• gland that lies posterior to the stomach
• produces enzymes that digest carbohydrates, fats, proteins, and nucleic acid.
• produces sodium bicarbonate which buffers stomach acid
• empties its contents into the duodenum

• acini
• Pancreatic islets

• Water
• Sodium Bicarbonate
• several enzymes

• Starch digesting enzymes (amylase)
• Protein digesting enzyme (trypsin, chymotrypsin, carboxypeptidase, and elastase)
• Enterokinase activate trypsinogen
• Fat digesting enzyme (pancreatic lipase)
• Nucleic acid digesting enzyme (ribonuclease and deoxyribonuclease)

• The liver makes bile (important in the emulsification of fats)
• The gallbladder stores bile until it is needed

• Carbohydrate, lipid, and protein, metabolism
• processing of drugs and hormones
• Bilirubin excretion
• Bile salt synthesis
• Storage
• Phagocytosis
• Vitamin D activation

• The majority of digestion and absorption
• Circular folds increase the surface area for digestion and absorption

• Intestinal juice provides a vehicle for absorption of substances from chyme as they come in contact with the villi
• Brush border enzymes, found on the surface of the microvilli of absorptive cells, break down food products

• Segmentation (Localized contractions)
• Peristalsis ( Propulsive contractions)

• Digestion of Carbohydrates (sucrase, lactase, and maltase)
• Digestion of proteins (convert to peptides)
• Digestion of Lipids (Tryglycerides and phospholipid to fatty acids and glycerol)

Liver activity 

Salivary amylase

1. Source: salivary glands
2. Substrates: Starches (polysaccharides)
3. Products: Maltose (disaccharide), maltotriose (trisaccharide) and a-dextrins

Lingual Lipase

1. Source: Lingual glands in tongue
2. Substrates: Triglycerides (fats and oils) and other lipids.
3. Products: fatty acids and diglycerides

Pepsin ( activated from pepsinogen by pepsin and Hydrochloric acid)

1. Source: Stomach Chief cells
2. Substrates: Proteins
3. Products: peptides

Gastric Lipase

1. Source: Stomach chief cells
2. Substrates: Triglycerides (fats and oils)
3. Products: Fatty acids and monoglycerides

1. Haustral Churning, peristalsis, and mass peristalsis drive contents of the colon into rectum
2. Bacteria in large intestine convert proteins to amino acids and produce some B vitamins and vitamin K
3. Absorption of some water, ions, and vitamins
4. Formation of feces
5. Defecation

The last stage of digestion occur through the bacterial action

• substances are further broken down by bacteria
• some vitamins are synthesized by bacterial action

• rectal wall distends
• stretch receptors send sensory nerve impulses to the sacral spinal cord
• motor impulses travel back to the descending colon, sigmoid colon, rectum, and anus
• Longitudinal rectal muscles contract and the internal anal sphincter opens
• If the external anal sphincter is voluntarily relaxed, defecation occurs and the feces are expelled.

• Activity: Bacterial
• Functions: Breaks down undigested carbohydrates , proteins, and amino acids into products that can be expelled in feces or absorbed and detoxified by the liver; synthesizes certain B vitamins and vitamin K

• Activity: secretes mucus, absorption
• Function: Lubercates colon; protects mucosa. Water absorption solidifies feces and contributes to body's water balance; solutes absorbed include ions and some vitamins

•  Haustral churning- Moves contents from haustrum to hastrum by muscular contractions,
• Peristalsis- moves contents along the length of colon by contractions of circular and longitudinal muscles
• Mass peristalsis- forces contents into sigmoid colon and rectum
• Defectaion reflex- eliminates feces by contractions in the sigmoid colon and rectum

Tongue- maneuvers food for mastication, shapes food into bolus, maneuvers food for deglutition, detects sensations of taste, and initiates digestion of triglycerides.

Salivary glands- saliva produced by these glands softens, moistens, and dissolves foods; cleanses mouth and teeth; initiates digestion of starch

Teeth- cut, tear, and pulverize food to reduce solids to smaller particles for swallowing

Pancreas- pancreatic juice buffers acidic gastric juice in chyme, stops the action of pepsin from the stomach, creates the proper pH For digestion in the small intestine, and participates in the digestion of carbohydrates, proteins, triglycerides, and nucleic acids.

Liver- produces bile, which is required for the emulsification and absorption of lipids in the small intestine.

Gallbladder- stores and concentrates bile and releases it into the small intestine

Pharynx- receives a bolus from the oral cavity and passes it into the esophagus

Esophagus- receives a bolus from the pharynx and moves it into the stomach; this requires relaxation of the upper esophageal sphincter and secretion of mucus.

Stomach- mixing waves combine saliva, food, and gastric juices, which activates pepsin, initiates protein digestion, kills microbes in food, helps absorb vitamin b12, contracts the lower esophageal sphincter, increases stomach motility, relaxes the pyloric sphincter, and moves chyme into small intestine

Small intestine- segmentation mixes chyme with digestive juices; peristalsis propels chyme toward the ileocecal sphincter; digestive secretions from the small intestine, pancreas, and liver complete the digestion of carbohydrates, proteins, lipids, and nucleic acids; circular folds, villi, and microvili help absorb about 90% of digested nutrients

Large intestine- Haustral churning, peristalis, and mass peristalsis drive the colon contents into the rectum; bacteria produce some B vitamins and vitamin K; absorption of some water, ions, and vitamins occur

Distension of stomach, partially digested proteins and caffeine in stomach, and high pH of stomach chyme stimulates gastrin secretion by enteroendocrine G cells, located mainly in the mucosa of the pyloric antrum of the stomach

Major effects- promotes secretion of gastric juice, increases gastric motility, promotes growth of gastric mucosa

minor effects: constricts lower esophageal sphincter, relaxes pyloric sphincter

Acidic chyme that enters small intestine stimulates secretion of secretin by enteroendocrine S cells in the mucosa of duodenum

Major effects- stimulates secretion of pancreatic juice and bile that are rich in HCO

Minor effects: inhibits secretion of gastric juice, promoted normal growth and maintenance of pancreas, enhances effects of CCK.

• decreased secretory mechanisms and motility 
• loss of strength and tone of digestive muscular tissue 
• changes in neurosecertory feedback 
• disminished response to pain and internal sensation. 

• tooth decay
• peridontal diseases 
• ulcers
• tumors 
• diverticula
• hepititis
• anorexia 

Long tube that is open at both ended for the transit of food during processing 

• Accessory structures 

not part of the GI tract, but contribute to food processing 

• teeth
• tounge 
• salivary glands 
• liver
• gallbladder
• pancreas

• decomposiition
• Chemical reactions that break down complex organic molecules into simpler ones. They produce more energy than they consume (exergonic)