Dietary lipids are primarily triglycerides ingested from plants and animals. They provide energy and material for cell growth. Lipids cannot be absorbed in their original form due to their insolubility in water. Digestion and absorption of lipids involves emulsification by bile salts and hydrolysis by pancreatic lipases. In the small intestine, pancreatic lipase breaks down triglycerides into fatty acids and monoacylglycerols. Bile salts form micelles to solubilize the breakdown products allowing absorption across the intestinal walls. Defects in emulsification, digestion, or absorption can result in excess fat in stool known as steatorrhea.

1. DIGESTION &ABSORPTION
OF
LIPIDS

2. • Dietary lipids – derived from plants
and animals.
• Essential for growth and
development.
• They are oxidized for energy or
stored as reserve fat in adipose
tissue.

3. FFA, 3%PL 5%cholesterol, 2%
TAG, 90%
Dietary Lipid contents
Triacylglycerols Cholesterol Phospholipid FreeFattyAcid
•Adult ingest about 60-150g of lipids per day.
• >90% of fat intake is as triacylglycerols.

4. DIGESTION
OF LIPIDS
• Lipid molecules are not soluble in
aqueous solution.
• Enzymes are soluble in aqueous
medium.
• Digestion of lipid presents a problem.
• This problem is solved by
emulsification of lipids by bile salts.

5.  Lingual lipase- secreted by dorsal
surface of tongue.
 But this enzyme is not significant in
humans.
 Little or no digestion of lipids occur
in mouth.

6. Gastric lipase secreted by stomach.
Hydrolyses TAG molecules,
especially short & medium chain
fatty acids.
In adults, stomach pH is acidic,
dietary lipids are not digested in
stomach.
Lipids requires neutral pH for
digestion.

7. •Acidic chyme containing dietary fat
contents passes from stomach to
duodenum.
•Stimulates the secretion of 
1.Cholecytokinin (CCK)
2.Secretin

8. Act on pancreas
release
bicarbonate
CHOLECYTOKININSECRETIN
Acts on gallbladder
 release bile
Acts on pancrease
 release pancreatic
enzymes

9. Major function
of bile
Isto provide emulsifying
agents:
•Bile salts
•Phosphtidylcholine

11. ACTION OF PANCREACTIC ENZYMES ON
DIETARY LIPIDS IN SMALL INTESTINE
PANCREATIC LIPASE
CHOLESTEROL
ESTERASE
PHOSPHOLIPASE –A2

12. HYDROLYSIS OF DIETARY TAG
Emulsification of Triacylglycerols – pancreatic
lipase.
Lipase acts on 1 & 3 position of TAG.
End product of Triacylglyceride digestion-
1.2-Monoacyl glycerol,
2.Glycerol,
3.Free fatty acids

13. OH
OH
OH
OH
OH
OH
Triacylglycerol (TAG) Diacylglycerol(DAG)
2-Monoacylglycerol
(2-MAG)
Glycerol
Fatty acidH20
Fatty acid
H20
H20 Fatty acid
HYDROLYSIS OF DIETARY TAG

14. HYDROLYSIS
OF DIETARY
PHOSPOLIPIDS

15. HYDROLYSIS OF CHOLESTEROL ESTER

16. (Small amount)

19. Micelles reaches brush border of
intestinal mucosal cells.
Lipids compounds from micelles
pass through mucosal cells and
are absorbed.
Site of absorption – jejunum &
ileum.

23. Of Bile Salts

26. STEATORRHEA-
A clinical condition
Daily excretion of fat in feces is >6 gm
per day.
CAUSES:
– Defective digestion of fat
– Defective absorption of fat

27. • Bile duct obstruction
due to Gall stone
• Emulsification defective
• Improper digestion
DEFECTIVE DIGESTION- 1

28. Disease of pancreas-
• Pancreatitis
• Tumor- of pancreas
• Partial or complete
pancreactomy
• Pancreatic juice blockage
• Absence of pancreatic lipase
• Unsplit fat in stool
DEFECTIVE DIGESTION- 2

29. DEFECTIVE ABSORPTION
Cystic Fibrosis:
• Genetic disorder
• Production of mucus i.e.,
thick & sticky.
• Severe pancreatic
lipase deficiency seen
in Cystic fibrosis results
in malabsorption of
lipids.

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