Gastrointestinal system

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  • Created by: gec114
  • Created on: 22-04-16 18:52
Roles of Saliva
Moisten and lubricates the food and digestion of complex sugars due to the enzyme amylase.
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Role of the Stomach
Arrival of food stimulates the secretion of pepsins, protein-digesting enzymes and hydrochloric acid. Dissolves and digests larger molecules, kills bacteria. End product is chyme.
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Role of the Small Intestines
where most of the digestion and absorption of nutrients, vitamins, minerals and water happens. large molecules are broken down by enzymes.
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Role of the duodenum
The first part of the small intestines. Bile is produced here which neutralises the chyme from the stomach.
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Purpose of contractions in the small intestine
1) mix the content 2) brings it into contact with the luminal wall where enzymes cause digestion and absorption 3) moves it along to the large intestine
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Purpose of the large intestines
extract the remaining water and minerals from the undigested material. All that is left after this is excreted. Motility is slow with 3-4 strong mass movements that lead to defecation if the sphinter muscles are relaxed.
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Structure of the gastrointestinal tract wall
multi-layered. highly vascularized, contains lymph ducts. Surface area is increased dues to villi that reach out into the lumen. these are covered in microvilli
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Processes in the mouth
mechanical break up of large particles. lubrication and dissolving because of saliva. digestion of polysaccharides.
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Regulation of secretion in the stomach
Fundus secretes HCl, mucus and pepsinogen. Antrum secretes pepsinogen, gastrin and mucus. Histamine and somatostatin are secreted throughout.
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Motility within the stomach
for mixing. to release small amounts of chime into the small intestines. Motility gets stronger as you pass through the stomach.
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Processes in the Pancreas
the chime is neutalised with HCO3- which , along with digestive enzymes, is secreted along the pancreatic duct to be relaeses at te sphincter of oddi. Enzymes are released in inactive forms and are activated in the duodenum.
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Processes in the Liver
secretes bile which is stored in the gall bladder and released through the common bile duct. Bile salts are reabsorbed and fed back into the liver.
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digestion of water
most water is absorbed in the small intestine. active solute absorption creates an osmotic gradient.
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digestion of vitamiins
fat soluble vitamins get absorbed in the same way as fat. water soluble vitamins are absorbed by diffusion or mediated transport.
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digestion of minerals
Na+ is the most abundant solute and is puned out using the Na+/K+ -ATPase pump
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Digestion of carbohydrates
polysaccharides cannot be digested but might be metabolzied by bacteria in the large intestine. Broken into monosaccharides in the mouth and small intestine (AMYLASE). monosaccharides diffuse into epithelial cells.
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Digestion of proteins
in the stomach pepsin and HCl destroy connective tissue. In the small intestine trypsin, peptidase and chymotrypsin break down the peptides into amino acids. these are transported to epithelial cells coupled to Na+.
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Digestion of fat
happens mainly in the small intestines. lipase splts the fatty acid from glycerol. lipids are water insoluble but lipase is water soluble so digestion can only happen at the surface of lipid drops. Bile salts bind to lipids to stabilise in water.
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What happens to the fatty acids and monoglycerides
These both diffuse into epithelial cells and are then reassembled into triglycerides in the endoplasmic recticulum. They are released into the lymph system as chylomicrons which are coated in amphipatic protein to emulsify them. released into blood.
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Other cards in this set

Card 2

Front

Arrival of food stimulates the secretion of pepsins, protein-digesting enzymes and hydrochloric acid. Dissolves and digests larger molecules, kills bacteria. End product is chyme.

Back

Role of the Stomach

Card 3

Front

where most of the digestion and absorption of nutrients, vitamins, minerals and water happens. large molecules are broken down by enzymes.

Back

Preview of the back of card 3

Card 4

Front

The first part of the small intestines. Bile is produced here which neutralises the chyme from the stomach.

Back

Preview of the back of card 4

Card 5

Front

1) mix the content 2) brings it into contact with the luminal wall where enzymes cause digestion and absorption 3) moves it along to the large intestine

Back

Preview of the back of card 5
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