Dermatome, Myotome, Sclerotome 696135

ELKA RIFQAH

130110110148 NBSS – A1

TOPOGRAPHIC OF SENSORIC DISTRIBUTION (DERMATOME, MYOTOME, SCLEROTOME) 1.

DERMATOME

Source : Atlas of Neuroanatomy and Neurophysiology Frank H. Netter Clinical Neuroanatomy 25th edition

ELKA RIFQAH

130110110148 NBSS – A1

The sensory component of each spinal nerve is distributed to a dermatome, a well-defined segmental portion of the skin (Fig 5–8).

   

The dermatomes for C5, C6, C7, C8, and T1 are confined to the arm, and the C4 and T2 dermatome are contiguous over the anterior trunk. The thumb, middle finger, and fifth digit are within the C6, C7, and C8 dermatomes, respectively. The nipple is at the level of T4. The umbilicus is at the level of T10.

The territories of dermatomes tend to overlap, making it difficult to determine the absence of a single segmental innervation on the basis of sensory testing (Fig 5–9).

Source : Atlas of Neuroanatomy and Neurophysiology Frank H. Netter Clinical Neuroanatomy 25th edition

ELKA RIFQAH

130110110148 NBSS – A1

2.

MYOTOMES

The term myotome refers to the skeletal musculature innervated by motor axons in a given spinal root. Testing of motor functions can be very useful in determining the extent of a lesion in the nerve, spinal cord segment, or tract, especially when combined with a careful sensory examination. Most muscles, are innervated by motor axons that arise from several adjacent spinal roots. Nevertheless, lesions of a single spinal root, in many cases, can cause weakness and atrophy of a muscle. Table 5–2 lists segment-pointer muscles, whose weakness or atrophy may suggest a lesion involving a single nerve root or a pair of adjacent nerve roots. Table 5–2. Segment-Pointer Muscles.

Root

Muscle

Primary Function

C3, C4

Diaphragm

Respiration

C5

Deltoid

Abduction of arm

C5

Biceps

Flexion of forearm

C6

Brachioradialis

Flexion of forearm

C7

Triceps

Extension of forearm

L3, L4

Quadriceps femoris

Extension of knee

L5

Extensor hallucis longus

Dorsiflexion of great toe

S1

Gastrocnemius

Plantar flexion

Modified, with permission, from Byrne TN, Waxman SG: Spinal Cord Compression. FA Davis, 1990.

3.

SCLEROTOME

A sclerotome is a deep somatic track that is innervated by the same signal spinal nerve and when the tissue of a sclerotome is irritated by mechanical or chemical stimuli pain is "experienced" as originating from all of the tissues that are innervated by the same nerve, or along the sclerotome. Chart shows spinal levels C-1 through S-3.

Source : Atlas of Neuroanatomy and Neurophysiology Frank H. Netter Clinical Neuroanatomy 25th edition

ELKA RIFQAH

130110110148 NBSS – A1

Source : Atlas of Neuroanatomy and Neurophysiology Frank H. Netter Clinical Neuroanatomy 25th edition