Download Comparative Vertebrate Physiology

Human Anatomy and
Physiology
Digestion and absorption of nutrients
Digestion of carbohydrates

Hydrolysis

Tri- and disaccharides
Monosaccharides
monosaccharides
Disaccharide
Digestion of carbohydrates

Sources



Sucrose (sugar), lactose (milk), starches (non-animal
products)
Fiber not digested by humans
Areas of breakdown



Mouth (salivary amylase)
Duodenum (pancreatic amylase)
Intestine (enterocytes - lactase, sucrase, maltase,
a-dextranase)
Digestion of carbohydrates
Digestion of proteins

Proteins
peptides
Stomach
Small intestine
amino acids
Small intestine
Digestion of proteins

Sources



Dietary (plants and animals)
Endogenous (enzymes, hormones, dead cells)
Areas of breakdown



Stomach (pepsin)
Duodenum (pancreatic secretions)
Intestine (enterocytes - peptidases)
Digestion of proteins
Stomach
Small
intestine
Digestion of fats


Triglycerides (neutral fats)
In blood: Triglycerides
fatty acids and 2 monoglycerides
fatty acids and glycerol
Digestion of fats

Sources


Area of breakdown -emulsion




Dietary - animal and plants
Mechanical disruption by stomach
Small intestine (bile emulsifies triglycerides, lipase
converts them into fatty acid and monoglyceride)
Lecithin prevents reaggregation
Digestion of triglycerides by pancreatic lipase
Digestion of fats
Small
intestine
Blood
Enterohepatic circulation

Bile pathway
 Liver, common hepatic
duct, gall bladder
(storage)
 Common bile duct,
duodenum, sphincter of
Oddi
 Absorption (95%),
hepatic portal vein, liver
Common
Hepatic
Duct
Fluid absorption

~ 8.2 liters of fluid into the tract (98.5% is
absorbed)
 Input


Absorbed


Intake 1.5L, salivary gland 1.0L, stomach 1.5L,
liver 1.0L, pancreas 1.0L, small intestine 2.0L,
colon 0.2L
Small intestine 7.2L, colon 0.85L
Output

Feces 0.15L
Absorption

Monosaccharides


co-transported with sodium by protein
transporters
Amino acids

similar mechanism
Absorption of lipids





Fatty acids and monoglycerides
diffuse into cell
Converted to triglyceride
Enter ER and Golgi - chylomicron
Exocytosis into lacteal
Eventually empty into neck veins
Absorption in the colon

Proximal


Distal



Sodium is actively absorbed
Secretion of bicarbonate (neutralizes acid from
bacterial action)
Absorption of chloride
Resultant gradient allows passive water
absorption leading to dry feces
Absorption in the colon
Disorders of the colon

Constipation




Decreased colon motility
Colon distention with fiber
Laxatives: decrease water absorption
Diarrhea


Increased colon motility, irritants
Decrease in water absorption, or water
secretion into the tract
Lactose intolerance

Small intestine
lactose
glucose + galactose
lactase
lactose
lactase
lactose
osmotic
gradient
water absorption
water uptake
distension,
cramps,
diarrhea