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32 Cards in this Set
- Front
- Back
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Where does chyme pass into after the stomach? |
small intestine |
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where does most digestion and absorption occur? |
small intestine |
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how many portions does the small intestine consist of? |
3 |
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name the 3 portions and the length of each as well as diameter |
-duodenum (25cm) -jejunum (1m) -Ileum (2m) (diameter = 2.5cm) |
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Function of small intestine? |
break down chyme chemically- most substances needed to do this are bile, enzymes and bicarbonate which are imported from the liver and gall bladder |
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name the 2 phases of mechanical digestion in the small intestine |
Peristalis and segmentation |
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describe peristalsis: |
sequential contraction and relaxation of smooth muscle to propel chyme through the digestive tract. chyme remains for about 3-5 hours |
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describe segmentation: |
contraction of alternative sections of the small intestine to mix the chyme, it maximises digestion and absorption |
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Name 4 things that maximise absorption surface area of the small intestine: |
1. circular fold (nearly 1cm deep) 2. Villi (finger-like projections of the mucosa) 3. microvilli (tiny projections of the plasma membrane of the of the cells on the surface of the villi) 4. length of small intestine |
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what do the circular folds do? |
force chyme to spiral through the lumen, slowing its movement and allowing more time for absorption |
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what do the villi do? |
contain blood capillaries and lacteals (lymphatic capillaries) for absorption |
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what do microvilli do? |
required for secretion of intestinal enzymes and absorption of nutrients. |
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what is chyme digested by? |
bile and pancreatic juice in the duodenum then by intestinal juice released from the walls of the small intestine |
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intestinal juice contains enzymes which convert : |
- disaccharides to monosaccharides to be absorbed. - peptides into amino acids to be absorbed |
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name the enzyme and product for maltose: |
substrate: maltose enzyme: maltase product: glucose + glucose |
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sucrose: |
substrate: sucrose enzyme: sucrase product: glucose + fructose |
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lactose: |
substrate: lactose enzyme:lactase product: glucose + galactose |
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peptides: |
substrate: peptides enzyme: peptidase product: amino acids |
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what is absorption? |
The movement of digested food into the blood or lymph. |
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monosaccharides are the smallest units of what? |
carbohydrates |
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amino acids are the smallest units of what? |
proteins |
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fatty acids + monoglycerides are the smallest units of what? |
Lipids |
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Name the 3 mechanical movements of the large intestine: |
1. Haustral churning 2. peristalsis 3. mass peristalis |
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describe haustral churning |
relaxed pouches (haustra) are filled and then contract to move chyme to next haustra |
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describe mass peristalis |
strong peristaltic waves beginning in the mid transverse colon to quickly move the contents towards the rectum. |
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what is mass peristalsis initiated by? |
food in the stomach |
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name the functions of the large intestine (colon) |
1. complete the absorption of water ions and vitamins 2. production and absorption of vitamin K and some B vitamins by bacteria 3. movement of contents of colon to the rectum 4. formation of faeces 5. defecation |
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describe the formation of faeces |
in the colon more water is absorbed, the chyme becomes more solid (semisolid) and is called faeces |
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what does faeces contain? |
- water - inorganic salted - sloughed off epithelial cells - bacteria - unabsorbed digested materials - indigestible parts of food |
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what is appendicitis caused by? |
a blockage (often by faeces) that traps infectious bacteria in its lumen. |
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what happens to the appendix with appendicitis? |
it swells and may become ischaemic and black. |
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what happens if the appendix ruptures? |
faeces containing bacteria will spray through the peritoneal cavity causing peritonitis |
