Dermatomes & Innervation of Limbs Quiz

Dermatomes & Segmental Innervation of the Upper & Lower Limbs

•  The presentation covers dermatomes and segmental innervation, specifically focusing on the upper and lower limbs.
•  Segmental innervation of the skin is visually mapped on a diagram of a human body, demonstrating the areas of skin supplied by each spinal segment.
•  The spinal cord is protected by the vertebral column, which contains 33 spinal vertebrae.
•  24 vertebrae are typical, while 9 are fused to form the sacrum and coccyx.
•  There are 5 distinct groups of spinal vertebrae: Cervical (n=7), Thoracic (n=12), Lumbar (n=5), Sacrum (fused-n=5), and Coccyx (fused n=4).
•  Each vertebra comprises a vertebral segment with a body, spine, transverse processes, superior and inferior vertebral notches, and vertebral foramen.
•  Consecutive vertebrae articulate to form intervertebral foramina, which allow the spinal cord to pass through.
•  Segmental spinal nerves exit the vertebral column through these foramina, carrying sensory and motor information.
•  The spinal cord consists of millions of nerve cell bodies and fibers, extending from the medulla to the conus medullaris.
•  The spinal cord runs through the vertebral foramina, forming the spinal canal.
•  The shape of the spinal cord varies from rostral (head end) to caudal (tail end), showing enlargements in the cervical and lumbar regions.
•  Cross-sectional views demonstrate regional specializations matching the four vertebral regions.
•  At each vertebral level, the spinal cord emits a pair of nerves, exiting through intervertebral foramina.
•  Each nerve is classified as a mixed spinal segmental nerve, containing branches of sensory (dorsal) and motor (ventral) fibers.
•  Each spinal segmental nerve comprises dorsal roots (sensory), ventral roots (motor), and ventral roots (autonomic).
•  The mixed spinal nerve emerges through the intervertebral foramen and divides into two branches: the posterior/dorsal ramus and the anterior/ventral ramus.
•  Both rami contain all functional modalities for their respective segmental level of origin and innervate their corresponding regions.
•  The upper limb receives its nerve supply primarily from cervical spinal segments C5-T1, forming the brachial plexus.
•  The brachial plexus involves roots (C5-T1), trunks (upper, middle, lower), divisions (anterior, posterior), and cords (lateral, medial, posterior), ultimately branching into individual nerves (radial, musculocutaneous, ulnar, median).
•  The presentation describes additional nerves of the upper limb (lateral pectoral, upper and lower subscapular, dorsal scapular, long thoracic, and axillary)
•  The lower limb receives its nerve supply from lumbar (L1-L4) and sacral (L4-S4) spinal segments, organizing into the lumbar and sacral plexuses.
•  The lumbar plexus originates behind the psoas major muscle and gives rise to nerves such as femoral, iliohypogastric, ilioinguinal, lateral cutaneous nerve of the thigh, obturator nerve, and lumbosacral trunk.
•  The sacral plexus creates within the pelvic cavity and supplies the lower limb via the sciatic nerve.
•  Dermatomes are mapped areas of skin innervated by a specific spinal nerve root.
•  The spinal cord controls general functions—somatic (skeletal muscles) and autonomic (smooth muscles, glands).
•  Dermatomes ensure accurate identification of areas involving impaired sensation or function.
•  Nerve damage leads to localized numbness or pain affecting the dermatome.
•  Functional overlap exists among dermatomes; usually 3 spinal nerves innervate each area of skin.

Further Information

• The slides also provide diagrams and illustrations to visualize the described anatomical structures and processes.