The digestive system
&
Liver function tests
I-The digestive system
Digestion
Digestion is the mechanical and chemical
breaking down of food into smaller components
that can be absorbed into a blood stream
Digestion is a form of catabolism: a break-down
of larger food molecules to smaller ones.
Digestive system
In mammals, food enters the mouth, being chewed by
teeth, with chemical processing beginning with
chemicals in the saliva from the salivary glands.
Then it travels down the esophagus into the stomach,
where hydrochloric acid kills most contaminating
microorganisms and begins mechanical break down of
some food (e.g., denaturation of protein), and chemical
alteration of some.
After some time (typically an hour or two in humans, the
results go through the small intestine, through the large
intestine, and are excreted during defecation.
Related terms
Gastr/o Stomach
Hepat/o Liver
Chol/e Gall, bile
cholecyst/o gallbladder
Lith/o Stone
Lapar/o Abdominal wall
Iasis (-osis) Abnormal condition
Emes/o Emesis Vomit
Melan/o Black pigment
Scopy Technique of veiwing
Rraphy Suture
Ectasis Dialation
- pepsia Digestion
-rrhagia Bursting forth (of blood)
Related terms
Entero intestine
Glosso tongue
Pyloro/pylorus gatekeeper
sigmoid/o sigmoid colon
Viscero body organs
Ile ileum
Cholelithiasis gallstones
rect/orectum Rectum
Stoma opening, mouth
RRhea Flow Discharge
-stasisto stop or control
Dys Diffeculty
Phagia Eating/Swallowing
Atresia no opening
-ptosis drooping /sagging
Labaro Abdomen
-stomy
This means a mouth or opening. Usually a stoma is formed by
surgery
e.g. a colostomy is an opening or the formation of an opening
into the colon.
This word component is also used in anastomosis, an operation
to form an opening/communication between two parts.
A stoma can be temporary or permanent.
-tomy
Means an incision as at the beginning of an operation .
Related conditions
Gastritis inflammation of stomach
Gastroenteritis Inflammation of the stomach and intestine
Gastrectomy Excision of stomach
Hepatitis inflammation of liver
Hepatoma tumor of liver
Laparotomy cutting into the abdomen
Laparoscopy visual exam of the abdomen
Related conditions
Cholelithotomy removal of gall stones
Cholelithiasis gall stones causing symptoms
Cholecystitis inflammation of gallbladder
Cholecystectomy removal of gallbladder
Emetic stimulating vomiting
Antiemetic stopping vomiting
Melanocyte cells produce melanin
Melanoma Melanin producing tumor
Related conditions
Lymphangiectasis Dialation of a lymph vessel
Dyspepsia Difficult digestion
Dysphagia Difficulty in swallowing
Splenorrhagia Bursting forth of blood from the spleen
Menorrhagia Heavy menstrual discharge
Sialolithiasis Salivary stones
Hematemesis Vomiting of blood
Related conditions
Esophageal atresia
no opening of the esophaagus at birth
Cecostomy
new opening of the first part of the colon to the outside
Jejunoje/junostomy
New opening between two parts of the jejunum
Pyloric Stenosis
Narrowing of the opening between the stomach and intestine
Hemoptysis
Spitting up blood from the respiratory tract and lungs.
Endoscopy
Use of a fiberoptic endoscope for direct visual examination.
GI studies include
Esophagogastroduodenoscopy
Proctosigmoidoscopy (rectum and distal colon)
Colonoscopy (all regions of the colon)
Gastroscopy (stomach)
Colic
Acute abdominal pain, such as biliary colic
caused by gallstones in the bile ducts
Paracentesis
Collection of peritoneal fluid
Cirrhosis
Chronic liver disease with degeneration of
liver tissue.
Bilirubin
A pigment released in the breakdown of
hemoglobin from red blood cells; mainly
excreted by the liver in bile
Icterus
Jaundice
Jaundice
A yellowish color of the skin, mucous
membranes, and whites of the eye caused by
bile pigments in the blood (from French jaune
meaning“yellow”). The main pigment is bilirubin.
peptic ulcer
A lesion in the mucous membrane of the
esophagus, stomach, or duodenum caused by
the action of gastric juice
ulcerative colitis
Chronic ulceration of the colon of unknown
cause
Anorexia
Loss of appetite. Anorexia nervosa is a
psychologically induced refusal or inability to eat
Constipation
Infrequency or difficulty in defecation and the
passage of hard, dry feces.
