Test Bank for LANGMAN’S Medical Embryology 20TH by
T. W. Sadler. National Board–Style MCQs with 100%
Correct Answers and Explanations
,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. 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.
2. 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
C. FGF8 and Serotonin (5-HT)
D. Notch
E. Cadherin
Answer>>C
Explanation: Laterality (left-right asymmetry) is established at the primitive node. Cilia
create a leftward flow of FGF8 and Serotonin (5-HT), which triggers a signaling cascade
involving NODAL and PITX2 on the left side only. Disruption leads to situs inversus or
heterotaxy.
3. During the formation of the neural tube, cells must change from an epithelial state to a
migratory mesenchymal state (EMT) to form the neural crest. This process requires the
downregulation of which cell-cell adhesion molecule?
, A. Integrin
B. Fibronectin
C. Laminin
D. N-Cadherin
E. Connexin
Answer>>D
Explanation: Cadherins are calcium-dependent adhesion molecules that hold epithelial
cells together. For Epithelial-Mesenchymal Transition (EMT) to occur, cells must
downregulate cadherins (like E-cadherin or N-cadherin) to break free from their neighbors
and migrate.
4. A fetus is exposed to high doses of a retinoid (Vitamin A derivative). The child is born
with defects in the hindbrain and craniofacial structures. Retinoic acid acts as a
morphogen by binding to nuclear receptors that function as:
A. G-protein coupled receptors
B. Ion channels
C. Transcription factors
D. Proteases
E. Extracellular matrix proteins
T. W. Sadler. National Board–Style MCQs with 100%
Correct Answers and Explanations
,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. 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.
2. 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
C. FGF8 and Serotonin (5-HT)
D. Notch
E. Cadherin
Answer>>C
Explanation: Laterality (left-right asymmetry) is established at the primitive node. Cilia
create a leftward flow of FGF8 and Serotonin (5-HT), which triggers a signaling cascade
involving NODAL and PITX2 on the left side only. Disruption leads to situs inversus or
heterotaxy.
3. During the formation of the neural tube, cells must change from an epithelial state to a
migratory mesenchymal state (EMT) to form the neural crest. This process requires the
downregulation of which cell-cell adhesion molecule?
, A. Integrin
B. Fibronectin
C. Laminin
D. N-Cadherin
E. Connexin
Answer>>D
Explanation: Cadherins are calcium-dependent adhesion molecules that hold epithelial
cells together. For Epithelial-Mesenchymal Transition (EMT) to occur, cells must
downregulate cadherins (like E-cadherin or N-cadherin) to break free from their neighbors
and migrate.
4. A fetus is exposed to high doses of a retinoid (Vitamin A derivative). The child is born
with defects in the hindbrain and craniofacial structures. Retinoic acid acts as a
morphogen by binding to nuclear receptors that function as:
A. G-protein coupled receptors
B. Ion channels
C. Transcription factors
D. Proteases
E. Extracellular matrix proteins
