Let's Journey Through the Digestive System
the organs of the gastrointestinal tract and
the accessory organs of the digestive
system and the function of their secretions.
the tissue layers that form the walls of
the digestive tract.
the processes associated with digestion.
the absorption of water-soluble nutri-
ents and the absorption of fat-soluble nutrients.
he cells in your body require many small
molecules to function properly, such as car-
and amino acids
Chapter 2). However, food is most commonly
available in much larger forms, such as your waffle, sau-
sage, and egg breakfast. Your cells cannot use the food in
such a meal directly, so the body must break down food
into smaller, usable components. This is the job of the
The digestive system basically consists of a long,
T h e d i g e s t i v e s y s t e m
F ig u r e 1 4 .1
(oral cavity) forms the
chamber where food is
food by chewing.
manipulates food and holds
lubricates food and begins
chemical digestion with the
is a muscular mixing chamber
and storage container for food.
• Contractions of stomach muscle
mechanically mix the food.
• Secretions of hydrochloric acid, pepsin,
and lipase chemically break down food.
• Intrinsic factor secretion assists
absorption of vitamin B12.
• Some absorption of water, ions,
short-chain fatty acids, and drugs
(alcohol, aspirin, ibuprofen) occurs in the
• Stomach controls rate of food expulsion
into the small intestine (gastric emptying).
conduits that propel
swallowed food from the
mouth to the stomach.
400 CHAPTER 14
The Digestive System, Nutrition, and Metabolism