The Digestive System 1
Digestion consists of reducing food to its constituent
parts and then absorbing the essential nutrients. Food
is broken down in the stomach and duodenum by the
action of enzymes released from the glands in the
mouth, stomach and pancreas. The absorption of
nutrients into the blood stream occurs mainly in the
small intestine. In the small intestine, water is
absorbed to leave semisolid waste which is passed via
the rectum as feces. The liver is the largest gland in
the body and is responsible for utilising the products of
digestion absorbed into the blood.
parotid gland
sublingual gland
submandibular
gland
esophagus
liver processes the products
of digestion
gallbladder
(stores bile)
liver
stomach mixes
food with enzymes
& acid
stomach
spleen
gallbladder
duodenum
pancreas
pancreas
secretes further
digestive
enzymes and
neutralizes
stomach acid
ileum (small
intestine)
colon (large
intestine)
appendix
rectum
anus
small intestine absorbs
nutrients into the
bloodstream
The stomach is a muscular bag
which mixes food received
from the oesophagus with
enzymes and acid secretions
from the stomach wall. The
food is reduced to a liquid,
which after several hours is
released into the duodenum by
the pyloric sphincter muscle. A muscle
thick mucous coat protects the layers
stomach lining from its own
acid.
folds of mucous
membrane
large intestine absorbs
water from waste material
esophagus
pyloric
sphincter
duodenum
www.physiquebodyshop.com
The Digestive System 2
A CROSS SECTION THROUGH
THE LIVER
gallbladder
hepatic duct
central vein
pancreas
bile duct
pancreatic
duct
duodenum
bile canaliculus
lobule
(mass of liver cells)
branch of hepatic duct
branch of portal vein
hepatic artery
lobule
The gallbladder stores bile made by
the liver and is released into the
duodenum in response to a fatty meal.
The pancreas secretes a number of
enzymes involved in the digestion of
proteins, carbohydrates and fats.
These
enzymes
pass via
the
pancreatic duct, which joins the bile
duct, into the duodenum.
The liver is an extremely complex gland with many vital functions. Through the
portal vein it receives nutrients absorbed from the intestines. It converts
poisonous ammonia compounds into nontoxic urea; it stores sugar for release into
the bloodstream when necessary; it synthesises complex proteins from simple
ones absorbed from food; it makes bile which is stored in the gallbladder and is
essential for fat absorption.
branch of
pancreatic
duct
cells
secrete
enzymes
into duct
TRANSPORTATION OF NUTRIENTS
muscle layers
thoracic
duct
superior vena cava
inferior vena cava
hepatic
vein
artery & vein
supplying
intestine
mucous membrane
bile
duct
pancreatic
duct
villi
The small intestine completes
digestion by absorbing nutrients.
The muscular intestinal walls
propel food along by “wavelike”
contractions
(peristalsis).
Numerous finger like villi absorb
fats (via the central lacteal) and
other nutrients (via the capillary
network).
portal
vein
thoracic
duct
MAGNIFIED VIEW OF VILLI OF
SMALL INTESTINE
central
lymph
vessel
(lacteal)
superior
mesenteric
vein
inferior
mesenteric
vein
muscle
fibres
meshwork
of capillaries
and veins
Numerous veins (right) transport nutrients from the intestines to the portal vein
which enters the liver. Materials processed by the liver drain into the inferior
vena cava for transport to the heart and around the body. Absorbed fats are
carried to the heart by the thoracic duct.
www.physiquebodyshop.com