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Blood
Chapter 12
Blood
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Specialized CT
Transports materials
Maintains stability of interstitial fluid
Distributes heat
Amount varies with body size, fluid concentration
changes, electrolyte concentration changes
• ~8% of body weight
• ~5L = adult blood volume
Blood Cells
• Form mostly in the red bone marrow
• Includes:
– Red Blood Cells (RBCs)
– White Blood Cells (WBCs)
– Platelets (cell fragments)
• Blood cells form from:
Hemocytoblasts in the red marrow
Hematopoietic stem cells in the red marrow
Capillary tube
Plasma = 55%
Mostly water, solutes (like proteins,
electrolytes, some gases)
Buffy coat
Leukocytes & platelets (<1%)
Red cells = 45%
(hematocrit)
Plug
Blood
45%
55%
Formed elements
Platelets
(4.8%)
Red blood
cells
(95.1%)
Plasma
White blood
Water Proteins Wastes Nutrients Gases
cells Electrolytes (92%) (7%)
(0.1%)
Vitamins
Hormones
BasophilsMonocytesLymphocytes
Neutrophils Eosinophils
Albumins Globulins Fibrinogen
(<1%)
(25–33%)
(3–9%)
(54–62%) (1–3%)
N2
O2
CO2
Red Blood Cells (Erythrocytes)
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Biconcave discs
One-third hemoglobin
Lack nuclei and mitochondria
RBC count = the number of RBCs in a cubic
millimeter or microliter of blood
RBC Production
• Low blood oxygen signals kidneys & liver to release
erythropoietin (EPO)
– Stimulates RBC production
– Feedback mechanism?
• New RBCs appear in the circulating blood within a
few days
Factor
Vitamin B12
Source
Absorbed from small intestine
Function
DNA synthesis
Iron
Absorbed from small
intestine; conserved during
RBC destruction
Hemoglobin
synthesis
Folic acid
Absorbed from small intestine
DNA synthesis
Types of Anemia
Type
Aplastic anemia
Cause
Defect
Toxic chemicals,
Damaged bone
radiation
marrow
Hemolytic anemia
Toxic chemicals
RBCs destroyed
Iron deficiency Dietary lack of iron
Hb deficient
anemia
Pernicious anemia Inability to absorb
Excess of
B12
immature cells
Sickle cell disease
Defective gene
Misshapen RBCs
Thalassemia
Defective gene
Hb deficient; RBCs
short-lived
White Blood Cells (Leukocytes)
• Protect against disease
• Five types of WBCs (two categories):
– Granulocytes
• Neutrophils
• Eosinophils
• Basophils
– Agranulocytes
• Lymphocytes
• Monocytes
Neutrophils
• Light purple granules when in neutral (acid-base)
stain
• Lobed nucleus
• First to arrive at infections
• Phagocytic
• 54-62% of leukocytes
• Elevated in bacterial infections
Eosinophils
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Deep red granules in acid stain
Bi-lobed nucleus
Moderate allergic reactions
Defend against parasitic worms
1-3% of leukocytes
Elevated in parasitic worm
infections and allergic reactions
Basophils
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Deep blue granules in basic stain
Releases heparin and histamine
Less than 1% of leukocytes
Similar to eosinophils in size, nucleus shape
Monocytes
• Largest of all blood cells
• Spherical
• Nucleus can be kidney-shaped, ovalular, or
lobed
• May leave bloodstream to become
macrophages
• 3-9% of leukocytes
• Phagocytic
Lymphocytes
• Slightly larger than RBCs
• Large, spherical nuclei surrounded by thin rim
of cytoplasm
• T cells and B cells
– Immunity
– (B cells produce antibodies)
• 25-33% of leukocytes
WBC Functions
• Protect against infection
• Squeeze between the cells of capillary wall
and the space outside the blood vessel
Connective
tissue
Blood capillary
Leukocyte
Splinter
punctures
1 epidermis
2
Bacteria are introduced
into the dermis
3 Bacteria
multiply
Injured cells
release
histamine,
4 causing blood
vessels to
dilate
Epidermis
Dermis
Blood vessels
5 Neutrophils move
through blood vessel
walls and migrate
toward bacteria
6 Neutrophils destroy
bacteria by
phagocytosis
WBC Counts
• Counts number of WBCs per cubic millimeter of
blood
• Typically 5,000 – 10,000 per cubic millimeter of blood
• Leukopenia – low WBC count (<5,000)
• Typhoid fever, flu, measles, mumps, chicken pox, AIDS
• Leukocytosis – high WBC count (>10,000)
• Acute infections, vigorous exercise, loss of body fluid
• Differential WBC count
• Lists percentages of each type of leukocyte
• May change in particular diseases
