Blood

Human biology
Dr .Zahraa Mohammed
 Blood
• Blood is a connective tissue.
• made up of cellular elements and an extracellular matrix.
• The cellular elements include red blood cells (RBCs), white
blood cells (WBCs), and platelets.
• The extracellular matrix is plasma,
• blood unique among connective tissues because it is fluid.
• Functions of Blood
• The primary function is deliver oxygen and nutrients to and
remove wastes from body cells
• defense mechanism
• distribution of heat,
• maintenance of homeostasis.
 Transportation

• Most of nutrients travel in the bloodstream directly to the liver,

where they are processed and released back into the bloodstream
for delivery to body cells.
• Oxygen diffuse from the breathing air into the blood, which moves
from the lungs to the heart,which then pumps it out to the rest of
the body.
• endocrine glands release their products hormones, into the
bloodstream, which carries them to distant target cells.
• Blood also picks up cellular wastes and byproducts, and transports
them to various organs for removal.
• blood moves carbon dioxide to the lungs for exhalation from the
body, and various waste products are transported to the kidneys
and liver for excretion from the body in the form of urine or bile.
 Defense

• Many types of WBCs protect the body from external

threats, such as disease-causing bacteria that have
entered the bloodstream in a wound.
• Other WBCs seek out and destroy internal threats,
such as cells with mutated DNA that could multiply to
become cancerous, or body cells infected with viruses.
• When damage to the vessels results in bleeding, blood
platelets and certain proteins dissolved in the plasma,
interact to block the ruptured areas of the blood
vessels involved. ,protects the body from further blood
loss.
 Maintenance of Homeostasis

• body temperature
• Blood also helps to maintain the chemical
balance of the body. Proteins and other
compounds in blood act as buffers, which
thereby help to regulate the pH of body
tissues.
• Blood also helps to regulate the water content
of body cells.
 Characteristics of Blood

• oxygenated blood in the lungs is bright red ,blood that

has released oxygen in the tissues is a more bluish red
(hemoglobin is a pigment that changes color,
depending upon the degree of oxygen saturation).
normal temperature of blood is slightly higher than
normal body temperature about 38 C .
• The pH of blood averages about 7.4; (7.35 to 7.45 ) .
• Blood contain many buffers help to regulate pH.
constitutes approximately 8 percent of adult body
weight. Adult males typically average about 5 to 6 liters of
blood. Females average 4‒5 liters.
 Blood Plasma

• plasma is composed 92 percent water:

• smaller number of regulatory proteins ( enzymes&
hormones).
• Three major groups of plasma proteins
• 1. Albumin: the most abundant of the plasma proteins
(54%.
• Manufactured by the liver,
• transport vehicles for fatty acids and steroid hormones.
• the most significant contributor to the osmotic pressure of
blood; that is, its presence holds water inside the blood
vessels and draws water from the tissues.
• helps to maintain both blood volume and blood pressure.
 Blood plasma
• 2. the globulin (38%) three main subgroups
(alpha, beta, and gamma globulins).
• The alpha and beta globulins transport iron,
lipids, and the fat-soluble vitamins A, D, E, and
K to the cells; also contribute to osmotic
pressure.
• The gamma globulins are proteins involved in
immunity (immunoglobulins)
 Blood plasma
• 3. fibrinogen (7%)is produced by the liver. It is
essential for blood clotting,
• Other Plasma Solutes include various
electrolytes,such as sodium, potassium, and
calcium ions; dissolved gases, such as oxygen,
carbon dioxide, and nitrogen;
• various organic nutrients, such as vitamins, lipids,
glucose, and amino acids; and metabolic wastes.
All of these non protein solutes combined
contribute approximately 1 percent to the total
volume of plasma.
 RBC
red blood cell (or RBC), erythrocytes make up about 25
percent of the total cells in the body.
. The primary functions of erythrocytes are to pick up inhaled
oxygen from the lungs and transport it to the body's tissues,
and to pick up some carbon dioxide waste at the tissues and
transport it to the lungs for exhalation.
Erythrocytes remain within the vascular network.
• As an erythrocyte matures in the red bone marrow, it
extrudes its nucleus and most of its other organelles.
• Lacking mitochondria, they rely on fermentation.
• lack endoplasmic reticula and do not synthesize proteins,
so they are unable to repair themselves. This is why the
lifespan of a red blood cell is approximately 115 days.
 RBC
• biconcave disks; that is , Since they lack most
organelles, there is more interior space for the
presence of the hemoglobin molecules that transport
gases.
• The biconcave shape also provides a greater surface
area across which gas exchange can occur, relative to
its volume. Capillary beds are extremely narrow,
slowing the passage of the erythrocytes and providing
an extended opportunity for gas exchange to occur .
their structural proteins are flexible, allowing them to
bend over themselves to , then spring back again when
they enter a wider vessel.
 Hemoglobin

• large molecule made up of proteins and iron.

