University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

394

Pages:

1
Author:

Mariam A.

Development of musculature     In week 5, myotomes from the somites invade the limb bud, creating a ventral and dorsal mass They differentiate into myoblasts and then become myofibrils (muscle fibres) Each compartment will then split into anatomically recognisable muscles of the upper and lower limb The upper limb rotates 90° laterally, so that the extensor muscles lie on the lateral and posterior surface, and the thumbs lie laterally, whereas the lower limb rotates approximately 90 degrees medially, placing the extensor muscles on the anterior surface and the big toe medially o Thus the flexor compartment of the upper limb is anterior and the extensor compartment posterior, while the flexor compartment of the lower limb is posterior and the extensor anterior Innervation    Nerves to upper limb are provided by ventral primary rami C5-C8, T1, T2 with a dorsal and ventral branch Nerves to lower limb are provided by ventral primary rami L2-L5 and S1-S3, forming an anterior and posterior division Initially dermatome segmentation is straight. However, due to medial and lateral rotation, innervation to the skin becomes somewhat “spiral-shaped” Clinical correlates   Suppression of limb bud (AER) in the 4 th week results in complete absence of the limb – Amelia If suppression occurs in the 5th week, Meromelia results which produces part limbs