Transcript Slide 1

The Liver and digestion
Dr. Than Kyaw
7 May 2012
The Liver
-
largest organ in the body
located behind the diaphragm
divided into lobes
performs multiple complex life sustaining functions
Many functions –
• related to the numerous liver enzymes
-- Some enzymes for "break down" of molecules
-- Some for "combination" of molecules forming new essential substances
for the body
-- intermediate metabolism
• Produces bile
Liver lobule
Non-digestive and
Digestive Functions of the Liver
Non-digestive Functions
1. Detoxification
(most medicines, alcohol, harmful substances from the body)
1. Production of blood clotting factors
2. Storage of glycogen
3. Storage of vitamins and minerals
4. Destruction of old non-functional red blood cells
5. Removal of hormones
6. Removal of ammonia from the body (urea formation)
7. Formation of plasma proteins
(globulin and albumin -- used for the building blocks of the body
and the immune system.)
Digestive Function
Bile production
Bile -- synthesized in the liver; stored in the gall bladder
-- released when stimulated by CCK which is secreted when chyme
enters duodenum
-- Bile duct joins with pancreatic duct before opening into the
duodenum
Bile -- contains no digestive enzyme
-- contains -- bilirubin (derived from break down of hemoglobin)
-- cholosterol
-- bile salts
-- phospholipids (lecithins)
(Man)
Digestive Function
Bile production
Bile salts – a range of lipids that assist in the break up of lipid
droplets to smaller droplets increasing surface areas
for digestion by lipase -- emulsifying action.
-- also aids the absorption of fatty acids and glycerol
along the small intestine
NOTE:
Equine digestive feature include:
1. low levels of amylase in saliva
2. absence of a gall bladder (there is a constant release of bile into the
intestine)
3. a relatively small stomach (about 1 gallon)
4. Large caecum - about 4 gallon
Impaired Liver Function and Jauncice
Jaundice or icterus
- Characterized by
yellowish discolouration of skin, mucous membranes,
and/or sclera
- Resulted from accumulation of bilirubin (bile pigment) in the
blood and tissues
Jaundice or icterus
Causes of jaundice
- liver damage
- occlusion of bile duct
- increased rate of erythrocyte destruction
(hemolytic diseases, e.g: anaplasmosis – the bile pigments
are liberated into the blood faster than the liver can
conjugate and secrete them – icterus results
Any factor that disrupts the movement of bilirubin from the blood to the liver
and then out of the body -- causes jaundice
Senescent RBCs
Hemolysed* RBCs
In MPS cells
releasing HB
*What are hemolytic
Fate of
Erythrocytes
agents?
(bacterial toxins,
snake venoms,
blood parasites,
hypotonic solutions)
Classifications of causes of jaundice
Three primary types:
Prehepatic Causes
- Those occurring before the blood passes through the liver
- Also referred to as hemolytic causes (result from a breakdown of red blood
cells – parasites:anaplamosis, babesiosis).
- Fatty infiltration of the liver (hepatic lipidosis)
- Inflammatory diseases of the liver (hepatitis), bile duct system (cholangitis),
or both (cholangiohepatitis)
- Toxins (e.g, heavy metals, chemical flea and tick dips and sprays)
- Certain drugs (e.g, diazepam, acetaminophen, griseofulvin)
- Cancer
- Infections - viral, bacterial, protozoal
Hepatic icterus
Chronic hepatitis:
• Hereditary hepatitis
• Drug-induced chronic hepatitis (e.g.; dog - phenobarbital)
Acute hepatitis:
• Toxic materials
• Infectious (leptospirosis, canine, infectious hepatitis, Yersinia, Salmonella)
Neoplasia:
• Lymphoma, hepatic metastases, etc.
Acute cholangitis
Posthepatic Causes
- Disorders that occur after blood passes through the liver
- Disorders or gall bladder diseases that block the bile flow from
the liver (gall stones, Fasciola hepatica, Ascaris, cancer, or
inflammation of the gall bladder and bile duct)
- Pancreatic diseases (pancreatitis and pancreatic cancer or
abscess)
- Intestinal diseases that block the bile ducts
Moderate yellow discoloration of the
mucosal membranes (sub-icterus).
Yellow discoloration of
pig viscera and carcass
caused by cirrhosis of
the liver.
Liver Enzymes (Human)
• Automatic biochemistry analyzer:
- aspartate aminotransferase (AST or SGOT)
- alanine aminotransferase (ALT or SGPT),
ALT: < 35U/L,
AST: <40U/L
Elevated ALT, AST : acute hepatitis (viral or toxic),
chronic hepatitis and cirrhosis, biliary obstruction
• Alkaline phosphatase (ALP) : 30-130 U/L ( 36-92 U/L)
Elevated ALP: bile duct obstruction, primary
hepatocellular carcinoma, hepatitis
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END OF LECTURE