II- Liver Function Tests
(LFT)
Liver
• The liver is the largest organ in the body
• It consists of two main lobes that
together weigh from 1400 to 1600 g in
the normal adult
• It is reddish brown in color and has a
rich blood supply 1500 ml/min from two
major vessels, the hepatic artery and
the portal vein
Structural Unit
• The lobule which measures 1-2 mm in diameter,
forms the structural unit of the liver.
• It is composed of cords of liver cells
(hepatocytes) radiating from a central vein.
• Between the cords of the liver cells are vascular
spaces, called sinusoids, that are lined by
endothelial cells and Kupffer’s cells
• The Kupffer’s cells are phagocytic macrophages
capable of ingesting bacteria or other foreign
material from the blood that flows through the
sinusoids
Physiology
The liver has a central role in the
metabolism of carbohydrates, lipids,
proteins, vitamins and hormones, as
well as a role as a storage and
excretory organ.
It has an important role in
detoxification and drug metabolism.
Liver Function Tests
• The routine liver function tests include the
measurement of :
1. Total , direct and indirect bilirubin
2. Total proteins and albumin
3. Liver enzymes include :
ALT ( Alanine transaminase )
AST ( Aspartate transaminase )
AlP ( Alkaline phosphatase )
GGT ( - Glutamyl transferase )
Except for the screening of healthy people (for insurance
examinations or occupational medicine), liver function tests
are usually employed in patients to:
•Confirm a clinical suspicion of the presence of liver disease.
•Give an idea about the severity and prognosis of the liver disease.
•Follow up the disease and evaluate therapy.
•Arrive at a differential diagnosis (e.g. cholestatic vs
hepatocellular liver disease).
Bilirubin Metabolism
It is mainly in reticulo-endothelial system (liver, spleen
and bone marrow), Liver and intestine
80% of bilirubin formed from heme each day arise from
red blood cells.
Iron is removed from the heme molecule and the
porphyrin ring is opened to form bilirubin.
Total serum bilirubin is equal to the sum of the two types
of bilirubin
Direct (conjugated) bilirubin.
Indirect (unconjugated) bilirubin
Jaundice may be classified into:
1. Pre-hepatic Jaundice:
• The production rate of bilirubin is increased, exceeding
the excretory capacity of the liver. Overproduction of
bilirubin occurs in all forms of hemolytic anemia, less
commonly, in conditions where there is much ineffective
erythropoiesis (e.g. pernicious anemia).
• There is increase in plasma indirect (unconjugated)
bilirubin .
• Bilirubin is not excreted in urine.
• Urinary urobilinogen concentration is increased.
2) Hepatocellular Jaundice:
• Hepatocellular damage due to viral hepatitis or
toxins may interfere with the uptake of bilirubin, or
with its conjugation or with secretion of
conjugated bilirubin into bile.
• Both indirect and direct hyperbilirubinemia may
occur in hepatocellular jaundice.
• Bilirubin and excess urobilinogen are found in
urine.
3) Obstructive (Cholestatic) Jaundice:
• It is due to impaction of gallstones in the common
bile duct or carcinoma of the head of pancreas or
of the biliary tree.
• Jaundice is due to conjugated (direct) bilirubin.
• Bilirubin is detected in urine.
Congenital Hyperbilirubinemias:
They are all due to inherited defects in
the mechanism of bilirubin transport.
Albumin
Albumin has a long half-life of 20 days and
levels fall slowly if no synthesis occur. Thus,
serum albumin is usually normal in acute
hepatitis.
However, in chronic liver diseases such as
cirrhosis, impaired synthesis may lead to low
serum levels.
Serum albumin levels may be low due to loss
into urine, gut or into a third compartment
(ascitis).
Serum Enzymes in liver disease
a) Aminotransferases (ALT & AST):
• Aminotransferases are involved in amino acid
metabolism.
• AST occurs in both the cytosol and mitochondria of
cells while ALT is a cytosolic enzyme.
• Increased amounts of both transaminases leak from
inflamed or damaged hepatocytes due to acute or
chronic hepatitis.
• ALT is more specific for liver disease than AST .
b) Alkaline Phosphatase (ALP):
• Originates from the liver, bone (reflecting
osteoblastic activity) and the placenta.
• Levels of ALP increase in cholestasis,
mainly because of increased synthesis.
c) - Glutamyl transferase (GGT):
Increased serum levels of GGT are found in both
hepatocellular and cholestatic disease.
Higher levels are found in cholestasis.
Increased synthesis of GGT is induced by
excessive ethanol intake.
N.B. Hepatic Enzymes:
• ALT and AST levels are raised mainly in
hepatocellular disease.
• AlP level is raised mainly in obstructive
disease.
• The increased in serum GGT levels are
modest in hepatocellular disease and
marked in obstructive disease.