• It consists of four folded chains of a protein called globin,
designated alpha 1 and 2, and beta 1 and 2
• Each of these globin molecules is bound to a red pigment
molecule called heme, which contains an ion of iron (Fe2+)
• Each iron ion in the heme can bind to one oxygen molecule;
therefore, each hemoglobin molecule can transport four
oxygen molecules.
• An individual erythrocyte may contain about 300 million
hemoglobin molecules
•
 Hemoglobin

• In the lungs, hemoglobin picks up oxygen, which binds

to the iron ions, forming oxyhemoglobin, travels to the
body tissues, where it releases some of the oxygen
molecules, becoming darker red deoxyhemoglobin.
• Oxygen release depends on the need for oxygen in the
surrounding tissues
• In the capillaries, carbon dioxide enters the
bloodstream.
• In patients with insufficient hemoglobin, the tissues
may not receive sufficient oxygen, resulting in form of
anemia.
 Lifecycle of Erythrocytes

• number of raw materials must be present in adequate amounts.

• same nutrients that are essential to the production and maintenance of
any cell, such as glucose, lipids, and amino acids.
• erythrocyte production also requires several trace elements: iron ,copper,
zinc, and several types of B vitamins.
• Erythrocytes live up to 120 days in the circulation, after that worn-out ,
removed by macrophage, located primarily within the bone marrow, liver,
and spleen.
• The components of the degraded erythrocytes' hemoglobin are further
processed, some retained by the body and others being released in the
urine and feces.
• The breakdown pigments formed from the destruction of hemoglobin is
• , biliverdin
 Blood Typing and Transfusions

• Blood groups determined by the presence or absence of

specific marker antigen molecules, on the plasma
membranes of erythrocytes.
• Antigens are substances that the body does not recognize
as belonging to the self and that therefore trigger a
defensive response from the leukocytes (WBC) of the
immune system.
• Antigens are generally large proteins
• Following an infusion of incompatible blood, erythrocytes
with foreign antigens appear in the bloodstream and
trigger an immune response. ,with production of Proteins
called antibodies (immunoglobulins)
 Antigens, Antibodies, and Transfusion
Reactions
• Antibody produced by certain B lymphocytes
called plasma cells, attach to the antigens on the
plasma membranes of the infused erythrocytes
and cause them to stick to one another (i.e.
agglutinate).
• As the erythrocyte clumps are degraded, in a
process called hemolysis, their hemoglobin is
released into the bloodstream.
• More than 50 antigens identified on erythrocyte
membranes, the most significant are two groups:
the ABO blood group and the Rh blood group.
 The ABO Blood Group

Both of A and B antigens are glycoproteins.

blood type A, in people with A antigen on
erythrocytes membrane
• and those whose erythrocytes have B antigens
are blood type B.
• AB in People have both A and B antigens on their
erythrocytes
• People with neither A nor B antigens are
designated blood type O.
 ABO blood group
• Individuals with type A blood without any prior exposure
to incompatible blood have preformed antibodies to the B
antigen circulating in their blood plasma ( anti-B antibodies)
, will cause agglutination and hemolysis if they ever
encounter erythrocytes with B antigens.
• Individual with type B blood has pre-formed anti-A
antibodies.
• Individuals with type AB blood, which has both antigens, do
not have preformed antibodies
• People with type O blood lack antigens A and B on their
erythrocytes, but both anti-A and anti-B antibodies
circulate in their blood plasma.
 Rh Blood Groups

• is classified according to the presence or

absence of erythrocyte (Rh).
• Only D is clinically important
• the Rh group is designated by adding the
word positive or negative to the ABO type.
• A positive (A+) means ABO group A blood
with the presence of Rh antigen
 Disorders of RBC
• Anemia result from decrease number of RBCs or hemoglobin
• There are more than 400 types of anemia
• three major groups: those caused by blood loss, those caused by
faulty or decreased RBC production, and those caused by excessive
destruction of RBCs.
• result in lower levels of oxygen delivered to body tissues.
• Since oxygen is required for tissue functioning, anemia produces
fatigue, lethargy, and an increased risk for infection. Decrease
oxygen in the brain impairs the ability to think clearly, and may
prompt headaches and irritability. Lack of oxygen lead to shortness
of breath, the heart and lungs work harder .
• Anemias caused by faulty or decreased RBC production include
sickle cell anemia, iron deficiency anemia, vitamin deficiency
anemia, and diseases of the bone marrow and stem cells.
 Polycythemia
• An elevated RBC count , elevated hematocrit.
• can occur transiently in a person who is dehydrated
• a type of bone marrow disease called polycythemia
vera causes an excessive production of immature
erythrocytes , dangerously elevate the viscosity of
blood, raising blood pressure
• relatively rare disease that occurs more often in men
than women, and is more likely to be present in elderly
patients those over 60 years of age.