The Digestive System
• Digestion
o Breakdown of ingested food
o Absorption of nutrients into the blood
• Metabolism
o Production of cellular energy (ATP)
• Cellular respiration
Organs of the Digestive
System
• Alimentary canal
i.e.: gastrointestinal (GI) tract
ocontinuous coiled hollow muscular
tube open at both ends
• Accessory digestive organs
Organs of the
Alimentary Canal
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Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
Mouth Anatomy
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Lips (labia) – protect
Cheeks – form walls
Hard palate – front roof
Soft palate – back roof
Uvula – fleshy projection
Tonsils
Tongue
Oral cavity – area contained
by the teeth
Figure 14.2a
Salivary Glands
• Saliva (spit)
o Contains enzyme amylase to begin starch
digestion
• mixes chewed food with saliva;
• helps us swallow the food;
• has papillae (bumps) that contain taste buds.
Functions of the Pharynx
• A passageway for air and food
• Food is propelled to the esophagus by
two muscle layers
operistalsis
Wavelike contractions of the muscle
layers
Esophagus
• Runs to stomach through the diaphragm
• Propels food by peristalsis
• Passageway for food only (respiratory
system branches off after the pharynx)
Stomach
• on the left side of the abdominal cavity
• Food enters at the esophageal sphincter
• Food empties into the small intestine at the pyloric
sphincter
Functions of the Stomach
• Acts as a storage tank for food
• Chemical breakdown of protein begins
• Delivers chyme (processed food)to the small intestine
Specialized Cells of the Stomach
•Chief cells – produce protein-digesting enzymes
•Parietal cells – produce hydrochloric acid
Ulcers
• An ulcer is an open, painful wound. Peptic ulcers
are ulcers that form in the stomach or the upper
part of the small intestine.
What causes ulcers?
• bacteria (Helicobacter pylori)
• overuse of anti-inflammatory drugs such as aspirin
or ibuprofen (Motrin & Advil)
• Smoking
• Drinking alcohol
• Uncontrolled Stress
Symptoms of ulcers
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loss of appetite
sharp stomach pains
Nausea and/or vomiting
frequent burping or hiccuping
bloody or blackish bowel movements
weight loss
Small Intestine
 MAJOR SITE OF NUTRIENT ABSORPTION
 8-18 feet long
•villi
Fingerlike structures to
increase surface area
•microvilli
Small projections of the
plasma membrane
Large Intestine
• Larger in diameter, but shorter than the small
intestine
• Absorption of water
• Eliminates indigestible food as feces
• Cecum – first part
o Appendix
• Colon
• Rectum
• Anus – external
Accessory Organs of the
Digestive System
Pancreas
• Produces digestive enzymes
• Produces hormones
 insulin
 glucagon
Insulin
• Insulin is secreted by the pancreas in response to
high blood sugar (glucose).
• After you eat, blood glucose levels rise and in
response to this, insulin is secreted into the blood
• In response to insulin, cells (muscle, red blood cells,
and fat cells) take glucose in from the blood to use
to generate energy (ATP)
• This lowers the blood glucose levels back to the
normal range
• As blood glucose falls, insulin secretion by the
pancreas decreases.
Diabetes
 A person with diabetes does not produce enough
insulin or produces no insulin at all.
 Without insulin, body cells can’t take the glucose out
of the blood
 Blood glucose levels become high which leads to
other health problems.
 So, even though the blood has plenty of glucose,
the cells are not getting it for their essential energy
and growth requirements.
 Diabetes Type 1 - You produce no insulin at all.
 Diabetes Type 2 - You don't produce enough
insulin, or your insulin is not working properly.
Liver
• Largest gland in the body
• Manufactures bile
o Bile breaks fat into smaller globs for (fatdigesting enzymes to work on.
• It’s connected to the gall bladder
Gall Bladder
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Small sac under the liver
Connected to the liver
Stores bile
When you eat fatty foods, bile is
released from the gallbladder.
What are gallstones?
o Made from cholesterol
o They can be as large as a golf ball.
o People who are overweight or who are trying to
lose weight quickly are more likely to get gallstones.
o You can live without your gallbladder