SBI 3U January 10 th, 2013

 Cells with similar functions come together to form tissues  Ex: stomach includes muscle tissue  4 types of tissue: connective tissue, epithelial tissue, nervous tissue and muscle tissue  Several types of tissues that come together to perform one overall function  organs

 Organ system  several organs working together to perform an important function  Maintenance of homeostasis  All cell require nutrients and oxygen  respiratory and digestive systems provide these and the circulatory system ensures that all cells get these essentials

 Digestive tract = Gastrointestinal tract = Alimentary canal  Digestive tract  series of hollow organs joined in a long, twisted tube from mouth to exit of body  Structure allows for food to enter through mouth, nutrients to be absorbed and wastes to be excreted

 Major organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine (colon), and anus  Accessory organs: salivary glands, pancreas, liver, and galbladder

 Lumen: central space  5 layers of tissue surrounding lumen 1. Mucosa 2. Submucosa 3. A circular layer of smooth muscle 4. Longitudinal layer of smooth muscle 5. Serosa

 Depending upon the section of the digestive tract: -mucosa protects digestive tract wall -secretes substances and; -absorbs the end products of digestion

 Lies outside the mucosa  Connective tissue consisting of blood vessels, lymphatic vessels, and nerve fibers

 Layer of muscle  Mouth and pharynx: consists of skeletal muscle  Rest of the digestive tract: consists of smooth muscle and nerve fibers

 Composed of connective tissue  Forms the covering of the digestive tract

 Function of digestive system: change the foods you eat into chemical forms your body can use  Ingestion: food is acquired  Food useful once it has been converted into diffusible substances  Prep of food for absorption is termed digestion

 Carbs  monosaccharides  Proteins  amino acids  Fats  fatty acids and glycerol  2 types of digestion: mechanical digestion & chemical digestion

 Mechanical: in mouth and stomach  Chemical: the breakdown of food into smaller and simpler compounds

 Shredding, tearing and grinding food  teeth  incisors, canines and pre-molars/molars  Herbivore teeth vs. Carnivore  Human teeth resemble both herbivore and carnivore

 Can occur once food has been broken down  Food mixed with various juices from digestive glands  Enzymes act upon broken-down food  Absorption: primarily in small intestine. Large intestine only for water and some vitamins  Elimination: occurs through rectum and anus

 Begins at the oral cavity  where food is manipulated by the mouth  Lips, tongue, teeth and jaw muscles used  Incisors, canines, molars  Salivary amylase  beginning of chemical digestion  Bolus created

 Bolus passes through pharynx  Epiglottis and trachea  Bolus drops into esophagus