First Five Describe the differences between: digestion and absorption physical/mechanical digestion and chemical digestion ingestion and egestion

Announcements Turn in the worksheets that were assigned last week: Photosynthesis & Respiration Human Digestive System Quiz on Monday (3/31) or Tuedsay (4/1): Digestive system, Respiration & Photosynthesis Finish all Coursework by Friday at 4:45 p.m. Work times: Mon, Wed, Thurs during LRL; Mon – Thurs after school until 5:30 p.m.

Human Digestion

Nutrition Definition: Taking in, absorbing and assimilating nutrients for energy, growth, and tissue repair

Types of Nutrients Micronutrients- vitamins, minerals, & water Macronutrients- proteins, lipids, carbohydrates

Four Parts of Nutrition Ingestion Digestion Absorption Egestion

Four Parts of Nutrition Ingestion taking substances into the body through the mouth Digestion Absorption Egestion

Four Parts of Nutrition Ingestion Digestion break-down of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes Absorption Egestion

Four Parts of Nutrition Ingestion Digestion Absorption movement of digested food molecules through the wall of the intestine into the blood Egestion

Four Parts of Nutrition Ingestion Digestion Absorption Egestion passing out of food that has not been digested, as feces, through the anus

Human digestive system

Ingestion takes place in the mouth mechanical digestion teeth break up food chemical digestion saliva amylase: an enzyme that digests starch mucin: a protein present in mucus that protects soft lining of digestive system and lubricates food for easier swallowing buffers: neutralize acid to prevent tooth decay anti-bacterial chemicals: kill bacteria that enter mouth with food

Esophagus Food moves through the Esophagus to the Stomach by Peristalsis Peristalsis: a series of involuntary wave-like muscle contractions which move food along the digestive tract

Stomach: function food storage disinfect food chemical digestion can stretch to fit ~2L food disinfect food HCl [pH 2] kills bacteria chemical digestion pepsin: an enzyme that breaks down proteins Food is further broken down into a thin liquid called chyme.

Which type of digestion is the following? Chewing a saltine? - 2. Saliva breaking the saltine down into molecules of glucose? - 3. Your tongue breaking pieces of a hamburger apart? 4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids? Mechanical Chemical Mechanical Chemical

Accessory Organs Pancreas Liver Gall Bladder

Pancreas An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine) Pancreatic juice contains enzymes which digest all major nutrient types. Pancreatic juice moves through the pancreatic duct into the duodenum (small intestine).

Pancreatic Juice Digestive enzymes amylase breaks down starch trypsin breaks down proteins to polypeptides lipase breaks down fats to fatty acids and glycerol Buffers neutralize acid from stomach

Liver converts excess glucose (monosaccharide) to glycogen (polysaccharide) for storage converts excess proteins and amino acids to other substances, such as fats, for storage produces bile for use in digestion

Gall bladder Stores bile until needed in the duodenum (small intestine) Moves bile through the bile duct The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

Bile Bile is a bitter, greenish-yellow alkaline fluid stored in the gallbladder between meals discharged into the duodenum(small intestine) upon eating aids the process of digestion Bile emulsifies lipids physically breaks apart large drops of fat into small drops of fat

Small intestine Functions: chemical digestion absorption of nutrients through lining small intestine has huge surface area = 300 m2 (~size of tennis court) About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles. As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme. At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine. A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.

Small intestine duodenum = mostly digestion Structure: 3 sections duodenum = mostly digestion jejunum = absorption of nutrients & water ileum = absorption of nutrients & water About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles. As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme. At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine. A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.

Duodenum the final stages of digestion are completed in the duodenum 1st section of small intestine acidic food from stomach mixes with digestive juices from: pancreas liver gall bladder the final stages of digestion are completed in the duodenum

Absorption by Small Intestines Absorption: movement of digested food molecules through the wall of the intestine into the blood

Absorption by the Small Intestine Digested nutrient molecules are small enough to pass through the wall of the small intestine into the blood. Water, mineral salts, and vitamins are also absorbed in the small intestine Villi finger-like projections in the wall of the small intestine increase the surface area of the small intestines greater surface area provides better absorption of materials

Absorption by Small Intestines Villi: finger-like projections that increase surface area for absorption

VILLI

Large Intestine/Colon Functions: reabsorption of water movement of undigested solid materials (fibers) Structure: shorter and wider than the small intestine

Rectum Last section of colon (large intestine) Eliminates feces undigested materials mainly cellulose from plants roughage or fiber

mouth break up food digest starch kill germs moisten food stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats small intestine finishes digestion absorption of nutrients contains villi pancreas produces enzymes to digest proteins & starch large intestine finishes digestion absorption of nutrients contains villi

Digestive System Classwork 1) Go through the digestive system animation to visualize how the digestive system works. http://kitses.com/animation/swfs/digestion.swf 2) Complete Build-A-Body: Digestive System. -- Build the digestive system -- Read through the Case Studies to answer the questions on the handout. http://www.brainpop.com/games/buildabodydigest ivesystem/ 3) Answer the follow-up questions on the handout. Finish as homework