BIOL 199 Study Guide - Final Guide: Trachea, Dysentery, Epiglottis

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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
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