Why is
liver called a Gland?
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Gland is a organ which can
secrete chemicals or hormones. In this case Liver produces bile, a substance
needed to digest fats. Bile’s salts break up fat into smaller pieces so it can
be absorbed more easily in the small intestine.
The liver is the largest
glandular organ in the body. Liver is the only organ in the body that can
regenerate itself in human body.
The liver is located in the upper
right-hand portion of the abdominal cavity, beneath the diaphragm, and on top
of the stomach, right kidney, and intestines. Shaped like a cone, the liver is
a dark reddish-brown organ that weighs about 3 pounds ( or 1.5 kgs average)
The liver consists of four lobes, they are - the left, right, caudate,
and quadrate lobes.
i) The left and right lobes are
the largest lobes and are separated by the falciform ligament. ii) The right
lobe is about 5 to 6 times larger than the tapered left lobe.
iii) The small caudate lobe
extends from the posterior side of the right lobe and wraps around the inferior
vena cava.
iv) The small quadrate lobe is
inferior to the caudate lobe and extends from the posterior side of the right
lobe and wraps around the gallbladder.
The liver lobes are made up of
thousands of lobules. These lobules are connected to small ducts that connect
with larger ducts to ultimately form the hepatic duct.
The liver is an accessory organ within the human
digestive system. This means that it assists with the digestive processes, e.g.
by supplying substances useful to the digestive process - but that ingested
material, does not pass through the liver. Albumin is a major protein which is
formed by the liver.
Sources of
Blood to Liver:
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There are two distinct sources
that supply blood to the liver, including the following:
- Oxygenated blood flows in from the hepatic artery
- Nutrient-rich blood flows in from the hepatic portal vein: The hepatic portal vein blood to the tissues of the liver where the contents of the blood are divided up into smaller vessels and processed before being passed on to the rest of the body. Blood leaving the tissues of the liver collects into the hepatic veins that lead to the vena cava and return to the heart.
The liver holds about one pint
(13 percent) of the body's blood supply at any given moment. The hepatic duct
transports the bile produced by the liver cells to the gallbladder and duodenum
(the first part of the small intestine).
The main
functions of liver as an accessory organ within the human digestive system
are:
|
a) The secretion of bile and bile salts: Liver cells called hepatocytes secrete bile, which is a a
yellow/green (though may appear as dark as brown) slightly alkaline liquid.
b) Phagocytosis of bacteria and dead or foreign materials: Within the
liver, blood passes through spaces called sinusoids - instead of through
capillaries (as elsewhere in the body). A special type of cell called Kupffer's Cells, which are also known
as stellate reticuloendothelial cells,
are located in the sinusoids and destroy many types of unwanted particles
present in the bloodstream through the liver. Kupffer cells are a type of
macrophage that capture and break down old, worn out red blood cells passing
through the sinusoids.Such particles include:
Bacteria,
Antigens, i.e. other substances
from outside of the body,
imperfect or no-longer
functioning blood cells( damaged leucocytes and erythrocytes).
c) Maintenance of normal blood glucose level: When blood glucose is
low the liver breaks stored glycogen down into glucose, for release into the
blood stream. The liver converts certain amino acids and lactic acid into
glucose. The liver can convert some other sugar molecules (e.g. fructose,
galactose) into glucose. When blood glucose is high the liver converts glucose
to glycogen and triglycerides (for storage).
d) Fat Metabolism: Break-down of fatty acids - generating adenosine
triphosphate (ATP), which is important for the contraction and relaxation of
muscles.
Synthesis of lipoproteins, which
are important for the movement of fatty acids, cholesterol and triglycerides to
and from cells.
Storage of certain triglycerides
Synthesis of cholesterol (as well
as using cholesterol to produce bile salts).
e) Protein Metabolism:
Synthesis of all plasma proteins
except for -globulins.
Plasma proteins produced in the
liver include:
albumin, lipoprotein,
transferrin, caeruloplasmin, globulins (but not -globulins), -antitrypsin,
-fetoprotein, fibrinogen, prothrombin, Factors V, VII, IX, X and XII, and XII.
De-amination of excess amino
acids, i.e. removal of the -NH2 part (called the "amino group") from
amino acids, enabling the remaining parts to be re-used, e.g. for conversion to
ATP, carbohydrates, or fats.
Conversion of the ammonia (NH3)
resulting from the de-amination of excess amino acids, into urea
f) Excretion of bilirubin: Bilirubin is a component of bile, which
is produced by the liver. The source of bilirubin is the heam of aged (i.e.
no-longer optimally functioning) red blood cells. Bilirubin is the main bile
pigment in humans which, when elevated causes the yellow discoloration of the
skin called jaundice.
g) Activation of vitamin D: The liver is one of the parts of the
body that, together with the skin and the kidneys, participate in forming the
active form of vitamin D.
h) Haematopoiesis: Haematopoiesis is the formation of the cellular
components of blood. The liver is the main site of embryonic haematopoiesis. However,
this function of the liver ceases before birth (bone marrow having been
supplementing the haematopoiesis performed by the liver from about 5 months
gestation).
Diseases
of Liver:
|
- Hemochromatosis is a disease in which too much iron builds up in your Liver .Its a genetical disease of Liver.
- Alpha-1 Antitrypsin Deficiency: Is an inherited disorder that may cause lung disease and liver disease. Its leads to decreased A1AT activity in the blood and lungs, and deposition of excessive abnormal A1AT protein in liver cells.
- Jaundice
- Alagille Syndrome
- Biliary Atresia
- Cirrhosis: Cirrhosis of the liver occurs when the organ becomes scarred and hardened so that it cannot function properly. This is most often caused by chronic liver disease brought on by long-term alcohol abuse or hepatitis C infection.
- Galactosemia
- Gallstones
- Gilbert’s Syndrome
- Hemochromatosis
- Porphyria
- Reye’s Syndrome
- Sarcoidosis
- Tyrosinemia
- Viral Hepatitis A, B, C
- Wilson Disease
Liver
Function Tests:
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These tests include prothrombin
time (PT/INR), aPTT, albumin, bilirubin (direct and indirect), and others.
Liver transaminases (AST or SGOT and ALP or SGPT) are useful biomarkers of
liver injury in a patient with some degree of intact liver function.
Liver dialysis—in which a machine
performs the detoxification function of the liver- still a new treatment not
fully developed yet.
Liver - Anatomy, Functions,
Diseases for General Studies & General Knowledge Biology for UPSC IAS,
Civil Service exams APPSC TPSC SSC & Bank PO Clerical Exams.
Also Read:
- Important Diagnostic Instruments in Medicine - for General Awareness
- HUMAN BRAIN - Structure, Functions & Diseases Explained
- Vitamins-Functions, Types, Characteristics, Chemical Name, Uses and Deficiency Diseases
- Deficiency diseases - for General Knowledge
- Important Vaccines and Persons who discovered them - GK for Competitive Exams
- Important Therapeutic Instruments in Medicine
- IMPORTANT DIAGNOSTIC TESTS - General Knowledge
- Sense Organs- Quiz in Biology for General Knowledge
- Blood Groups for General Knowledge
- Endocrine Glands & Their Hormones
- Structure and Working of Eye - Simple Review
- DISEASES AND AFFECTED ORGANS - for General Knowledge
- Diseases of Eyes
- What are Chromosome? Their Role in Cell Division? Chromosome number in different species
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