Digestion Lecture 29

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hepatocytes

arranged in lobules

sinusoids

--- in between hepatocytes are blood-filled spaces

kupffer cells

--- phagocytize microbes and foreign matter

bile

Pathway of --- Secretion:
-Bile canaliculi
-Hepatic ducts
-Common Hepatic duct
-Cystic duct from gallbladder and common hepatic duct join to form common bile duct
-Common bile duct and pancreatic duct empty into duodenum

gluconeogenesis

Liver functions in carbohydrate metabolism: turn amino acids into glucose

gluconeogenesis

Liver functions in carbohydrate metabolism: turn triglycerides into glucose

glycogenesis

Liver functions in carbohydrate metabolism: turn excess glucose into glycogen and store in the liver

glycogenolysis

Liver functions in carbohydrate metabolism: turn glycogen back into glucose as needed

Liver

--- Functions in lipid metabolism:
-Synthesize cholesterol
-Synthesize lipoproteins such as HDL and LDL, which are used to transport fatty acids and chlesterol in the bloodstream
-Stores some fat
-Breaks down some fatty acids

Deamination

Liver functions in protein metabolism:
---: removes NH2 (amine group) from amino acids so can use what is left as energy source
-Converts resulting toxic ammonia (NH3) into urea for excretion by the kidney

Transamination

Liver functions in Protein Metabolism:
---: Converts one amino acid into another
-Synthesizes plasma proteins utilized in the clotting mechanism and immune system

Detoxifies

Other liver functions: --- the blood by removing or altering drugs & hormones (thyroid & estrogen)

bilirubin

Other liver functions:
Removes ---: a waste product of red blood cell breakdown

bile salts

Other liver functions:
Releases --- to help digestion by emulsification of lipids

fat

Other liver functions:
Stores --- soluble vitamins, including A D E K

iron

Other liver functions:
Stores --- copper and vitamin B12

phagocytosis

Other liver functions:
--- of worn out blood cells and bacteria

vitamin d

Other liver functions:
Activates --- part of the vitamin activation pathway

Hepatitis

Liver disease:
Inflammation of the liver that can be caused by a variety of viruses, drugs or alcohol
- can lead to cirrhosis

Cirrhosis

Liver disease:
Scarred liver caused by chronic inflammation due to hepatitits, chemicals, parasites or alcohol

Pancreatic Juice

Composition and Functions of ---
1.5 quarts/day at pH 7.1 to 8.2
-contains water, enzymes & sodium bicarbonate
-Digestive enzymes: pancreatic amalyase, pancreatic lipase

trypsinogen

proteases: --- activated by enterokinase (a brush border enzyme)

chymotrypsinogen

proteases: --- activated by trypsin 1

procarboxypeptidase

proteases: --- activated by trypsin 2

proelastase

proteases: --- activated by trypsin 3

trypsin inhibitor

proteases: --- combines with trypsin produced inside pancreas

ribonuclease and deoxyribonuclease

proteases: --- digest nucleic acids

Secretin

Regulation of Pancreatic Secretion:
acidity in intestine causes increased sodium bicarbonate release

CCK

Regulation of Pancreatic Secretion:
Fats and proteins cause increased digestive enzyme release

smooth muscle

Function of the Large Intestine:
Mechanical digestion

peristaltic waves

Function of the Large Intestine:
3 to 12 contractions/minute

haustral churning

Function of the Large Intestine:
relaxed pouches are filled from below by muscular contraction; when full, they contract and move contents to next pouch

bacteria

Function of the Large Intestine:
--- ferment undigested carbohydrates into carbon dioxide & methane gas, and undigested proteins into simpler substances

Gastroilial reflex

Function of the Large Intestine:
when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty into large intestine

gastrocolic reflex

Function of the Large Intestine:
when stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum

defecation

-Gastrocolic reflex moves feces into rectum
-Stretch receptors signal sacral spinal cord
-parasympathetic nerves contract muscles of rectum and relax internal anal sphincter
- external anal sphincter in voluntarily controlled

diarrhea

Digestive Health:
-chyme passes too quickly through intestine
-H2O not absorbed

constipation

Digestive Health:
-decreased intestinal motility
-too much water is absorbed
-remedies are fiber, exercise and water

insoluble fiber

Digestive Health Fiber:
-Woody parts of plants (wheat bran, vegetable skins)
-Speeds up transit time & reduces colon cancer

soluble fiber

Digestive Health Fiber:
-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 bils

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