Anatomy

Question 1

basic anatomy of the digestive tract

Answer 1

mouth 
esophagus 
stomach 
small intestine 
large intestine 
rectum 
anus

Question 2

where does digestion begin?

Answer 2

in the mouth with alpha amylase in the saliva- breaks down starch into polysaccharides.

Question 3

what is chewed food called?

Answer 3

bolus! : pushed into the esophagus by swallowing and then moved down the esophagus via peristaltic action.

Question 4

does digestion occur in the esophogous?

Answer 4

no

Question 5

how is chyme made?

Answer 5

stomach mixes and stores food reducing it to a semifluid mass called chyme .
important function of the stomach is to start protein digestion with the enzyme pepsin.

Question 6

what are the four major cell types in the stomach?

Answer 6

• mucous cells
• chief (peptic cells)
• parietal cells
• G cells.

Question 7

what do the mucous cells do?

Answer 7

line the stomach wall , lubricate the stomach walll so that food can slide along its surface without causing damage and mucous protects the epithelial lining from the acidic env of the stomach.

Question 8

what do the chief cells do?

Answer 8

are found deep in the exocrine glands. they secrete pepsinogen , which is a zymogen precursor to pepsin. pepsinogen is activated to pepsin by the low pH of the stomach . once activated pepsin begins protein digestion

Question 9

what do the parietal cells do?

Answer 9

secrete HCL

they also secret intrinsic factor which helps the ileum absorb B12

Question 10

What do the G cells do?

Answer 10

secret gastrin. gastrin is a peptide hormone which stimulates parietal cells to secrete HCL.

Question 11

what are the major hormones that affect the secretion of the stomach juices?

Answer 11

acetylcholine- increases the secretion of all cell types
gastrin
histamine
gastrin and histamine mainly increase HCL secretion.

Question 12

about 90% of the digestion and the absorption occurs in the ?

Answer 12

small intestine.

the SI is divided into 3 parts , from smallest to largest : duodenum, jejunum and ileum.

Question 13

most of the digestion occurs in which part of the SI?

Answer 13

duodenum

Question 14

where does most of the absorption occur?

Answer 14

jejunum and ileum.

Question 15

the SI wall has finger like projections called villi

Answer 15

villi inc the SA allowing for greater digestion and abs .

Question 16

on the apical surface (lumen side) surface of the cells of each villus are much smaller finger like projections called microvilli

Answer 16

the microvilli inc the SA of the intestinal wall still further.
under the microscope the microvilli appear as a fuzzy covering which is called the brush border. the brush border has membrane bound digestive enzymes.

Question 17

goblet cells in the intestine are epithelial cells

Answer 17

they secrete mucus to lubricate the intestine and help protect the brush border from mechanical and chemical damage.

Question 18

the semifluid chyme is squeezed out of the stomach thru the pyloric spinster and into the duodenum. the fluid inside the duodenum has a pH of 6 mainly due to bicarb ion secreted by the pancreas.

Answer 18

pancreas also acts as an exocrine gland releasing enzymes through the pancreatic duct into the duodenum

Question 19

the major enzymes released by the pancreas are:

Answer 19

trypsin
chymotrypsin 
pancreatic amylase 
lipase 
ribunuclease
deoxyribonuclease
all enzymes are released as zymogens . 
trypsin is activated by the enzyme enterokinase located 
in the brush border. activated trypsin then activates other enzymes

Question 20

trypsin and chymotrypsin do what?

Answer 20

degrade proteins into small polypeptides.

Question 21

what does pancreatic amylase do?

Answer 21

like salivary amylase, it hydrolyzes polysaccharides into disaccharide and trisaccharides. however the pancreatic amylase is much more powerful.

Question 22

what does lipase do?

Answer 22

breaks down fat, specifically triglycerides.

Question 23

where is bile made and stored?

Answer 23

made in the liver and stored in the gall bladder.

the gall bladder releases bile though the cystic duct, which empties into the common bile duct shared with the liver.

Question 24

what does bile do?

Answer 24

emulsify the fat. this inc the SA of the fat, allowing the lipase to degrade it .

Question 25

what does bile contain?

Answer 25

bilirubin! - end product of hemoglobin breakdown. much of the bile is reabsorbed by the small intestine and is transported back to the liver.

Question 26

the large intestine or the colon has 4 parts:

Answer 26

ascending colon, transverse colon , descending colon, sigmoid colon

Question 27

what are the major function of the large intestine?

