DIGESTIVE SYSTEM

• The primary purpose of the digestive system is to breakdown food to facilitate the effective transport of nutrients to different parts of the body.
• 4 Digestion process:

  1. Ingestion - intake of food to body;mouth

  2. Digestion

  -Mechanical and chemical digestion

  -breakdown of larger molecules into simpler, soluble substances

  3. Absorption

  -digestive materials are absorbed by cells

  4. Elimination

  -passaging of digestive material out of digestive tract
• The digestive system is also called the "Alimentary canal" or "Gastrointestinal Tract"
• Bolus(boli) - A ball of food, chewed food

  Chyme - semi-liquid mass of food

  - from stomach
• Bolus and chyme

  food->mouth->esophagus->bolus->stomach->small intestine->chyme->large intestine->anus->feces
• Mechanical vs Chemical Digestion

  -breaking down of food by - breakdown foods using

  physical means. enzymes.

  -grinding, chewing, mixing food - breakdown of complex food

  -stomach and mouth into soluble substances.

  - hydrochloric reactions

  - protein, starch and fat
• Enzymes - protein molecules

  - found in saliva
• Mouth- where digestion begins

  - both mechanical and chemical due to chewing and enzymes in saliva

  - where food is masticated or chewed/grind

  - starch turned into simple sugar
• Pharynx - also known as the throat

  - lead to esophagus, thinly lined, hollow and a muscular tube

  - where chewed food or bolus is pushed through the pharynx or throat.

  - passage of food and air
• Epiglottis - flap-shaped leaf

  - covers opening of larynx
• Esophagus - came from the greek word that means, "to carry what is eaten."

  -muscular tube (25cm)

  -connection between mouth and stomach

  -food is lubricated with mucus and moved by peristalsis

  -no digestion occurs

  -where bolus food travels
• peristalsis - the wave-like contraction of the muscles of the alimentary canal to push down food
• Stomach - j-shaped

  - the principal organ

  -composed of strong layers

  peristaltic and churning action further breakdown foods

  - contains "Gastric juice"

  Gastric juice is composed of:

  mucus

  pepsinogen

  hydrochloric acid
• food stays in stomach for 3-6 hrs. Some food at 24hrs
• Small intestine - longest part ( 7meters)
• Sections of the small intestine

  
• Duodenum - first section of the small intestine

  - receives partially digested foods
• Jejunum - middle section of the small intestine

  - absorption takes place
• Ilium - last section of the small intestine connected to large intestine.

  - vitamin 12 and bile salt is absorbed
• After food is breakdown into simplest form, it will be absorbed by the body through the small intestine and eventually into the bloodstream this is called "assimilation"
• large intestine - also known as "colon"

  - larger but shorter than small intestine

  (1.5 meters long)

  -absorb undigested foods-no enzymes produced but their is mucus for better flow of chyme
• 5 sections of large intestine:

  1. cecum - 1st part
  2. ascending - pataas
  3. transverse colon - middle
  4. descending colon - pababa
  5. sigmoid colon - end

  
• Rectum and Anus

  Rectum

  >storage of stool/feces

  >strong muscular walls expand that holds the feces until nerves signal the brain that you need to excrete it through your anus
• Accessory Organs of Digestive System

  1.) Tongue -allows circulation of sounds

  - strongest muscle

  - helps chew food and pushes chewed food at the back of the mouth to enter the pharynx
• Accessory Organs of Digestive System

  2.) Salivary Glands - produces saliva and other substances that helps with digestion
• Accessory Organs of Digestive System

  3.) liver - right side, under diaphragm

  - largest organ

  - produces bile that help digest protein and fats

  - bile

  >stored in gallbladder
• Accessory Organs of Digestive System

  4.) pancreas - between stomach and spine

  - produces pancreatic juice

  -releases insulin

  > help regulate blood sugar
• Accessory Organs of Digestive System

  5.) appendix - located in the junction of the small and large intestine

  -a vestigial organ

  - has unknown purpose, but scientist believed that its purpose is to help the digestive tract restore good bacteria