Blood!
Components of blood
Cardiovascular System
A pump (the heart)
A conducting system (blood vessels)
A fluid medium (blood)
- Is specialized fluid of connective tissue
- Contains cells suspended in a fluid matrix
Physical Characteristics of Blood
Three General Characteristics of Blood
1.38°C (100.4°F) is normal temperature
2.High viscosity
3.Slightly alkaline pH (7.35–7.45)
Blood volume (liters) = 7 percent of body weight (kilograms)
- Adult male: 5–6 liters
- Adult female: 4–5 liters
Important Functions of Blood
Transportation of dissolved substances
- Oxygen and carbon dioxide
- Nutrients
- Hormones
- Immune system components
- Waste products
Protection
- Restriction of fluid losses at injury sites
- Defense against toxins and pathogens
Regulation
- Stabilization of body temperature
- Regulation of pH and ions
Hemopoiesis - Blood formation
Process of producing formed elements
Myeloid and lymphoid stem cells form from pluripotent stem cell
- cells with capacity to develop into several types of cells
Fractionation:
Process of separating whole blood into plasma and formed elements for clinical analysis
Breakdown of Whole Blood
Whole Blood
Plasma: A fluid consisting of:
- Water
- Dissolved plasma proteins
- Other solutes
Formed elements
- RBC = red blood cell or erythrocytes (Transport oxygen)
- WBC = white blood cells or leukocytes (Part of the immune system)
- Platelets = Cell fragments involved in clotting
Plasma
Makes up 50–60 percent of blood volume
More than 90 percent of plasma is water
Extracellular fluids
Interstitial fluid (IF) and plasma
Plasma and IF exchange materials across capillary walls
- Water
- Ions
- Small solutes
Intracellular vs extracellular
Plasma proteins
More than 90 percent made in liver
Antibodies made by plasma cells
Peptide hormones made by endocrine organs
•Albumins (60 percent)
- •Transport substances such as fatty acids, thyroid hormones, and steroid hormones
•Globulins (35 percent)
- Antibodies, also called immunoglobulins
- Transport globulins (small molecules): hormone-binding proteins, metalloproteins, apolipoproteins (lipoproteins), and steroid-binding proteins
- Help to transport ions, hormones and lipids
•Fibrinogen (4 percent)
- Molecules that form clots and produce long, insoluble strands of fibrin for clotting
•Other Plasma Proteins
•1 percent of plasma
•Changing quantities of specialized plasma proteins
•Peptide hormones normally present in circulating blood
•Insulin
•prolactin (PRL)
•glycoproteins thyroid-stimulating hormone (TSH)
•follicle-stimulating hormone (FSH)
•luteinizing hormone (LH)
Formed Elements
Red blood cells (RBCs; 99%)
White blood cells (WBCs; less than 1%)
Neutrophils
Lymphocytes
Monocytes
Eosinophils
Basophils
Platelets – cell fragments
Serum
Liquid part of a blood sample
•In which dissolved fibrinogen converts to solid fibrin
Red Blood Cells
•Red blood cells (RBCs)
•Make up 99.9 percent of blood’s formed elements
•Hemoglobin
•The red pigment that gives whole blood its color
•Binds and transports oxygen and carbon dioxide
•Abundance of RBCs
•Red blood cell count – the number of RBCs in 1 microliter of whole blood
•Male: 4.5–6.3 million
•Female: 4.2–5.5 million
•Three Important Effects of RBC Shape on Function
1.High surface-to-volume ratio
•Quickly absorbs and releases oxygen
2.Discs form stacks called rouleaux
•Smooth the flow through narrow blood vessels
3.Discs bend and flex entering small capillaries
•A 7.8-µm RBC passes through 4-µm capillary
Produced and enter circulation at same rate destroyed (about 2 million per second)
Red Blood Cell (con't)
•Life Span of RBCs
•Lack nuclei, mitochondria, and ribosomes
•No cell repair
•Anaerobic metabolism
•Live about 120 days
Hemoglobin
•Protein molecule that transports respiratory gases
•Normal hemoglobin (adult male)
•14–18 g/dL whole blood
•Normal hemoglobin (adult female)
•12–16 g/dL whole blood
Hemoglobin Structure
•Complex quaternary structure
•Four globular protein subunits
•Each with one molecule of heme
•Each heme contains one iron ion
Hemoglobin function
•Carries oxygen
•With low oxygen (peripheral capillaries):
•Hemoglobin releases oxygen
•Binds carbon dioxide and carries it to lungs
•Forms carbaminohemoglobin
•Fetal Hemoglobin
•Strong form of hemoglobin found in embryos
•Takes oxygen from mother’s hemoglobin
Erythropoiesis
Process of RBC formation
Begins in the red bone marrow
Proerythroblast ejects its nucleus, becomes a reticulocyte, and enters the bloodstream
Within 1 to 2 days become mature erythrocyte
Typically, rate equals blood cell destruction to maintain oxygen-carrying capacity of blood
Hypoxia (cellular oxygen deficiency) stimulates release of erythropoietin by the kidneys, that speeds the development of reticulocytes
Blood Groups and Types
- Based on genetically determined cell surface protein antigens called agglutinogens
- Plasma typically contains antibodies called agglutinins, which react with antigens not on RBC surface
- Blood groups based on presence or absence of antigen, including ABO and Rh groups, but also several others
- With each group, two or more different blood types
ABO Blood Group
- Type A blood – antigen A; anti-B antibodies
- Type B blood –antigen B; anti-A antibodies
- Type AB blood – both antigen A and antigen B; no antibodies
- Type O blood – neither antigen; both anti-A and anti-B antibodies
Blood Transfusions
Incompatible when the recipient’s antibodies (agglutinins in plasma) bind to antigens on the donated blood’s RBCs, which causes agglutination (clumping) and hemolysis (RBC rupture)
Universal recipients – Type AB: in theory can receive blood from donors of all 4 blood types because they have no antibodies to attack the donated RBCs
Universal donor – Type O: in theory can donate blood to all 4 blood types because no antigens on RBCs to trigger transfusion reaction
To avoid mismatches, recipient’s blood is typed, then cross-matched to potential donor
Rh Factor
- Based on the presence (+) or absence (-) of the Rh antigen, first discovered in the Rhesus monkey
Blood Types
- Type Rh+ blood - has antigen
- Type Rh- blood – no antigen;
An Rh- person will only produce anti-Rh antibodies in plasma if exposed to Rh+ antigen, such as during incompatible blood transfusion, sharing hypodermic needles, or when a pregnant Rh- woman is carrying an Rh+ fetus (hemolytic disease of the newborn)!
