Pancreas, Liver, GB
and
Small and Large
Intestine
Pancreas
• Found posterior to stomach
• Extends across the abdomen
• Only gland to produce enzymes to digest
every type of food
• Amylase – carbs
• Lipase – fats
• Proteinase - proteins
• Secretes enzymes into the duodenum
• Enzymes are mixed with an alkaline fluid that
neutralizes the acidic chyme coming from
stomach
• When chyme enters the duodenum the
hormone cholecystokinin is released to signal
the release of pancreatic juice
• Hormones also produced by the pancreas
• Insulin
• Glucagon
Gallbladder
• Pear shaped sac found in hollow of liver
• Bile made by liver is stored in gallbladder
• Bile storage sac (bile produced in liver)
• Bile digests fatty food - bile goes into the
duodenum from the gallbladder
• Cholecystokinin signals the gallbladder to
release bile
• Gallstones are crystallized cholesterol
which can cause blockages
Liver
• Largest gland in the body
• Located on the right side of the body
under the diaphragm
• Consists of four lobes suspended from the
diaphragm and abdominal wall by a
ligament
• Connected to the gallbladder via the
common hepatic duct
• Can regenerate if part of it is damaged or
removed
Metabolic Functions of the
Liver
• Store glycogen
• Convert glycogen to glucose
• Create new glucose
Metabolism of Carbohydrates
• Hyperglycemia—excessively high levels of
glucose in the blood
• Excess glucose is stored in body cells as
glycogen
• If blood glucose levels are still too high,
excesses are converted to fat
• Hypoglycemia—low levels of glucose in the
blood
• Liver breaks down stored glycogen and
releases glucose into the blood
Protein Metabolism
• Proteins are conserved by body cells
because they are used for most cellular
structures
• Amine groups are removed from proteins
as ammonia
• The rest of the protein molecule enters the
Krebs cycle in mitochondria
• The liver converts harmful ammonia to
urea which can be eliminated in urine
Fat Metabolism
• Fats and fatty acids are picked up by the
liver
• Uses some fats to make ATP
• The rest are broken down into simpler
compounds and released into the blood
• Body cells remove fat and cholesterol to
build membranes and steroid hormones
Fat Metabolism
• Most cholesterol is produced in the liver
(85%) and is not from diet (15%)
• Cholesterol is not used to make ATP
• Functions of cholesterol
• Serves as a structural basis of steroid
hormones and vitamin D
• Is a major building block of plasma
membranes
Role of the Liver in Metabolism
• Several roles in digestion
• Manufactures bile
• Plays a central role in carbohydrate, fat and
protein metabolism
• Stores glycogen and vitamins
• Produces cholesterol, blood proteins
(albumin and clotting proteins)
• Detoxifies drugs and alcohol
• Decomposes red blood cells
• Degrades hormones
Bile
• Produced by cells in the liver
• Composition is
• Yellow/green color – not an enzyme
• Salt
• Cholesterol
• Electrolytes
• Function—
• emulsify fats by physically breaking large fat
globules into smaller ones
• Breakdown Red Blood cells
Small Intestine
• The body’s major digestive organ
• Site of nutrient absorption into the blood
• Muscular tube extending from the pyloric
sphincter to the ileocecal valve
• Suspended from the posterior abdominal
wall by the mesentery
Subdivisions of the Small
Intestine
• Duodenum
• Attached to the stomach
• Curves around the head of the pancreas
• Finishes digestion – pancreas and GB
attached
Subdivisions of the Small
Intestine
• Jejunum
• Attaches anteriorly to the duodenum
• 2/5ths of absorption
• Ileum
• Extends from jejunum to large intestine
• 3/5ths of absorption
Small Intestine Anatomy
• Villi – increase surface area
• Villi—fingerlike structures formed by the
mucosa
• Microvilli—tiny projections of the
plasma membrane (create a brush
border appearance)
• Circular folds (plicae circulares)—deep
folds of mucosa and submucosa
Small Intestine Physiology
• All about absorption and transporting the
nutrients to the blood stream
• Peristalsis moves the chyme through the SI
to the LI through the ileocecal sphincter
Small Intestine Physiology
• Mucus – secreted by cells for easy passage
and to help absorption
• Peptidase – breaks down protein
• Sucrase – breaks down sugars
• Lipase – splits fats
Large Intestine
• Larger in diameter, but shorter in length,
than the small intestine
• Frames the internal abdomen
• Reabsorption of water and electrolytes
Large Intestine Anatomy
• Cecum—saclike first part of the large
intestine – attached to SI by ileocecal valve
• Appendix
• No digestive purpose
• lymphatic tissue that sometimes
becomes inflamed (appendicitis)
• Hangs from the cecum
Large Intestine Anatomy
• Colon
• Ascending—travels up right side of
abdomen
• Transverse—travels across the
abdominal cavity
• Descending—travels down the left side
• Sigmoid—enters the pelvis (S shaped)
• Rectum and anal canal —also in pelvis
Large Intestine Anatomy
• Anus—opening of the large intestine
• External anal sphincter—formed by
skeletal muscle and under voluntary
control
• Internal involuntary sphincter—formed
by smooth muscle
• These sphincters are normally closed
except during defecation
Large Intestine Anatomy
• No villi present
• Banded muscles
• Mucus – lubricate for feces passage
• Haustra (pocketlike sacs) – pouches for
holding fecal material
Large Intestine Physiology
• Little to no digestive function
• Vitamin B and K – bacteria living in LI
produce these vitamins
• Reabsorb water, vitamins and minerals
Large Intestine Physiology
• Peristalsis and mixing occur 2-3 times a
day
• Mass Movement – movement of material
happens in large sections that constrict at
once
• Defecation reflex – forces out rectum
when sphincter relaxes