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* Produces various chemicals to break down the food * Filters out harmful substances * Gets rid of solid wastes *
*Mouth *Pharynx *Oesophagus *Stomach *Small and large intestines *
*Changes the physical form of food: * Chew * Tear * Grind * Mash * Mix *
*Changes the chemical composition of food *With the aid of digestive enzymes: *Carbs *Protein *Lipid *Digestive enzymes are special proteins *Help break up large molecules of food into very tiny molecules *So that they can be absorbed *Used by cells in the form of nutrition *
*Ingestion *Movement *Digestion *Absorption *Further digestion *
* *Alimentary canal and the accessory digestive organs. *Alimentary canal (also called the gastrointestinal tract/gi) is the continuous, muscular digestive tube that winds through the body. *It digests food and absorbs the digested fragments through its lining into the blood. *These organs help breakdown the food, either mechanically or chemically.
*Teeth *Tongue *Gall bladder *A number of large digestive glands salivary glands *Liver *Pancreas *
*A long muscular tube *Many sections & areas *Begins with the mouth *End with the anus *
*PARTS OF DIGESTIVE TRACK: *Mouth *Pharynx *Esophagus *Stomach *Small intestine *Large intestine *
*Organs that are not in the digestive tract, but helps in the digestion: *Teeth *Tongue *Salivary glands *Liver *Gall bladder *pancreas *
*Function: *Food enter mouth *Tasting *Mechanical breakdown of food *Secretion of salivary glands *
*Structures in the mouth that helps with digestion: *Teeth cut, tear, crush and grind food *Salivary glands produce & secrete saliva in oral cavity: *Beneath the teeth *Below the jaw bone *Below tongue *Saliva moistens food *Contains enzymes ptyalin & salivary amylase
*Mixes & roll food into tiny mashed up bits *Bolus *Pushes the bolus towards the pharynx *Into the esophagus when swallowing *
*It is a coordinated activity of the * *Tongue *Soft palate *Pharynx *Esophagus *Phases: *Food is pushed into the pharynx by tongue *Tongue blocks the mouth *Soft palate closes off the nose *Larynx(adam s apple) rises *Epiglottis(a flap of tissue) closes the opening of the trachea
* *A straight muscular tube *25cm long *Connect the mouth with the stomach *Food takes about 4-8 seconds as it passes through the stomach *Walls contain smooth muscle *It contracts in a wavy motion peristalsis *Peristalsis move food & liquid slowly down the esophagus into stomach *Cardiac Sphincter (ring like valve) relaxes to allow food into the stomach
* J shaped muscular sac *Has inner folds that increase the surface area of the stomach *Churns & grinds together the bolus into smaller pieces *Food is mixed with gastric juices *Secreted by the stomach walls *
*Pepsin: *Major enzyme *Converts proteins into peptides *Mucus: *Lubricates food *Protects the gastric lining form strong digestive juices *Converts the bolus into a liquid( chyme) *4 hours of mechanical & chemical digestions *Chyem passes through the pyloric sphincter into: *Small intestine
*Long coiled tube beneath stomach *About 7 meters long *Has 3 parts: *Duodenum: * Upper part * 23-28 cm * Connected to stomach * Where the digestive juices form pancreas & liver combine with chyme * Making it thin & watery *Jejunum *Ileum - *
*The processing of food by the digestive system involves six essential activities: *The digestive tract can be viewed as a disassembly line * Food becomes less complex at each step of processing *Nutrients become available to the body. *
* Ingestion * The taking of food into the digestive tract via the mouth. * Propulsion * Movement of food through the alimentary canal. * It includes swallowing, which is initiated voluntarily, and peristalsis, an involuntary process. * Peristalsis, the major means of population, involves alternate waves of contraction and relaxation of muscles of the organ walls. * Its main effect is to squeeze food from one organ to the next, but some mixing occurs as well. * Peristaltic waves are so powerful that, once swallowed, food and fluids will move to your stomach even if you stand on your head.
Mechanical digestion *Physically prepares food for chemical digestion by enzymes. *Mechanical processes include chewing, mixing of food and saliva by the tongue, mixing of food in the stomach, and by rhythmic local contractions of the intestine. *Segmentation mixes food with digestive juices and increase the efficiently of absorption by repeatedly moving different parts of food mass over the intestinal wall.
Chemical digestion *Is a series of catabolic steps in which complex food molecules are broken down to their chemical building blocks. *It is accomplished by enzymes secreted by various glands into the lumen of the alimentary canal. *The enzymatic breakdown of foodstuffs begins in the mouth, and is essentially complete in the small intestine.
Absorption *The passage of digested end products from the lumen of the GI tract into the blood or lymph. *For absorption to occur, these substances must first enter the mucosal cells by active or passive transport processes. *The small intestine is the major absorptive site. Defecation *Eliminates indigestible substances from the body via the anus in the form of faeces.