Transcript digestion
DIGESTIVE SYSTEM Gaining nutrients PURPOSE To gain nutrients and water Digestion involves: mechanical breakdown Mastication (chewing) Churning Chemical breakdown Enzyme activity Absorption Important note: Faeces is made up of all the products not absorbed in the intestines, some metabolic waste and some water – this is not part of the excretory system! HUMANS STRUCTURE A. B. C. D. E. F. G. H. I. J. K. L. Oesophagus Bile duct Stomach Pancreas Small intestines Large intestines Rectum Appendix Duodenum Gall Bladder Liver Salivary glands FEATURES Teeth Salivary glands – produce salvia (containing amylase) to lubricate food and start the chemical breakdown process Oesophagus – moves, via peristalsis, the bolus of food down using rings of muscles Stomach – muscular walls churn food coating it in digestive enzymes (eg. pepsin). Has a thick mucous wall to protect the muscle layer from the enzymes. Duodenum – connects the stomach to the small intestine FEATURES Bile duct – delivers bile from the liver and gall bladder into the digestive tract Small intestine – Major site of absorption. Contains hundreds of villi to increase the surface area Appendix – role unknown Large intestine – site where water is taken into the digestive tract to soften the faeces Rectum – where the faeces gathers and compacts before release Sphincters – rings of muscle located along the digestive tract to control the direct and timing of movement VILLI Small protrusions in the small intestines increase the surface area. Allowing for more efficient absorption. Each vilus contains capillaries to collect the absorbed nutrients OTHER ANIMALS TYPES OF FERMENTER HINDGUT FERMENTER Hindgut fermenter Have natural flora (bacteria) in their caecum or lower intestines to aide the chemical breakdown of food Can have an extended or larger caecum The caecum is often larger in animals that feed on rough plant material Foregut fermenter (ruminant) Have natural flora (bacteria) in their stomach compartment/s to aide the chemical breakdown of food Often re-masticate their food to gain maximum nutrient absorption THE CAECUM THE CAECUM In ‘soft-plant’ herbivores In ‘rough-plant’ herbivores Smaller to non-existent In carnivores Very large In omnivores large Smaller to non-existent In nectar/pollen eaters Non-existent Very basic digestive tract as no breakdown is required DENTITION Canines – pointed teeth for ripping and tearing meat from bone Incisors – scissor-like teeth for snipping away plant matter Molars – can be flat or pointed for grinding up matter Herbivores have incisors and molars at most Carnivores have canines and pointed molars at most Omnivores have a combination of canines, incisors and molars HERBIVORE DENTITION CARNIVORE DENTITION OMNIVORE DENTITION PLANTS PLANTS Plants gain nutrients from their roots It is taken up via the xylem vessels Detritivores (like worms) breakdown dead matter in simple nutrients which can be taken up by the plant