BIOL 199 Study Guide - Final Guide: Trachea, Dysentery, Epiglottis
Functions
• The main goal of the digestive system is to break down food into biologically
important molecules and eliminate any waste
• It completes this process in five steps:
1. Mechanical processing
2. Secretion
3. Digestion
4. Absorption
5. Elimination of waste
Mechanism
Processing
• Chewing breaks food into smaller pieces
• Glands in the mouth produce saliva to help with this process
o Saliva acts as a chemical barrier to neutralize or kill bacteria
o Saliva also liquefies food, dissolves substances, and cleanse teeth
• The tongue muscle helps to move food toward the pharynx and is also the home
of taste receptors
Epiglottis – door that keeps food from entering the trachea
Esophagus – muscular tube that helps to push the bolus down toward the stomach
Esophagus – an involuntary reflex to food causes contractions behind the food
Sphincter – muscular door that regulates when food can enter and exit the stomach
• The stomach turns food into chyme and doses it into the small intestine
o Gastric glands produce pepsinogen and hydrochloric acid to help
generate chyme (production decreases once the stomach is emptied)
Digestion and Absorption
• The small intestine is the site of digestion and absorption
o It breaks food down physically (smooth muscle contractions) and
chemically (digestive enzymes)
o The small intestine has tons of surface area to allow for every opportunity
of absorption
• The pancreas is signaled by the presence of food to produce digestive enzymes
and bicarbonate to buffer the chyme
• The liver produces bile which helps to digest fat
• The large intestine is the site of water reabsorption
o Sodium ions, potassium ions, and vitamins follow the water
Elimination
• Both smooth and skeletal muscles are involved, so we can control our waste
removal
Hunger