Blood Platelets
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Platelets = thrombocytes
Cell fragments of megakaryocytes
Lack nucleus; half the size of a RBC
130,000-360,000 per cubic mm of blood
Repair damaged blood vessels by sticking to
broken surfaces
Blood Plasma
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Liquid portion of blood; straw-colored
55% of blood volume
92% water
Transports nutrients, gases, vitamins
Regulates fluid & electrolyte balance,
maintains pH
Plasma Proteins
• The most abundant dissolved substances
(solutes) in plasma
Non-protein Substances
• Gases, nutrients
• Nitrogenous substances
– Urea – product of protein catabolism (~50%)
– Uric acid – product of nucleic acid catabolism
– Amino acids – product of protein catabolism
– Creatine – stores phosphates
– Creatinine – product of creatine metabolism
– BUN – blood urea nitrogen (kidney health indicator)
Hemostasis
• Stoppage of bleeding
• Actions:
– Blood vessel spasm (smooth muscle of vessel contracts)
• Triggered by pain receptors, platelet release, or serotinin
– Platelet plug formation (platelets adhere to surface)
• Triggered by exposure of platelets to collagen
– Blood coagulation
• Causes formation of blood clot via a cascade of reactions
• Triggered by cellular damage, blood contact with foreign
substances
Endothelial lining
Collagen fiber
Platelet Plug
Formation
1 Break in
vessel wall
Platelet Red blood cell
2 Blood escaping
through break
3 Platelets adhere
to each other,
to end of broken
vessel, and to
exposed collagen
4 Platelet plug
helps control
blood loss
Extrinsic Clotting Mechanism
• Chemical outside blood vessel triggers
coagulation
• Triggered when blood contacts a damaged
blood vessel wall or tissues
• Positive feedback mechanism
Intrinsic Clotting Mechanism
• Chemical inside blood triggers blood
coagulation
• Triggered when blood contacts a foreign
substance
Fate of Blood Clots
• After a blood clot forms it retracts and pulls the
edges of a broken blood vessel together while
squeezing the fluid serum from the clot
• Smooth muscle cells and fibroblasts stimulated to
repair damaged blood vessel walls
• Plasmin digests the blood clots
• Thrombus = abnormal blood clot
• Embolus = blood clot moving through the blood
vessels
Prevention of Coagulation
• Smooth lining of blood vessels discourages
accumulation of platelets & clotting factors
• As clot forms fibrin absorbs thrombin,
prevents clot from spreading
• Anti-thrombin inactivates additional thrombin
to block unnecessary clotting
• Basophils and mast cells can secrete heparin
(anti-coagulant)
Arteriosclerosis/Atherosclerosis
• Arteriosclerosis
– Thickening and loss of elasticity in artery walls
• Atherosclerosis
– Specifically, fat plaques that are filled with
cholesterol, other lipids, form in the artery
Hypertension
• Persistently elevated arterial pressure
– High sodium intake, obesity, stress, arteriosclerosis
– Left ventricle works harder to pump blood
– The myocardium thickens
– Coronary blood vessels cannot support this
overgrowth, and heart muscle can die, replaced with
fibrous tissue
– Enlarged, weakened heart will eventually die
• Also contributes to atherosclerosis – plaque can
accumulate and cause coronary thrombosis or
embolism, or stroke in the brain
Blood Types – Terms to Know
• Agglutination – clumping of RBCs in response
to reaction between an antibody and antigen
• Antigens – a chemical that stimulates cells to
produce antibodies
• Antibodies – a protein that reacts against a
specific antigen
ABO Blood Group
• Type A, B, or O
• Based on presence/absence of either of two
major antigens on the RBC cell membrane:
– Antigen A
– Antigen B
Red blood cell
Red blood cell Anti-B antibody
Antigen A
Anti-A antibody
Antigen B
Type B blood
Type A blood
Red blood cell
Anti-A antibody
Anti-B antibody
Antigen A
Antigen B
Red blood cell
Type AB blood
Type O blood
Antigen A
Red blood cell
Anti-B antibody
(a)
Agglutinated red
blood cells
Anti-A antibody
(b)
Rh Blood Group
• Rhesus monkey
• Rh positive or negative
– Presence/absence of “Antigen D” or other Rh antigens
• Fetus can develop erythroblastosis fetalis
(hemolytic disease)
– Can happen in Rh-negative mother on the second or
subsequent Rh-positive pregnancy