Digestive System Notes Biology - Ms. Spinale

There are two kinds of digestion. Physical/mechanical - physically break down food into smaller pieces to increase surface area for more enzyme action. Chemical - enzymes break down food into smaller molecules to be absorbed; creates a chemical reaction

Digestive Organs - GI Tract Gastrointestinal Tract (GI Tract) - large tube with organs and other organs outside the tract that deliver fluids that aid in digestion.

Digestive Organs - Mouth Teeth = mechanical digestion - breaks up food into smaller pieces and increases surface area of food. Saliva = chemical digestion - softens and secretes salivary amylase that begins to break down starch into disaccharides. Epiglottis - flap that blocks trachea (windpipe) to prevent food and water from entering.

Digestive Organs - Esophagus Two layers of muscle. Ranges from the pharynx to stomach. Peristalsis - muscle contractions that move food. Like a tube of toothpaste.

Digestive Organs - Esophagus Peristalsis

Digestive Organs - Stomach Three layers of smooth muscle. Mechanical digestion occurs here. Muscles contract to churn food.

Digestive Organs - Stomach Chemical digestion also occurs here. Mucus - lubricates and protects stomach lining from acids (very acidic environment). Hydrochloric acid (HCl) - has a pH of 1-2 which is used to activate enzymes, dissolve minerals, and kill bacteria. Pepsin - breaks complex proteins into smaller polypeptides and amino acids.

Digestive Organs - Stomach Stomach Ulcers Occur when the bacterium H. pylori infects the stomach causing the HCl in the stomach to destroy the mucus lining the stomach.

Digestive Organs - Sphincters A thick ring of muscle that opens and closes to allow food in and out of the stomach. Cardiac/lower esophageal sphincter - between esophagus and stomach (beginning of stomach). Pyloric sphincter - between stomach and small intestine (end of stomach).

Digestive Organs - Sphincters Cardiac sphincter Pyloric sphincter

Digestive Organs - Sphincters Acid Reflux

Digestive Organs - Liver The liver is not apart of the digestive tract. The liver, stores glycogen. detoxifies substances from blood. Secretes biles into small intestine that breaks up fat droplets. Bile is stored in the gallbladder until required for digestion.

Digestive Organs - Liver

Digestive Organs - Pancreas The pancreas is not apart of the digestive tract. The pancreas secretes pancreatic fluid (digestive enzymes) into the small intestine and neutralizes fluids from stomach. Balances out the low pH of stomach acid.

Digestive Organs - Pancreas

Digestive Organs - Small Intestine Receives small secretions from gallbladder and pancreas to complete digestion of all macromolecules. Most of the absorption of nutrients takes place here.

Digestive Organs - Small Intestine The lining of the small intestine has finger-like projections called villi. Villi increase surface area, contain capillaries, and absorb water and nutrients.

Digestive Organs - Small Intestine

Digestive Organs - Large Intestine Absorbs water from food material. Absorbs vitamins produced by bacteria (E. coli in intestines). Eliminates feces from anus through anal sphincter.

Digestive Organs - Large Intestine

Important Enzymes in Digestion Pepsin - utilized in stomach. Breaks down proteins into amino acids Trypsin - utilized in small intestine. Breaks down proteins into amino acids. Amylase - utilized in mouth and small intestine. Breaks down starch into simple sugars.

Important Enzymes in Digestion Lipase - utilized in small intestine. Breaks down fat into fatty acids and glycerol.

Tongue Mouth Salivary glands Esophagus Liver Stomach Gall Bladder Pancreas Large Intestine Small Intestine Rectum