The Abdominal Muscles

This chapter focuses on the respiratory control of the abdominal muscles. It provides an overview of the ontogeny, morphology, innervation, and neural control of the axial muscles comprising the abdominal wall. The chapter shows how abdominal motoneurons process and explores the heterogeneous sensory inputs to produce, often simultaneously, the muscles’ plethora of functions including coughing, sneezing, vomiting, and speech. The abdominal wall differentiates into a deep and superficial group of muscle layers. The deep group is comprised of the psoas magnus, the psoas parves, the illiacus, and the quadratus lumborum. In most respects, abdominal muscle fibers have characteristics similar to those of other skeletal muscles. Cutaneous stimulation evokes an abdominal contraction, a nociceptive reflex, that protects the viscera against impact. Dissociation of the abdominal skin and stretch reflexes is diagnostic for localizing lesions causing spastic paralysis.