Transcript Lecture # 16 Date

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Chapter 14, Section 1 of 2.
Blood
Functions of Blood:
1. Transports gasses, (O2 and CO2)
2. Transport nutrients, wastes,
electrolytes, and hormones
3. Distributes heat throughout the body
4. Contains buffers
5. Immunity
Introduction
Characteristics of Blood:
Blood is a connective tissue
1. Cells are called= formed elements
• Red Blood Cells
• White Blood Cells
• Platelets
2. Liquid Matrix = plasma
Centrifuged Blood:
1. Plasma, 55%
2. Buffy Coat, <1%
• Proteins and WBCs
3. Red Blood Cells, 45%
• Hematocrit = packed RBCs
Hematopoiesis
Hematopoiesis is the formation of new blood cells.
• Occurs within red bone marrow
• Blood stem cells are called, hemocytoblasts ( or hematopoietic stem cells)
• Hemocytoblasts can give rise to additional blood stem cells
• Can differentiate into any of the blood cells
• The fate of hemocytoblast depends on hematopoietic growth factors
Example:
Erythropoietin (EPO = growth factor)
Hemocytoblast
erythroblast
reticulocyte
erythrocyte (RBC)
Erythrocytes: red blood cells (corpuscles)
Characteristics of erythrocytes
1. Biconcave cells
2. anucleated (nucleus dislodged during formation)
3. Average diameter = 7.5µm
4. 1/3 volume is hemoglobin
• Oxyhemoglobin – bright red
• Deoxyhemoglobin – dark brick red
Red Blood Cell Counts
RBC counts is the number of RBCs in a cubic
millimeter or microliter of blood
1. Male
2. Female
3. Child
4.6 - 6.2 million cells per µL
4.2 - 5.4 million cells per µL
4.5 - 5.1 million cells per µL
Erythropoiesis: RBC production
Sites of Erythropoiesis
Adult – Erythropoiesis occurs primarily in red bone marrow, which is found
within
• flat bones (sternum, pelvis, ribs, skull)
• Proximal end of long bones (femur, humerus)
Child
• Erythropoiesis occurs within the yolk sac, liver, and spleen
Example of erythropoiesi:
Erythropoietin (EPO)
In red bone marrow
circulation
Erythrocytes: feedback loop
Erythopoiesis is stimulated by low blood oxygen.
• Decreased blood O2 may cause the
kidneys and the liver (to a lesser extent)
to release erythropoietin (EPO)
• EPO stimulates RBC production
• This is a negative feedback
mechanism
• Within a few days many new blood
cells appear in the circulating blood
Dietary Factors of Erythropoiesis
• Iron – required for hemoglobin production
• Vitamin B12 & Folic Acid – required for DNA synthesis
(and thus, cell production)
Lifespan of Red Blood Cells
Red blood cells survive about 120 days in circulation.
• With age, RBCs become fragile and easily rupture.
• Old RBCs are removed by the liver and spleen
• Hemoglobin is liberated and recycled in new RBCs
Hemoglobin breakdown
Hemoglobin
Heme
+
Globin
Amino acids
• recycled by body
Biliverdin
+
Iron (Fe2+)
• Reused by liver in synthesis of
new hemoglobin
Bilirubin
• Excreted as bile pigment
Jaundice: yellowish staining of skin caused by the accumulation of bile pigments.
Jaundice may indicate increased RBC destruction, destruction of liver
tissue, or blockage of the biliary tract.
Red Blood Cell Disorders
Erythrocytosis (polycythemia) is an excess number
of RBCs in the blood.
• Causes include
1. Genetic mutations
2. Poor blood oxygen levels or delivery
3. tumor
Polycythemia. The surplus of RBCs causes
the blood to be more viscous and it slows
its flow through the body. This increases
the likelihood of clot formation.
Anemia
• Low oxygen capacity of blood, several types
1. Iron deficiency – body cannot form
hemoglobin
2. Hemolytic – excess RBC destruction
3. Sickle cell – sickle-shaped RBCs
4. Aplastic – inability to produce RBCs
Sickle cell anemia. RBCs take on a thin sickle shape when
deoxygenated. The sickle cells sludge in capillaries, further
reducing blood flow and oxygen levels
Leukocytes (White Blood Cells)
Functions of WBCs
1. Protect against infection
2. Remove worn out cells & debris
3. immunity
Colony Stimulating Factors and Interleukins
are growth factors that promote the development
of white blood cells.
