This document summarizes fat digestion and absorption. It notes that most dietary fat consists of triglycerides which are broken down into fatty acids and glycerol by lingual lipase in the mouth, gastric lipase in the stomach, and pancreatic lipase in the small intestine. Bile salts are also required to emulsify fat into micelles to allow absorption. The fatty acids and glycerol are reassembled into triglycerides and incorporated into lipoproteins for transport through the lymphatic system and blood. Disorders that can interfere with fat digestion or absorption include pancreatic problems causing steatorrhea, gallstones obstructing bile flow, and intestinal diseases impairing absorption.

1. Dr. SOHIL TAKODARA

3.  50-150gms of fat per day
 90% Tri Acyl Glycerol(TAG)/Triglycerides(TG),
 10% ( Cholesterol. Phospholipids, Fatty
Acids(FA))
 Common dietary sources: Milk, Curd, paneer,
sweets, ghee, butter, oils, eggs

4.  Energy – 1 gm fat ( 9 Kcal)
 TAG- Emergency source of energy
(Starvation)
 Phospholipids-Insulation, surfactant etc
 Biological membrane formation
 Cholesterol- Steroid hormones, Bile Acids
 Lipoproteins- Lipid transporters of the body

5. TRI ACYL GLYCEROLS (TG/Neutral Fat)
Glycerol + Fatty acid ----> TAG
CH2-OH HOOC-R
CH-OH + HOOC-R’ ------->
CH2-OH HOOC-R’’

6. • Lingual Lipase
Mouth
• Gastric Lipase
Stomach
• Pancreatic juice
• Lipase and colipase
• Phospholipase A2
• Cholesterol Esterase
• Bile salt
Intestine

7.  Lingual lipase- Dorsum of the tongue
 Secreted on Saliva
 Very little digestion
 Action continues in stomach ( pH= 2.5-5)
 It Splits TAGs into Fatty Acids and Glycerol

8.  Gastric Lipase- Chief cells of gastric mucosa
 Digests around 30% of TAG
 Acts on Sn-3 ester linkage of TAGs containing
short and medium chain FA (Butter,Ghee)
 Produces 1,2 Diacylglycerol ( DAG) and Free
Fatty Acids ( FFA)

10. Pancreatic
Juice
Lipase
/colipase
Phospho
lipase A2
Cholesterol
esterase
Bile salt

12.  Its essential for efficient lipid digestion
 Bile salts- Synthesized in Liver, Secreted in
Bile
 Sodium and potassium salt of Bile acids
 Mixed micelle formation of Bile salt, PL,
cholesterolesters

18.  BREAKSDOWN Cholesterolesters into free
fatty acids and free cholesterol

19.  ACTS ON PHOSPHOLIPID (LECITHIN)
 PRODUCES LYSOLECITHIN AND FREE
CHOLESTEROL

20. LIPASES SITE OF ACTION SUBSTRATE PRODUCTS
Lingual and
gastric lipase
Mouth,Stomach Medium chain FA
+ TG (Milk)
FFA,DAG
Pancreatic
Lipase
Duodenum Longchain FA
containing TG
FFA,Glycerol,2M
AG
Phospholipase A2 Small Intestine Phospholipids at
Sn-2
FFA,Lysolecithin
Intestinal Lipase Small Intestine TAG with
medium chain
FA
FFA,Glycerol
Lipoprotein
Lipase
Capillary walls TAG in
Chylomicron,
VLDL
FFA,Glycerol
Hormone
sensitive Lipase
Adipose tissue TAG stores FFA,Glycerol

22.  Digested lipid products are packed into
micelle and move towards intestinal mucosa
 Bile salts undergo enterohepatic circulation
for reutilization (1 % excreted)

23.  2-acyl glycerol gets reconverted to TAG
 1-acyl glycerol is broken into FFA and
glycerol
 Long chain utilizes this glycerol to form TAG
 TAGs, PL, CE are incorporated with Apo A and
Apo B48 forms a and circulated

26. DISORDERS
Steatorrhea- excretion of fatty foul smelling stools.
Defective digestion - chronic disease of pancreas
surgical removal of pancreas
defective bile synthesis(
OBSTRUCTIVE JAUNDICE)
gall stones
Defective absorption- intestinal diseases-
Enteritis
Tropical sprue
Crohn’s disease

28. Chyluria- milky urine
due to abnormal connection between lymphatic drainage of
intestine and urinary tract - chylous fistula
Chylothorax- milky pleural fluid
Chyle may leak into the pleural cavity from the thoracic duct
or its tributaries as a result of trauma (stabwounds, crush
injuries, surgical injury) or obstruction by tumour. It is
commonly mistaken for pus. Chyle contains fat globules.
Colipase defeciency- steatorrhoea
Cholelithiasis – failure to keep cholesterol in solution by bile
salts.
FSV def manifestations are common.