Somatic Innervation #1: Development of Dermis, Musculoskeletal, and Somatic Nervous Systems

Vocabulary flashcards covering key embryological terms and innervation concepts from the lecture notes.

Somatic Structures

Bones, ligaments, joints, tendons, skeletal muscles, and dermis that originate from somatic mesoderm and receive somatic nervous system innervation.

Somatic Mesoderm

Portion of mesoderm that forms somatic structures of the musculoskeletal system and most of the dermis.

Somatic Nervous System

Division of the peripheral nervous system providing voluntary motor and sensory innervation to somatic structures.

Somatic Motor (Somatomotor) Neuron

Multipolar neuron with its cell body in the ventral gray horn whose axon exits via the ventral root to innervate skeletal muscle.

Somatic Sensory (Somatosensory) Neuron

Pseudounipolar neuron with its cell body in a spinal (dorsal root) ganglion that carries afferent signals from skin, joints, and muscles to the spinal cord.

Neural Tube

Embryonic dorsal midline structure that develops into the brain and spinal cord (central nervous system).

Neural Crest Cells

Migratory cells that detach from the neural tube and give rise to spinal (dorsal root) ganglia and other peripheral structures.

Spinal (Dorsal Root) Ganglion

Cluster of somatic sensory neuron cell bodies derived from neural crest cells and located along each dorsal root.

Paraxial Mesoderm

Mesodermal tissue flanking the neural tube that segments into somites.

Somite

Segmented block of paraxial mesoderm that differentiates into dermatomyotome and sclerotome.

Dermatomyotome

Dorsolateral portion of a somite that forms the dermis of the back and limbs and the skeletal muscles of the neck, trunk, and limbs.

Sclerotome

Ventromedial portion of a somite that develops into vertebrae and ribs.

Lateral Plate Mesoderm

Mesodermal layer that forms the appendicular skeleton and the remaining dermis (except facial skin); also called somatic mesoderm when forming body wall.

Dermatome (Embryology)

Area of skin innervated by sensory fibers from a single spinal nerve, reflecting its somite of origin.

Myotome (Embryology)

Group of skeletal muscle fibers innervated by motor fibers from one spinal level.

Dorsal Ramus

Branch of a spinal nerve that innervates intrinsic back muscles and the overlying skin.

Ventral Ramus

Branch of a spinal nerve that supplies the anterior and lateral body wall, limbs, and associated skin and muscles.

Dorsal Root

Sensory root of a spinal nerve carrying afferent fibers into the spinal cord.

Ventral Root

Motor root of a spinal nerve carrying efferent fibers from the spinal cord to peripheral targets.

Spinal Nerve

Mixed nerve formed by union of dorsal and ventral roots that carries motor and sensory axons from a single spinal segment.

Level-Specific Innervation

Rule that somatic structures are innervated by spinal nerves adjacent to their embryological origin, producing consistent dermatomal and myotomal patterns.

Intrinsic Back Muscles

Deep muscles of the back derived from the dermatomyotome and supplied by dorsal rami.