Theme 1 - Part III Flashcards
ENS
Large network of neutrons in GIT wall
GIT [5]
the mouth the esophagus the stomach the small intestine the large intestine
Accessory glands [4]
the salivary glands,
the liver
the gallbladder
the pancreas
Structure of GIT wall [4]
Mucosa
Submucosa
Muscularis Externa
Serosa
Mucosa [3]
Epithelium - exocrine gland, endocrine cell
Lamina propia - small BV, nerve fibre and lymphatic cells
Muscularis mucosa - thin layer SM
Submucosa
Submucosal nerve plexus
Muscularis Externa
Circular muscle
Myenteric nerve plexus
Longitudinal muscle
GALT
Secrete antibodies - tolerance
Extrinsic innervation pathway
The gut-brain axis.
The ENS is linked to the central nervous system (CNS) via the sensory and motor nerves of the parasympathetic nervous system (PNS ”rest and digest”) and the sympathetic nervous system (SNS - ”fight or flight”).
Intrinsic innervation pathway
The enteric nervous system (ENS).
The ENS is functionally organized as the submucosal plexus and the myenteric plexus.
Myenteric (Auerbach’s) plexus - control of gut motility and innervates the longitudinal and circular smooth muscle layers.
Submucosal (Meissners) plexus coordinates intestinal absorption and secretion through its innervation of the glandular epithelium, intestinal endocrine cells, and submucosal blood vessels.
Extrinsic innervation - sympathetic [3]
Preganglionic fibres from T8-L2.
Postganglionic cell bodies in celiac, inferior and superior mesenteric ganglia.
Sympathetic activity inhibits gut motility and secretion;
constrict sphincters
Extrinsic innervation - parasympathetic
Preganglionic Vagus nerve innervates oesophagus, stomach, small intestine, liver, pancreas, caecum, appendix, ascending colon, traverse colon
Pelvic nerve innervates remainder of the colon via hypogastric plexus.
Parasympathetic activity stimulates motility and secretions.
Intrinsic innervation - Auerbach’s/Myenteric [4]
Between the circular and longitudinal muscle layers
A thin layer array of ganglia, ganglion cells, and inter-ganglionic nerve tracts that serve to interconnect the plexus.
Innervate longitudinal muscles and the outer lamella of the circular muscle layer.
Many of these neurons have projections into adjacent muscle layers, where they are either excitatory or inhibitory
control of gut motility
Intrinsic innervation - Submucosal or Meissner’s plexus [3]
Between the submucosal layers and circular muscle
Neurons that are functionally distinct from those of the myenteric plexus and, relative to intestinal motor function,
appear to be projecting mainly to the inner lamella of the circular muscle layer.
Coordinates intestinal absorption and secretion
Hirschsprung’s disease [2]
Congenital absence of the myenteric plexus, usually involving a portion of the distal colon.
The pathologic aganglionic section of large bowel lacks peristalsis and undergoes continuous spasm, leading to a functional obstruction and severe constipation.
