Digestive System

Front 1

Pathway of ingested food

Back 1

Mouth→pharynx→esophagus→stomach→small intestine (duodenum, jejunum, ileum)→large intestine→colon (ascending, transverse, descending, sigmoid)→rectum→anus

Front 2

2 processes of digestive breakdown

Back 2

1) Mechanical--teeth, tongue, stomach

2) Chemical-almost everywhere

Front 3

2 digestive properties of mouth

Back 3

1) Salivary α-amylase breaks down starch→maltose (disaccharide)

2) Mechanical breakdown and formation of BOLUS

Front 4

Pharynx

Back 4

Location of the epiglottis which directs bolus down esophagus away from the trachea

Front 5

Esophagus

Back 5

-serves as conduit for bolus, contracting smooth muscle through peristalsis action

-no enzymatic function

Front 6

What is the common reaction in digestion of macromolecules?

Back 6

Hydrolysis

Front 7

Bile function

Back 7

-Complex non-enzymatic alkaline mixture of substances that emulsify large clumps of fat→small fat molecules to ↑ SA for lipase action

-Produced in liver→cystic duct→gallbladder→ common bile duct→pancreatic duct→duodenum

Front 8

Bile is produced and stored in the gallbladder (T/F)

Back 8

False. It is produced in the liver and stored in the gallbladder.

-Produced in liver→cystic duct→gallbladder→ common bile duct→pancreatic duct→duodenum

Front 9

What separates the esophagus and stomach?

Back 9

Cardiac sphincter or lower esophageal sphincter

Front 10

Stomach function

Back 10

-flexible pouch that mixes and stores food→chyme

-low pH (~2) → denatures proteins & kills bacteria

Front 11

What are the 4 major cell types of the stomach?

Back 11

1) mucous cells: secrete mucous; lubrication+damage control

2) chief (peptic) cells: found in deep exocrine glands; secrete pepsinogen→pepsin in stomach

3) parietal (oxyntic) cells: secrete HCl, use lots of mitochondria for manufacture. H+ into lumen and bicarbonate into blood (↓ lumen pH, ↑ blood pH). Also secretes intrinsic factor→helps ileum absorb B12

4) G cells: secretes gastrin into interstitium→ absorbed in blood→stimulates parietal cells to secrete HCl

Front 12

What 3 hormones affect secretion of stomach juices?

Back 12

-acetylcholine: all cell types

-gastrin: parietal cells→HCl

-Histamin: parietal cells→HCl

Front 13

Pepsin

Back 13

Digests proteins→polypeptides

Front 14

90% of digestion and absorption takes place in the ___?

Back 14

Small intestine
-duodenum→ digestion
-jejunum and ileum→ absorption

Front 15

What is villi and what does each contain?

Back 15

-villi ↑ SA of intestinal wall allowing for greater digestion and absorption

-each contains microvilli, enterocytes (apical side), capillary network and a lacteal (lymph vessel)

Front 16

The brush border contains numerous enzymes (T/F)

Back 16

True.
Some include: dextrinase, maltase, sucrase, lactase, peptidases, nucleosidases

Front 17

Goblet Cells

Back 17

Secrete mucous in the intestine
-helps protect brush border from mechanical/chemical damage

Front 18

Crypts of Lieberkuhn

Back 18

-intestinal exocrine glads located deep btwn each villi

-secretes: -intestinal juice pH 7.6
-lysozyme→regulate bacteria
-enteropeptidase

Front 19

What separates the stomach and small intestine?

Back 19

Pyloric sphincter

Front 20

The pH of the small intestine is mostly due to what ion?

Back 20

Bicarbonate secreted by pancreas
-buffers intestine at a pH ~6

Front 21

Enteropeptidase or Enterokinase

Back 21

-activates zymogen trypsinogen→trypsin

-secreted by the crypts of Lieberkuhn

Front 22

Major protein enzymes

Back 22

-trypsin
-chymotrypsin
-carboxypolypeptidase (cleaves aa sides)

Front 23

Major carbohydrate enzymes

Back 23

-salivary amylase: degrades starch into small polypeptides

-pancreatic amylase: more powerful enzyme that hydrolyzes polysaccharides→di/trisaccharides

-Others: dextrinase, maltase, sucrase, lactase

Front 24

Major nucleotide enzymes

Back 24

-ribonuclease
-deoxynuclease

Front 25

Lipase

Back 25

Degrades fats, specifically TRIGLYCERIDES

Front 26

Major functions of large intestine

Back 26

-water resorption

-electrolyte resorption

-symbiosis with bacteria for bacteria production

Front 27

What 4 vitamins do E. Coli produce in the large intestine?

