Download Chapter 3 Digestion

Chapter 3
Digestion,
Absorption,
Transport
Food must
be digested
in order to
be useful to
the body.
Digestion
What is the basic anatomy of the GI
tract?
mouth → esophagus → stomach →
small intestine → large intestine →
rectum → anus
GI Tract
Anatomy
Epiglottis
Trachea
Esophagus
Esophageal
sphincters
Stomach
Pyloric
sphincter
Appendix
Salivary
glands
Pharynx
Epiglottis
Lower
esophageal
sphincter
Esophagus
Trachea
(to
lungs)
Pancreas
Pancreatic duct
Stomach
Pancreas
Pancreatic duct
Small intestine
(duodenum,
jejunum, ileum)
Liver
Bile duct
Ileocecal
valve
Ileocecal valve
(sphincter)
Mouth
Upper
esophageal
sphincter
Gallbladder
Pyloric
sphincter
Small intestine
Anatomy
Appendix
Liver
Rectum
Gallbladder
Anus
Bile duct
Large
intestine
(colon)
Large intestine
(colon)
Rectum
Anus
ELIMINATION
Fig. 3-1, p. 73
Close-Up View of the Organs
of the Digestive System
Gland
A cell or group of cells that
secrete a substance that the
body requires
Types of Glands
Exocrine Glands:
ƒ secrete their materials “out”
(into the GI tract or onto the skin)
Endocrine Glands:
ƒ secrete their materials “in”
(into the blood)
Head
Salivary
glands
Fig. 3-5, p. 76
Bolus
The portion of food which is
swallowed at one time
pH
The unit of measure
expressing a solution’s
relative acidity or
alkalinity
pH of common substances:
Basic
Concentrated lye
pH
Oven cleaner
Household ammonia
pH neutral
Baking soda
Bile
Pancreatic juice
Blood
Water
Saliva
Urine
Coffee
Orange juice
Vinegar
Lemon juice
Gastric juice
Acidic
Battery acid
Fig. 3-6, p. 77
Chyme
The semi-liquid mass of
partially digested food
that is expelled from the
stomach into the
duodenum
Picture
Longitudinal
Circular
Diagonal
Fig. 3-2, p. 75
Picture
Esophagus
Circular
muscle
Longitudinal muscle
Esophagus muscles
relax, opening the
passageway.
Stomach
Diaphragm muscles
relax, opening the
passageway.
Esophagus muscles
contract, squeezing
on the inside.
Diaphragm muscles
contract, squeezing
on the outside.
Fig. 3-4, p. 76
Esophagus
Picture
Reflux
Diaphragm
Weakened lower
esophageal sphincter
Stomach
Acidic stomach
contents
Gastroesophageal
Reflux
Fig. H3-4, p. 96
Peristalsis
Successive waves of
involuntary muscular
contractions passing
along the length of
the GI tract
Peristalsis
The small intestine has
two muscle layers that
work together in
peristalsis and
segmentation.
Circular muscles are
inside.
Longitudinal muscles
are outside.
Fig. 3-3a, p. 75
Details of Peristalsis
PERISTALSIS
Chyme
The inner circular
muscles contract,
tightening the tube
and pushing the food
forward in the intestine.
When the circular
muscles relax, the outer
longitudinal muscles
contract, and the
intestinal tube is loose.
As the circular and
longitudinal muscles
tighten and relax, the
chyme moves ahead
of the constriction.
Fig. 3-3b, p. 75
Details of Segmentation
SEGMENTATION
Chyme
Circular muscles
contract, creating
segments within the
intestine.
As each set of circular
muscles relaxes and
contracts, the chyme is
broken up and mixed
with digestive juices.
These alternating
contractions, occurring
12 to 16 times per
minute, continue to mix
the chyme and bring the
nutrients into contact
with the intestinal lining
for absorption.
Fig. 3-3c, p. 75
Please click out of WebCT and go to
the following website to learn more
about heartburn and other GI
problems.
http://www.gihealth.com