Introduction
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
The muscularis of the mouth, pharynx, and superior and middle parts of the esophagus contains skeletal muscle that produces voluntary swallowing. Skeletal muscle also forms the external anal sphincter, which permits voluntary control of defecation. Throughout the rest of the tract, the muscularis consists of smooth muscle that is generally found in two sheets: an inner sheet of circular fibers and an outer sheet of longitudinal fibers. Involuntary contractions of the smooth muscle help break down food physically, mix it with digestive secretions, and propel it along the tract. Between the layers of the muscularis is a second plexus of the enteric nervous system—the myenteric plexus or plexus of Auerbach. The myenteric plexus contains enteric neurons, parasympathetic ganglia, parasympathetic postganglionic neurons, and sympathetic postganglionic neurons that innervate the muscularis. This plexus mostly controls tract motility, in particular the frequency and strength of contraction of the muscularis.
Stomach and duodenum
Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie in Bailey & Love's Short Practice of Surgery, 2018
As with the entire gastrointestinal tract, the stomach and duodenum possess both intrinsic and extrinsic nerve supplies. The intrinsic nerves exist principally in two plexuses, the myenteric plexus of Auerbach and the submucosal plexus of Meissner. Compared with the rest of the gut, the submucosal plexus of the stomach contains relatively few ganglionic cells, as does the myenteric plexus in the fundus. However, in the antrum the ganglia of the myenteric plexus are well developed. The extrinsic supply is derived mainly from the vagus nerves (CN XI), fibres of which originate in the brainstem. The vagal plexus around the oesophagus condenses into bundles that pass through the oesophageal hiatus (Figure63.2), the posterior bundle being usually identifiable as a large nerve trunk. Vagal fibres are both afferent (sensory) and efferent. The efferent fibres are involved in the receptive relaxation of the stomach and the stimulation of gastric motility, as well as having the well-known secretory function. The sympathetic supply is derived mainly from the coeliac ganglia.
Introduction to bowel management
Victoria A. Lane, Richard J. Wood, Carlos A. Reck-Burneo, Marc A. Levitt in Pediatric Colorectal and Pelvic Surgery, 2017
Loperamide is an opioid receptor agonist and acts on the μ-opioid receptors in the myenteric plexus of the intestine, but does not affect the central nervous system. The mechanism of action is to reduce the activity of the myenteric plexus, which in turn decreases the tone of the circular and longitudinal smooth muscles of the intestinal wall, thus increasing the time that the digested material remains in the large intestine, allowing for more water to be reabsorbed. Loperamide also suppresses gastrocolic reflex, thereby decreasing colonic mass movements.Diphenoxylate and atropine combinations (e.g., Lomotil). Diphenoxylate is an opioid agonist and acts as an anti-diarrheal agent by slowing intestinal contractions and peristalsis (atropine is added to prevent overdose as this causes tachycardia).
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.
Role of the microbiota in circadian rhythms of the host
Published in Chronobiology International, 2020
Victor Schmalle, Axel Lorentz
The vagus nerve connects the intestine to the brain, and sensory neurons of the myenteric plexus are directly exposed to the gut microbiota (Li et al. 2018). The gut-brain axis is a bidirectional information network formed by a connection of the enteric nervous system (ENS) and the vagus nerve. Because of the influence that the microbiota inflicts on the ENS, this axis can be expanded to the microbiota-gut-brain-axis (MGB-axis) (Kaczmarek et al. 2017; Li et al. 2018; Wang and Wang 2016). Along the MGB-axis, the brain affects gastrointestinal functions like motility and secretion, and in return, the gut signals hunger, pain, and discomfort to the central nervous system (CNS) (Mazzoli and Pessione 2016). Bacterial metabolites like D-lactic acid and ammonia could pass through the vagus nerve into the CNS, where they can disturb brain function, stress responses, and sleep structure (Li et al. 2018).
Segmental Dilatation of Ileum Involving Bronchogenic Cyst in a Newborn
Published in Fetal and Pediatric Pathology, 2023
Özkan Okur, Malik Ergin, Akgun Oral, Munevver Hosgor
Miroscopically, the cystic structure was lined with pseudostratified respiratory ciliated epithelium. Seromucinous glands and cartilage islands were present in the lamina propria and submucosa. The cyst epithelium had a respiratory type appearance and contained dense cilia on its surface. This appearance was consistent with a bronchogenic cyst (Fig. 4). The intestinal muscle layer was thinner around the cystic structure, where the usual circular and longitudinal muscularis propria with normal myenteric plexus were present. Immunohistochemical staining revealed myenteric ganglion cells showing Ret-oncoprotein positivity and interstitial Cajal cells showing CD117 positivity (Fig. 4). Ganglion cells with usual distribution were observed in the myenteric nerve plexus. The calretinin staining shows that lack of mucosal punctate positivity in the ganglionic SID segment, (Fig. 5), suggesting defective innervation. It would suggest that the innervation is defective. In the sections from the dilated segment normal ganglion cells could be demonstrated histologically, no hypertrophy of the muscles layers was seen in other areas there were no any other findings in mucosa and intestinal wall.
Related Knowledge Centers
- Gastrointestinal Tract
- Mucous Membrane
- Muscular Layer
- Medulla Oblongata
- Parasympathetic Nervous System
- Vagus Nerve
- Submucosal Plexus
- Secretomotor
- Lumen
- Vagal Trigone