There are five types of white blood cells within 2 categories
Granulocytes
• Visible lysosomes “granules” in cytoplasm
1. Neutrophil
2. Eosinophil
3. Basophil
Agranulocytes
• No visible granules in cytoplasm
1. Monocyte
2. Lymphocyte
Neutrophils
Overview:
1. Neutrophils stain in acid-base stains
2. Constitutes 54-62% of WBCs
3. Also called polymorphonuclear leukocytes “polymorphs”
4. Contain 2-5 nuclei + fine purple granules
5. 12 hour lifespan
Functions
1. Phagocytosis
• Kill bacteria, protozoa, fungi, parasites
• Remove dead cells, debris, and foreign particulate
2. First to arrive at the site of infection
• Fast moving cells
neutrophil, 1000x
Eosinophils
Overview:
1. Constitute 1-3% of all WBCs
2. Bi-lobed nucleus
3. Granules stain bright red in acid stain
Functions
1. Defend against parasitic worms (tapeworm, hookworm, fluke worm, ect)
2. mediates allergic reaction and asthma attacks
eosinophil, 1000x
Basophils
Overview:
1. Constitutes <1% of WBCs
2. Deep blue granules stain in basic dye
3. Bilobed nucleus is usually obscured by the darkened granules
Functions
1. Secretes histamines
• Histamines promote inflammation
2. Secretes heparin
• Heparin is an anticoagulant “prevents clotting”
basophil, 1000x
Monocytes
Overview:
1. Constitutes 3-9% of WBC
2. Largest of all WBCs
3. Large kidney-shaped nucleus
4. May live for several weeks up to a month
Functions
1. Leave the blood to become macrophages
2. Phagocytize bacteria, dead cells and other debris
platelet
monocyte, 1000x
Lymphocytes
Overview:
1. Constitutes 23-33% of all WBCs
2. Formed in red bone marrow and in lymphatic tissues
3. Large spherical nucleus with a thin sliver of cytoplasm
4. May live for many months to several years
5. Includes T-cells & B-cells
Functions
1. Lymphocytes provide immunity
• T-cells directly attack microorganisms and tumor cells
• B-cells produce antibodies
lymphocyte, 1000x
Functions of white blood cells
1. Leukocytes (primarily neutrophils & monocytes) are motile
• Exhibit amoeboid movement
• Neutrophils & Monocytes are the most mobile of WBCs
2. Leukocytes are capable of diapedesis.
• They can squeeze between the cells of a capillary wall and enter the tissue space
outside the blood vessel.
3. Leukocytes exhibit chemotaxis.
• They are attracted to chemicals released by damaged tissues.
4. Leukocytes contribute to the formation of pus.
• Pus is the accumulation of bacteria, damaged tissue, and dead white blood cells.
Figure 14.15 illustrates diapedesis of a WBC from
a capillary into the surrounding connective tissue.
Activation of WBCs
Figure 14.16 When bacteria invade the tissues, leukocytes migrate into the region
and destroy the microbes by phagocytosis.
White Blood Cell Counts
A typical white blood count contains 4,500-10,000 WBCs per µL (mm3)
Leukopenia is a low WBC count (below 4,500 cells/µL)
• Often associated with viral infections (influenza, chicken pox, measles, AIDS)
Leukocytosis is a high WBC count (above 10,000 cells/µL)
• Acute infection, exercise, emotional distress
DIFF (differential WBC count)
• Measures the percentages specific types of WBC
Table 14.4 illnesses associated
with various DIFF counts
Thrombocytes (platelets)
TPO
Overview
1. Platelets are cell fragments released from Megakaryocytes within
red bone marrow
2. Approximately 150,000 - 450,000 platelets per µL (mm3) of blood.
3. Thrombopoietin (TPO) = growth factor that promotes formation of
platelets.
4. Functions include blood coagulation and blood vessel repair
Figure 14.4. Development of platelets from hemocytoblasts.
