Blood
Cardiovascular System
Blood Functions
1. Transports
• Dissolved gasses
• Nutrients
• Waste products to lungs and kidneys
• Enzymes
• Hormones from endocrine organs
2. Regulates
• pH
• Electrolyte concentration of body fluids
• Body temperature
3. Restricts fluid loss
4. Defends pathogens and toxins
Blood Composition
1. Formed elements
• Erythrocytes
• Leukocytes
• Platelets
2. Plasma
Overview of Blood Circulation
• Blood leaves the heart via arteries that branch repeatedly
until they become capillaries
• Oxygen (O2) and nutrients diffuse across capillary walls and
enter tissues
• Carbon dioxide (CO2) and wastes move from tissues into the
blood
• Oxygen-deficient blood leaves the capillaries and flows in veins
to the heart
• This blood flows to the lungs where it releases CO2 and picks
up O2
•
The oxygen-rich blood returns to the heart
Blood Physical Characteristics
and Volume
Sticky, opaque fluid with a metallic taste
• Color varies from scarlet (oxygen-rich) to dark red (oxygen-poor)
• pH of blood is 7.35–7.45
• Temperature is 38C, slightly higher than “normal” body
temperature
• Blood accounts for approximately 8% of body weight
• Average volume of blood is 5–6 L for males, and 4–5 L for
females
Plasma
•
Plasma accounts for 55 % of the volume of whole blood.
•
92% of plasma is water, the rest consists of electrolytes and dissolved
organic compounds.
Blood plasma contains over 100 solutes, including:
•
Proteins – albumin, globulins, clotting proteins, etc…
•
Non-protein nitrogenous substances – lactic acid, urea, creatinine
•
Organic nutrients – glucose, carbohydrates, amino acids
•
Electrolytes – sodium (Na+), potassium (K+), calcium (Ca++),
chloride (Cl-), bicarbonate (HCO3-)
•
Respiratory gases – oxygen and carbon dioxide
Plasma Proteins
• Albumin
1. Contributes to the osmotic pressure of the blood
2. Provides a transport mechanism for specific insoluble or
valuable materials in the blood.
• Globular proteins
1. Binding and transporting hormones, lipids (lipoproteins),
and metal ions.
2. The immunoglobulins (antibodies) are proteins that
attack foreign proteins and pathogens.
• Fibrinogen molecules aggregate to form large insoluble
strands of fibrin that establish the basis for a blood clot.
Erythrocytes
• Biconcave discs
• RBCs have no nuclei or organelles (anucleate)
allow for a huge surface area to volume ratio
• Hematocrit – % of RBCs out of the total blood volume.
(Ave) 46 adult men & 42 adult women.
• There are roughly 5 million RBCs in each microliter of
blood
• Erythrocytes are unable to perform normal maintenance
operations and usually degenerate after about 120 days in
the circulation.
Hemoglobin
• Hemoglobin (Hgb), a globular protein formed
from four subunits.
• Heme molecules bind to oxygen when plasma
concentrations are high; the oxygen is
released when plasma concentrations decline.
• Carbon dioxide molecules can be bound to the
globin portion of the hemoglobin molecule.
Hemoglobin
Composed of:
• The protein globin, made up of two alpha and two beta chains, each bound
to a heme group
• Each heme group bears an atom of iron, which can bind one to oxygen
molecule
• Each hemoglobin molecule can transport four molecules of oxygen
Oxyhemoglobin – hemoglobin bound to oxygen
•
Oxygen loading takes place in the lungs
Deoxyhemoglobin- hemoglobin after oxygen diffuses into tissues (reduced
Hgb)
Carboxyhemoglobin – hemoglobin bound to carbon dioxide
•
Carbon dioxide loading takes place in the tissues
• The fetus forms HbF, which has a higher affinity for oxygen than adult
hemoglobin
What happens to old RBC’S?
• Damaged or expired red blood cells are
recycled by phagocytes.
• Proteins are disassembled into amino acids
• Iron gets bound to transferrin for
transport to the bone marrow and liver
• Heme units are not recycled, but removed
from the circulation by the liver
Fate and Destruction of Erythrocytes
• The life span of an erythrocyte is 100–120 days
• Dying erythrocytes are engulfed by macrophages
• Heme & globin are separated and the iron is salvaged
for reuse
Fate of Hemoglobin
• Heme is degraded to a yellow pigment called bilirubin
• The liver secretes bilirubin into the intestines as bile
• The intestines metabolize it into urobilinogen
• This degraded pigment leaves the body in feces, in a
pigment called stercobilin or as urobilinogen in urine
• Globin is metabolized into amino acids and is released
into the circulation
Iron transport
Blood Types
• Agglutinogens A, B, and D (Rh) on the exposed surfaces of
the red blood cells determine an individual's blood type.
