Download Anatomy and Physiology of the Hematological and Immune Systems

Chapter 45:
Anatomy and Physiology of the
Hematological and Immune
Systems
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Functions of the Blood
• Supplies the tissues with
oxygen and nutrients
• Takes away byproducts of
metabolism like CO2 to
organs for excretion
• Maintains acid-base balance
• Fights off infection
• Transports hormones to
target organs
• Prevents hemorrhage by
circulating clotting factors
• Maintains body temperature
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Components of the Blood
• Plasma
• Plasma proteins
–
Liquid portion
–
90% water/10% solutes
–
Contains plasma proteins
–
Immunoglobins
–
Fibrinogen
–
Electrolytes
–
Nutrients
–
Albumin/fibrinogen
produced by liver
• Albumin is carrier
substance and controller
of colloidal osmotic
pressure
• Fibrinogen is a key
component in clotting
–
Immunoglobins produced
by B lymphocytes
• Help prevent infection
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Components of the Blood (cont.)
• All components come from the pluripotent stem cell
• Hematopoiesis is the production of blood cells
• Two-stage process
– Proliferation (cellular or mitotic division)
– Maturation (differentiation into red or white cells or
platelets)
• Controlled by biochemical signals
• Takes place in bone marrow
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Major Maturational Stages of Blood Cells
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Question
Substances that can stimulate red blood cell production in
a patient with anemia include which of the following?
A. Iron, vitamin C, glucose
B. Calcium, potassium, iron
C. Phosphate, potassium, iron
D. Iron, vitamins B6 and B12, folic acid
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Answer
D. Iron, vitamin B6 and B12, folic acid
Rationale: Patients with anemia should be given vitamins
B6 and B12 and folic acid as well as iron.
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Erythrocytes: The Red Blood Cells (RBCs)
• Produced in the red bone marrow, primarily in the sternum, ribs,
pelvis, skull, and vertebrae
• Approximately 5 million/mm3
• To prevent anemia, iron, vitamins B6 and B12 plus folic acid are
needed to aid in RBC production
• The immature RBC is called a reticulocyte. Reticulocytes increase in
number when the demand for RBCs increases.
• Mature RBC has no nucleus
• RBCs look like a soft ball compressed between two fingers. Very
flexible with large surface areas.
• RBCs have thin walls that allow them to pass into the
microcirculation. After they release O2, they regain their shape.
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Erythrocytes: The Red Blood Cells (RBCs)
(cont.)
• Each RBC contains 12 to 18 g/dL of hemoglobin
• Loosely combines with oxygen, creating oxyhemoglobin
• Life of RBC is around 120 days
• Liver stores heme portion for new RBC formation
• Excess is excreted in the feces and urine as bilirubin
• Major function is respiration
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Leukocytes: White Blood Cells (WBCs)
• Major job is defending the body against invading
organisms
• Usually 5,000 to 10,000/m3
• Two major types: granulocytes and agranulocytes
• Granulocytes have granules that stain a certain color
• Agranulocytes do not have granules
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Question
Which of the following represents the largest percentage of
granulocytes?
A. Neutrophils
B. Basophils
C. Lymphocytes
D. Macrophages
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Answer
A. Neutrophils
Rationale: Granulocytes represent 70% of the total white
cell count, and of these, neutrophils represent 57% to
67% of the total. Neutrophils are released as an early
response to inflammation. Basophils are a type of
granulocyte that play an important role in the allergic
response. Lymphocytes and macrophages are
agranulocytes.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Platelets
• Also called thrombocytes
• Not technically cells but fragmented particles from
megakaryocytes
• Their function is to maintain capillary integrity, accelerate the
clotting process, and retract clots
• Live around 10 days
• Produced by the liver under the influence of thrombopoietin
• Normal value is 250,000 to 500,000/mm3
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Blood Coagulation
• Blood coagulation is mediated by platelets
• Platelets secret thromboxane A2, a powerful
vasoconstrictor that slows blood loss
• Platelets also plug small leaks in the endothelium
(intima)
• Collagen exposure from endothelium increases the
stickiness of platelets, leading to a small clot
• Also activation of the intrinsic pathway of the clotting
cascade by release of platelet factor 3
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Intrinsic Factor or Extrinsic?
