Chapter 17
BLOOD
Blood Composition & Functions
• Blood is the ONLY fluid tissue (connective)
– Why is a fluid considered a tissue?
• Composed of formed elements suspended in
plasma
Fun Facts!
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• The color of blood depends on
the amount of Oxygen it is
carrying
Scarlet = Oxygen Rich
Dark Red = Oxygen Poor
Blood accounts for approx. 8% of
your body weight
Average adult male has 5-6L
Average adult female has 4-5L
3-4 pounds of “baby weight” can
be attributed to increased blood
volume
Functions of blood
Distribution
– Delivers oxygen and nutrients to the cells of the body
– Transports metabolic waste products to lungs (CO2) and
kidneys (nitrogenous wastes) for elimination
– Transports hormones
Regulation
– Maintains body temperature
– Maintains pH in body tissues
– Maintains fluid volume in the circulatory system
Protection
– Prevents catastrophic blood loss
– Prevents infection
Blood Plasma
• Straw-colored sticky fluid that is 90%
water
• Remaining 10% contains proteins (most
abundant 8%), nitrogenous wastes,
nutrients, electrolytes, respiratory
gases, hormones
• Albumin makes up 60% of plasma
protein and is vital for helping to keep
water in the blood stream
• Plasma proteins are not the same
proteins used by your cells for energy!
• Fibrinogen (4% of plasma proteins) is
the plasma protein that facilitates blood
clot formation
Check Point!!!!
• What is the hematocrit? What is a normal value?
The % of blood made up by erythrocytes approx. 45%
is the normal range
• List 2 protective functions of blood
Blood clotting and protection from infection
• Are plasma proteins used as fuel for body cells?
No…they serve other functions such as transport and
fluid volume regulation
Formed Elements
• Erythrocytes aka: Red Blood Cells (RBCs)
• Not a true cell
• Does not contain a nucleus
• Leukocytes aka: White Blood Cells (WBCs)
• Platelets aka: Thrombocytes
• Not a true cell
• Does not contain a nucleus
• Actually only a cell fragment
Erythrocytes (RBCs)
• Small biconcave disc shaped cells with depressed
centers
• Lack a nucleus (anucleate) and organelles
• Contain primarily hemoglobin (97%) which is the
protein that binds to and transports respiratory
gases
• Since they do not have mitochondria, they
generate ATP anaerobically and do not consume
any of the oxygen they carry
• RBCs are the major factor that contributes to
blood viscosity
RBCs and Hemoglobin…
• Transportation of respiratory gases O2 and CO2
bound to hemoglobin
• Hemoglobin is made up of the protein globin which
is bound to a heme group
• Globin consists of 4 polypeptide chains each bound
to a heme group
• Each heme group contains an iron atom
• Each hemoglobin can transport 4 molecules of
oxygen because each iron atom can bind with one
oxygen molecule
• A single RBC contains about 250 million
hemoglobin molecules so each little cell can hold
around a billion molecules of oxygen!
Hemoglobin inside RBC
Function of the RBCs
• Oxygen loading occurs in the capillaries surround
the alveoli of the lungs
• Oxygen diffuses through the capillaries and binds
to the iron attached to the hemoglobin of oxygen
poor RBCs and becomes bright red
oxyhemoglobin
• After the RBC leaves the lungs and reaches
tissues that need O2 the oxygen detaches from
the iron resulting in deoxyhemoglobin and
becomes dark red again
Function of the RBCs
• About 20% of CO2 carried in the blood binds
to the globin’s amino acids rather than the
heme group
• This usually occurs in the deoxyhemoglobin
state when the cell is oxygen poor
• CO2 loading occurs in the tissues where it is
then carried back to the lungs to be
eliminated from the body
Hematopoiesis
aka: production of blood cells
• Occurs in the red bone marrow
• In adults it occurs primarily in the axial skeleton and flat
portions of the girdles as well as the proximal epiphyses of
the humerus and femur
• Each type of blood cell is produced in different numbers
depending on the bodies needs at the time
• The entire process takes about 15 days
• All the formed elements of blood take place and originate
from the same stem cells (hemocytoblasts) which later
become differentiated into a specific type of blood cell
• Reticulocytes are immature RBCs and account for
approximately 1-2% of all erythrocytes in healthy people
• Reticulocyte counts below or above this percentage rate
indicate abnormal rates of RBC function
Erythropoiesis
Red Blood Cell
formation
• rate of RBC production is controlled by
hormone called Erythropoietin (EPO)
• erythropoietin is produced by the kidneys and
stimulated by blood level of oxygen
low 02 = more erythropoietin
high O2 = less erythropoietin
Erythropoiesis
Red Blood Cell formation
The drop in normal blood oxygen levels that
triggers EPO formation can result from:
– Reduced numbers of RBCs due to hemorrhage or
excessive RBC destruction
– Insufficient hemoglobin per RBC (iron deficiency)
– Reduced availability of oxygen, i.e. high altitudes
or respiratory illness such as pneumonia
Note: low oxygen levels alone do not activate
the bone marrow, rather it stimulates the
kidneys to release more EPO
EPO: The Good, The Bad, & The Ugly
Renal dialysis patients whose kidneys fail to produce enough erythropoietin
to support adequate RBC formation often times have hematocrits less than
half of healthy individuals. Genetically engineered injectable EPO can
dramatically help patients like this in increase their RBC formation and
improve their quality of life
In groups of 2, please answer the following questions and turn them in
with both names on the paper
What symptoms do you think a patient with a low hematocrit would have?
