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Development of the Limbs and Body Wall Quiz
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Which lineage pairing correctly builds the early limb?
- A Somatic lateral-plate mesoderm supplies skeleton and connective tissue; somitic myogenic precursors supply muscle You picked ✓
- B Splanchnic lateral-plate mesoderm supplies muscle, while neural crest supplies the limb skeleton and connective tissue You picked ✕
- C Somites form the limb cartilage and bone, while lateral plate forms its skeletal muscle You picked ✕
- D Intermediate mesoderm supplies the limb skeleton, while sclerotome supplies the limb connective tissue You picked ✕
- E Somatic lateral-plate mesoderm supplies skeleton and connective tissue; neural crest cells supply the limb skeletal muscle You picked ✕
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The answer is A: Somatic lateral-plate mesoderm supplies skeleton and connective tissue; somitic myogenic precursors supply muscle
Explanation
Why A is correct
See Limb Buds: Timing and Origin. Option A is correct because the limb bud is built from two different mesodermal sources that meet inside one patterned bud. Mesoderm is the middle layer of the early embryo. The core of the bud is somatic lateral-plate mesoderm, the part of the lateral plate (a sheet of mesoderm at the side of the embryo) that lies next to the surface ectoderm and the body wall. It supplies the skeletal elements and much of the limb's connective tissue, including the connective framework that helps pattern tendons and muscles. The skeletal muscle has a different origin: myogenic precursors, the cells destined to become muscle, leave the hypaxial part of nearby somites (the blocks of mesoderm either side of the midline, with hypaxial meaning the ventral part) and migrate into the bud. Nerve fibres then grow into this prepared territory. So the framework is made by one lineage, and the muscle is brought in by another. Remember it as: the lateral plate builds the frame, and the somites bring the muscle.
- Skeleton and connective tissue: they come from somatic lateral-plate mesoderm in the core of the bud
- Muscle: myogenic precursors migrate in from the hypaxial part of nearby somites
- Memory aid: the lateral plate builds the frame and the somites bring the muscle
Why the other options are incorrect
- B. Splanchnic lateral-plate mesoderm supplies muscle, while neural crest supplies the limb skeleton and connective tissue: Splanchnic lateral-plate mesoderm gives rise to visceral structures, not limb skeletal muscle, and neural crest does not supply the limb skeleton. The limb skeleton and connective tissue come from somatic lateral-plate mesoderm. Your answer
- C. Somites form the limb cartilage and bone, while lateral plate forms its skeletal muscle: This swaps the two sources. The somatic lateral-plate mesoderm supplies the skeleton, while the muscle precursors come from the somites. Your answer
- D. Intermediate mesoderm supplies the limb skeleton, while sclerotome supplies the limb connective tissue: Intermediate mesoderm is the source of the urogenital system, not the limb skeleton, and sclerotome contributes to the axial skeleton rather than limb connective tissue. The limb skeleton and connective tissue come from somatic lateral-plate mesoderm. Your answer
- E. Somatic lateral-plate mesoderm supplies skeleton and connective tissue; neural crest cells supply the limb skeletal muscle: The first half is right, but limb skeletal muscle comes from myogenic precursors that leave the somites, not from neural crest cells. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
What is the core role of the apical ectodermal ridge in early limb development?
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2
During lateral folding of the embryo, the right and left somatic body-wall folds move towards the ventral midline. Which outcome correctly describes this process?
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