Digestive system Flashcards
What are the 4 layers of the gut membrane?
- Mucosa
- Submucosa
- Muscularis externae
- Serosa (peritoneal membrane)
What is the mucosa made up of?
- Epithelium
- Lamina propria
- Muscularis mucosae
What is the lamina propria?
A connective tissue layer in the mucosa membrane which contains glands
What is the composition of the submucosa?
A connective tissue layer containing glands, arteries, veins and nerves
What 2 muscle types are found in the muscularis externa?
Longitudinal and circular
What are the functions of the GI tract?
Mechanical and chemical digestion, food storage, kill pathogen, absorb nutrients, eliminate waste
What does salvia contain?
Amylase, lipase, calcium, immunoglobulin A antibody
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
What mechanical digestion occurs in the mouth?
Chewing by the teeth and movement by the tongue
What is the transport that propels the bolus through the oesophagus
Peristaltic transport
What is unusual about the gut wall in the oesophagus
It has no serosa
What type of epithelium lines the oesophagus
Stratified squamous non keratinised
What is the outer layer of the oesophagus if there is no serosa
A thin layer of connective tissue called the adventitia
What mechanical digestion occurs in the stomach?
Churning
What is different about the gut wall of the stomach?
Its muscularis externae has 3 layers (additional oblique smooth muscle)
What is the folding in the stomach called?
Rugae
Why can the stomach act as a food store?
It allows for receptive relaxation (wall relaxes preventing a rise in pressure)
What is secreting into the lumen of the stomach?
Acid and enzymes
What protects the lining of the stomach from the acid
Mucus
What is chyme?
Partially digested food
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?
- Synthesis vitamins K, B12, thiamine and riboflavine
- Breaks down primary bile acids to secondary
- 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
