Axial Musculoskeletal Development & Mesoderm Differentiation
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Questions and Answers

What is the main component of the annulus fibrosus?

  • Hyaline cartilage
  • Bone tissue
  • Fibrocartilage (correct)
  • Adipose tissue

Which condition involves the fusion of two or more vertebrae?

  • Scoliosis
  • Kyphosis
  • Hemivertebrae
  • Block vertebrae (correct)

What type of cells do myoblasts differentiate into during myogenesis?

  • Fibroblasts
  • Chondrocytes
  • Myotubes (correct)
  • Adipocytes

What is the significance of the cranial and caudal halves of a sclerotome unit?

<p>The cranial half allows neural penetration while the caudal half inhibits it. (A)</p> Signup and view all the answers

Which part of the musculature of the body wall develops into extensors of the vertebral column?

<p>Epimere (B)</p> Signup and view all the answers

How many ossification centers contribute to the formation of the axis (cervical vertebra 2)?

<p>5 (C)</p> Signup and view all the answers

What role do satellite cells have in skeletal muscle?

<p>Regenerate muscle fibers after damage (D)</p> Signup and view all the answers

What is the primary process involved in the formation of most bones from mesenchymal cells?

<p>Endochondral ossification (C)</p> Signup and view all the answers

What role do undifferentiated stem cells play in adult bone health?

<p>They provide repair capabilities for cartilage and bone. (D)</p> Signup and view all the answers

Which type of vertebral malformation is characterized by a wedge shape?

<p>Hemivertebrae (A)</p> Signup and view all the answers

In the context of muscle development, what is myogenesis?

<p>The formation and differentiation of muscle cells. (A)</p> Signup and view all the answers

What is the fate of myoblasts once they have fused to form myotubes?

<p>Further division becomes impossible (C)</p> Signup and view all the answers

Which of the following describes a common vertebral malformation associated with improper sclerotome development?

<p>Scoliosis (C)</p> Signup and view all the answers

How are hypaxial muscles primarily innervated?

<p>Ventral branches of spinal nerves (B)</p> Signup and view all the answers

What defines the structure of intervertebral discs?

<p>A central nucleus pulposus surrounded by annulus fibrosus. (D)</p> Signup and view all the answers

What is the primary function of the sclerotome during development?

<p>Formation of connective tissue, cartilage, and bone in the axial skeleton (D)</p> Signup and view all the answers

What characteristic is true of satellite cells in muscle regeneration?

<p>They are essential for the repair and regeneration of damaged muscle fibers. (A)</p> Signup and view all the answers

Which signaling molecule is essential for sclerotome formation?

<p>Sonic hedgehog (Shh) (C)</p> Signup and view all the answers

What is the role of the dermatome during somite differentiation?

<p>It develops into the dermis and carries sensory nerve fibers. (B)</p> Signup and view all the answers

How do the dorsal portions of sclerotomes contribute to vertebral structure?

<p>They are induced by surface ectoderm to form vertebral arches. (D)</p> Signup and view all the answers

In which stage of axial skeletal development do mesenchymal cells specialize into cartilage or bone?

<p>Chondrogenesis (C)</p> Signup and view all the answers

What is the significance of Hox genes in somite development?

<p>They determine cranial-caudal regionalization of vertebrae. (C)</p> Signup and view all the answers

What is the role of myotomes during development?

<p>They migrate to form skeletal muscle associated with segmental nerves. (D)</p> Signup and view all the answers

What is the characteristic matrix produced by mesenchymal cells that indicates their differentiation?

<p>Cartilage or bone matrix (D)</p> Signup and view all the answers

Flashcards

Sclerotome differentiation

The sclerotome differentiates into connective tissues like cartilage and bone, forming the axial skeleton.

Vertebral body formation

The ventral part of the sclerotome migrates to surround the notochord and forms the vertebral bodies.

Vertebral arch formation

The dorsal part of the sclerotome surrounds the neural tube, and gets signaled by the surface ectoderm to form the vertebral arches.

Dermatome function

Dermatome cells migrate under the ectoderm to form the dermis, carrying sensory nerves.

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Myotome function

Myotome cells migrate to form skeletal muscles of the trunk and limbs, following segmental nerves.

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Chondrogenesis/Osteogenesis

Cartilage and bone development from mesenchymal cells, which create their specific matrices.

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Mesenchymal cells

Indistinguishable cells that differentiate into cartilage or bone.