• Intrinsic factor
– A result of factors released at the site of injury
• Extrinsic factor
– Initiated by injury outside the blood vessel (burn
injury)
• Both pathways converge at factor Xa (prothrombinase or
Stuart-Prower factor)
– Prothrombin is converted to thrombin, and this
results in fibrin formation (clot)
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The Coagulation Cascade
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Sequence of Thrombus Formation
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The Immune System
• Comprises organs (spleen, thymus, lymph node, bone
marrow, appendix, tonsils, and adenoids) and cells (B
and T lymphocytes, eosinophils, basophils, phagocytes)
• Role is to recognize and destroy antigens and microbes,
degrade RBCs, and monitor and destroy cancer cells
• Organs and cells circulate to both blood and lymphatic
system
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The Immune System (cont.)
• Adds in “self/non-self” recognition, where the body
combats foreign bodies entering it
• Immunocompetency refers to the ability of the body to
mount a defense against non-self cells or foreign bodies
• An antigen is a substance that elicits an attack response
by the body
– Infection and cancers result when body doesn’t
produce antigens
• An antibody combats an antigen
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Types of Immunity
GENERAL (INNATE)
SPECIFIC (ACQUIRED)
• Ability of body to prevent
bacterial invasion
• Patient develops own
antibodies
• Phagocytes and natural
killer cells (NKCs)
• Antibodies against antigens
have memories (quicker
response with second
exposure)
• Nonspecific and has no
memory
• Limits response until
specific response can be
mounted
• Second line of defense
• First line of defense
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Types of General Immunity
• Physical barriers (skin, mucous membranes, epiglottis,
etc.)
• Chemical barriers (antibodies, acidic solutions)
• Mechanical barriers (urinary flow, tears)
• Biological defenses (colonized flora of gut, skin, etc.)
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Types of General Immunity (cont.)
• Phagocytes and phagocytosis (ingestion of unwanted
bacteria/cells by macrophages and monocytes)
• Inflammatory responses (localized or systemic response to
injury); three stages:
– Vascular stage
– Cellular exudate stage
– Tissue repair and replacement stage
• Cytokines (interleukins are messengers that tell leukocytes
what to do)
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Question
In the inflammatory response to tissue injury, the most
important result is the collection of neutrophils and
macrophages, resulting in destruction of the causative
organism.
A. True
B. False
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Answer
A. True
Rationale: The first wave of defenders (neutrophils) and
the second wave (macrophages and more long-term
processes) ensure that a swift, sustained resistance is
mounted as part of the normal inflammatory response.
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Types of Specific Immunity: Cell-Mediated
• Cell-mediated involves B and T lymphocytes
– T lymphocytes are activated by specific antigens and can
bind to a specific receptor site
– T lymphocytes also produce clones that migrate and attack
antigens and malignant cells
– Macrophages are also stimulated and produce cytokines
– Cytokines liberate and stimulate B cells and phagocytes
– Impaired cellular immunity results in risk for viruses,
fungi, and parasites
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Types of Specific Immunity: Humoral
Immune Response
• The humoral system involves the immunoglobins and
complement, which are serum proteins
• Humoral response occurs outside the cell in the blood
and tissue fluids
• Immunoglobins come from B lymphocytes that
differentiate into memory and plasma cells
• Result in antigen-antibody complexes, which are
phagocytosed
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Question
Which of the following immunoglobins is involved with
secretions of the respiratory and GI tracts?
A. IgA
B. IgM
C. IgD
D. IgE
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Answer
A. IgA
Rationale: IgA has two component types that aid body
fluids in destroying microbial invaders.
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