Back 27

-Vitamin K
-B12
-Thiamin
-Riboflavin

Front 28

Gastrointestinal local peptide hormones: Name and function.

Back 28

Secretin- Stimulates pancreatic NaHCO3 secretion. Activated by HCl in duodenum

Cholecytokinin- Causes gallbladder contraction and pancreatic enzyme secretion. Stimulated by food (fats)

Gastric Inhibitory peptide- decreases motor activity of stomach. Stimulated by fats/proteins (some carbs) in duodenum.

Front 29

Common main function of gastrointestinal local peptide hormones. When is it released?

Back 29

-Regulates process of stomach releasing small amounts of food at a time for maximum absorption

-Released after a meal. INCREASES BLOOD INSULIN.

Front 30

Major carbohydrates consumed in human diet

Back 30

-starch: straight chain of glucose
-lactose: disaccharide of glucose+galactose
-sucrose: disaccharide of glucose+fructose

Front 31

Carbohydrate absorption of glucose, galactose, and fructose

Back 31

Glucose: Active transport into enterocyte down Na+ gradient (glucose binds protein first). Under high [glucose], diffuses through tight junctions to basolateral side

Galactose: similar to glucose

Fructose: absorbed via facilitated diffusion. Most fructose→glucose inside enterocyte

Front 32

What happens to digested carbs after absorption into enterocytes?

Back 32

Facilitated diffuse through enterocyte into portal vein to the liver:
-converted to glucose, glycogen, or fatty acids & triglycerides if saturation point of glycogen is reach

Front 33

All cells absorbed glucose via facilitative diffusion (T/F)

Back 33

False. ALMOST ALL except:
-apical surface of enterocytes
-cells of the renal tubule

Front 34

How does enterocyte keep Na+ levels low for active transport of glucose into cell?

Back 34

-Na+/K+ pump: pumps Na+ out on basolateral surface

Front 35

Where are polypeptides first digested?

Back 35

In the stomach by pepsin

Front 36

Absorption of digested proteins occurs via ___? (2)

Back 36

-cotransport down Na+ gradient in entercytes (similar to glucose)

-some aa are transported via facilitated diffusion

Front 37

Once broken down into amino acids in enterocytes and absorbed into blood via portal vein, amino acids may be transported into cells by facilitated, active, or passive means. (T/F)

Back 37

False.
-Too LARGE and POLAR to passively diffuse

-Cells quickly turn aa→proteins to lower cellular [aa]

Front 38

Virtually all polypeptides are broken down into amino acids before absorbed into blood. (T/F)

Back 38

True.
-protein that is not broken down may cause allergic rxns

Front 39

Energy burned measured in cal/g of: protein, fat, and carbohydrate

Back 39

Protein: 4 cal/g

Fat: 9 cal/g

Carbohydrates: 4.5 cal/g

Front 40

Micelle significance in small intestine

Back 40

-Shuttles monoglycerides & FA from intestinal lumen→brush border

-responsible for the absorption of complicated lipids (e.g, lecithin, hyrdrolyzed cholesterol/phospholipids) and lipid soluble vitamins (A, D, E and K)

Front 41

Albumin

Back 41

"molecular taxi"
-Free fatty acids (3-30) are transported in the blood bound to albumin, a serum protein secreted by the liver

Front 42

Apoproteins

Back 42

Bind lipids to make up LIPOPROTEINS

Front 43

Lipoproteins & chylomicron

Back 43

-Differ in ratio of protein to lipids, and in the particular apoproteins and lipids that they contain. -They are classified based on their density:
-chylomicron (largest; lowest in density due to high lipid/protein ratio; highest in triacylglycerols as % of weight)
-VLDL (very low density lipoprotein; 2nd highest in triacylglycerols as % of weight)
-IDL (intermediate density lipoprotein)
-LDL (low density lipoprotein, highest in cholesteryl esters as % of weight)
-HDL (high density lipoprotein, highest in density due to high protein/lipid ratio).

Front 44

Pathway of digested lipid absorption

Back 44

Fats + bile→emulsified fats + lipase→MGs, FAs packaged & shuttled by micelle to brush border→diffuse through enterocyte membrane→MGs, FA's converted back to TGs at SER→FA's, cholesterol, etc orient into micelle in lumen & transported by apoprotein to golgi→exocytosis of "chylomicrons" into lacteal lymph system→thoracic duct→ liver and adipose tissue

Front 45

All fatty acids are are directed to the lymph system

Back 45

False.
-small amounts of more water soluble (short chain) FAs are absorbed directly into blood of villi