Lecture #27: Digestive Syste--Pancreas, Liver, and Large Intestine

Question 1

What enteroendocrine cells are secreted in the pancreas?

Answer 1

Secretin: acidity in intestine causes increased sodium bicarbonate release

CCK (Cholesystokinin): fats and proteins cause increased digestive enzyme release

Question 2

What are the major exocrine secretions of the pancreas?

Answer 2

• Pancreatic Juice (1200-
1500mL per day)
– Clear colorless liquid (pH of
7.1 to 8.2) consisting of:
1. water
2. salts
3. sodium bicarbonate
4. several enzymes 

Enzymes secreted by the
pancreas

Question 3

What enzymes are secreted by the pancreas?

Answer 3

1. Pancreatic AMYLASE
2. Trypsin
3. Chymotrypsin
4. Carboxypeptidase
5. Elastase
6. Pancreatic LIPASE
7. Ribonuclease
8. deoxyribonuclease

2-5 are proteases-secreted as inactive precursors (like pepsinogen in the stomach)

7-8 are nucleases

Enteropeptidase (on brush-border cells) activates trypsinogen to trypsin.
Trypsin then activates chymotrypsinogen, procarboxypeptidase & proelasease

Question 4

What are the functions of the liver?

Answer 4

• Metabolism of carbohydrates, proteins & lipids
• Detoxifies the blood by removing or altering drugs & hormones (thyroid & estrogen)
• Removes bilirubin (waste product of red blood cell breakdown)
• Releases bile salts to help digestion by emulsification of lipids
• Stores fat-soluble vitamins (A, D3, E, K)
• Stores iron, copper and vitamin B12
• Phagocytosis of worn out blood cells and bacteria
• Plays a role in the vitamin D activation pathway

Question 5

Draw and describe the blood flow through the liver.

Answer 5

In the liver, blood from the hepatic arteries and hepatic portal vein mixes, and the mixed blood flows through the sinusoidal capillaries of the liver before returning to venous circulation.

Question 6

What is the liver lubule consist of?

Answer 6

• Hepatocytes are the primary cells of the
liver, doing most of the work.

• Hepatocytes arranged in grids in lobules
• Spaces between hepatocytes are either blood-filled sinusoids or bile canaliculi.

• Kupffer cells phagocytize
microbes and foreign matter

Question 7

What is the pathway of bile secretion?

Answer 7

• Bile canaliculi join to
form bile ducts which
form the hepatic ducts

• L & R hepatic ducts form
the common hepatic duct

• The cystic duct from
gallbladder and the
common hepatic duct
join to form common bile
duct

• Common bile duct &
main pancreatic duct
empty into duodenum

Question 8

What happens in the metabolic functions of the liver if it has carbohydrate metabolism?

Answer 8

• Turn amino acids into glucose -gluconeogenesis
• Turn triglycerides into glucose -gluconeogenesis
• Turn excess glucose into glycogen & store in the liver - glycogenesis
• Turn glycogen back into glucose as needed - glycogenolysis

Question 9

What happens in the metabolic functions of the liver if it has lipid metabolism?

Answer 9

• Synthesize cholesterol

• Synthesize lipoproteins,
such as HDL and LDL, which
are used to transport fatty
acids and cholesterol in the
bloodstream

Stores some fat

• Breaks down some fatty
acids

Question 10

What happens in the metabolic functions of the liver if it has protein metabolism?

Answer 10

• Deamination: removes -NH2
(amine group)
from amino acids so we can use what is left
as an energy source

• Converts resulting toxic ammonia (NH3) into urea for excretion by the kidney
• Transamination: converts one amino acid into another
• Synthesizes plasma proteins utilized in the clotting mechanism and immune system

Question 11

What is hepatitis?

Answer 11

• Inflammation of the liver that
can be caused by a variety of
viruses, drugs or alcohol

• Can lead to cirrhosis

Question 12

What is Cirrhosis?

Answer 12

• Scarred liver caused by chronic inflammation due to hepatitis, chemicals, parasites or alcohol

Question 13

What is the function of the large intestine?

Answer 13

• smooth m. - mechanical digestion

• peristaltic waves (3 to 12
contractions/minute)

• haustral churning - relaxed pouches are filled from below by muscular contractions; when full, they contract and move contents to next pouch

• bacteria ferment undigested
carbohydrates into carbon dioxide & methane gas, and undigested proteins into simpler substances

Question 14

What reflexes are in the large intestine?

Answer 14

Gastroilial reflex
Gastrocolic reflex
Defecation reflex

Question 15

What is Gastroilial reflex?

Answer 15

when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty into large intestine

Question 16

What is Gastrocolic reflex?

Answer 16

when stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum

Question 17

What is defecation reflex?

Answer 17

when rectum fills, input to sacral spinal cord return commands to expel feces

Question 18

What happens in the defecation reflex?

Answer 18

• Gastrocolic reflex moves feces
into rectum

• Stretch receptors signal sacral
spinal cord

• Parasympathetic nerves contract
muscles of rectum & relax
internal anal sphincter

• External anal sphincter is
voluntarily controlled

Question 19

What is Diarrhea?

Answer 19

– chyme passes too quickly
through intestine

– not enough H20 is absorbed

Question 20

What is Constipation?

Answer 20

– decreased intestinal motility

– too much water is absorbed

– remedies are fiber, exercise
and water

Question 21

What is insoluble fiber?

Answer 21

– woody parts of plants (wheat
bran, vegetable skins)

– speeds up transit time &
reduces colon cancer

Question 22

What is soluble fiber?

Answer 22

– gel-like consistency - beans,
oats, citrus white parts, apples

– lowers blood cholesterol by
preventing reabsorption of bile
salts so liver has to use
cholesterol to make more bile