Pancreas, Liver, GBand

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