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Prefixes Suffixes

dia- through, across

extra- away from, outside, external

infra- below, beneath

mal- bad, inadequate

micro- small

para- beside, near

poly- much, many

supra- excessive, above

trans- through, across

ultra- beyond

-algia pain

-dipsia thirst

-eal pertaining to

-ectomy excision, surgical removal

-iasis pathological condition or state

-ic pertaining to

-itis inflammation

-lith stone

-penia deficiency

-phage eating, swallowing

-plasty surgical repair

-rrhea flow, discharge

-scopy visual examination

-stenosis narrowing, stricture

-stomy mouthlike opening

Structure and Function

The digestive system is also known as the gastrointestinal (GI) system. It includes all the structures of the alimentary canal, from the mouth to the anus, and the accessory organs. The digestive system has two key functions: digestion and excretion. The organs of the GI system break down food into usable nutrients and then eliminate bulk waste in the form of feces.

We will discuss the parts of the GI system in the same order in which food passes through the system. While we do this, please refer to Figure 9-1 to see the various parts of the GI system.


The gastrointestinal system.

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The first or most proximal part of the digestive system is the mouth, also known as the oral or buccal cavity. When we take a bite of food (ingestion) and begin chewing it, our tongue and teeth aid in the process of mechanical digestion as food is broken down into smaller and smaller parts. It is mixed and moistened with saliva, which is secreted from three different salivary glands. Saliva also contains ptyalin, a chemical that starts to break down starches. The tongue helps to form chewed food into a bolus, which is a rounded mass ready to be swallowed. The tongue also allows us to taste food. Specific areas on the tongue identify sweet, salty, sour, and bitter flavors (Fig. 9-2). Because taste can make eating an enjoyable process, there are times when we may overeat. When we eat more calories than we burn through our daily activities or exercise, we gain weight (Box 9-1).


The tongue with structure of a taste bud and taste cells. (From Eagle, S., et al. The professional medical assistant. Philadelphia, PA: F. A. Davis Company, 2009. p. 540; with permission)

The uvula is a small, finger-shaped portion of soft tissue that hangs from the upper back of the mouth. It prevents food from entering the nasal cavity while we eat. At the back of the mouth is ...

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