SCIENCE

• The digestive system breakdown food to simple forms of molecules (digestion), small enough to absorbed and used by the cells of the body (absorption). unabsorbed substances are eliminated as stool(elimination).
• saliva also helps moisten and lubricate the food which turn into bolus.
• bolus is a mass of food that is easier to swallow.
• the tongue and teeth work together to breakdown food mechanically.
• canines are used for tearing
• incisors for cuting
• molars for grinding food
• when the food has been chewed, the bolus is pushed by the tongue against the palate, forcing to move toward the pharynx and esophagus
• as the food passes to the pharynx, the epiglottis is tipped backward, preventing the food's passage to the larynx.
• the wavelike muscular contraction and relaxion of the esophagus which is call peristalsis
• after passing through the esophagus (approximately 25 cm long) the mass of food reaches the stomach where protein digestion begins
• where the food mixed with stomach secretions and converted into a semifluid acidic mixture called chyme

  
• chemical digestions gastric juices on takes place in the when the stomach secretes its gastric juices
• Fat digestion takes place in the stomach with the aid of lipase
• lipase an enzyme that breaks down fats
• the first of the small intestine called duodenum

  
• in duodenum it is where the remaining carbohydrates and proteins broken down
• the jejunum and ileum is the second and third part of the small intestine, respectively, perform the critical function of absorbing nutrients and transferring them to the circulating blood

  
• the folded lining of the small intestine has many finger like extenstions called villi in singular villus
• most of the cells composing the surface of vili have numerous projections resembling a fine brush called microvilli
• the pancreas secretes a variety of digestive enzymes that break down carbohydrates into simple sugars.

  
• pancreas also split proteins into amino acids and fats into fatty acids
• the pancreas, an important accessory organ, produces bicarbonates that neutralize acidic enzymes for starch, proteins, and fats
• because digestive enzymes cannot act efficiently on large fat globules, the liver secrets the bile a greenish fluid the emulsifies fats by breaking fat globules into smaller droplets
• gallbladder is a green muscular sac that is attached to the liver

  
• gallbladder stores the bile
• it takes 18 to 24 hours for food to pass through large intestine
• the large intestine absorbs water, secretes mucus, and eliminates undigested materials
• alkaline mucus secretions in the large intestine protect epithelial tissues and they neutralize acids produced by action bacteria
• the large intestine stores the feces until they eliminated by the process of defecation
• endoscopy is a diagnostic procedure used to examine a patients digestive tract
• marasmus is caused by combined protein and energy deficiency, which is commonly seen where adequate quantities of food are unavailable
• kwashiorkor is caused by a deficiency of protein in the presence of adequate energy
• vitamin a also know as retinol is naturally synthesized from plants
• vitamin a deficiency cause blindness