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Gastric Motility & Secretions

Gastric Motility & Secretions. Mel & Dave (plus Poppy helped). Any errors found in this presentation are Mel’s fault, anything good thank Dave. GASTRIC ANATOMY. GASTRIC MOTILITY. Receptive Relaxation Stomach is empty and contracted initially

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Gastric Motility & Secretions

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  1. Gastric Motility & Secretions Mel & Dave (plus Poppy helped) Any errors found in this presentation are Mel’s fault, anything good thank Dave

  2. GASTRIC ANATOMY

  3. GASTRIC MOTILITY Receptive Relaxation Stomach is empty and contracted initially Mucosa and sub-mucosa start highly folded into rugae Food swallowed – muscle in wall of orad region relaxes Mediated by the vagus nerve Enteric neurons release NO and serotonin Gastric contents remain in a relatively undisturbed state Mixing Gastric contractions begin in body and move towards antrum Contractions derive from two basic patterns of electrical activity Co-ordinated contractions of smooth muscle Powerful contraction occurs as wave reaches antrum Pyloric sphincter closes Retropulsion occurs Emptying Co-ordinated contractile activity of stomach, pylorus and proximal small intestine Regulated by cholecystokinin (CCK), gastrin, gastric inhibiting polypeptide (GIP) and secretin

  4. GASTRIC MOTILITY It is important to regulate gastric motility because the duodenum cannot is not as adapted as the stomach is to food storage. Gastric emptying is regulated in response to contents which are: • High in fat • Highly acidic • Very hypertonic Receptors in the mucosa of the duodenum and the jejunum sense these properties and release the enteric hormones which inhibit antral contractions and/or elicit contractions of the pyloric sphincter The hormones that cause contraction of the pyloric sphincter are cholecystokinin (CCK), gastrin, gastric inhibiting polypeptide (GIP) and secretin (this is why they regulate emptying, see previous slide!)

  5. GASTRIC SECRETIONS Stomach secretes up to 3L of gastric juice per day The main components of gastric juice are: • Hydrochloric acid • Mucus • Enzymes – Pepsinogen and Gastric Lipase • Intrinsic Factor These are secreted from different cells within the gastric glands of the gastric mucosa

  6. GASTRIC SECRETIONS Gastric hormones are also secreted by the gastric glands – these are responsible for controlling the secretion of gastric juice. The gastric hormones include: • Gastrin • Histamine • Somatostatin

  7. CONTROL OF GASTRIC ACID SECRETION I tried to simplify the diagram given in your lectures – if this doesn’t help just stick to yours! Also I’ve not included the specific receptors as I don’t think that’s important

  8. GI Tract Secretion Overview

  9. Histology Overview Type of epithelium? Stratified squamous Simple columnar Submucosal glands? Villi? Yes No Yes No Oesophagus Anus Small bowel Taenia coli? Submucosal glands? Yes No Yes No Colon Lymphoid follicles? Duodenum Peyer’s patches? Yes No Yes No Ileum Jejunum Appendix Stomach

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