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WWA #2 Ch. 3 The Alimentary Canal: Digestion and Absorption - Coggle…
WWA #2 Ch. 3 The Alimentary Canal: Digestion and Absorption
Physiology of G.I Tract
alimentary canal: extending from the mouth to the anus, comprises all the body parts through which food passes
chemical action: hydrolysis reactions occur in the digestive tract for nutrients in food to be utilized
Protein + H20 --> amino acides
Fat +H20 ---> fatty acids + glycerol
Carbohydrates +H20 ---> monosaccharides
mechanical action: peristalsis: involuntary rhythmic waves of contraction traveling the length of the alimentary tract
valves or sphincter muscles: designed to a) retain food in each segment until completion of the mechanical actions and digestive juices b) allow measured amounts of food to pass into the next segment c) prevent food from "backing up"
Digestive functions of saliva
mucous - glycoprotein - lubricates food for easier passage and protects the lining of the G.I tract
ptyalin (salivary amylase) - enzyme - initiates hydrolysis of complex carbohydrates to simple sugars
lypozyme (antibody) - enzyme - breaks down cell walls of some ingested bacteria
salivary lipase - enzyme - initiates hydrolysis of lipids
saliva
remove debris and microorganisms
provide antibacterial action
lubricates oral tissues in the oral cavity and taste buds
neutralize, dilute, and buffer bacterial acids
promote ease of speech
remineralize (restoration or renewal of calcium, phosphates, and other minerals to areas damaged by incipient caries, abrasion, or erosion
facilitate taste
prevent plaque accumulation
digestive function organs
liver: regulates biochemical reactions; filters harmful substances, stores fat soluble vitamins and minerals; helps in metabolism of micronutrients; synthesizes proteins; produces bile
gallbladder: stores and secretes bile
stomach: mixes food with hydrochloric acid and enzymes to aid in digestion and kill harmful microorganisms; semi-liquid mixture is called chyme, limited absorption
pancreas: produces bicarbonates to neutralize stomach acid; secretes several digestive enzymes and insulin that regulates blood glucose
esophagus: transports food via peristalsis
small intestine: completes digestion by enzymes and bile; absorption of most nutrients
salivary glands: produces saliva to moisten food and produces digestive enzymes
large intestine: absorbs water and some ions; forms and store feces
pharynx: helps prevent food entering the lungs
rectum: stores and expels feces
mouth: breaks up food particles for swallowing and digestion
exit for fecal expulsion
key points
lower esophageal sphincter (LES) comprises a group of very strong circular muscle fibers just above the stomach
pancreatic enzymes enter the duodenum through the pancreatic duct and function best in neutralized chyme
digestion of food is facilitated by increasing its surface area
approximately 80-90% of fluid intake is absorbed in the small intestine by osmosis
larger pieces of food may obstruct airway (asphyxiation)
low pH of stomach contents
activates gastric enzymes
hydrolyzes some carbohydrates
denatures proteins and facilitates hydrolysis to amino acids
increases solubility and absorption of calcium and iron
kills or inhibits growth of most bacteria