Lab

 Gastrointestinal tract (GIT) – continuous passageway which contains the food from the time it enters the body until it leaves; organs include:
 mouth (oral cavity), pharynx (oropharynx
& laryngopharynx), esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), anal canal, anus
 Accessory organs - participate in digestive processes; organs include:
 teeth, tongue, salivary glands, liver, gall bladder, pancreas

 To break down food into a “usable”
(absorbable) form – occurs through mechanical processing & chemical digestion
 To supply our cells with the nutrients they need for energy, growth & repair

 carbohydrates – including
 polysaccharides (“complex” carbohydrates )
 starch
 disaccharides (“simple” sugars)
 maltose, sucrose, lactose
 proteins
 fats (lipids/triglycerides)
 vitamins
 minerals
 water
No digestive processes necessary, just absorption

 Mechanical processing – physical breakdown of food; e.g. mastication, emulsification, mixing waves, segmentation
 Chemical digestion – chemical breakdown of food; disassembling of organic molecules into their component parts; requires enzymes
 carbohydrates (polysaccharides)  disaccharides  monosaccharides
 proteins  amino acids
 lipids (triglycerides)  fatty acids & glycerol
(monoglycerides)

Digestion (mechanical & chemical) begins within the oral cavity –
 mastication
 production of saliva by salivary glands
Sublingual gland
Parotid gland
Submandibular gland saliva – made of H
2
O, salts & salivary amylase ; moistens foods to create “bolus” to help with deglutition, & begins chemical digestion of starch amylase
Starch (polysaccharide) Maltose (disaccharide)

Mechanical digestion – mixing waves to change bolus of food to “chyme”
Chemical digestion - secretions from cells of stomach to begin protein digestion: Peptic (chief) cells – pepsinogen
Parietal cells – hydrochloric acid ( HCL )
Pepsinogen + HCL  Pepsin
Proteins
Pepsin
HCL polypeptides

Chyme from stomach (with partially digested starch & proteins) + Bile from liver & gall bladder
+ Pancreatic juice from pancreas – released into duodenum of small intestine
Segmentation mixes chyme with other secretions
Fats + bile  emulsified fats bile

Pancreatic juice – mixture of enzymes & buffers (sodium bicarbonate) secreted by acinar cells into pancreatic duct & released into duodenum
 pancreatic amylase
Starch maltose
 lipase
Lipids (triglycerides) fatty acids + monoglycerol
 proteases (trypsin, chymotrypsin, carboxypeptidase)
Proteins & polypeptides dipeptides)
 nucleases – digest RNA & DNA small peptides (tripeptides &
Stomach
 sodium bicarbonate – neutralizes acidic chyme because enzymes in small intestine need an alkaline pH
Head
Body
Tail

Cells in jejunum and ileum produce peptidases and disaccharidases for final digestion of proteins and sugars small polypeptides, tripeptides, dipeptides peptidases amino acids maltose maltase sucrose lactose sucrase lactase glucose + glucose glucose + fructose glucose + galactose

Absorption of monosaccharides
(glucose, fructose, galactose), amino acids and fatty acids (as well as vitamins/minerals) occurs in small intestine (into blood or lymph (fatty acids)
Absorption of water (and some vitamins) occurs in large intestine