Transcript Blood 2a

Blood
• Blood is composed of the liquid part and the
solid part.
• The liquid is called plasma, a yellowish slightly
viscous liquid, made up of dissolved proteins
and salts.
• The solid part of blood is made up of cells (small
round discs which can be seen only by
microscope).
• There is approximately 55 % plasma and 45 %
solid part (cells floating in this plasma).
Blood
• is an essential component of the human body
• about five litres of the vital liquid circulating through the adult human
• is essential in the transport of necessary elements to the cells and in
the removal of harmful wastes.
• is responsible for multiple tasks. (oxygen from the lungs to the cells ‘
returns carbon dioxide, a waste product of cellular respiration, to the
lungs)
• Helps regulate body temperature
• aids in growth and repair by transporting nutrients to the various
tissues that require them.
• Harmful metabolic wastes are transported to the kidneys by blood.
• disease fighting substances are transported in the blood.
• chemical hormones are carried to various receptor cells via blood.
• is a living part of the body.
Blood Cells
• Red blood cells (erythrocytes),
• White blood cells (leucocytes) and
• Platelets (called also thrombocyte).
Red Blood Cells
• The red cells are the cells responsible for the
red colour of blood and constitute 75% of the
solid part of the blood.
• They contain a complex protein called
haemoglobin, which is necessary to carry
oxygen from the lungs to the body.
• haemoglobin needs iron to be formed.
• Vitamin B12 is needed to help in the formation
and development of this red cell in the bone
marrow.
• life span of the red cell is about 120 days
Red Blood Cells
• also known as erythrocytes, are flattened, doubly concave cells
about 7 μm in diameter
• mature erythrocytes lack a nucleus.
• They are small, 4 to 6 million cells per cubic millimeter of blood, and
have 200 million hemoglobin molecules per cell.
• The average human would have a total of 25 trillion red blood cells
(about 1/3 of all the cells in the body).
• hemoglobin gives blood its red colour.
• Hemoglobin binds with oxygen molecules and gives blood its
oxygen carrying capabilities.
• hemoglobin molecule delivers oxygen molecules to the cells and it
carries carbon dioxide away from the cells.
• erythrocytes are continuously manufactured in bone marrow.
• Dead erythrocytes are destroyed in the liver and spleen but the iron
from the hemoglobin is recovered and returned to the bone marrow.
White Blood Cell
White Blood Cells
• White blood cells, also known as leukocytes, are larger
than erythrocytes, have a nucleus, and lack hemoglobin.
• They function in the cellular immune response. White
blood cells (leukocytes) are less than 1% of the blood's
volume. They are made from stem cells in bone marrow.
• There are five types of leukocytes. Each is an important
component of the immune system. If a germ or infection
enters the body various forms of leucocytes go into
action.
• Neutrophils destroy foreign substances such as
bacteria. The neutrophils enter the tissue fluid by
passing through capillary walls. They destroy foreign
substances through phagocytosis.
WBC (cont’d)
• Macrophages release white blood cell growth factors,
causing a population increase for white blood cells.
• Lymphocytes fight infection.
• T-cells attack cells containing viruses.
• B-cells produce antibodies.
• The life cycle of a leucocyte is shorter than that of a
erythrocyte, living from a few days to a few weeks. In the
event of an infection white blood cell counts increase
significantly. As a result doctors will use blood cell counts
as a way to diagnose infections or diseases such as
leukemia.
Platelets
• minute cells and they play a very important part in the
clotting of blood.
• The liquid part of blood (plasma) contains manydissolved substances among which are the clotting
factors.
• The main clotting factors are: prothrombin, calcium, and
fibrinogen.
• When there is a cut, thromboplastin is released from
body tissues into the blood.
• When thromboplastin meets with the above-mentioned
clotting factors and platelets, a series of chemical
reactions starts.
• Ultimately in healthy persons a blood clot is formed to
stop bleeding.
Brief Summary
• prothrombin + calcium + thromboplastin
(from damaged tissues) = thrombin
• thrombin + fibrinogen = fibrin (fine threads)
• fibrin + platelets = blood clot (mesh or net)
Plasma
• is the relatively clear liquid protein and salt
solution which carries the red cells, white cells,
and platelets.
• Normally, 55% of our blood's volume is made up
of plasma.
• About 95% of it consists of water.
• As the heart pumps blood to cells throughout the
body, plasma brings nourishment to them and
removes the waste products of metabolism.
Plasma
• Microbe-fighting antibodies travel to the
battlefields of disease by hitching a ride in
the plasma.
• The plasma has a buffering capacity and
maintains blood pH at or near 7.4.
• In addition the liquid plasma carries the
solid cells and the platelets which help
blood clot.
Blood Types
• Blood cells are classified based upon the
presence of certain protein molecules
called antigens. There are essentially 2
types of antigens - A antigens and B
antigens. Blood type is determined by
which of these are present or absent.
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Type A Blood
Blood has only A antigens.
Type B Blood
Blood has only B antigens.
Type AB Blood
Blood has a mixture of both A and B antigens.
Type O Blood
Blood lacks both A and B antigens.
• If two different blood types are mixed
together, the blood cells may begin to
clump together in the blood vessels,
causing a potentially fatal situation.
Therefore, it is important that blood types
be matched before blood transfusions take
place.
• A person with type A blood can donate blood to a person
with type A or type AB.
• A person with type B blood can donate blood to a person
with type B or type AB.
• A person with type AB blood can donate blood to a
person with type AB only.
• A person with type O blood can donate to anyone.
• Because of these patterns, a person with type O blood is
said to be a universal donor. A person with type AB blood
is said to be a universal receiver.
• Blood is further classified based upon the presence or
absence of molecules called Rh factors.
• If a persons blood has an Rh factor it is designated
positive.
• If it lacks an Rh factor it is designated negative.
• Consequently each of the four blood types described
above can be further divided into positive or negative for
Rh factor.
• For example an individual whose blood has only A
antigens and which lacks the Rh factor would have Type
A negative blood.
• On the other hand if an individual had only A antigens
and possessed the Rh factor they would have Type A
positive blood
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