digestive system

• Digestion - breaking down of food into simpler substances
• The breaking down of food into simpler substances for use by the body is the work of the digestive system
• The journey of the food starts from the mouth down to the anus and takes about 18 hours - 2 days
• physical digestion - mechanical breakdown of food into smaller particles
• Chemical digestion - breakdown of complex molecules, such as proteins, starch and fats contained in food, into simple, soluble molecules by digestive enzymes
• Ingestion - Taking in food substances into the body through the mouth
• Digestion - Break down of food molecules into smaller molecules for absorption of the cells
• Absorption - Passing of the soluble food molecules in the wall of the small intestine
• Assimilation - Movement of digested food nutrients into the blood vessels of the small intestine through diffusion
• Egestion or Elimination - Release of undigested food collected in the rectum called feces and pushed out of the body through the anus
• Mouth - Teeth mechanically break down food into small pieces
• Tongue mixes food with saliva forming into a moist ball called bolus so it can be easily swallowed
• pharynx - common passage of food and air
• a flap-like cartilage called epiglottis covers the larynx so that no food particle enter the trachea during swallowing
• esophagus - a tube that attaches the mouth to the stomach
• esophagus came from a Greek word that means “to carry what is eaten”
• A series of wave-like muscle contractions known as peristalsis push and transport food and liquids in small sections to the stomach
• Stomach - a j-shaped, bag-like muscular organ that can hold approximately one liter of fluid and food
• • carbohydrates turns into sugars
  • proteins turns into amino acids
  • fats turns into fatty acids
• Small intestine - about 6 meters long, consist of three parts, the u-shaped duodenum, the jejunum, and the much-coiled ileum
• after 3-5 hours, most food in the small intestine is digested
• liver - largest gland in the body. Its lower surface is in contact with the stomach and small intestine
• aid digestion by producing a greenish-yellow liquid called bile, stored in a greenish-yellow bag attached to the liver called gallbladder
• gallbladder - releases bile through a duct into the small intestine to help in breaking up of large fat particle into smaller ones
• pancreas - soft triangular gland lying between stomach and small intestine
• large intestine - undigested food leaves the small intestine and passes into the large intestine
• large intestine is 1.5 meters long, shorter and much boarder than small intestine
• anus - materials that are not absorbed in the large intestine form a solid waste known as feces, made up of dead bacteria, some fat and protein, dried out digested juices, mucus and discharged intestinal cells is stored temporarily in the rectum
• when the rectum contacts, the feces is expelled out through the anus