“THE BLOOD”
Long before modern medicine, blood was viewed as magical—an elixir that held the mystical
force of life—because when it is drained from the body, life departed as well. is the river of life
that surges within us, transporting nearly everything that must be carried from one place to
another. Today centuries later, blood still has enormous importance in the practice of
medicine. Clinicians examine it more often than any other tissue when trying to determine the
cause of disease in their patients.
Blood is an opaque, red connective tissue fluid that is pumped by the heart through
vessels (arteriesg arteioles, venules and veins) of the system. Blood
pulsates through the arteries to every part of the body, interacts with individual ceils via
an extensive capillary network, and returns to the heart through the venous system.
Many of the functions of blood are undertaken in the capillaries, where the blood flow
stows dramatically, allowing the efficient diffusion and transport of oxygen, glucose, and
other molecutes across the mono|ayer of endothe\ial cells that form the thin capillary
walls.
The blood is part of the extracellular fluid (12 Liters). Extraceliufar fluid (ECF) is present
outside the ceiß. Of 12 liters of ECF, 3 L is present inside the blood vessels as ptasma
0T intravascular fluid. The remainder is present around the cells as interstitial fluid.
Some of the extracelluiar fluid is present in specialized compartments as cerebrospinal
fluid, synovial fluid in joint cavities, pleural fluids lining the tungs peritoneal fluid in the
abdomen, intraocular fluid in the eyes, gastrointestinaf fluid iß the form of secretions and
urine.
FUNCTIONS OF BLOOD
Blood performs a number of functions, all concerned in one way or another with
substance distribution, regulating blood levels of particular substances, or body
protection.
1. Distribution
Distribution functions of blood include
Delivering oxygen from the lungs and nutrients from the digestive tract to ail body cells.
Transporting metabolic waste products from cells to elimination sites (to the lungs for
elimination of carbon dioxide, and to the kidneys for disposal of nitrogenous wastes in
urine). Transporting hormones from the endocrine organs to their target organs.
2. Regulation
Regulatory functions of blood include
Maintaining appropriate body temperature by absorbing and distributing heat throughout
the body and to the skin surface to encourage heat loss.
Maintaining normal pH in body tissues. Many blood proteins and other blood borne solutes
act as buffers to prevent excessive or abrupt changes in blood pH that could jeopardize
normal cell activities. Additionally, blood acts as the reservoir for the bodVs "alkaline
reserve" of bicarbonate atoms.
Maintaining adequate fluid volume in the circulatory system. Salts (sodium chloride and
others) and blood proteins act to prevent excessive fluid toss from the bloodstream into
the tissue spaces. As a result, the fluid volume in the blood vessels remains ample to
1
,support efficient blood circulation to all parts of the body.
3. Protection
2
,Protective functions of blood include
Preventing blood loss. When a blood vessel is damaged, platelets and plasma proteins
initiate clot formation, halting blood loss.
Preventing infection. Drifting along in blood are antibodies, complement proteins, and
white blood cells, all of which help defend the body against foreign invaders such as
bacteria and viruses.
Blood Volume and Its Composition
The normat circulating blood volume is about 8% of the total body weight; 5600 ml in a-
70 Kg man. About 55% of this volume is protein rich fluid called plasma and 45% is
composed of formed (cellular) elements.
3
, “PLASMA”
The plasma forms 55% portion of the blood. The plasma is composed of 90% water, 7% as
plasma proteins and remainder 3% as electrolytes, urea, and organic substances like
glucose, lipids (cholestrol and fatty acids), minerals etc.
PLASMA PROTEINS
Plasma contains over 200 hundred individual proteins that are structurally and functionally
different from each other. Plasma proteins are large molecules with molecular weights
rangimg from 50,000 to 300,000 daltons. Plasma concentration of these proteins is 6.3 to
8.8 g/dl. These proteins are divided into three types
Albumin
Albumin is the most abundant protein in the plasma which accounts for 55-60% of the total
plasma proteins. It is produced exclusively in the liver so its level falls in hepatic disorder. Its
molecular weight is 69,000 daltons, Due to its low molecular weight, it is the first protein to
appear in the urine after damage.
Functions: Albumin performs following functions
Maintenance of Oncotic Pressure and Fluid BaEance: As the capillary walls are
impermeable to plasma proteins, albumin exerts an osmotic force across the capmary
wafts. This force helps to retain water in the intravascular compartment This is called
plasma oncotic pressure or or colloid osmotic pressure and is calculated to be 25 mmHg.
Loss of albumin called hypoalbuminemia, therefore, results in a significant reduction in
osmotic pressure of blood, with consequent movement of water into interstial spaces,
causing swelling. This condition is called oedemaa
Transport and hormone reservoir Function: Albumin is involved in the transport of severah
substances because of its polar nature Nearally 40% of calcium is bound with albumin.
Bilirubin, free fatty acids and many non-polar drugs are bound up and are transported by
the albumin. Albumin also forms complexes with steroid hormones, thus preventing their
filtration in the glomerulia Such complexes acts as circulating reservoir of the hormones
which tissues can draw at the time cf need.
Buffer Function: Albumin alongwih other proteins accounts for 15% of the total buffering
capacity of the blood. Among these proteins, atbumin provides maximum buffering
action,
Nutritive Function: Albumin degradation is vital source of amino acids during malnutrition
which are required for the maintenance of the organism's vital processes, Serum
albumin concentration is therefore, measured for assessment of person's protein status.
Globulin
Globulins comprise a number of proteins which are subdivided into four distinct
classes; Alphal ((11), Alphaz Beta (ß)and Gamma (Y) globulins. All g\obulins are
formed by the liver exceot gamma globulins that is formed by the plasma cells.
