sf biology ii1 biology ii gut function & regulation dr alan tuffery — physiology...

SF Biology II 1

BIOLOGY IIBIOLOGY II

Gut Function & Regulation

Dr Alan Tuffery — Physiologyatuffery@tcd.ie

PunctualityMobiles

SF Biology II 2

Nutrition & ExcretionNutrition & Excretion

•Regulation of Motility & Secretion

•Digestion, Absorption & Defaecation

•Mammalian Kidney: Filtration, Reabsorption & Secretion; Regulation

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Useful TextbooksUseful Textbooks

Germann & StanfieldPrinciples of Human Physiology(612 P23 Hamilton Reserve; S-LEN)

Sherwood Human Physiology From Cells to

Systems(612 M98*2Hamilton Reserve; S-LEN)

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1. Overview of Gut1. Overview of Gut

General Function of GutGeneral structure assumed

Accessory organs: salivary glands, pancreas, liver

Motility

Secretion (e.g. pancreas)

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Gut — General FunctionsGut — General Functions

• Motility• Secretion• Digestion• Absorption• (Immunological)

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General structure of the gutGeneral structure of the gut

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Liver lobuleLiver lobule

• Flow of nutrients– From hepatic portal

vein

• Hence gradient of stored nutrients from HPV to central vein

• ’bipolar’ hepatocytes

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PancreasPancreas

• Endocrine– Insulin,glucagon

• Exocrine– Enzymes

(acini)

– Bicarbonate (ducts)

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Motility — definedMotility — defined

• The movement of the wall of the gut*

– Peristalsis (rel. rare)– Segmentation (main)– Haustration (large intestine = segmentation)

• *NOT movement of the contents of the gut

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Motility — segmentationMotility — segmentation

• Commonest• Alternating

contraction• Mixing

AND• Propulsion• Frequency

decreases distally

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Motility — peristalsisMotility — peristalsis

• Relatively rare

• Waves of contraction

• Rapid propulsion– ‘clearing’

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PancreasPancreas

• Endocrine– Insulin,glucagon

• Exocrine– Enzymes

(acini)

– Bicarbonate (ducts)

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Pancreas — exocrine functionPancreas — exocrine function

• Stimulus: H+

• Signal: secretin

• Effector : pancreatic duct cells

• NEGATIVE FEEDBACK

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Pancreas — Endocrine functionPancreas — Endocrine function

• Acts to prevent rise in glucose following digestion/absorption

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Gut — Control mechanismsGut — Control mechanisms