Blood
Chapter 12
Bio160
Blood Composition
• Red blood cells
• White blood cells
• Platelets
• Plasma
Red Blood Cells
• Red blood cells (Erythrocytes)
Biconcave disks that contain oxygen-carrying
hemoglobin
When oxygen combines with hemoglobin
bright red oxyhemoglobin results whereas
deoxygenated blood (deoxyhemoglobin) is
darker.
Red Blood Cells
Red blood cells discard their nuclei during
development and so cannot reproduce or
produce proteins.
The number of red blood cells is a measure of
the blood's oxygen-carrying capacity.
Red Blood Cells
• Red blood cell production
In the embryo and fetus, red blood cell
production occurs in the yolk sac, liver, and
spleen; after birth, it occurs in the red bone
marrow.
The average life span of a red blood cell is 120
days.
Red Blood Cells
The total number of red blood cells remains
relatively constant due to a negative
feedback mechanism utilizing the hormone
erythropoietin, which is released from the
kidneys and liver in response to the
detection of low oxygen levels.
Red Blood Cells
Vitamins B12, folic acid and iron are needed for
red blood cell production
A deficiency in red blood cells or quantity of
hemoglobin results in anemia.
Red Blood Cells
• Red blood cell destruction
With age, red blood cells become increasingly
fragile and are damaged by passing through
narrow capillaries.
Macrophages in the liver and spleen
phagocytize damaged red blood cells.
Red Blood Cells
Hemoglobin from the decomposed red blood
cells is converted into heme and globin.
Heme is decomposed into iron, which is stored
or recycled, and biliverdin and bilirubin,
which are excreted in bile.
White Blood Cells
• White blood cells (Leukocytes)
Defend the body from disease.
They are formed from hemocytoblasts.
Leukocytes can squeeze between cells lining
walls of blood vessels by diapedesis and
attack bacteria and debris.
White Blood Cells
• Neutrophils
Have red-staining fine cytoplasmic granules
and a multilobed nucleus; they comprise 54-
62% of leukocytes.
They are phagocytic.
White Blood Cells
• Eosinophils
Have coarse granules that stain deep red, a
bilobed nucleus, and make up only 1-3% of
circulating leukocytes.
Eosinophils moderate allergic reactions as well
as defend against parasitic infections.
White Blood Cells
• Basophils
Have fewer granules that stain blue; they
account for fewer than 1% of leukocytes.
Basophils migrate to damaged tissues and
release histamine to promote inflammation
and heparin to inhibit blood clotting.
White Blood Cells
• Monocytes
The largest blood cells, have variably shaped
nuclei, and make up 3-9% of circulating
leukocytes.
They are phagocytic, engulfing large particles.
White Blood Cells
• Lymphocytes
Long-lived, have a large, round nucleus, and
account for 25-33% of circulating leukocytes.
The major players in specific immune
reactions and some produce antibodies.
Platelets
• Blood platelets
Blood platelets are fragments of
megakaryocytes.
Platelets help repair damaged blood vessels by
adhering to their broken edges.
Blood Plasma
• Blood Plasma
Plasma is the clear, straw-colored fluid portion
of the blood.
– Plasma is mostly water but contains a variety
of substances.
– Plasma functions to transport nutrients and
gases, regulate fluid and electrolyte balance,
and maintain a favorable pH.
Blood Plasma
Plasma proteins
– The albumins help maintain the osmotic
pressure of the blood and account for 60% of
the plasma proteins.
– The globulins, comprising 36% of the plasma
proteins, are designated as alpha, beta, and
gamma globulins.
Action Potentials
Alpha and beta globulins function in
transporting lipids and fat-soluble
vitamins.
Gamma globulins are a type of antibody.
– Fibrinogen (4%) plays a primary role in blood
coagulation.
Blood Plasma
Gases and nutrients
– The most important blood gases are oxygen
and carbon dioxide.
– The plasma nutrients include amino acids,
monosaccharides, nucleotides, and lipids.
Blood Plasma
Nonprotein Nitrogenous Substances
– Nonprotein nitrogenous substances generally
include amino acids, urea, and uric acid.
Blood Plasma
Plasma Electrolytes
– They include sodium, potassium, calcium,
magnesium, chloride, bicarbonate, phosphate,
and sulfate ions.
– Some of these ions are important in
maintaining osmotic pressure and pH of the
plasma.
Hemostasis
• Hemostasis
Hemostasis refers to the stoppage of bleeding.
– Blood vessel spasm - muscles in vessel wall
contract
– Platelet plug formation - platelets stick to the
exposed edges of damaged blood vessels,
forming a net with spiny processes protruding
from their membranes.
Hemostasis
– Blood coagulation – complex series of steps
that leads to blood clot formation by
conversion of fibrinogen into net-like fibrin,
which catches blood cells before they can
leave the body.