What is the deep muscular plexus?

The Deep Muscular Plexus: Structure and Function

The deep muscular plexus (DMP) is a specialized network of nerves and interstitial cells of Cajal located within the circular muscle layer of the small intestine that mediates enteric motor neurotransmission between the nervous system and smooth muscle cells. 1

Anatomical Structure

• The deep muscular plexus is positioned between a thin inner layer of smooth muscle (one to five cells thick) and the bulk of the circular muscle in the small intestine 2
• It contains specialized cells called interstitial cells of Cajal of the deep muscular plexus (ICC-DMP) that are structurally similar to smooth muscle cells but with distinct organizational differences 2
• ICC-DMP have a continuous basal lamina, caveolae, intermediate filaments, dense bodies, and well-developed subsurface smooth endoplasmic reticulum, distinguishing them from fibroblasts or macrophages 2

Development

• ICC-DMP develop largely after birth, appearing first in the jejunum and then in the ileum 1
• In human fetuses, ICC-DMP begin to differentiate around birth, with incomplete differentiation at birth 3
• The development of ICC-DMP occurs in parallel with the maturation of related nerve plexuses and muscle layers 3

Physiological Function

• ICC-DMP mediate excitatory and inhibitory neural inputs in the small intestine 1
• They generate spontaneous calcium (Ca²⁺) transients that consist of localized Ca²⁺ events and limited propagating Ca²⁺ waves 4
• These Ca²⁺ transients display variable characteristics: from discrete, highly localized events to regionalized waves with variable rates of occurrence, amplitude, duration, and spatial spread 4
• ICC-DMP are in close, synapse-like contact with nerve terminals of the deep muscular plexus, facilitating neurotransmission 2

Neurotransmission Role

• ICC-DMP mediate both cholinergic excitatory and nitrergic inhibitory neural responses in the small intestine 1
• They are suppressed by the ongoing release of inhibitory neurotransmitters, as evidenced by increased Ca²⁺ transients when tetrodotoxin (TTX) is applied 4
• The calcium signaling in ICC-DMP involves both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP₃Rs), with Itpr1 and Ryr2 subtypes displaying the highest expression 4

Clinical Significance

• Damage to ICC-DMP has been associated with loss of distention-induced burst-type muscle activity, which is important for normal peristalsis 5
• In inflammatory conditions such as Trichinella spiralis infection, injury to ICC-DMP correlates with impaired excitatory innervation of smooth muscle cells 5
• Recovery of ICC-DMP parallels the recovery of distention-induced electrical activity, highlighting their importance in normal gut motility 5

Comparison to Other Plexuses

• While the deep muscular plexus is specific to the small intestine, other neural plexuses exist throughout the body, including the brachial plexus (C5-T1) and lumbosacral plexus (L1-S4) 6, 7
• Unlike these somatic nerve plexuses that primarily innervate skeletal muscles, the deep muscular plexus is part of the enteric nervous system that regulates gastrointestinal function 1, 2