• Anti-Rh agglutinins are only synthesized after an Rh-negative
individual becomes sensitized to the Rh agglutinogen. (During
pregnancy)
• Testing for compatibility involves the determination of blood
type and a cross-match test.
• Standard blood typing detects the A, B, and D (Rh)
agglutinogens. The most common blood type used for
transfusion is O-negative (universal donor – NO ANTIGENS).
AB-positive (Universal recipient – NO ANTIBODIES)
Blood
Rh Type Percent
Type
A
B
AB
O
+
34 %
-
6 %
+
9 %
-
2 %
+
3 %
-
1 %
+
38 %
-
7 %
Erythroblastosis Fetalis
Hemolytic Disease of the Newborn
(Erythroblastosis fetalis)
• Rh+ antibodies of a sensitized Rh– mother cross
the placenta and attack and destroy the RBCs of
an Rh+ baby
• Rh– mother become sensitized when Rh+ blood
(from a previous pregnancy of an Rh+ baby or a
Rh+ transfusion) causes her body to synthesis Rh+
antibodies
• The drug RhoGAM can prevent the Rh– mother
from becoming sensitized
• Production of Blood Cells
• Hematopoiesis – blood cell formation
• Hematopoiesis occurs in the red bone marrow of
the:
- Axial skeleton and girdles
- Epiphyses of the humerus and femur
Hemocytoblasts give rise to all formed elements
• Circulating stem cells give rise to embryonic blood
cells which migrate into the liver, spleen, thymus,
and bone marrow.
Erythropoiesis
• Occurs within red marrow of the sternum, vertebrae,
skull, scapulae, pelvis, and proximal limb bones.
• Red blood cell formation increases under erythropoietin
stimulation. This hormone is released from the kidneys
when they are not receiving adequate supplies of oxygen.
• Erythropoiesis is hormonally controlled and depends on
adequate supplies of iron, amino acids, and B vitamins
• Reticulocytes (immature RBC’s) usually account for 0.8
percent of circulating red blood cells.
Erythropoietin
Erythropoietin (EPO) release by the kidneys is
triggered by:
• Hypoxia due to decreased RBCs
• Decreased oxygen availability
• Increased tissue demand for oxygen
Erythropoiesis increases the:
• RBC count in circulating blood
• Oxygen carrying ability of the blood increases
Erythropoiesis requirement
• Proteins, lipids, and carbohydrates
• Iron, vitamin B12, and folic acid
The body stores iron in Hgb (65%), the liver,
spleen, and bone marrow
Intracellular iron is stored in protein-iron
complexes such as ferritin and hemosiderin
Circulating iron is loosely bound to the transport
protein transferrin
Erythrocyte pathophysiology
Anemia – blood has abnormally low oxygencarrying capacity
• Blood oxygen levels cannot support
normal metabolism
• Signs/symptoms include fatigue,
paleness, shortness of breath, increased
heartrate, low blood pressure, and chills
Anemia: Insufficient Erythrocytes
• Hemorrhagic anemia
– result of acute or chronic loss of blood
(e.g.Trauma & Menstruation)
• Hemolytic anemia
– prematurely ruptured erythrocytes
• Aplastic anemia
– destruction or inhibition of red bone
marrow
• Sickle cell anemia
Anemia: Decreased Hemoglobin
Content
Iron-deficiency anemia results from:
• A secondary result of hemorrhagic anemia
• Inadequate intake of iron-containing foods
• Impaired iron absorption
Pernicious anemia results from:
• Deficiency of vitamin B12
• Often caused by lack of intrinsic factor
needed for absorption of B12
Pernicious Anemia
Anemia: Abnormal Hemoglobin
Thalassemias – absent or faulty globin chain
in hemoglobin
•
Erythrocytes are thin, delicate, &
deficient in hemoglobin
Sickle-cell anemia – results from a defective
gene coding for an abnormal hemoglobin called
hemoglobin S (HbS)
Polycythemia
• Excess RBCs that increase blood viscosity
• Blood doping in athletics
Leukocytes
• White blood cells are components of the
immune system that defends the body
against pathogens, toxins, wastes, and
abnormal or damaged cells and tissues.
• There are 6,000-9,000 white blood cells
in each microliter of whole blood
Leukocytes
•
Normal response to bacterial or viral invasion
•
Move through tissue spaces
•
Granular leukocytes include neutrophils, eosinophils , and basophils.
•
Neutrophils are abundant, highly mobile phagocytes.
•
Eosinophils are attracted to foreign compounds coated with antibodies.
