The Digestive System
The Digestive System: Function
• Preparation of
food for
absorption and
use by the millions
of body cells
• Alimentary canal
- tube through
your body that
performs the
above function.
The Mouth Structure
• Lips: outer
boundary
• Cheeks: mucous
membrane lateral
boundary
• Hard/soft palate
- uvula extends
from
• Tongue
Tongue
• Places food during
chewing
• Papillae contain
taste buds
• Multiple blood
vessels under tongue
= high absorption of
soluble drugs into
circulation
– Ex. Nitroglycerin
pills for heart attack,
– Vitamins
Salivary Glands
• Parotid = largest
– Located in front of and
below ear
– Produces watery
substance with enzymes
• Submandibular
– Located below mandibular
angle
– Produces enzymes and
mucous
• Sublingual = smallest
– Under floor of mouth
– Produces mucous type of
saliva
Salivary Glands: Function
• Begins the break
down of food
through
hydrolysis.
• Carbohydrate
digestion begins in
the mouth with
aid of saliva.
Teeth
• Crown - exposed
covered with enamel
• Neck - surrounded
by gums (gingiva)
• Root - fits into
socket
Teeth Coverings
• Enamel - Hardest
substance in body
• Dentin - tissues,
nerves, blood
vessels
• Cementum - covers
dentin
Dentition
• Deciduous Teeth
– Baby teeth
– Primary teeth
• 20 total
– 8 incisors
– 4 cuspids
– 8 molars
Dentition
• Permanent Teeth
– Adult teeth
– Secondary teeth
• 32 Total
• 3rd set of molars
come in after age
17 (wisdom teeth)
Other Organ Components
• Pharynx
– Receives bolus (rounded
mass of food)
– Carries bolus to
esophagus
• Esophagus
– Collapsible tube that
enters the stomach
– Posterior to trachea and
heart
– Protected by a thick layer
of mucus
Esophagus Continued
• Food (Bolus) moves
through the
esophagus and the
rest of the
alimentary canal by
peristalsis involuntary muscle
contractions.
Stomach
• Located below
diaphragm and liver
• Enlarges after meals
then collapses
• Size of large
sausage
Stomach Divisions
• Fundus - large
portion at end of
esophagus
• Body - central
portion
• Pylorus - lower
portion near small
intestine
Sphincter Muscles
• Guard openings to
stomach
– Cardiac - esophagus to
stomach
– Pyloric - lower portion
of stomach to small
intestine.
• Pylorospasm - muscle will
not relax to allow
passage of bolus =
vomiting
Stomach Function
• Food storage
• Secretion of gastric juices
• Churning of food and breakdown
into chyme - liquid food.
• Absorption = water, alcohol, and
drugs
• Glands of stomach
– Gastric - secret gastric juice
– Mucus - contains enzymes and
hydrochloric acid.
Small Intestines
• 20 feet long
• Divisions
– Duodenum = uppermost
area, attaches to
stomach.
– Jejunum = middle area
– Ileum = end portion,
leads to large
intestine.
• All set in place by
mesentery
(membrane)
Small Intestines Continued
• This is where most
digestion occurs.
• Absorption of digestive
products.
• Inside surface of small
intestines covered with
tiny projections called
villi.
– 1mm projections
– Increase surface area by
160x
Large Intestines
• 5-6 feet long
• Divisions
– Ascending colon - right side
of abdomen
– Transverse colon horizontally across
abdomen and under liver
– Descending colon - left side
of abdomen
– Rectum - last 7-8 inches
– Anus - contains many
arteries and veins
• Hemorrhoids - enlargement
of veins in anal canal.
Large Intestines Continued
• Water/electrolyte
absorption
• Forms/stores feces
Large Intestines Continued
• Appendix
– Located just behind
cecum
– No functional
importance in
digestion.
– Appendicitis =
inflammation of the
appendix
Accessory Organs
• Liver structure
– Largest gland in body
– Under diaphragm
– Able to regenerate
• Liver function
– Detoxifies many
substances
– Makes and secretes bile
– Metabolizes proteins,
fats, and carbs
Accessory Organs
• Gall bladder
– Stores bile, increases its
concentration
• Bile breaks down fat.
– During digestion,
empties bile into small
intestines
Accessory Organs
• Pancreas
– Secretes digestive
enzymes
– Secretes insulin
– Secretes glucagon
2
3
1 - Uvula
4
5
7
9
6
14
8 – Pyloric sphincter/Duodenum
15
Transverse colon
11. Ascending
colon
13. Appendix
10 - Ileum
12. Descending colon