Which of the following enzymes work most effectively at a very low pH?
A. Salivary amylase
B. Trypsin
C. Pepsin
D. Pancreatic amylase
E. Pancreatic lipase
In zero gravity environment of space, how does food swallowed by an astronaut reach her stomach?
A. Swallowing hard
B. Running around wheel creates -> artificial gravity
C. Involuntary muscle contractions
D. IV administration of nutrients
Which of the following organs is incorrectly paired with its function?
A. Stomach –protein digestion
B. Oral cavity -starch digestion
C. Large intestine –bile production
D. Small intestine –nutrient absorption
E. Pancreas –enzyme production
Salivary glands Secretes enzymes that digest carbohydrates
Liver Secretes molecules required for digestion of fats
Gall bladder Stores secretions from liver; empties into small intestine
Pancreas Secretes enzymes and other materials into small intestine
1. Mouth Mechanical and chemical processing (chewing reduces size of food; saliva digests carbohydrates)
2. Esophagus Transports food
3. Stomach Mechanical and chemical processing (digestion of proteins)
4. Small intestine Chemical processing and absorption (digestion of proteins, fats, carbohydrates; absorption of nutrients and water)
5. Large intestine Water absorption and feces formation
End of esophagus
Sphincter seals offstomach from esophagus
Sphincter seals offstomach from smallintestine
Lumen(interior)
Beginning ofsmall intestine
Layersof muscle
Stomach
HCO3– HCO3
–
Cl– Cl–
To blood
From blood
CO2 + H2O H2CO3
H+
Cl–
H+/K+ pump
Chloride channel
Cl–
H+
HClto lumen
Canal emptiesto lumenParietal cell
Secretion of HCI by parietal cells
K+
Enzymes, Hormones, other?
•Enzymes: pepsinogen (inactive)-> pepsin (protease) from chief cells
•Other: HCl -> denature ECM bacteria, from parietal cells, activator of pepsin•Other: Mucins/mucus protective from goblet or mucus cells•Other: mechanical churning -> acid chyme
•Hormones: Gastrin (+), CCK/secretin (-), enterogastrone (-- pyloric sphinct)
4. Lipase digests the small fat droplets into glycerol and free fatty acids.
DIGESTION OF LIPIDS IN SMALL INTESTINE
1. Large fat globules are not digested efficiently by lipase.
2. Bile salts (produced in liver) act as emulsifying agents.
3. Small fat droplets result from emulsification.
Lipase
Glycerol
Fatty acids
Lumen of small intestine
Na+
Glucose
Na+/glucose cotransporter
GLUT-2 transport protein
Na+/K+-ATPaseK+
K+
Blood
Osmosis
H2OOsmosis
ATP
ADP
Glucose
Basolateral side
Apical side
H2O
Na+
GlucoseGlycogen
Insulin causes cells in the liver and skeletalmuscle to synthesize glycogen; fat storage
cells synthesize triglycerides.
HOMEOTASIS(normal glucoselevels in blood)
Glucoselevels fall
Glucoselevels rise
GlucoseGlycogen
If glucoselevels too high
If glucoselevels too low
Glucagon causes cells in liver and skeletalmuscle to catabolize glycogen; fat storage
cells catabolize fatty acids.
Pancreas secretesGLUCAGON
Pancreas secretesINSULIN