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The structure of the wall of the small intestine allows it to move, digest and absorb food.
Understandings
The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes
and moves it along the gut.
Enzymes digest most macromolecules in food into monomers in the small intestine.
The pancreas secretes enzymes into the lumen of the small intestine.
Villi increase the surface area of epithelium over which absorption is carried out.
Villi absorb monomers formed by digestion as well as mineral ions and vitamins.
Different methods of membrane transport are required to absorb different nutrients.
Applications
Processes occurring in the small intestine that result in the digestion of starch and transport of the
products of digestion to the liver.
Use of dialysis tubing to model absorption of digested food in the intestine.
Skills
Production of an annotated diagram of the digestive system.
Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a
micrograph.
DIGESTIVE SYSTEM
Production of an annotated diagram of the digestive system.
Two major groups of organs which comprise the human digestive system:
alimentary canal consists of organs through which food actually passes.
oesophagus
stomach
small & large intestines
, accessory organs aid in digestion but do not actually transfer food.
salivary glands
pancreas
liver
gall bladder
Alimentary Canal
Oesophagus
hollow tube connecting the oral cavity to the stomach.
separated from the trachea by the epiglottis.
food is mixed with saliva and then is moved in a bolus via the action of peristalsis.
Stomach
temporary storage tank where food is mixed by churning.
protein digestion begins.
lined by gastric pits that release digestive juices, which create an acidic environment
(pH ~2).
, Small intestine
long, highly folded tube where usable food substances (nutrients) are absorbed.
consists of three sections – the duodenum, jejunum and ileum.
Large intestine
final section of the alimentary canal, where water and dissolved minerals (i.e. ions) are
absorbed.
consists of the ascending / transverse / descending / sigmoidal colon, as well as the
rectum.
Accessory Organs
Salivary glands
release saliva to moisten food and contains enzymes (e.g. amylase) to initiate starch
breakdown.
include the parotid gland, submandibular gland and sublingual gland.
Pancreas
produces various enzymes that are released into the small intestine via the
duodenum.
also secretes certain hormones (insulin, glucagon), which regulate blood sugar
concentrations.
Liver
takes the raw materials absorbed by the small intestine and uses them to make key
chemicals.
roles: detoxification, storage, metabolism, bile production and haemoglobin
breakdown.
Gall bladder
stores the bile produced by the liver (bile salts are used to emulsify fats).
bile stored in the gall bladder is released into the small intestine via the common bile
duct.
Human Digestive System
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