What possible reasons do you think someone would have to abuse this
medication?
What possible complications do you think could arise from this abuse?
Destruction of
RBCs
• Due to being anucleate RBCs only have a lifespan of
100-120 days
• As they age, the become more inflexible and fragile and
hemoglobin begins to deteriorate
• Old cells are often destroyed by macrophages
• The iron core of the heme group is saved and stored for
reuse the rest is broken down into bilirubin
• Most broken down bilirubin leave the body through the
feces and attributes to the brown coloring of fecal
material
• Buildup of excessive amounts of bilirubin in the blood
can lead to jaundice
Erythrocyte Disorders
Anemia – “Lacking Blood”
• A sign of a disorder rather than a disease of its own
• Condition in which the blood has abnormally low
oxygen-carrying capacity
• People with anemia often are fatigued, pale, short
of breath, and chilly
• Many different types of anemia with different
causes
Causes of Anemia
1. An insufficient number of red blood cells
Common Causes:
• Hemorrhage – usually due to trauma or illness that
causes internal bleeding i.e. gastric ulcers
• Excessive blood cell destruction (hemolytic anemia) –
RBC’s rupture prematurely. Can be caused by
hemoglobin abnormalities, transfusion of mismatched
blood, or bacterial or parasitic infections
• Bone marrow failure (aplastic anemia)- results from
the destruction or inhibition of the red bone marrow.
Can be caused by certain drugs or chemicals, radiation,
or viruses. Often times the cause may be unknown.
Blood transfusions will help until a bone marrow
transplant can occur
Causes of Anemia
2. Low Hemoglobin Content - Occurs when
hemoglobin molecules are normal, but RBCs contain
fewer than usual
• Iron deficiency anemia – usually a result of
hemorrhagic anemias, but may occur due to low intake
of iron-rich foods or impaired iron absorption
• Pernicious anemia – due to a deficiency of vitamin B12
which is found in meats, poultry, and fish so is not
usually a dietary disorder except for strict vegetarians.
It is usually caused by a lack of intrinsic factor which is
produced in the stomach and allows for vitamin B12
absorption.
Causes of Anemia
3. Abnormal hemoglobin
• Thalassemia- typically found in those of Mediterranean
decent (Greeks and Italians). One of the globin chains is
absent or faulty, and the RBCs are thin, fragile, and
deficient in hemoglobin
• Sickle-cell Anemia– caused by a change in one of the
146 amino acids in the beta chain of the globin
molecule. Causes the beta chains to link together under
low-oxygen conditions. Causes the cells to become
sickle shaped when they unload O2 molecules or when
O2 content in blood is lower than normal. Cells are
fragile and lyse easily and cause the blood vessels to
clog. Depending on where the crisis is occuring patients
may experience severe pain, shortness of breath,
infection, or stroke. Occurs primarily in African
Americans but can be seen in other ethnicities as well
Polycythemia…Too much of a good thing!
• Excessive amount of RBCs that increase blood
viscosity, causing it to sludge and flow slowly
– Increases risk for stroke and heart failure
• Secondary polycythemia- occurs when less
oxygen is available or EPO production increases
• Blood doping – dangerous practice used by
some athletes competing in aerobic events is an
artificially induced polycythemia
Leukocytes (WBC’s)
• The only formed elements that are complete cells
• Account for less than 1% of total blood volume
• Vital for our defense against disease by protecting us
from bacteria, viruses, parasites, toxins, and tumor
cells
• WBCs only use the circulatory system as a method of
transportation
• WBCs are able to travel out of the blood vessels
(diapedesis) and create a defense where they are
needed.
