Download Figure 41.13 The human digestive system

DIGESTION – the breakdown of
food into simpler substances by
the body or by a cell.
Intracellular Digestion in Paramecium
Paramecium
Extracellular Digestion in a Gastrovascular
Cavity
Alimentary Canals (complete digestive tracts)
The Human Digestive System
Digestive System
MOUTH
• Taste Buds
• Salivary Glands
•Amylase – digests starches
PHARYNX – at the back of the
mouth; leads to the esophagus
and trachea
Adult Mouth
From Mouth to Stomach: the Swallowing
Reflex and Esophageal Peristalsis
Cardiac sphincter
ESOPHAGUS -about 25 cm/1 ft
•
peristalsis occurs within to
move bolus of food
•
cardiac sphincter at the end
STOMACH
•hydrochloric acid breaks down
food (in gastric juice)
•pepsin digests protein
•mucus lining protects
•churning of food makes chyme
The Duodenum (Active Hormones)
Enterogastrone
pyloric sphincter
Cardiac sphincter
Gastrin
•Secretin
CCK
Secretes NaHCO3, pancreatic juices
that digest macromolecules
Homeostatic Regulation of Cellular Fuel
Pancreas
Pancreas
Secretion of Gastric Juice
Anatomy and Histology of the Stomach
Enzymatic Digestion in the Human Digestive
System
SMALL INTESTINE
•about 23 feet long in adults
•pancreas secretes pancreatic
fluid (contains NaHCO3)
•amylases break down starches
•proteases break down proteins
•lipases break down fats
Activation of Protein-Digesting Enzymes in
the Small Intestine (secreted by pancreas)
These proteases cleave
bonds adjacent to certain
amino acids
The Structure of the Small Intestine
SMALL INTESTINE (con’t)
•Liver makes bile to break
down fats; it is stored by the
gall bladder ; it is what gives
solid waste its color
•villi – loaded with blood vessels
Howdy
Ho!
LARGE INTESTINE/COLON
• about 3m/9 ft in adults
•removes water from waste
•waste moves to rectum where it is
held before excretion at the anus
Large Intestine (Colon)
goblet cells
The Digestive Tracts of a Carnivore (coyote) and a
Herbivore (koala) Compared
• Polyps are small growths arising from
the epithelial lining that may be benign
or cancerous.
• Diarrhea and constipation are two
common complaints of the large
intestine.
• Causes of diarrhea include infection of
the lower tract and nervous
stimulation, both moving feces more
rapidly than normal, but also causing
dehydration if prolonged.
Ruminant Digestion
(removes water)
(Boluses enter – microbes
break down)
(enzymatic digestion)
(boluses enter and
microbes break
down)
List the following in the order in
which food would move in the
digestive process:
esophagus, small intestine,
stomach, large intestine, mouth,
pharynx, cardiac sphincter.
What activates pepsin in the
stomach?
Ulcers are caused by . . .
List three substances involved in
food digestion and:
a.from where they are released
ex: amylases from pancreas
b.their target ex. duodenum
c.what they do ex; digest carbs
Compare the function of the small
intestine to the large intestine.
The main function of the large
intestine is to. . .
What is the cecum?
The “friendly” bacteria in
large intestine function to. .
Food is prevented from entering the
trachea because it is blocked by the:
Muscular contractions called ________
occur when muscles in the esophagus
squeeze the food as it pass through it.
Compare the function of the small
intestine to the large intestine.