Moving along the GI tract

Incisors Molars Premolars Canines Starch Amylase via Saliva Disaccharides Canines

Saliva Food Bolus

Gastric juice (digestive enzymes-pepsinogen [via chief cells], HCl [via parietal cells], mucus) Causes the release of Gastric juice From mucosa Hormone Gastrin Gastric juice stops action of amylase, activates pepsinogen (active form pepsin) which breaks proteins down to amino acids

-Liver produces and secretes bile (excess stored in gall bladder), to emulsify fats, breaking them into tiny droplets called micelles Acidic chyme activates prosecretin into hormone secretin (stimulates -liver [make more bile] and pancreas [secrete lipid and protein enzymes & release bicarbonate ions (HCO3-) to neutralize the acidic chyme and raise the pH from about pH 2.5 to pH 9.0.] 1 3 2 4 Pancreas secretes surface attacking enzyme lipase, which breaks down lipids into fatty acids, depends on bile to break lipids into smaller balls

- Pepsin is inactivated in the basic pH conditions (no more protein digestion) - Pancreas releases trypsinogen, enzyme called enterokinase converts it into active trypsin which continues the work begun by pepsin in the stomach, further breaking down any partially digested proteins that remain Mucosa is stimulated by fatty chime causing release of hormone called cholecystokinin (CCK) CCK signals the pancreas to secrete a variety of substances, including ones that control the pH of the intestine and enzymes that are needed for lipid, carbohydrate, and protein digestion

2 inner surface has folds (like rugae in stomach) that are lined with little fingers (villi- home to blood capillaries), each little cell that makes up the villi is covered in its own microscopic projections (microvilli) which increases the surface area (x500) 1 3

-Absorbs excess water via osmosis from remaining waste - Vitamins B, K (which are a by-product of bacteria activity in the large intestine), sodium (Na+), and chloride (Cl–) ions are also absorbed…