Introduction
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
The submucosa consists of areolar connective tissue that binds the mucosa to the muscularis. It contains many blood and lymphatic vessels that receive absorbed food molecules. Also located in the submucosa is the submucosal plexus or plexus of Meissner, an extensive network of neurons. The neurons are part of the enteric nervous system (ENS), the “brain of the gut.” The ENS consists of about 100 million neurons in two plexuses that extend the entire length of the tract. The submucosal plexus contains sensory and motor enteric neurons, plus parasympathetic and sympathetic postganglionic neurons that innervate the mucosa and submucosa. Enteric nerves in the submucosa regulate movements of the mucosa and vasoconstriction of blood vessels. Because its neurons also innervate secretory cells of mucosal and submucosal glands, the ENS is important in controlling secretions by the GI tract. The submucosa may also contain glands and lymphatic tissue.
Healing and Repair
William J. Snape, Stephen M. Collins in Effects of Immune Cells and Inflammation on Smooth Muscle and Enteric Nerves, 2020
In the deeper layers of the bowel wall are the submucosal plexus of Meissner, the muscular plexus of Auerbach, both of which contain ganglion cells, glia and interstitial cells of Cajal. There is possibly also a fragmented plexus immediately superfical to the muscularis propria, the so-called plexus muscularis profundus, which likely contains the interstitial cells of Cajal which may initiate and modulate intestinal motility. Further, nerve stains of the muscularis mucosae and propria show them to be richly endowed with nerves. It is totally unclear how much of the specialized cells and their ramifications are capable of regenerating following injury, or the effect that this has on normal physiological function. A further poorly realized feature of the muscularis propria is that the predominant inflammatory cell occurring there seems to be the mast cell, and these may be staggeringly numerous and frequently associated with the inherent neural plexus.
The oesophagus
Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie in Bailey & Love's Short Practice of Surgery, 2018
The oesophagus is a muscular tube, approximately 25 cm long, mainly occupying the posterior mediastinum and extending from the upper oesophageal sphincter (the cricopharyngeus muscle) in the neck to the junction with the cardia of the stomach. The musculature of the upper oesophagus, including the upper sphincter, is striated. This is followed by a transitional zone of both striated and smooth muscle with the proportion of the latter progressively increasing so that, in the lower half of the oesophagus, there is only smooth muscle. It is lined throughout with squamous epithelium. The parasympathetic nerve supply is mediated by branches of the vagus nerve that has synaptic connections to the myenteric (Auerbach's) plexus. Meissner's submucosal plexus is sparse in the oesophagus.
Disruption of the network between Onuf’s nucleus and myenteric ganglia, and developing Hirschsprung-like disease following spinal subarachnoid haemorrhage: an experimental study
Published in International Journal of Neuroscience, 2019
Ozgur Caglar, Binali Firinci, Mehmet Dumlu Aydin, Erdem Karadeniz, Ali Ahiskalioglu, Sare Altas Sipal, Murat Yigiter, Ahmet Bedii Salman
The plexus of Meissner is closely related to the external surface of the lamina muscularis mucosae with an enveloping connective tissue. Glial cells cover the ganglial neurons as connecting strands [29]. Ganglial submucosal plexus is located in submucosa and between smooth muscle cells [29]. External submucosal plexus (Meissner) consists of more small ganglia under submucosal plexus and Peyer plaques around the blood vessels in the lamina propria of intestines. Nerve fibres are not present in the apex of the follicles. Lymphoid organs consist of richly innervated nerve fibres of the submucosal plexus. Auerbach’s plexus is a network of small meshes in the appendix, while ileal Peyer patches are composed of a network of large meshes [30]. In the present study, we showed that myenteric network is innervated by Onuf’s nucleus’s centralized S2–4 nerve roots and that any lesion of that network may induce Hirschsprung- or Ogilvie-like pathologies.
Communication between the gut microbiota and peripheral nervous system in health and chronic disease
Published in Gut Microbes, 2022
Tyler M. Cook, Virginie Mansuy-Aubert
The enteric nervous system is comprised of sensory, motor, and interneurons organized into networks or plexuses located within the gut, which are capable of operating independently of the CNS. The submucosal plexus lies between the mucosa and circular muscle, and it regulates secretion and blood flow.39 Enteric neurons between the circular and longitudinal muscle make up the myenteric plexus (Auerbach plexus), which controls gut motility by action on smooth muscle. Enteric sensory neurons known as IPANs (intrinsic primary afferent neurons) detect various chemicals or distension caused by a food bolus, and then coordinate the electrical activity of submucosal and myenteric neurons. Finally, interneurons link the activity of ascending and descending motor networks to allow the “little brain” of the gut to function autonomously (Figure 3).39,51 The enteric nervous system is also supported by local glial cells, which also respond to changes in gut microbiota signaling,52 but we will focus on enteric neurons in this review.
Autoimmune gastrointestinal dysmotility: the interface between clinical immunology and neurogastroenterology
Published in Immunological Medicine, 2021
Shunya Nakane, Akihiro Mukaino, Eikichi Ihara, Yoshihiro Ogawa
The ENS performs multiple roles: determining the patterns of movement of the GI tract, controlling gastric acid secretion, regulating movement of fluid across the epithelial lining, changing local blood flow, modifying nutrient handling, and interacting with the immune and endocrine systems of the gut [10]. The GI tract is innervated by intrinsic neurons belonging to the ENS and by the axons of extrinsic sympathetic, parasympathetic, and visceral afferent neurons [11,12]. For the intrinsic innervation of the GI, the ENS is composed mainly of two ganglionated plexuses that form a network of neurons and glial cells (Figure 3): an outer plexus lying between the longitudinal and circular muscle layers, called the myenteric plexus or Auerbach’s plexus, and an inner plexus, called the submucosal plexus or Meissner’s plexus, which lies in the submucosa [10–12]. The nerve connections within and between these two plexuses are also shown in Figure 3. Enteric neurons include intrinsic primary afferent neurons (IPANs), interneurons, motor neurons, secretomotor neurons, and vasomotor neurons. These ENS neurons are synaptically interconnected to form parallel reflex circuits [10–13]. The neurochemical signaling within the ENS is extremely complex. In an attempt to improve the understanding regarding the multiple functions of the ENS, some research groups have identified neurotransmitters that are released by the nerve endings of different types of enteric neurons. Acetylcholine (ACh) mostly stimulates GI activity such as up-regulation of Cl- current across the epithelial lining and of GI smooth muscle contractility. The other major transmitters include nitric oxide (NO), vasoactive intestinal polypeptide (VIP), substance P, neuropeptide Y (NPY), and adenosine-triphosphate (ATP) [10–12]. The specific functions of many of these are becoming clear.