Transcript The DIGESTIVE System

The DIGESTIVE System
Digestion defined
Breakdown of food into useable
nutrients
 Two kinds
 Mechanical
 Chemical
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Chemical Vs Mechanical Digestion
Chemical: Enzymes break down for
absorption--ENZYMES
 Mechanical: broken down into
smaller parts--MASTICATION AND
MACERATION
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Alimentary canal
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Tube food passes
through
Begins at mouth ends with anus
Food is chewed
Bolus created
Bolus swallowed
Pharynx
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Bolus moves into
pharynx
fancy word for
throat
has three parts
– Nasopharynx
– Oropharynx
– Laryngopharynx
Esophagus
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8-12 inches long
Smooth muscle
contractions called:
Peristalsis-rhythmic
Cardiac (aka
Gastroesophageal)
sphincter
Has no mucous
membrane to protect
from Hcl from stomach
Stomach
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J-shaped
3 sets of muscle in different
directions
Hcl= chemical breakdown
Pepsin begins protein
disgestion
Contain rugae to increase
surface area
Change bolus into chyme
Mucus protects stomach
lining
Small intestine
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3 parts
Duodenum--most chemical
digestion takes place here
Jejunum-absorption
continues
Ileum absorption continues
15-22 ft long
Absorbs some of the water
in food & what you drink
Villi
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Nutrients are absorbed through structures
called villi
Large intestine
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called the colon
Main function
water absorption +
Vit K absorption
Begins with cecumcontains lymphatic
organ called
appendix
Ascending colon
Large intestine
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Ascending colon
Transverse colonmakes hunger
sounds
Descending colon
Sigmoid colon
Rectum
Anal canal
Anus
Accessory organs
CONTRIBUTE to digestion process
 NOT part of the canal or tube
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Food DOES NOT pass through them
Tongue and teeth
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Teeth break food
down into smaller
pieces
Tongue moves food
to the back of throat
Parts of a tooth
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Crown = exposed
portion above gum
line
Neck = between
crown & root
Gingivae-gums
Root = one to three- embedded in
mandible &
maxillae
Parts of a tooth
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Enamel = outermost
part, protects from
wear & tear
– the hardest substance
in the body
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Dentin = calcified
connective tissue
Gives tooth it’s basic
shape & rigidity
Parts of a tooth
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Pulp Cavity = large
cavity enclosed by
dentin--filled with
pulp
Cementum = a
bone-like substance
covers--dentin of
roots
Parts of a tooth
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Periodontal
Ligament
an area of dense
fibrous connective
tissue
anchors teeth in
position
serves as a shock
absorber when
chewing
Salivary glands
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Saliva is:
Mostly water
Enzymes that digest
carbs—Amylase—
breaks starch into
maltose
Soften and moisten
food
Salivary glands
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total--3 pair
 Parotid,
submandibular,
and sublingual
Liver and Gall Bladder
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Liver makes bile
Bile is stored in gall
bladder (sac)
Bile breaks down
fats--emulsification
Secreted as it is
needed
Eliminated through
intestines
Pancreas
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Located posterior to
stomach
Secretes enzymes to
chemically breakdown
fats, carbs, and
proteins
Increases pH of chyme
Pancreatic juice—thru
pancreatic duct—thru
heptopancreatic
sphincter
Mastication
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Chewing--makes
bolus
Teeth mechanically
break down food
Food is mixed with
saliva
Deglutition
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Swallowing
Tongue pushes food to
back of throat
Oropharynx--second
part of throat
Smooth Muscles
contract causing
peristalsis
Voluntary
Peristalsis
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General term for
wave-like
contractions in
esophagus and
intestines
Rhythmic smooth
muscle contractions
Maceration
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Stomach contracts
and Bolus mixed
with gastric juices
and Hcl until it is
liquid-like
Bolus is changed to
chyme
Empties through
pyloric sphincter
Segmental contraction
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Each segment of
small intestine
contracts
Helps mix bile and
pancreatic juices
with chyme
Smooth Muscle
contractions
peristalsis in each
segment
Absorption
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Nutrients absorbed in
jejunum and illeum
Some nutrients &
water absorbed thru
stomach
Some water absorbed
through small intestine
Most water absorbed
through large intestine
Haustral churning
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Each segment in
large intestine is
called a haustra
Smooth muscle
contractions move
contents along
(type of peristalsis)
Water is absorbed
in large intestine
Defecation
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Elimination of
material that is
undigestible
Plant fiber-necessary for health
of the intestines
Formation of feces
and elimination of
feces
Nutrients are broken down in different
places in digestive system
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Carbohydrates
Begin digestion in
mouth with enzyme
AMYLASE from
salivary glands
Amylase breakdown
continues in stomach
Finish breakdown in
duodenum (pancreatic
juice)
Fats
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Fats begin mixing with
gastric juices in
stomach
Bile from gall bladder
goes into small
intestine to break them
down
Pancreas secretes
enzymes (lipase) to
finish chemical
breakdown
Proteins
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Begin mixing with
pepsin in stomach
Finish with
secretions from
pancreas into
duodenum
Digestion system End