•
Basophils migrate into damaged tissues and release histamine, aiding in the
inflammation response.
•
Monocytes migrating into peripheral tissues become free macrophages.
•
Lymphocytes, cells of the lymphatic system, include T cells and B cells. T
cells migrate to peripheral tissues and attack foreign or abnormal cells; B
cells produce antibodies.
Leukopoiesis
•
Granulocytes and monocytes are produced by stem cells in the bone marrow
•
Lymphocytes are produced in bone marrow, thymus, & spleen
Granulocytes
Which WBC’s are granulocytes?
Neutrophils (Polymorphonuclear)
• 60-70% of WBC’s
Neutrophils have two types of granules that:
• Take up both acidic and basic dyes
• Give the cytoplasm a lilac color
• Contain peroxidases, hydrolytic enzymes, and
defensins (antibiotic-like proteins)
Neutrophils are our body’s bacterial slayers
Lifespan : 1 day in blood; 1-2 days in tissue
Eosinophils
• 1-4% of WBC’s
• Have red-staining, bi-lobed nuclei connected via a broad
band of nuclear material
• Lead the body’s counterattack against parasitic worms
• Lessen the severity of allergies by phagocytizing immune
complexes
• Lifespan: 1 day in blood; weeks in tissue
Basophils
• 0.5-1% of WBC’s
• Have large, purplish-black (basophilic)
granules that contain histamine
• Histamine – inflammatory chemical that
acts as a vasodilator & attracts other
WBCs
• Lifespan: 1 day in blood; hours in tissue
Agranulocytes
Which WBC’s are
agranulocytes?
Lymphocytes
• 20-25% of WBC’s
• Have large, dark-purple, circular nuclei with a thin rim of blue
cytoplasm
• Found mostly enmeshed in lymphoid tissue (some circulate in the
blood)
• There are two types of lymphocytes: T cells and B cells
• T cells function in the immune response
• B cells give rise to plasma cells, which produce antibodies
• Lifespan: Years
Monocytes
• 3-8% of WBC’s
• They are the largest leukocytes
• They have abundant pale-blue cytoplasms
• They have purple staining, U- or kidney-shaped nuclei
• They leave the circulation, enter tissue, and differentiate
into macrophages
• Lifespan: Days in blood; years in tissue
Leukocyte pathophysiology
• Leukemia refer to cancerous conditions involving white blood cells
• Immature white blood cells are found in the bloodstream in all
leukemias
• Bone marrow becomes totally occupied with cancerous leukocytes
• The white blood cells produced, though numerous, are not
functional
• Death is caused by internal hemorrhage and overwhelming infections
• Acute leukemia involves blast-type cells and primarily affects children
• Chronic leukemia is more prevalent in older people
Leukemia
Common symptoms of leukemia:
• Anemia
• Fever
• Weakness and fatigue
• Frequent infections
• Loss of appetite and/or weight
• Swollen or tender lymph nodes, liver, or spleen
• Easy bleeding or bruising
• Tiny red spots (called petechiae) under the skin
• Swollen or bleeding gums
• Sweating, especially at night
• Bone or joint pain.
Thrombocytes
• Platelets
• Megakaryocytes in the bone marrow release
packets of cytoplasm, called platelets, into the
circulating blood. There are 150,000-500,000
platelets in each microliter of whole blood.
• Platelet granules contain serotonin, Ca2+, enzymes,
ADP, and platelet-derived growth factor (PDGF)
• Platelets function in the clotting mechanism by
forming a temporary plug that helps seal breaks in
blood vessels
Blood
clotting
Cascade
Blood clotting
• The coagulation process requires
calcium ions, and Vitamin K must be
available for the synthesis of five of
the clotting factors.
Hemostasis Pathophysiology
• Thromboembolytic Disorders
Thrombus – a clot that develops and persist in an unbroken
blood vessel
Embolus – a thrombus freely floating in the blood stream
Thrombocytopenia – condition where the number of
circulating platelets is deficient
Hemophilias – hereditary bleeding disorders caused by lack
of clotting factors
Hemophilia
Hemophilia A – most common type (83% of all cases) due to a
deficiency of factor VIII
•
•
Hemophilia B – results from a deficiency of factor IX
Hemophilia C – mild type, caused by a deficiency of factor
XI
• Symptoms include prolonged bleeding and painful and
disabled joints
• Treatment is with blood transfusions and the injection of
missing factors
Hemophilia after injection
Prevention of undesirable clots
Substances used to prevent undesirable clots
include:
• Aspirin
• Heparin
• Warfarin (Coumadin)
• Flavonoids – substances found in tea, red wine, and
grape juice that have natural anticoagulant activity
Leukocyte
Differential
Practice
Are we done yet?