11 Digestive system
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Transcript of 11 Digestive system
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AMouthB
B
Salivary gland
Salivary glandsPharynxC
DEpiglottis
EOesophagus
StomachFLiverGGall bladder H
IPancreasJDuodenum
KSmall intestineLColon
MCaecum
NAppendix
Large intestineORectum
P
QAnus
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Mouth
• Mechanical breakdown of food
• Saliva – lubrication
• Salivary amylase – breakdown of starch and carbohydrates
• Tongue – gathers food in to a bolus
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Oesophagus
• Entry regulated by epiglottis
• Soft muscular tube
• Moves food through rhythmic muscular movement called peristalsis
• DEMONSTRATION
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Stomach
• Can expand from an empty volume of 50ml to a full volume of 1.5 L
• Gastric juices are a mixture of mucouse, enzymes, hydrochloric acid and water
• Pepsin – breaks down proteins• Muscular contractions – further
mechanical breakdown• Hormones secreted to pre-warn pancreas
and gall bladder of incoming chyme
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Pancreas
• Creates enzymes and other products and secretes them in to the common bile duct:
• Bicarbonate – neutralise stomach acid
• Amylase – continue breakdown of carbs
• Protease – continue breakdown proteins
• Lipase – breaks down lipids
• Nucleases – breaks down DNA, RNA and cellular organelles
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Liver & Gall Bladder
• The liver secretes bile (greenish fluid containing bile salts, cholesterol & pigment) in to common bile duct.
• Bile stored in gall bladder if no digestion is taking place.
• Bile salts emulsify fat (break it in to smaller droplets (eg milk & detergent)
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Pancreatic disorders – Cystic Fibrosis
• A CF patient’s blocked pancreatic duct
• The amount of enzyme replacement capsules required to be taken every day
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Small Intestine
• Composed of the duodenum, jejunum and ileum• Food spends 3 to 6 hours here• Around 90% of absorption of nutrients takes
place here• Surface area is greatly increased by entire inner
lining covered in villi, and each of these villi covered in microvilli.
• Also approx. 8.5L of water is absorbed from food daily.
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Villi
• Each villus has a huge network of capillaries running through it.
• Absorption of nutrients is by means of diffusion and active transport.
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Large Intestine
• Composed primarily of the colon, caecum and the rectum
• Any undigested food gets further processed by bacterial breakdown
• Another 0.5L of water is reabsorbed daily
• Waste called faeces (undigested food, water, dead cells & bacteria) passes out of the rectum through the anus.
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Flatus
• A gas called flatus also passes through the anus, it is the result of swallowed air or gas produced during bacterial breakdown
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