1. Digestion and absorption

2. Digestion Break-down of large foodstuff All components of food
Carbohydrates
Proteins
Fats
Monomer level
Process
Mechanical
Chemical

3. Absorption Amount of absorption Site of absorption
Ingestion (1.5 L) plus secretion (7 L)
83 % absorbed in the small intestine
Site of absorption
Stomach
Very poor
No absorptive villi/membrane
Large intestine
Proximal half
Water and electrolytes

4. Small intestine Increased surface size Folding (3 X) Villi (10 X)
Brush border (20 X)

5. Villus Adaptation for increased nutrient absorption Vasculature
Lymph vessel
Constant movement of microvilli

6. Hydrolysis Universal process
Break down of large molecules by addition of water
Break of the polymers into smaller fragments
Break bonds
Process
Different enzymes based on the macromolecule

7. Digestion of Carbohydrates
Starches
Maltose glucose polymers
Maltase + -dextinase
Glucose
Galactose
Lactose
Sucrose
Lactase
Fructose
Sucrase
- amylase (saliva)
pancreatic amylase

8. Location of digestion Mouth Stomach Small intestine
5 % of all starches
Stomach
Inhibition of amylase activity (too acidic)
30-40 % of starch converted to maltose
Small intestine
Amylase from pancreas
Enzymes on the enterocytes of villi

9. Absorption of carbohydrates
Glucose
80 % of carbohydrates being absorbed
Secondary active transport
Sodium-glucose co-transporter
Use of sodium concentration gradient as an energy
Concentration gradient generated by removal of sodium from intestinal epithelium to the blood

10. Other monosaccharides
Absorbed as they are
Converted to glucose

11. Digestion of proteins
(Stomach)
(Duodenum and jejunum)
(Enterocytes)

12. Absorption of proteins
Individual amino acids
99 % of final products of protein digestion
Transported via sodium-AA co-transporter
The same mechanism as glucose transport
Multiple transporter proteins to accommodate different amino acids
Some amino acids
Transported without co-transporters

13. Fat digestion Dietary fats Site of digestion and absorption
Triglycerides
Majority
Phospholipids
Cholesterol
Site of digestion and absorption
Small intestine

14. Process Emulsification Starts in the stomach
Majority takes place in the duodenum
Combination with bile products
Fragmentation of large molecules
Increased surface area

16. Cholesterol and phospholipids
Transport
Micelle
Cholesterol and phospholipids
Cholesterol esterase and phospholipase A2

17. Absorption of fats Monoglycerides and free fatty acids
Diffuse out of the micelle when contact with epithelial membrane
Enters SER and forms new triglycerides
Released into the central lacteal
Transported to the thoracic duct to enter the circulation
Short chain fatty acids
Directly into the circulation

18. Absorption of other materials
Water
Osmosis
Active transport
Calcium
Iron
Other ions

19. Sodium ions Active transport Diffusion Increased by aldosterone
Epithelium to paracellular spaces
Diffusion
From intestinal lumen to the epithelium
Increased by aldosterone

21. Effects of sodium absorption
Increased chloride ion absorption
Increased osmosis
Secretion of hydrogen ions
Counter-transport
Formation of carbonic acid
CO2 (dissolve in blood)
Water (excreted/reabsorved)

22. Absorption at the large intestine
Proximal half
Absorption
Sodium
Chloride
Water
Secretion
Bicarbonate ions
Counter-transport with chloride ions

23. Feces Dead bacteria (30 %) Fat (10-20 %) Inorganic matter (10-20 %)
Undigested plant matter (30 %)
Proteins (2-3 %)
Metabolic waste (bilirubin metabolites)

24. Abnormalities Esophagus Swallowing problem
Entrance of food materials into the respiratory system
Closure of glottis
Entrance of food materials into the nasal cavity
Failure of lower sphincter to relax
Achalasia

25. Stomach Inflammation of gastric mucosa (gastritis) Bacterial infection
Irritant substances
Damage to tight epithelial junction
Gastric ulcer

26. Gastric atrophy Triggered by chronic gastritis Loss of HCL secretion
Achlorohydria
Hypochlorohydria
Diminished secretion
Loss of pepsin function

27. Peptic ulcer
Imbalance between gastric secretion and gastric protection
Loss of mucosal barrier
Reduced acid neutralization
Excess gastric secretion
Causes
Chronic bacterial infections
Chemicals that increase gastric secretion and breakdown of mucosa

28. Small intestine Loss of digestion Pancreatitus Blockage of ducts
Excessive alcohol consumption
Blockage of ducts
Gallstone
Digestion of pancreas
Loss of pancreatic functions

29. Malabsorption of nutrients
Spruce
Idiopathic
Gluten enteropathy
Inflammation caused by infection
Malabsorption
Lipids
Vitamin K, folic acid, and B12
Calcium

30. Large intestine Constipation Obstruction of intestinal passage
Irregular bowel habits
Spasm of a small segment within the sigmoid colon
Insufficient ganglions
Megacolon

31. Diarrhea Enteritis Psychogenic Inflammation caused by infection
Irritation of mucosa
Excess secretion
Psychogenic
Excessive parasympathetic stimulation
Motility
Secretion

32. Vomiting Removal of materials from upper GI tract Sensory information
Excessive irritation
Overdistention
Overexcitation
Sensory information
Pharynx
Esophagus
Stomach
Upper small intestine

33. Nausea Irritation impulse from the GI tract
Impulse from the lower brain associated with motion sickness
Impulse from the cerebral cortex to initiate vomiting
Excitation of medulla near the vomiting center