The Digestive System
The Digestive System (Do Not Copy) a system of organs that: - takes in and breaks down food - absorbs nutrients - removes solid waste from the body There are more similarities than differences among animal digestive systems
The Human Digestive System There are 4 stages of digestion in humans: 1) Ingestion: taking in food (eating) 2) Digestion: physical and chemical breakdown of food a) physical: chewing action of teeth and churning action of stomach
The Human Digestive System 2) Digestion (continued) b) chemical: enzymes in saliva, stomach and small intestine chemically break down food into small molecules (nutrients) liver, gall bladder & pancreas release substances (including enzymes) into small intestine
The Human Digestive System Absorption: nutrients, water, vitamins and minerals from the small and large intestine are absorbed into the bloodstream then can travel to other cells in the body 4) Egestion: removal of solid waste products through the colon, rectum and anus
The Human Digestive System
The Human Digestive System esophagus stomach liver gall bladder pancreas small intestine large intestine appendix rectum anus 7
Cool Facts (Do Not Copy) Small intestine is lined with millions of villi (folds of the membrane) to maximize surface area for absorption If all villi were unfolded, they would take up the area of a tennis court Large intestine is full of “good” bacteria that help produce vitamins from nutrients Our salivary glands produce 2 litres of saliva/day
Bacteria in our digestive system
Digestive Systems in Other Animals Herbivores have much longer digestive systems than carnivores of the same size. Why? Plant products are more difficult to digest More time and surface area needed
The Fish Digestive System Most fish are carnivores Use teeth to grasp and swallow prey (no physical digestion) Long straight stomach allows fish to swallow animals almost the same size
The Fish Digestive System Pyloric caeca (where stomach and intestine meet) carries out most digestion and absorption Remaining nutrients absorbed in intestine with egestion through anus
The Bird Digestive System Birds collect food in beak, but little physical digestion occurs there Crop: special storage pouch Food travels into first stomach segment – digestive juices added Then into the gizzard that contains small stones to grind food Absorption in intestine and egestion through cloaca (all- purpose “hole”)
The Frog Digestive System Mouth is adapted to capture prey Long tongue is sticky and moves very quickly to catch prey Two types of teeth in upper jaw to hold prey as it is swallowed (no physical digestion) Food can be held in gullet (wide, elastic esophagus) Rest is similar to human, but egestion occurs through cloaca
The Frog Digestive System
The Frog Digestive System Esophagus Liver Lungs Gall bladder Pancreas Stomach Small Intestine Spleen Large Intestine Cloacal vent Cloaca
Homework Digestive System Comparison Worksheet