Digestive System
DIGESTIVE SYSTEM
Main function:
• Breaks down food into
nutrients that can be
absorbed by body cells
• Peristalsis = contraction &
relaxation of the smooth
muscle in digestive tract;
helps to move the food
down
(said ‘peri stahl sis’)
• Mouth = teeth ↑ surface
area of food ; salivary
glands produce enzyme
amylase which begins to
break down carbohydrates
• Uvula = prevents food
from entering the nasal
cavity
• Epiglottis = prevents food
from entering the trachea
(chewing while talking or with mouth
open allows the epiglottis to remain open
and therefore increases your likelihood of
choking or having your food/drink ‘go
down the wrong pip’
• Esophagus = takes the swallowed food
into the stomach
• Stomach = continues to break down
carbohydrates and digestion of proteins
begins (contains HCl & enzyme pepsin)
(HCl is hydrochloric acid)
• Small intestine =
– digestion of carbohydrates &
proteins continues and ends
– digestion of fats begins & ends
– uses bile and many digestive
enzymes
– broken down nutrients pass through
the intestinal walls into the
bloodstream
Small Intestine Cont.
• 7 m long (1 meter is about the width of a doorway)
• 1st part = duodenum, receives bile from gallbladder
& digestive enzymes from pancreas (25 cm)
• 2nd part = jejunum (2.5 m)
• 3rd part = ilium (3.5 m)
Small Intestine Cont.
• Large surface area due to the presence of villi
• Villi – one cell thick; ↑ surface area for diffusion
• Next to each villus are blood vessels which carry
nutrients to other cells of the body
• Liver = secretes bile needed for
digestion of fats
• Gallbladder = stores bile &
releases it into small intestine
• Pancreas = releases digestive
enzymes into small intestine
• Large intestine (colon) = water
is removed from the undigested
food
• Rectum = last 8 inches of the
large intestine; pass the
undigested food out of the body
through anus
Action of Bile
• Emulsifies (breaks down) fats (↑ surface area to help
enzyme action)
• Bile also neutralizes any excess stomach acid
(C.H.O.)
carbohydrase
Glucose
and simple
sugars
WATER
PROTEINS
CARBOHYDRATES
FATS + OILS
(C.H.O.)
lipase
Glycerol
and fatty
acids
(C.H.O.N.)
protease
Amino
acids
VITAMINS + SALTS
(H2O)
(various elements)
Keeping
the body in
good
health
excess
Many uses
in the body
Excess broken
down in liver
Excess
stored in
liver as
glycogen
Energy
produced in
cell
respiration
Stored
under the
skin
Form
proteins in
the body
urea
glucose
Passed to the
kidneys by blood
for removal as
urine
Some out in
sweat
How much do we remember?
1.
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4.
5.
What enzyme is in saliva?
What does this enzyme help break down?
What type of food is broken down in the stomach?
What happens to food that can’t be digested?
What is the function of bile?
Talk about the questions and answers with a friend.