Answer 27

water absorption , electrolyte absorption

when this function fails, diarrhea occurs.

Question 28

the large intestine has Ecoli , what does E coli do?

Answer 28

produces Vitamin K, B12, thiamin and riboflavin

Question 29

what local peptide hormones are secreted by the small intestine after a meal?

Answer 29

secretin
cholecystokinin
gastric inhibitory peptide
each of these hormones inc blood insulin levels esp in presence of glucose.

Question 30

what does the gastric inhibitory peptide do?

Answer 30

is released in response to fat and protein digestates in the duodenum and to a lesser extent in response to carbs.

Question 31

what causes secretin release?

Answer 31

HCL in the stomach!

secretin stimulates sodium bicarb secretion by the pancreas

Question 32

what causes the release of cholecystokinin?

Answer 32

food in the upper duodenum. especially fat digestates
cholecystokinin causes gallbladder contraction and pancreatic enzyme secretion.
it also decreases the motility of the stomach allowing the duodenum more time to digest fat.

Question 33

enterokinase does what?

Answer 33

converts trypsinogen to trypsin

Question 34

what does lactase do?

Answer 34

converts lactose into galactose and glucose.

Question 35

what does sucrase do?

Answer 35

converts sucrose to fructose and glucose.

Question 36

can cellulose be digested by humans?

Answer 36

no

Question 37

how is glucose absorbed?

Answer 37

by secondary active transport down the concentration gradient of sodium. sodium is actively pumped out of the enterocyte on the basolateral side. the low sodium in the enterocyte drags sodium into the cell through a transport protein, but only after glucose has also attatched itself to the protein. as the concentration of the glucose builds inside the cell, it moves out of the cell on the basolateral side via facilitated transport. at high concentrations of lumen plc, glucose builds up in the paracellular space and raises the osmotic pressure there. the aqueous solution of the lumen is dragged into the paracellular space pulling glucose along with it. glucose is abs by this second method only when present in high concentrations

Question 38

all carbs are absorbed into the bloodstream and carried by the portal vein to the?

Answer 38

liver ! : whose job is to maintain constant glucose level.

Question 39

in all cells except ___ glucose is transported from high concentration to low concentration via facilitated diffusion

Answer 39

except enterocytes and cells of the renal tubule

Question 40

when glycogen stores are full, glucose is converted to

Answer 40

fat - long term form of energy storage

Question 41

where does the conversion of glucose to fat take place?

Answer 41

in the liver and adipocytes and stored in the adipocytes

Question 42

fat is insoluble in water so requires a carrier ..

Answer 42

which can be a lipoprotein or albumin

Question 43

what are the 4 types of lipoproteins ?

Answer 43

very low density lipoproteins
intermediate density lipoproteins
low density lipoproteins
high density lipoproteins
all are made from triglycerides, cholesterol , phospholipids and protein.
as the density increases the amount, the amount of triglycerides decrease .
the very low density triglycerides have a lot of triglycerides.

Question 44

fats are broken down into?

Answer 44

monoglycerides! and then put back together again into triglycerides.

Question 45

The liver receives blood from?

Answer 45

beds of the intestines, stomach, spleen and pancreas via the hepatic portal vein. this blood is worked upon by the liver. a second blood supply which oxygenates the liver is received through the hepatic artery

Question 46

all blood recieved by the liver moves through large flattened spaces called hepatic sinusoids and collects in the hepatic vein , which leads to ..?

Answer 46

vena cava

Question 47

what are the functions of the liver?

Answer 47

blood storage : liver can expand to act as a blood reservoir for the body
blood filtration: kupffer cells phagocytize bacteria picked up from the intestines
carb metabolism
fat metabolism: liver makes bile from cholesterol and coverts carbs and proteins into fat. it oxidizes fatty acids for energy and forms most lipoproteins
protein metabolism: dominates aa, forms urea from ammonia , makes plasma proteins like fibrinogen, prothrombin, albumin, and most globulins and it makes non essential aa.
detoxification: detoxified chemicals are excreted by the liver as part of bile or polarized so the kidney can remove them
erythrocyte destruction : kupffer cells also destroy irregular erythrocytes, but most irregular erythrocytes are destroyed by the spleen
vitamin storage: vitamin A,D B12. liver also stores iron combining it with protein apoferritin to form of ferritin.

Question 48

what happens when the liver mobilizes fat for energy?

Answer 48

it makes acids called ketone bodies! this often results in condition called ketosis or acidosis.
so know that when the liver moves fat or protein for energy the blood acidity will increase.