
cholesterol inhibitors) prevents the brain from dividing into two hemispheres, leading to
holoprosencephaly.
2. A patient presents with a rare skeletal dysplasia characterized by the premature fusion
of cranial sutures (craniosynostosis). The condition is traced to a "gain-of-function"
mutation in a receptor that normally regulates mesenchymal cell proliferation and
differentiation through tyrosine kinase activity. This receptor belongs to which family?
, A. Hedgehog receptors (Patched)
B. Fibroblast Growth Factor Receptors (FGFRs)
C. Notch receptors
D. Frizzled receptors
E. Integrin receptors
Answer>>B
Explanation: FGFRs are receptor tyrosine kinases. Gain-of-function mutations in FGFR1, 2,
or 3 are the primary causes of various craniosynostosis syndromes (like Apert or Pfeiffer
syndrome) and achondroplasia. They play a critical role in regulating bone growth and
suture patency.
3. In a laboratory experiment, the "Notch signaling pathway" is blocked in a developing
vertebrate embryo. The researcher observes that the boundaries between somites fail to
form properly, resulting in fused vertebrae. This occurs because Notch signaling is
primarily involved in:
A. Long-range paracrine signaling via diffusion
B. Juxtacrine signaling through cell-to-cell contact
C. Autocrine signaling to regulate the cell's own growth
D. Steroid hormone-mediated gene activation
E. Morphogen gradient establishment over many cell diameters
Answer>>B
Explanation: Notch signaling is a classic example of juxtacrine signaling, where a
transmembrane protein (Delta/Serrate/Jagged) on one cell binds to a transmembrane
receptor (Notch) on an adjacent cell. This pathway is essential for "lateral inhibition" and
establishing sharp boundaries, such as those between somites.
4. A newborn is found to have situs inversus totalis (organs are a mirror image of their
normal positions). This condition is often linked to a defect in "nodal" cilia that fail to create
a leftward flow of signaling molecules. Which of the following molecules is critical for
establishing the "left side" of the embryo?
A. BMP4
B. Shh
Edition) by T. W. Sadler. National Board–Style MCQs
with 100% Correct Answers and Explanations Top
Rated
,Table of Contents
Part 1: General Embryology
● Introduction: Clinical Relevance and Historical Perspective
● Chapter 1: Introduction to Molecular Regulation and Signaling
● Chapter 2: Gametogenesis: Conversion of Germ Cells into Male and Female
Gametes
● Chapter 3: First Week of Development: Ovulation to Implantation
● Chapter 4: Second Week of Development: Bilaminar Germ Disc
● Chapter 5: Third Week of Development: Trilaminar Germ Disc
● Chapter 6: Third to Eighth Weeks: The Embryonic Period
● Chapter 7: The Gut Tube and the Body Cavities
● Chapter 8: Third Month to Birth: The Fetus and Placenta
● Chapter 9: Birth Defects and Prenatal Diagnosis
Part 2: Systems-Based Embryology
● Chapter 10: The Axial Skeleton
● Chapter 11: Muscular System
● Chapter 12: Limbs: Growth, development, and musculature
● Chapter 13: Cardiovascular System
● Chapter 14: Respiratory System
● Chapter 15: Digestive System
● Chapter 16: Urogenital System
● Chapter 17: Head and Neck
● Chapter 18: Central Nervous System
● Chapter 19: Ear:
● Chapter 20: Eye
● Chapter 21: Integumentary System
,Topic 1: Introduction to Molecular Regulation and Signaling
1. A child is born with holoprosencephaly, a severe midline defect of the brain and face.
The underlying molecular cause is a "haploinsufficiency" of a signaling molecule that
normally establishes the midline. Which pathway is most likely affected?
A. Wnt pathway
B. Fibroblast Growth Factor (FGF) pathway
C. Notch pathway
D. Sonic Hedgehog (Shh) pathway
E. Transforming Growth Factor-beta (TGF-β) pathway
Answer>>D
Explanation: Sonic Hedgehog (Shh) is the "master gene" for midline paflerning in the
CNS. Loss of one Shh allele (haploinsufficiency) or interference with its signaling (e.g., by
cholesterol inhibitors) prevents the brain from dividing into two hemispheres, leading to
holoprosencephaly.
2. A patient presents with a rare skeletal dysplasia characterized by the premature fusion
of cranial sutures (craniosynostosis). The condition is traced to a "gain-of-function"
mutation in a receptor that normally regulates mesenchymal cell proliferation and
differentiation through tyrosine kinase activity. This receptor belongs to which family?
, A. Hedgehog receptors (Patched)
B. Fibroblast Growth Factor Receptors (FGFRs)
C. Notch receptors
D. Frizzled receptors
E. Integrin receptors
Answer>>B
Explanation: FGFRs are receptor tyrosine kinases. Gain-of-function mutations in FGFR1, 2,
or 3 are the primary causes of various craniosynostosis syndromes (like Apert or Pfeiffer
syndrome) and achondroplasia. They play a critical role in regulating bone growth and
suture patency.
3. In a laboratory experiment, the "Notch signaling pathway" is blocked in a developing
vertebrate embryo. The researcher observes that the boundaries between somites fail to
form properly, resulting in fused vertebrae. This occurs because Notch signaling is
primarily involved in:
A. Long-range paracrine signaling via diffusion
B. Juxtacrine signaling through cell-to-cell contact
C. Autocrine signaling to regulate the cell's own growth
D. Steroid hormone-mediated gene activation
E. Morphogen gradient establishment over many cell diameters
Answer>>B
Explanation: Notch signaling is a classic example of juxtacrine signaling, where a
transmembrane protein (Delta/Serrate/Jagged) on one cell binds to a transmembrane
receptor (Notch) on an adjacent cell. This pathway is essential for "lateral inhibition" and
establishing sharp boundaries, such as those between somites.
4. A newborn is found to have situs inversus totalis (organs are a mirror image of their
normal positions). This condition is often linked to a defect in "nodal" cilia that fail to create
a leftward flow of signaling molecules. Which of the following molecules is critical for
establishing the "left side" of the embryo?
A. BMP4
B. Shh