Long before modern medicine, blood was viewed as magical—an elixir that held the mystical
force of life—because when it is drained from the body, life departed as well. is the river of life
that surges within us, transporting nearly everything that must be carried from one place to
another. Today centuries later, blood still has enormous importance in the practice of
medicine. Clinicians examine it more often than any other tissue when trying to determine the
cause of disease in their patients.
Blood is an opaque, red connective tissue fluid that is pumped by the heart through
vessels (arteriesg arteioles, venules and veins) of the system. Blood
pulsates through the arteries to every part of the body, interacts with individual ceils via
an extensive capillary network, and returns to the heart through the venous system.
Many of the functions of blood are undertaken in the capillaries, where the blood flow
stows dramatically, allowing the efficient diffusion and transport of oxygen, glucose, and
other molecutes across the mono|ayer of endothe\ial cells that form the thin capillary
walls.
The blood is part of the extracellular fluid (12 Liters). Extraceliufar fluid (ECF) is present
outside the ceiß. Of 12 liters of ECF, 3 L is present inside the blood vessels as ptasma
0T intravascular fluid. The remainder is present around the cells as interstitial fluid.
Some of the extracelluiar fluid is present in specialized compartments as cerebrospinal
fluid, synovial fluid in joint cavities, pleural fluids lining the tungs peritoneal fluid in the
abdomen, intraocular fluid in the eyes, gastrointestinaf fluid iß the form of secretions and
urine.
FUNCTIONS OF BLOOD
Blood performs a number of functions, all concerned in one way or another with
substance distribution, regulating blood levels of particular substances, or body
protection.
1. Distribution
Distribution functions of blood include
Delivering oxygen from the lungs and nutrients from the digestive tract to ail body cells.
Transporting metabolic waste products from cells to elimination sites (to the lungs for
elimination of carbon dioxide, and to the kidneys for disposal of nitrogenous wastes in
urine). Transporting hormones from the endocrine organs to their target organs.
2. Regulation
Regulatory functions of blood include
Maintaining appropriate body temperature by absorbing and distributing heat throughout
the body and to the skin surface to encourage heat loss.
Maintaining normal pH in body tissues. Many blood proteins and other blood borne solutes
act as buffers to prevent excessive or abrupt changes in blood pH that could jeopardize
normal cell activities. Additionally, blood acts as the reservoir for the bodVs "alkaline
reserve" of bicarbonate atoms.
Maintaining adequate fluid volume in the circulatory system. Salts (sodium chloride and
others) and blood proteins act to prevent excessive fluid toss from the bloodstream into
the tissue spaces. As a result, the fluid volume in the blood vessels remains ample to
1
,support efficient blood circulation to all parts of the body.
3. Protection
2
,Protective functions of blood include
Preventing blood loss. When a blood vessel is damaged, platelets and plasma proteins
initiate clot formation, halting blood loss.
Preventing infection. Drifting along in blood are antibodies, complement proteins, and
white blood cells, all of which help defend the body against foreign invaders such as
bacteria and viruses.
Blood Volume and Its Composition
The normat circulating blood volume is about 8% of the total body weight; 5600 ml in a-
70 Kg man. About 55% of this volume is protein rich fluid called plasma and 45% is
composed of formed (cellular) elements.
3
, “PLASMA”
The plasma forms 55% portion of the blood. The plasma is composed of 90% water, 7% as
plasma proteins and remainder 3% as electrolytes, urea, and organic substances like
glucose, lipids (cholestrol and fatty acids), minerals etc.
PLASMA PROTEINS
Plasma contains over 200 hundred individual proteins that are structurally and functionally
different from each other. Plasma proteins are large molecules with molecular weights
rangimg from 50,000 to 300,000 daltons. Plasma concentration of these proteins is 6.3 to
8.8 g/dl. These proteins are divided into three types
Albumin
Albumin is the most abundant protein in the plasma which accounts for 55-60% of the total
plasma proteins. It is produced exclusively in the liver so its level falls in hepatic disorder. Its
molecular weight is 69,000 daltons, Due to its low molecular weight, it is the first protein to
appear in the urine after damage.
Functions: Albumin performs following functions
Maintenance of Oncotic Pressure and Fluid BaEance: As the capillary walls are
impermeable to plasma proteins, albumin exerts an osmotic force across the capmary
wafts. This force helps to retain water in the intravascular compartment This is called
plasma oncotic pressure or or colloid osmotic pressure and is calculated to be 25 mmHg.
Loss of albumin called hypoalbuminemia, therefore, results in a significant reduction in
osmotic pressure of blood, with consequent movement of water into interstial spaces,
causing swelling. This condition is called oedemaa
Transport and hormone reservoir Function: Albumin is involved in the transport of severah
substances because of its polar nature Nearally 40% of calcium is bound with albumin.
Bilirubin, free fatty acids and many non-polar drugs are bound up and are transported by
the albumin. Albumin also forms complexes with steroid hormones, thus preventing their
filtration in the glomerulia Such complexes acts as circulating reservoir of the hormones
which tissues can draw at the time cf need.
Buffer Function: Albumin alongwih other proteins accounts for 15% of the total buffering
capacity of the blood. Among these proteins, atbumin provides maximum buffering
action,
Nutritive Function: Albumin degradation is vital source of amino acids during malnutrition
which are required for the maintenance of the organism's vital processes, Serum
albumin concentration is therefore, measured for assessment of person's protein status.
Globulin
Globulins comprise a number of proteins which are subdivided into four distinct
classes; Alphal ((11), Alphaz Beta (ß)and Gamma (Y) globulins. All g\obulins are
formed by the liver exceot gamma globulins that is formed by the plasma cells.
