Gastric motility secretions
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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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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 ANATOMY


Gastric motility

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


Gastric motility1

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!)


Gastric secretions

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


Gastric secretions1

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


Control of gastric acid secretion

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


Gi tract secretion overview

GI Tract Secretion Overview


Histology overview

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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