Exposure to TPO promotes the formation of megakaryocytes,
which release thrombocytes from their plasma membrane.
Overview of Blood Cells
End of Section 1 of 2.
Plasma
Overview
1. Plasma is the liquid portion of blood
2. Makes up 55% of blood volume
3. Straw colored
4. Components include Plasma proteins, Dissolved gasses, Wastes, Electrolytes,
Nutrients, Hormones
Chapter 14, Section 2 of 2.
Plasma proteins
1. Albumin
• 60% of plasma proteins
• Synthesized in liver
• Creates an osmotic that helps
maintain blood pressure
2. Globulins
• 36% of plasma proteins
• Alpha & Beta globulins
o Are produced by liver
o Transports lipids
• Gamma globulins
o Are produced by
lymphatic tissues
o function as antibodies
3. Fibrinogen
• 4% of plasma proteins
• Primary role in blood coagulation
Plasma proteins
Plasma Gasses & Nutrients
• Blood Gasses:
• Oxygen
•Most is bound to hemoglobin. Less than 2% of
oxygen is dissolved in plasma
• Carbon dioxide
•Most CO2 is transported as bicarbonate (HCO3-)
• About 7% is dissolved in plasma
• Nutrients:
• Amino acids
• Simple sugars
• Nucleotides
• Lipids
• Hydrophobic lipids are bound to plasma proteins
within the plasma
Nonprotein Nitrogenous Substances
• These are molecules containing nitrogen but are not proteins
• In plasma they include:
• Urea – product of protein catabolism; about 50% of nonprotein
nitrogenous substances
• Uric acid – product of nucleic acid catabolism
• Amino acids – product of protein catabolism
• Creatine – biproduct of creatine phosphate metabolism
• Creatinine – product of creatine metabolism
Common tests that evaluate kidney functions:
•Creatinine test – measures creatinine
•BUN – blood urea nitrogen; indicates health of kidney
Plasma Electrolytes
• Plasma contains a variety of these ions called electrolytes
• They are absorbed from the intestine or released as by-products of
cellular metabolism
• They include:
• Sodium (most abundant with chloride)
• Potassium
• Calcium
• Magnesium
• Chloride (most abundant with sodium)
• Bicarbonate
• Phosphate
• Sulfate
Hemostasis
• Hemostasis refers to the stoppage of bleeding
• Actions that limit or prevent blood loss include:
1. Blood vessel spasm (vasospasm)
2. Platelet plug formation
3. Blood coagulation
hemostasis, step 1: vasospasm
• Blood vessel spasm (vasospasm)
• Cutting or breaking a vessel wall stimulates the smooth
muscles in its walls to contract.
•Vasospasm reduces blood loss almost immediately, and may
close small blood vessels completely.
hemostasis, step 2: platelet plug formation
1. Platelet adhesion – platelets
adhere to collagen fibers that
become exposed due to the
damage in a vascular walls
2. Platelets undergo a shape
change, producing several
processes to which additional
platelets bind.
3. In addition, platelets secrete
thromboxanes, which attract
additional platelets to the site of
injury.
4. A platelet plug may control blood
loss from a small break.
hemostasis, step 3: coagulation
• Blood coagulation
• Is triggered by cellular damage and blood contact with foreign surfaces
• Coagulation is a cascade reaction involving several biochemicals (clotting factors)
• The major event is formation of a blood clot when fibrin (a thread-like protein)
forms a mesh surrounding the damaged vessel.
•
The
1.
2.
3.
cascade is divided into three events
Extrinsic mechanism
Intrinsic mechanism
Common pathway
Coagulation
• Extrinsic clotting mechanism
• A chemical released from tissue outside the blood
vessels trigger the extrinsic pathway
•Damaged tissues releases thromboplastin
(also called factor III)
•Factor III initiates a cascade reaction that, in the
presence of Calcium, activates factor X.
•Activation of factor X initiates the common
pathway
Coagulation
• Intrinsic clotting mechanism
• An inactive clotting factor within the
blood (Hageman, or factor XII) is
activated when foreign tissue, such as
collagen enters the bloodstream.
•Factor XII proceeds through a cascade
of reactions in the presence of Calcium
to activate factor X.
