Session 9 - Digestive System Flashcards by Mira Chainrai

What are the 4 layers of the gut membrane?

Mucosa
Submucosa
Muscularis externae
Serosa (peritoneal membrane)

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What is the mucosa made up of?

Epithelium
Lamina propria
Muscularis mucosae

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What is the lamina propria?

A connective tissue layer in the mucosa membrane which contains glands

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What is the composition of the submucosa?

A connective tissue layer containing glands, arteries, veins and nerves

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What 2 muscle types are found in the muscularis externa?

Longitudinal and circular

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What are the functions of the GI tract?

Mechanical and chemical digestion, food storage, kill pathogen, absorb nutrients, eliminate waste

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What does salvia contain?

Amylase, lipase, calcium, immunoglobulin A antibody

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What is the role of IgA in salvia?

It is bacteriostatic and so binds to bacteria, preventing them binding/entering the epithelium lining the GI tract

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What mechanical digestion occurs in the mouth?

Chewing by the teeth and movement by the tongue

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What is the transport that propels the bolus through the oesophagus

Peristaltic transport

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What is unusual about the gut wall in the oesophagus

It has no serosa

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What type of epithelium lines the oesophagus

Stratified squamous non keratinised

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What is the outer layer of the oesophagus if there is no serosa

A thin layer of connective tissue called the adventitia

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What mechanical digestion occurs in the stomach?

Churning

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What is different about the gut wall of the stomach?

Its muscularis externae has 3 layers (additional oblique smooth muscle)

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What is the folding in the stomach called?

Rugae

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Why can the stomach act as a food store?

It allows for receptive relaxation (wall relaxes preventing a rise in pressure)

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What is secreting into the lumen of the stomach?

Acid and enzymes

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What protects the lining of the stomach from the acid

Mucus

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What is chyme?

Partially digested food

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What is the Tonicity of the chyme?

Hypertonic as the food is broken down to lots of molecules, increasing the osmotic pressure

What type of epithelium lines the stomach?

Simple columnar

What can damage mucous secreting cells?

Alcohol and aspirin

What is the role of parietal cells in gastric glands

Secrete hydrogen ions into the lumen to produce the HCL. Also produce bicarbonate ions into capillaries which moves to mucus cells to help make mucus

What is the role of chief cells in the gastric glands

Secrete pepsinogens which are converted into Pepsins which hydrolyse proteins

What is the role of enteroendocrine cells in gastric glands

Include G cell which secrete gastrin.

What is the first section of the small intestine?

Duodenum

What type of glands are found in the duodenum

Brunners glands

What do brunners glands do

Secrete bicarbonate rich mucus to neutralise acidic chyme

What happens to the Tonicity of the chyme in the duodenum

It becomes isotonic as water is drawn in to the chyme

What is released into the duodenum

Bile, Alkali from the pancreas and liver and enzymes from the pancreas and liver.

What does bile do?

Bile salts emulsified fats

What does bile contain?

Water, Alkali and bile salts

What is the second part of the small intestine?

Jejunum

What are the extension in the jejunum called?

Plicae circulares

What increases the surface area of the intestine?

Villi, micro villi, folding

What type of epithelium lines the small intestine?

Simple columnar epithelium

What is a lacteal and where is it found

Dilated Lymphatic vessel found in a microvilli

What does the duodenum absorb?

Iron

What does the jejunum absorb?

Sugars, amino acids and fatty acids

What does the ileum absorb

Vitamin B12, bile acids and remaining nutrients

What is the type of epithelia found in the large intestine

Simple columnar epithelium

What is the role of the large intestine

Water recovery

What is the uses of the bacteria in the colon?

1. Synthesis vitamins K, B12, thiamine and riboflavine 2. Breaks down primary bile acids to secondary 3. Converts bilirubin to non pigmented metabolites

What 3 mechanisms control the digestive system?

Neural, paracrine and endocrine

Which 2 features are under the control of the somatic nervous system

Ingestion and excretion

What post ganglionic neurones form plexuses in the GI tract

Submucosal plexus (between submucosa and muscularis externae) and myenteric plexus (between muscle layers)

What substances are released for paracrine control of the GI tract?

Histamine (controls production of stomach acid) and vasoactive substances (affect blood flow)

What gorges are released which are involved in the endocrine control of the GI tract?

Secretin, cholecystokinin, gastrin

What is the role of secretin

Promotes bicarbonate secretion from cells in the pancreas. Promotes bile production in the liver. Inhibits secretion of acid by parietal cells

What is the role of cholecystokinin (CCK)

Secreted by enteroendocrine cells Release bile from gall bladder Promotes release of digestive enzymes from pancreas

What is the role of gastrin

Promotes HCl production by parietal cells