Blood• Cells in the body are fixed within tissues and
must have nutrients and oxygen brought to them and waste removed.
• The blood is classified as a fluid matrix connective tissue– The cells and cell fragments are the formed
elements and the matrix of the blood is fluid (plasma).
– Formed elements make up about 45% and plasma 55% of the total blood volume.
– Blood volume: 4-5 L in females, 5-6 L in males.
Blood Functions• Distribution and transportation
– Respiration
– Nutritive
– Excretory
– Negative Aspects
• Regulation and Maintenance
– Hormonal regulation
– Thermoregulation
– pH / acid-base balance
– Fluid volume
• Protection
– Clotting
– Immunity
Major Components of the Circulatory System
• Two divisions: Cardiovascular and lymphatic systems.– Cardiovascular: Heart, blood vessels
• Heart• Vessels
– Lymphatic: lymphatic vessels and lymphoid tissues in spleen, thymus, tonsils, and lymph nodes.
• The fluid portion of the blood (plasma) passes through the capillary walls under hydrostatic pressure (interstitial fluid).
• Some interstitial fluid returns to the blood and some enters the lymphatic system
– Lymphatic vessels carry interstitial fluid now called lymph back to the venous blood.
– Lymph nodes along the way filter and cleanse the blood before it is returned.
Erythrocytes• Structure
– Biconcave, anucleate– 4.8 million/mm3 in
women. – 5.4 million/mm3 in men.– 7.5 um in diameter
• Components– Hemoglobin– Lipids, ATP, carbonic
anhydrase• Function
– Transport oxygen from lungs to tissues and carbon dioxide from tissues to lungs
Hemoglobin
• Consists of: – 4 globin molecules: 2 alpha and 2 beta chains
• 280 million per RBC.• Transport carbon dioxide (carbonic anhydrase involved), nitric
oxide.
– 4 heme molecules: Transport oxygen• Iron is required for oxygen transport
Erythropoiesis
• Production of red blood cells
– Stem cells proerythroblasts early erythroblasts intermediate late reticulocytes
• Erythropoietin: Hormone to stimulate RBC production
Anemias • Result of either a decrease in hemoglobin / RBC or in the
number of RBCs.
• Symptoms: pale, lethargic, shortness of breath, tired.
• Aplastic anemia: inability of red bone marrow to produce RBCs
• caused by: damage to Red bone marrow, Iron of Folate deficiency
• Pernicious anemia - Vitman B12 deficiency
• Hemorhagic anemia - results from loss of blood
• Hemolytic anemia - erythrocytes rupture or are destroyed at an increased rate.
• Thalasemia - defective hemoglobin production
Formed Elements• Red blood cells (erythrocytes)• White blood cells (leukocytes)
– Granulocytes• Neutrophils
• Eosinophils
• Basophils
– Agranulocytes • Lymphocytes
• Monocytes
• Platelets (thrombocytes)
Production of Formed Elements
• Hematopoiesis or hemopoiesis: Process of blood cell production
• Stem cells: All formed elements derived from single population– Proerythroblasts: Develop into red blood cells– Myeloblasts: Develop into basophils,
neutrophils, eosinophils– Lymphoblasts: Develop into lymphocytes– Monoblasts: Develop into monocytes– Megakaryoblasts: Develop into platelets
Neutrophil
• Appearance– 2-5 lobes – 10-12 um– 54-62% of white cells
• Characteristics– Fights bacterial and
fungal infections– Contains peroxidases and
defensins– Numbers increase with
meningitis and appendicitis
Eosinophil
• Appearance– Bilobed nucleus– Red granules– 11-14 um– 1-3% of white blood cells
• Characteristics– Fights parasitic infections.– Releases anti-
inflammatory chemicals.– Secretes enzymes that
break down clots.
Basophils
• Appearance– Two indistinct lobes– Blue-purple granules– 10-12 um– Less than 1% of WBC
• Characteristics– Release histamine– Chemoattractant for other
WBCs– Releases heparin to
prevent clots.Basophil Eosinophil
Monocyte
• Apearance
– Nucleus round, kidney or horseshoe shaped
– 12-20 um
– 3-9 % of WBC
• Characteristics
– Transforms into macrophages
Lymphocyte
• Appearance– Round nucleus– 6-14 um– 25-33% of WBC
• Characteristics– Found in lymphoid tissue– Provides specific immune
response• T - lymphocytes
• B - lymphocytes
Hemostasis
• Arrest of bleeding• Events preventing excessive blood loss
– Vascular spasm: Vasoconstriction of damaged blood vessels
– Platelet plug formation – Coagulation or blood clotting
Thrombocytes
• Cell fragments pinched off from megakaryocytes in red bone marrow
• Important in preventing blood loss
– Platelet plugs
– Promoting formation and contraction of clots
Coagulation
• Stages
– Activation of prothrombinase
– Conversion of prothrombin to thrombin
– Conversion of fibrinogen to fibrin
• Pathways
– Extrinsic
– Intrinsic
Blood Grouping
• Determined by antigens (agglutinogens) on surface of RBCs
• Antibodies (agglutinins) can bind to RBC antigens, resulting in agglutination (clumping) or hemolysis (rupture) of RBCs
• Groups– ABO and Rh
Rh Blood Group
• First studied in rhesus monkeys• Types
– Rh positive: Have these antigens present on surface of RBCs
– Rh negative: Do not have these antigens present
• Hemolytic disease of the newborn (HDN)– Mother produces anti-Rh antibodies that cross
placenta and cause agglutination and hemolysis of fetal RBCs
Diagnostic Blood Tests
• Type and crossmatch
• Complete blood count
– Red blood count
– Hemoglobin measurement
– Hematocrit measurement
• White blood count
• Differential white blood count
• Clotting