MOUTH

Lipids: TriacylglycerolsCholesterol estersPhospholipids

Triacylglycerols

STOMACH

FFA + DAGs (small amounts)

Lingual Lipase("acid-stable")

1b

FFA + DAGs (miniscule amounts)

Lingual Lipase

1a

STEP 1: Digestion in the Mouth and Stomach

Courtesy of Dr. Marc Tischler

CCK-PZ causes contraction

EXOCRINEPANCREAS

trypsinogen,procolipase,lipase, esterase,HCO3

-, proPLA2

CCK-PZstimulatessecretion

Endocrine cell Cholecystokin-

pancreozymin (CCK-PZ)via bloodstream

Trypsinogen

Pancreatic lipase

Pancreatic esterase

PancreaticProcolipase

Pancreatic ProPLA2

FFA

from stomach

SMALL INTESTINEduodenum/jejunum

STEP 2: Enzymatic Digestion in the Duodenum/Jejunum – secretion of zymogens/bile salts

Bile Saltstorage

Bile AcidSynthesis Conjuga-tion LIVER

GALL BLADDER

Courtesy of Dr. Marc Tischler

Mixed Micelles

4

Released bile acids

3b

STEP 3b: Bile Acid RecyclingSTEP 4: Lipid Absorption

Reabsorbed by ileum

Capillaries

FFA, 2MG

cholesterollysolecithinvitamin A

Short/medium chain FFA

LIVER

Enterohepatic circulation of bile acids

3b

Portal vein

SMALL INTESTINEduodenum/jejunum

Courtesy of Dr. Marc Tischler

6a

B48

Coating with apolipoprotein(with TTP)

Chylomicronvitamins D, E, K

Triacyl-glycerol

Cholesterol esterPhospholipid

FFA, 2MG

cholesterollysolecithinvitamin A

reesterification

5 ACAT

6b To lacteals and thoracic duct (lymphatic system)

STEP 5: Re-esterificationSTEP 6: Chylomicron

Assembly and Export

SMALL INTESTINEduodenum/jejunum

Acyl CoA: cholesterol acyl transferase

Triacylglycerol transfer protein

Courtesy of Dr. Marc Tischler

LIVER

ApoB48 aids with chylo-micron assembly

Lymph system:Chylomicrons to capillaries via lymph

I N T E S T I N E

non-hepatic tissuesnon-hepatic tissues

C E C EC EC E C E

C EC E C E

C E

Chylomicrons carry dietary fatty acids to tissues and the remnants take cholesterol to the liver

Nascent chylo-microns acquire apo CII (C) and E (E) from HDL

chylomicron interacts with lipoprotein lipase removing FFA

LIVER

ApoB48chylomicron remnants lose CII to HDL

non-hepatic tissuesnon-hepatic tissues

C E C E

E

E

E

EC

C

C

C EC E C E

C E

EE E

Liver: apo E receptor takes up remnants to deliver cholesterol

Lymph system:

I N T E S T I N E

C E C EC E

chylomicron acquires apo CII (C) and E (E) from HDL

chylomicron interacts with lipoprotein lipase removing FFA

Chylomicrons carry dietary fatty acids to tissues and the remnants take cholesterol to the liver

Courtesy of Dr. Marc Tischler