Submucosal plexus of GIT

Two major networks of nerve fibers are intrinsic to the gastrointestinal tract: the myenteric plexus (Auerbach's plexus), between the outer longitudinal and middle circular muscle layers, and the submucous plexus (Meissner's plexus), between the middle circular layer and the mucosa. Collectively, these neurons constitute the enteric nervous system. The system contains about 100 million sensory neurons, interneurons, and motor neurons in humans--as many as are found in the whole spinal cord and the system is probably best viewed as a displaced pa of the central nervous system (CNS) that is concerned with the regulation of gastrointestinal function. It is sometimes referred to as the "little brain" for this reason. It is connected to the CNS by parasympathetic and sympathetic fibers but can function autonomously without these connections. The myenteric plexus innervates the longitudinal and circular smooth muscle layers and is concerned primarily with motor control, whereas the submucous plexus innervates the glandular epithelium, intestinal endocrine cells, and submucosal blood vessels and is primarily involved in the control of intestinal secretion. The neurotransmitters in the system include acetylcholine, the amines norepinephrine and serotonin, the amino acid g-aminobutyrate (GABA), the purine adenosine triphosphate (ATP), the gases NO and CO, and many different peptides and polypeptides. Some of these peptides also act in a paracrine fashion, and some enter the bloodstream, becoming hormones. Not surprisingly, most of them are also found in the brain.REF: GANONG&;S REVIEW OF MEDICAL PHYSIOLOGY, KIM BARRETT, HEDDWEN BROOKS, SCOTT BOITANO, SUSAN BARMANTWENTY THIRD EDITIONPAGE NO:448