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Sonic Hedgehog (Shh) role

Shh, from the notochord, plays a role in sclerotome formation.

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Vertebral malformations

Abnormal structures of the vertebrae, such as fused vertebrae (block vertebrae) or wedge-shaped vertebrae (hemivertebrae).

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Block Vertebrae

Two or more vertebrae fused together.

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Hemivertebrae

Wedge-shaped vertebrae.

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Myotome

The part of the somite that gives rise to skeletal muscle.

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Myoblasts

Immature muscle cells that can divide and fuse to form muscle fibers.

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Myotubes

Multinucleated structures formed by fused myoblasts.

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Epaxial muscles

Extensor muscles of the vertebral column.

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Hypaxial muscles

Lateral and ventral flexor muscles of the trunk.

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Intramembranous Ossification

Bone formation directly from condensed mesenchyme layers, found in flat bones like the skull.

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Endochondral Ossification

Bone formation where cartilage models are replaced by bone, typical for most bones.

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Primary Ossification Center

The initial site of bone formation within a long bone, located in the diaphysis.

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Secondary Ossification Center

Additional sites of bone formation that appear in the epiphyses of long bones.

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Sclerotome Cells

Cells from each somite that migrate medially to surround the notochord and neural tube, forming the vertebral column.

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What is the pattern of condensed and loosely packed sclerotome cells?

Condensed (dense) caudal sclerotome cells restrict nerve growth, while loose cranial sclerotome cells allow nerve fibers to pass easily.

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First motor axons exit where?

First motor axons exit the vertebral canal opposite the cranial half of a sclerotome unit, where the loosely packed cells allow for easy passage.

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What is the function of stem cells in adult cartilage and bone?

Undifferentiated stem cells in the perichondrium and periosteum allow for repair of cartilage and bone tissues.

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Study Notes

Axial Musculoskeletal Development

  • Embryonic origin of vertebrae is described.
  • Ossification centers are pivotal in bone formation.
  • Hox genes and Sonic hedgehog influence vertebral column development.
  • Somite segmentation directly impacts vertebral anatomy and associated muscles.
  • Somites contain sclerotome, dermatome, and myotome.
  • Spinal nerves and dorsal root ganglia placement is dependent on somite positioning.
  • Intervertebral discs develop from the notochord and sclerotome remnants.
  • Various developmental defects are influenced by embryonic origins.

Differentiation of Mesoderm

  • Mesoderm initially forms a thin sheet.
  • Cells organize into paraxial, intermediate, and lateral plate mesoderm.
  • Paraxial mesoderm forms somitomeres, then somites.
  • Somitomeres initially form to become somites and eventually vertebrae.
  • Somitomere and somitogenesis patterning demonstrates segmentation.
  • Timing of somitogenesis is consistent, allowing for embryonic age estimation.

Differentiation of Somites

  • Somites differentiate into sclerotome (forms axial skeleton), dermatome (forms dermis), and myotome (forms skeletal muscle).
  • Sclerotome cells migrate, forming the vertebral column.
  • Factors from nearby tissues, including Sonic hedgehog are pivotal in differentiation.
  • Sclerotome-neural tube relationships shape nerve pathway organization.
  • Caudal versus cranial half of sclerotome cells have different characteristics.
  • Crucial events in vertebral formation include sclerotome resegmentation.

Axial Skeletal Development

  • Cartilage and bone form the body's framework.
  • Mesenchymal cells differentiate into cartilage or bone.
  • Hyaline cartilage forms as a model for some bones.
  • Endochondral ossification is the process where cartilage is replaced by bone.
  • Ossification centers play a crucial role in bone formation.

Muscular System

  • Skeletal muscles originate from myotome cells.
  • Myotome cells migrate to form their respective positions.
  • Myoblasts fuse to form myotubes and then muscles.
  • Epaxial muscles are extensors of the vertebral column, while hypaxial muscles are flexors.
  • Muscle innervation follows segmental patterns from spinal nerves.
  • Muscle formation spans multiple segments.
  • Satellite cells remain and enable future muscle repair.

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Chapter 16 Axial Musculoskeletal Development PDF

Description

Explore the intricate process of axial musculoskeletal development, focusing on the embryonic origin of vertebrae and the critical role of ossification centers, Hox genes, and Sonic hedgehog. This quiz also covers mesoderm differentiation, including the organization of paraxial, intermediate, and lateral plate mesoderm, and how somitogenesis contributes to vertebral anatomy.

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