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●● The digestive system provides nutrients to the organs of
the urinary system.^
●● The liver converts harmful ammonia from the diges-
tion of proteins to harmless urea and provides bile to
emulsify fats.
Reproductive System
●● When a woman is pregnant, the fetus crowds the
abdominal organs and the mother may experience
constipation.^
●● The digestive system provides nutrients for mainte-
nance, growth, and repair of the reproductive organs
and supplies the developing fetus with nutrients.
Summary Outline
Introduction
- Digestion is the process by which food is broken
down mechanically and chemically into simpler
substances that can be used by the body’s cells and
converted into high-energy ATP molecules.^
- The five basic activities of the digestive system are
ingestion, peristalsis, digestion, absorption, and
defecation.
General Organization
- The digestive tract includes the mouth, pharynx,
esophagus, stomach, small intestine, large intestine,
and anus.^
- The accessory organs of the tract include the teeth,
tongue, salivary glands, liver, gallbladder, and pancreas.^
- The four coats, or tunics, of the tract, from the inside
out, are the mucosa, submucosa, muscularis, and
adventitia or serosa.
The Oral Cavity
- The functions of the oral cavity are taste, mechanical
breakdown of food using the teeth, and chemical
digestion of carbohydrates using the salivary enzyme
amylase.^
- The oral cavity is lined with mucous membrane. The
floor of the cavity is formed by the tongue, the roof by
the hard and soft palate, and the sides by the cheek.
The opening is guarded by the lips.^
- The functions of the tongue are manipulation of the
food, taste through some of its papillae, and assis-
tance in speech.
Chapter 16- The three pairs of salivary glands are the parotid, the
submandibular or submaxillary, and the sublingual.
Saliva lubricates the food, begins the digestion of
complex carbohydrates, and controls certain bacteria.^ - A tooth is composed of the crown, the neck or cervix,
and the root. The crown of the tooth is covered with
enamel. A tooth is made up of dentin. The periodontal
ligament anchors the tooth into the alveolar socket.
The Pharynx- The pharynx is a common passageway for food and
air. It is divided into the nasopharynx, the orophar-
ynx, and the laryngopharynx.^ - Its function is to begin the process of swallowing or
deglutition.
The Esophagus- The function of the esophagus is to secrete mucus and
transport food to the stomach through an open-ing in
the diaphragm called the esophageal hiatus.^ - Peristalsis, caused by smooth muscle contractions,
pushes the food bolus into the stomach through the
lower esophageal sphincter.
The Stomach- The main function of the stomach is to begin the
chemical breakdown of proteins through the en-zyme
pepsin. It also breaks up food mechanically by
churning its contents. It absorbs some water, salts,
alcohol, and certain drugs like aspirin.^ - The four parts of the stomach are the cardia, fundus,
body, and pylorus. The pyloric sphincter guards the
connection into the small intestine. The empty stom-
ach lining has many folds or rugae that allow the
stomach to expand and hold large amounts of food.^ - The gastric glands of the stomach mucosa contain
three kinds of secretory cells: (1) the zymogenic or
chief cells that secrete pepsinogen, (2) the parietal
cells that secrete hydrochloric acid, and (3) the mu-
cous cells that secrete mucus.
The Pancreas- The pancreas has a dual function. Its acini produce
digestive enzymes that get carried by the pancreatic
duct to the duodenum of the small intestine. Its pan-
creatic islets secrete the hormones insulin and glu-
cagon into the blood to control blood sugar levels.^ - The pancreas is divided into the head, body, and tail.