Digestive System • Mechanically & chemically breaks down food so the body can use nutrients • The major organs are the stomach, liver, pancreas, and intestines See Figure 3.14A on p. 97
Mouth Pharynx Esophagus Mouth • Teeth break down food into smaller pieces • Enzymes (protein) in saliva begin chemical digestion • Swallowed food passes through the pharynx to the esophagus Esophagus • Is a muscular tube that contracts & relaxes to push chunks of food down to the stomach • Waves of muscle contraction is called peristalsis
Stomach • Contains liquids called gastric juices that chemically break down the food more • are highly acidic • Stomach muscles mix the contents, which continues the mechanical breakdown of food • churning action of stomach & gastric juices cause food to break down into a liquid • Food is pushed into small intestine
Small Intestine • Divided into 3 sections: 1. duodenum where the rest of digestion takes place 2. jejunum 3. ileum where absorption of nutrients takes place • Pancreas, liver, and gall bladder release digestive enzymes into the duodenum via small tubes called ducts • Walls of the small intestine are covered with little projections called villi (& microvilli) • they increase the surface area so that more nutrients and water can be absorbed into the bloodstream See Figure 3.15 on p. 98 See Figure 3.16 on p. 98
Large Intestine • Includes the colon, rectum, & anus (oh geez) • Absorbs water, vitamins salts from digested food • achieved by bacteria in the gut like E.coli • Remaining (undigested) food is eliminated as feces
Sooooo… let’s recap • The path of a meal from start to finish: • mouth pharynx esophagus stomach small intestine large intestine • Weird facts: • it takes 24 to 33 hrs for a meal to go from beginning to end of this system • the small intestine is between 6 – 10 m in an adult
Quizzy, quizzy… • Identify the structures A. – E. • Name 3 organs that help digest food that enters the small intestine. • Name the 3 sections of the small intestine. • Give 4 organs in the digestive system that chemically break down food and explain how each occurs. • Which part of the digestive systems mechanically breaks down food?
Urinary (Excretory) System • Composed of the kidneys, ureter, bladder, urethra, and blood vessels • Eliminates liquid wastes from the body • Interacts closely with the circulatory & digestive systems
Kidneys: Liquid Waste’s Last Stop • As blood passes through the kidneys, it is filtered and wastes are removed • Remember nephrons? Those are the tiny structures within the kidneys that do the filtering • Urine forms from excess water and unneeded salts in the blood (called urea) • Urine is stored in the bladder and then excreted through the urethra
Urine trouble if you don’t know the answers to these questions! • Name the 4 major structures that compose the urinary system. • How is the urinary system different from the digestive system? • What tiny structure in the kidney is responsible for filtering blood of its wastes?