Digestive system

Function of the digestive system Supply chemical energy Ex. Sugars are broken down to make ATP Supply organic molecules Need proteins so they can make their own proteins to catalyze reactions in the cell Supply essential nutrients Your body needs calcium to help build bones

Draw the outline of a person now!

Food is pushed along by peristalsis, rhythmic contractions of muscles in the wall of the canal Valves called sphincters regulate the movement of material between compartments

The first stage- In the oral cavity Mechanical - Teeth chew food Chemical – Salivary glands: deliver saliva to lubricate food Amylase – an enzyme that hydrolyzes starch Mucin – glycoprotein that protects lining of mouth Buffers Antibacterial agents (ex. Lysozyme)

Pharynx and esophagus The esophagus conducts food from the pharynx down to the stomach by peristalsis Swallowing causes the epiglottis to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe

Draw the oral cavity, pharynx and Esophagus Put notes next to the structures and also determine what is broken down in this part of the digestive system (use figure 887 for help)

Draw the stomach Add notes using page 886 Address these questions What is the main function of the stomach What is digested in the stomach What are the enzymes and what are their functions

Stomach The stomach stores food and secretes gastric juice, which converts a meal to acid chyme

Stomach – Gastric juice HCl Parietal cells secrete hydrogen and chloride ions separately Pepsin Chief cells secrete inactive pepsinogen - activated to pepsin when mixed with HCl Mucus protects gastric juices from harming the stomach cells

Small intestine Main site of digestion and absorption Digests lipids, proteins, carbohydrates and nucleic acids

Small intestine - Duodenum Pancreatic secretions include Bicarbonate Neutralizes acidity Enzymes Trypsin Chyotrypsin *activated when in the duodnum Gallbladder secretions Bile (made in liver) Digestion of lipids Epithelial lining secretions Digestive enzymes

Small intestines – jejunum and ileum Absorption of nutrients and water Able to do this because of the large surface area

Draw the small and large intestine Address the Following What is the main function What is digested What are the enzymes and what are their functions (if there are any)

Large intestine Main function is to recover water