Objective: You will be able to identify the structures of the digestive system. Do Now: Read all of page 978 Give the function of the digestive system

Figure The four stages of food processing Pieces of food Small molecules Mechanical digestion Food Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Undigested material INGESTION 1 DIGESTION2 ELIMINATION 4 ABSORPTION 3

Figure The human digestive system

Oral Cavity Mechanical digestion breaks food into smaller pieces –Increases surface area for chemical digestion Chemical digestion of starch occurs here –Done by salivary amylase

Esophagus No digestion occurs here It moves food from oral cavity to stomach by using muscles –Called peristalsis

Esophagus Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)

Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2) Esophagus Epiglottis down Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted Glottis up and closed Esophageal sphincter relaxed

Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3) Esophagus Epiglottis down Tongue Pharynx Glottis Larynx Trachea Bolus of food Epiglottis up To lungs To stomach Esophageal sphincter contracted Glottis up and closed Esophageal sphincter relaxed Glottis down and open Esophageal sphincter contracted Epiglottis up Relaxed muscles Contracted muscles Relaxed muscles

Pepsin (active enzyme) HCl Parietal cell Chief cell Stomach Folds of epithelial tissue Esophagus Pyloric sphincter Epithelium Pepsinogen Interior surface of stomach. The interior surface of the stomach wall is highly folded and dotted with pit leading into tubular gastric glands. Gastric gland. The gastric glands have three types of cells that secrete different components of the gastric juice: mucus cells, chief cells, and parietal cells. Mucus cells secrete mucus, which lubricates and protects the cells lining the stomach. Chief cells secrete pepsino- gen, an inactive form of the digestive enzyme pepsin. Parietal cells secrete hydrochloric acid (HCl). 1 Pepsinogen and HCI are secreted into the lumen of the stomach. 2 HCl converts pepsinogen to pepsin. 3 Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. 5 µm Small intestine Cardiac orifice

Stomach Mechanical digestion occurs by the grinding of the stomach’s muscles Chemical digestion of proteins begins here –Gastric glands in stomach release a HCl and protease –The HCl provides a highly acidic environment –The protease actually breaks down the protein

Figure The duodenum LiverBile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Small Intestine Lipid digestion starts here Most of the chemical digestion occurs here –Intestinal glands and the accessory organs help to digest food Liver, gall bladder and pancreas All of the absorption of food into the body occurs here No food is digested AFTER it leaves the small intestine

Figure The duodenum LiverBile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Accessory organs The liver makes the bile but it stores it in the gall bladder It’s the gall bladder that actually secretes bile into the small intestine –Bile emulsifies fats (breaks them down) The pancreas secretes amylase, protease and lipase

Figure The duodenum LiverBile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Large Intestine This organs main function is to absorb water It does NOT absorb food nor does it digest food!!!!

End of the line Strong peristaltic action from the rectum pushes waste out of the anus

Group Roles Leader – keeps the group focused and on task Recorder – Writes down the work for the group Reporter – Informs the class/teacher about the work done by the group Noise monitor – Makes sure that the group works quietly

Activity Create story about the digestive canal of horrors where a group of teenage worm friends enter a tunnel but end up being digested by enzymes Remember that only some of the carbohydrate and protein digestion happens outside intestines Be sure to include each structure and describe in full detail what they do.

Objective: You will be able list and describe the disorders that affect the digestive system. Do Now: Read “Absorption in the small intestine” on p Describe the structure of the villi

Figure The structure of the small intestine Epithelial cells Key Nutrient absorption Vein carrying blood to hepatic portal vessel Villi Large circular folds Intestinal wall Villi Epithelial cells Lymph vessel Blood capillaries Lacteal Microvilli (brush border) Muscle layers

Figure Ulcer-causing bacteria 1 µm Bacteria Mucus layer of stomach

Disorders of the Digestive System Ulcers are erosions of the digestive tract Appendicitis is the infection and inflammation of the appendix Gallstones is the accumulation of hardened cholesterol deposits on the gall bladder

Disorders continued Constipation occurs when the large intestine absorbs too much water Diarrhea occurs when the large intestine does NOT absorb enough water

Objective: You will be able to answer review questions on the digestive system. Do Now: Read all of page 971 Besides energy, what are the other uses of food?