Leukocytes (WBCs)
Have a nucleus
- Lack hemoglobin
- Classified based on presence or absence of visible cytoplasmic granules (vesicles)
Granulocytes – differential staining visible in light microscope
- Neutrophil (also called polymorphonuclear leukocytes PMNs)
- Eosinophil
- Basophil
Agranulocytes – granules present, but small and don’t stain, so not visible under light microscope
- Lymphocyte
- Monocyte
Granulocytes
Neutrofil
- Phagocytosis of pathogens
- Destroy with lysozyme, oxidants, and defensins
Eosinophil
- Stop the effect of histamine and other inflammation mediators in allergic reactions
- Also attack parasitic worms and antigen-antibody complexes
Basophil
- Release heparin, histamine, and serotonin to intensify the inflammatory response
- Involved in hypersensitivity of allergic reactions
Agranulocytes
Monocyte
Monocyte
Migrate into tissues, enlarge and differentiate into macrophages – fixed or wandering
Phagocytosis of microbes, with many lysosomes
Also clean up cellular debris
Lymphocyte
Function in immune responses
B cells produce antibodies, effective on bacteria
T cells combat viruses, fungi, transplanted cells, cancer cells and some bacteria
Continually recirculate from blood to interstitial fluid and lymph, and back
Leukocyte (WBC) Function
- Adhesion molecules slow down select WBC with receptors to assist movement through capillary wall
- Except for lymphocytes, once leave blood vessel do not return to blood vessel
Chemotaxis
- Pathogens and inflamed tissue release chemicals that attract phagocytic cells
- Neutrophils respond most rapidly to infection site, and monocytes arrive later but in large numbers
The Lifecycle of a Leukocyte
Most live only a few days
- During infection, some live only a few hours
- Some lymphocytes (B and T cells) can live for several months or years
Differential white blood cell count
- Measures number of each type of WBC in a sample of 100 WBCs
- Because each type of WBC plays a different role in immune response, determining percentage of each type in the blood at a particular time can assist in diagnosing the condition
Platelets (Thrombocytes)
- Disc shaped cell fragments that lack a nucleus
- Develop from megakayoblasts under influence of hormone thrombopoietin
- Stop blood loss in damaged vessels
- Form a platelet plug in the vessel wall
- Release chemicals that promote blood clotting
- Life span of 5 to 9 days - removed by fixed macrophages in spleen and liver
Hemostasis
Sequence of responses to stop blood loss from a damaged blood vessel
Quick, localized to region of damage, and carefully controlled by positive feedback
1. Vascular spasm
2. Platelet plug formation
Platelet adhesion
Platelet release reaction
Platelet aggregation
3. Blood Clotting
- Clot is a thickened gel of blood with a network of insoluble protein fibers that trap formed elements
- Cascade of reactions involving calcium ions and clotting factors that activate one another
- Prothrombinase enzyme is formed by one of two pathways (extrinsic or intrinsic)
- Prothrombinase converts prothrombin into thrombin
- Thrombin enzyme converts soluble fibrinogen into insoluble fibrin
- Fibrin forms the threads of the clot
- Clot retraction pulls blood vessel edges together
Extrinsic vs Intrinsic
Extrinsic pathway
- Occurs rapidly, within seconds if trauma is severe
- Tissue factor leaked into blood from outside blood vessels
Intrinsic pathway
- More complex and slower, usually requiring several minutes
- Activators in direct contact with blood without outside tissue damage or contained within the blood
Common pathway
- Same steps to clot formation once prothrombinase is formed by either pathway
- Thrombin has positive feedback effects
Controlling clotting
Because of positive feedback cycles, a clot has a tendency to enlarge and potentially block blood flow through undamaged vessels
- Fibrinolysis - Dissolve small, inappropriate clots
- Activate enzyme plasmin to digest fibrin threads and inactivate fibrinogen and prothrombin
- Anticoagulants-Substances that suppress or prevent clotting present in blood, including heparin from basophils block the action of clotting factors
Blood Clots
Initiation of clots within blood vessels
Atherosclerosis – accumulation of fatty substances on arterial walls
Trauma or infection roughening endothelial lining of blood vessel
Thrombosis - clotting in unbroken blood vessel to form a thrombus
Embolus- a thrombus that dislodges and carried in blood; can block blood flow to organ in smaller diameter vessel further in circulation (stroke, kidney failure, heart attack, pulmonary embolism)