The Digestive System and Nutrients Elli Kim, Vanessa Tam, Penny Ryu

Parts of the Digestive System Digestive tract organs Mouth Pharynx Esophagus Stomach Small intestine Large intestine Rectum Anus Accessory organs Salivary glands Liver Gallbladder Pancreas

Digestive Tract Organs Mouth – teeth chew food; tongue tastes and pushes food for chewing and swallowing Pharynx – passageway where food is swallowed Esophagus – passageway where peristalsis pushes food to stomach Stomach – secretes acid and digestive enzyme for protein; churns, mixing food with secretions, and sends chyme to small intestine

Pharynx

Digestive Tract Organs (Cont.) Small intestine – mixes chyme with digestive enzymes for final breakdown; absorbs nutrient molecules into body; secretes digestive hormones into blood Large intestine – absorbs water and salt to form feces Rectum – stores and regulates elimination of feces Anus – you know what it is

Accessory Organs Salivary glands – secrete saliva; contains digestive enzyme for carbohydrates Liver – major metabolic organ: processes and stores nutrients; produces bile for emulsification of fats Gallbladder – stores bile from liver; sends it to the small intestine Pancreas – produces pancreatic juice: contains digestive enzymes, and send it to the small intestine; produces insulin and secretes it into the blood after eating

When the food gets eaten…

The Process of Digestion Mouth: breaks down food Teeth chew the food to break it down to smaller pieces Saliva is produced by the salivary glands Saliva contains an enzyme (salivary amylase) that begins to digest the starch from food into smaller molecules Pharynx: throat swallows food (voluntary) Esophagus: squeezes the food down (involuntary) Layer of muscle enables walls to move Propels food and liquid through the system Mix the contents Compare with squeezing mentos Arrives at the Lower Esophageal Sphincter

The Process of Digestion Lower Esophageal Sphincter: ring-like organ that closes the passage between two organs  As food approaches the sphincter, it relaxes so that the food can pass through Peristalsis: food moves from one organ to the next Stomach: excretes stomach acid to break food down  Thick mucus layer (pepsinogen): protects the interior stomach walls to prevent stomach acid from dissolving stomach tissues (or else: peptic ulcer) Produces stomach acid (gastric juice: digestive enzymes + HCl; regulated by gastrin) and a protein-digestive enzyme Stores food and liquid: upper stomach muscles relaxes and absorbs food Lower stomach mixes: mixes food, liquid, and digestive juice made by the stomach to make chyme Push materials into small intestines through the pyloric sphincter

The Process of Digestion Small Intestines: digest and absorb Duodenum: (1st 25 cm) digests starch (pancreatic amylase), protein (proteolytic), fat (lipase) , nucleotides (phosphatases), disaccharides (maltase, lactase) - Mix digestive juice produced by: Pancreas: enzymes that break down carbohydrates, fats, and proteins (trypsin, chymotrypsin, lipase, pancreatic amylase); stimulated by secretin (produced by duodenim) Liver: bile (squeezed out from the gallbladder through bile ducts) dissolves fat into liquid; stimulated by cholecystokinin (produced by small intestines) Interior glands of the small intestines Jejunum (first part), Ileum (second part) Villi and Microvilli: large surface area allows better absorption into capillaries

The Process of Digestion Large Intestines (colon): absorbs water and produce feces Cecum: appendix is attached at the end (tail-like) Ascending colon: food going Trasverse Colon: food is going horizontal Descending colon: food going down Sigmoid Colong Concentrates waste materials Pushes the waste through rectum to anus Anus: waste is excreted

Problem with the Stomach and the Intestine Diarrhea: contents of the intestines move too fast  isn't enough time for water to be absorbed before the feces are pushed out of the body Constipation: contents of the large intestines do not move along fast enough  waste materials stay in the large intestine so long  too much water is removed and the feces become hard.

Nutrients Protein-------amino acids Starch------simple sugars Fats------fatty acids & glycerol Vitamins Minerals

Proteins Ex./ meat, eggs, beans enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of big molecules into small molecules absorbed from hollow of the small intestines into the blood and into the rest of the body

Carbohydrates -Ex./ bread, potatoes, pastries, rice, fruits, table sugar (many of these contain both starch & fiber) Digestible carbohydrates are broken down by enzymes in the saliva Starch is digested in 2 steps… 1) enzyme in the saliva & pancreatic juice breaks the starch into maltose then maltase splits the maltose into glucose molecules 2) glucose is carried to the liver

Fats dissolved into watery content of the intestinal cavity bile acids (produced by liver) are natural detergents to dissolve fat into water, allowing the enzymes to break large fat molecules into smaller molecules (fatty acids & cholesterol) bile acids help fatty acids and cholesterol to move into mucosa In mucosa, small molecules are formed back into big molecules  theses molecules pass into lymphatic vessels near the intestine  these vessels carry these fats to the veins blood carries these to different parts of the body