• Capable of ameboid movement both in the blood
vessels and in the tissues
Leukocytes
Grouped into 2 main categories
Granulocytes
– Contain specialized membrane-bound cytoplasmic
granules
– Include neutrophils, eosinophils, and basophils
– PHIL eats Grains
Agranulocytes
– lack obvious granules
– Include lymphocytes and monocytes
– No grains in sight (cyte)
Types of Leukocytes
in order of abundance
Remember! Never Let Monkeys Eat Bananas
Neutrophils
Leukocytes
Monocytes
Eosinophils
Basophils
Neutrophils
• Granulocyte
• Accounts for 50-70% of WBCs
• Named for the fact that they are “neutral” when stained
and the granules in the plasma pick up both red and blue
stain creating a lilac appearance of the plasma
• Multi-lobed nucleus with 2-5 lobes
• 1st cells to arrive to an injury site
• Actively phagocytic and partial to bacteria
• Most have a short lifespan (10 hours) and upon their death,
they release chemicals that attract new neutrophils
• A mixture of dead neutrophils, cellular debris, and other
waste products form the pus associated with infected
wounds
Eosinophils
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Granulocyte
Account for 2-4% of all leukocytes
Bi-lobed nucleus
Named because of the deep red stain the
granules take on with acid dye (eosin)
• Best defense cell for parasitic worms (flatworms
& roundworms)
• Attack objects that are coated with antibodies
• Their numbers increase with parasitic infections
and allergic reactions
Basophils
• Granulocytes
• Rarest of the WBCs and account for less than 1% of
the WBC count
• Granules stain a dark blue with basic dyes
• Granules contain heparin (prevents clotting) and
histamine (dilates blood vessels and produces
inflammation) that are released at an injury site
which increases WBC response
Lymphocytes
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Agranulocytes
Account for 25% or more of the WBC population
2 types (T lymphocytes & B lymphocytes)
T lymphocytes act directly against virus-infected cells and
tumor cells
• B lymphocytes give rise to plasma cells that produce
antibodies
• When stained they have a very large dark blue stained
nucleus that makes up most of the cell volume
• Few lymphocytes circulate in the blood and are most
frequently found in lymph tissue
Monocytes
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Agranulocytes
Account for 3-8% of all WBCs
Larges of the WBCs
U or Kidney shaped purple staining nucleus with
lots of plasma that stains pale blue
• Travel to the tissues and transform into
Macrophages
• Defend against viruses, bacterial parasites, and
chronic infections
• Activate lymphocytes to mount the immune
response
Check Point!!!!
• Identify the 5 types of Leukocytes
Neutrophils
Lymphocytes
Monocyte
Eosinophil
Basophils
• Which type of WBC would you expect to find in an infected cut?
Neutrophils , they are usually the first to arrive on scene and actively
phagocytize bacteria
• Which type of WBC would you find in elevated numbers in a
person producing large amounts of circulating antibodies to
combat a virus?
Lymphocytes usually attack viruses and produce antibodies in
response to infections
White Blood Cell Count
Normal White Count: 4800-10,800/µL
Leukopenia- indicates a reduced number of WBCs.
May be caused by diseases, medications, and
genetic deficiencies.
Leukocytosis- excessive numbers of WBCs due to
any cause
Leukemia- indicated in extreme leukocytosis with
white counts in excess of 100,000/µL or more
Leukemias
• Cause is not well understood, but it is believed to be a combination
of genetic and environmental factors
• In all leukemias, the red bone marrow becomes almost completely
occupied by cancerous leukocytes and immature WBCs that flood
the blood stream
• Other blood cells are crowded out so severe anemia and bleeding
problems result
• Other signs and symptoms include:
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Fever or chills
Persistent fatigue, weakness
Frequent or severe infections
Losing weight without trying
Swollen lymph nodes, enlarged liver or spleen
Easy bleeding or bruising
Recurrent nosebleeds
Excessive sweating, especially at night
Bone pain or tenderness
Leukemias
• The leukemia is named for the type of abnormal cell involved
Ex. Myelocytic leukemia Lymphocytic leukemia
Acute leukemia. In acute leukemia, the abnormal blood cells are
immature blood cells (blasts). They can't carry out their normal
functions, and they multiply rapidly, so the disease worsens quickly.
Acute leukemia requires aggressive, timely treatment.
Chronic leukemia. There are many types of chronic leukemias. Some
produce too many cells and some cause too few cells to be produced.
Chronic leukemia involves more mature blood cells. These blood cells
replicate or accumulate more slowly and can function normally for a
period of time. Some forms of chronic leukemia initially produce no
early symptoms and can go unnoticed or undiagnosed for years.
• All are fatal if not treated or if treatment is ineffective
Leukemia
The major types of leukemia are:
• Acute lymphocytic leukemia (ALL). This is the most common
type of leukemia in young children. ALL can also occur in
adults.