•Activation of factor X initiates the
common pathway.
Coagulation
•Common Pathway
•Is the point at which intrinsic & extrinsic pathways converge
•Activated factor X (with help of Calcium & factor V) leads to the
release of prothrombin activator from platelets.
•Prothrombin activator converts prothrombin into thrombin.
•Thrombin, in turn converts fibrinogen into long threads of fibrin.
•Fibrin forms an insoluble clot at the site of injury.
Coagulation
Figure 14.19c. Schematic of the common pathway in the
blood clotting mechanism
Figure 14.18 A scanning electron micrograph of fibrin
threads. The insoluble fibers trap blood cells and
platelets, which contribute to the blood clot formation.
hemostasis: review
Blood Clot Dissolution
• 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
• Platelet-derived growth factor stimulates smooth muscle cells and
fibroblasts to repair damaged blood vessel walls
• Plasmin digests the blood clots
Blood Clot Disorders
•A thrombus is an abnormal blood clot
•Deep vein thrombosis – prolonged immobility causes blood to pool, especially
in the deep veins of the legs or pelvis.
• An embolus is a blood clot moving through the blood vessels
•Pulmonary embolism – may occur when part of a thrombus breaks away from
the clot and lodges in a pulmonary artery. Rapidly fatal.
•Atherosclerosis – accumulation of fatty deposits along arterial lining
•May cause inappropriate clotting
•Most common cause of thrombosis in medium-sized arteries
•Arteriosclerosis – hardening of an artery.
•Stenosis – abnormal narrowing of a passage in a body
•Atherosclerosis of an artery narrows the passage through which blood flows in
an artery, and increases the likelihood of an embolism at that site.
Blood Clot Disorders
Figure 14.20 Artery cross sections.
(a) light micrograph of a normal
artery.
(b) The inner wall of an artery
changed as a result of atheroclerosis.
Ultrasound image of stenosis within the internal carotid artery.
Blood Typing
Blood typing is the process of identifying an individual’s blood group.
(eg. Type A, B, AB or O)
• Terms to become familiar with:
•Antigen – a chemical (or membrane protein) that stimulates cells to
produce antibodies
• Foreign antigens in the body stimulate the immune response.
• Antibodies – a plasma protein that reacts against a specific antigen
• Agglutination – clumping of red blood cells in response to a
reaction between an antibody and an antigen
ABO Blood Group
• This blood group is based on the presence (or absence) of two
antigens on red blood cell membranes: Antigen A & Antigen B
antigens
Type A blood contains A-antigens on the surface
of its RBCs.
Type B blood contains B-antigens on the
surface of its RBCs. and anti-A antibodies in its
plasma.
Type AB blood contains A-antigens and Bantigens on the surface of its RBCs. and has
neither antibody
Type O blood contains neither A or B antigen
on the surface of its RBCs
Blood Typing
antibodies
Type A blood plasma contains anti-B antibodies.
Type B blood plasma contains anti-A antibodies.
Type AB blood plasma contains neither antibody
Type O blood plasma contains both anti-A and anti-B antibodies.
ABO Blood Group
Rh Blood Group
• The Rh blood group was named for the rhesus monkey
•Rh positive (Rh+) indicates the presence of D-antigen (or other Rh
antigen) on the red blood cell membranes
• Rh negative (Rh-) lacks the D-antigen
• When Rh- blood is exposed to the D antigen, it becomes sensitized
and develops anti-D antibodies
• Anti-D antibodies are formed only after a person is exposed to Dantigen (Rh sensitization).
erythroblastosis fetalis
•The seriousness of the Rh blood group is evident in a fetus that develops the
condition erythroblastosis fetalis or hemolytic disease of the newborn.
• If the mother is Rh- and has been sensitized to the D-antigen, her own
antibodies may attack the red blood cells of a fetus that is Rh+.
erythroblastosis fetalis
•Erythroblastosis fetalis can be prevented for women at high risk by administering a
serum that contains anti-D antibodies into the mother during the pregnancy and after
birth (before she becomes sensitized to D-antigen).
•The injected antibodies quickly agglutinate any fetal red blood cells, thereby preventing
her from becoming sensitized to the D-antigen.
End of Section 2 of 2.