• Acute myelogenous leukemia (AML). AML is a common type of
leukemia. It occurs in children and adults. AML is the most
common type of acute leukemia in adults.
• Chronic lymphocytic leukemia (CLL). With CLL, the most
common chronic adult leukemia, you may feel well for years
without needing treatment.
• Chronic myelogenous leukemia (CML). This type of leukemia
mainly affects adults. A person with CML may have few or no
symptoms for months or years before entering a phase in
which the leukemia cells grow more quickly.
Platelets
• Cell fragments of much larger cells called
megakaryocytes
• Essential for the clotting process that occurs with
blood vessel damage
• Form a temporary plug that helps seal the
damaged vessel
• Anucleate so they age quickly and degenerate if
not used in about 10 days
Hemostasis
the stoppage of bleeding
• Fast, localized, and carefully controlled response
• Involves many clotting factors normally present in
the plasma as well as extra substances that are
release by the platelets and injured tissue cells
• Three step process
1. Vascular spasm
2. Platelet plug formation
3. Coagulation, or blood clotting
Vascular Spasm
(Blood vessel constriction)
Caused by:
• Chemicals released into the blood stream by the
cells of the torn vessel, platelets, and as a reflex
initiated by pain receptors
• As tissue damage increases, so too does vascular
spasm
• Important response because strongly constricted
arteries can significantly reduce blood loss for up
to 20-30 minutes allowing time for a platelet plug
to form and for coagulation to occur
Platelet Plug Formation
• Intact vessels prevent platelets from sticking together
by producing chemicals that prevent platelet
aggregation
• Once the tissue is damaged, collagen fibers of the
damaged tissue are exposed and platelets adhere to
them
• Platelets swell, form spiked projections, become
stickier, and release chemical messengers that attract
more platelets and increase vascular constriction
• More platelets = more chemicals = more platelets and
so on…(think back to semester one…what type of a
feedback mechanism is this?)
Coagulation
(blood clotting)
• Reinforces the platelet plug with fibrin threads
that act as a molecular glue
• Blood is transformed from a liquid to a gel in a
multi-step process than include chemicals called
clotting factors and procoagulants
• There are 12 different clotting factors which
include Ca+ ions
• Coagulation occurs in 3 distinct phases about 30
seconds after damage has occurred
• Most of the clotting factors are produced by the
liver
Phases of Coagulation
Phase 1: Prothrombin Activator Formation
(2 pathways)
• Intrinsic pathway
– Triggered by negatively charged surfaces such as activated
platelets, collagen, or glass
– Called intrinsic because the factors needed for clotting are
present within (intrinsic to) the blood
– Slower because it has many intermediate steps
• Extrinsic Pathway
– Triggered by exposing blood to tissue factor (TF) found in the
tissues underneath the damaged endothelium
– Called extrinsic because the tissue factor it requires is found
outside of blood
– Faster because it bypasses several steps of the intrinsic
pathway.
Phases of Coagulation
Phase 2: Common Pathway to Thrombin
•
Prothrombin activator initiates (catalyzes) the
transformation of the plasma protein prothrombin to the
active enzyme thrombin
Phases of Coagulation
Phase 3: Common Pathway to the Fibrin Mesh
• Thrombin initiates the transformation of fibrinogen to
fibrin
• Fibrin molecules join together to form long hair-like
insoluble fibrin strands
• Fibrin strands glue the platelets together and make a
web that forms the structural basis of the clot
• Fibrin makes plasma become gel-like and traps formed
elements that try to pass through it
• Fibrin + calcium ions activate factor XIII that binds fibrin
strands tightly together which strengthens the clot
• Clot formation is usually complete within 3-6 minutes
after blood vessel damage
Human Blood Groups
• RBC plasma membranes are covered in antigens
called agglutinogens
• ABO blood groups are based on the presence or
absence of 2 agglutinogens (type A and type B)
• Depending on which of these you inherit, your
blood type will be either A, B, AB, or O
• O blood group has neither agglutinogen and is the
most common blood group
• AB with both antigens is the most rare
• The presence of either the A antigen or the B
antigen alone results in either A type or B type
blood
Human Blood Groups
• Plasma contains antibodies called agglutinins
which seek out and destroy any cells that carry
agglutinogens (antigens) that are not found on
a person’s own RBCs
• Newborns lack these antibodies, but they begin
to appear within 2 months
• A person with AB blood type contains neither
antibody
• Type O blood contains both antibodies
Homework!!!!!
See if your parents know what their blood type
is…if they both know, then make and educated
guess at to what your blood type could be!