Blood Keri Muma Bio 6

Functions of Blood Transport  Oxygen and nutrients to the cells  Waste away from cells  Hormones Regulation  Maintain body temperature by absorbing and distributing heat Protection  Prevents infection  Blood clotting prevents blood loss

Composition of Blood Plasma – 90% water along with dissolved compounds  Proteins – albumin, antibodies, clotting proteins  Electrolytes – sodium, potassium, calcium, magnesium, chloride, bicarbonate Formed elements – erythrocytes, leukocytes, platelets

Components of Plasma Proteins in plasma – maintain osmotic pressure  Albumin – 60% of plasma proteins Transports substances such as bilirubin and bile salts  Globulins α, β – transports hormones, cholesterol, and iron; angiotensinogen and clotting factors Gamma globulins - antibodies  Fibrinogen Precursor for the clotting protein fibrin

Erythrocytes Erythrocytes (red blood cells)  Biconcave shape  Contains no nucleus or organelles  Enzymes in cytoplasm: Glycolytic enzymes to carry out glycolysis Carbonic anhydrase – converts CO2 to HCO3-  Last ~120 days and are then destroyed by the spleen or liver

Erythrocytes Function – to transport oxygen and to a lesser extent carbon dioxide Contains hemoglobin  Made of 4 globin polypeptides and 4 heme groups

Erythrocytes Erythropoiesis – production of new erythrocytes (~3 million per second) Occurs in the red bone marrow Rate of production is controlled by erythropoietin produced by the kidneys in response to blood oxygen levels

Erythrocytes Anemia - decrease in oxygen carrying ability of the blood  Causes: Decreased number of RBC (low hematocrit) Deficient or abnormal hemoglobin Deficiency in iron or vitamin B12 Kidney disease, decrease in EPO Blood loss Malaria, sickle-cell anemia

Erythrocytes Polycythemia – increased numbers of erythrocytes / hematocrit  Causes: cancer, high altitudes, lung and heart disease, dehydration

Leukocytes Leukocytes – white blood cells  Protect against infection and initiates inflammation  Destroy cancerous cells  Tissue repair

Types of Leukocytes Granulocytes – granule containing cells with lobed nuclei  Neutrophils (60 – 70%) Phagocytes First on the scene of infection and triggers inflammation  Eosinophils (1-4%) Associated with allergies and parasite infections  Basophils (< 1%) Contain and release histamine

Types of Leukocytes Agranulocytes  Monocytes (2 - 6%) Travel into the tissue and mature into macrophages  Lymphocytes (25 – 33%) Specific immune defenses B cells & T cells

Hematopoiesis All blood cells arise from a common stem cell found in the red bone marrow

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Platelets Platelets (a.k.a thrombocytes)  Irregular shaped cell fragments from megakaryocytes  Play a role in blood clotting

Platelets Hemostasis –prevents the loss of blood when blood vessels are damaged 3 phases:  Vascular spasm  Platelet plug formation  Coagulation

Hemostasis Platelet plug formation  Broken or damaged blood vessels cause platelets to become sticky and cling to the site  Release chemicals that attract other platelets (ADP)  Release chemicals that cause vasoconstriction: serotonin, epinephrine, thromboxane A2

Platelet plug formation Normal endothelial cells release prostacyclin and NO to inhibit platelet aggregation

Hemostasis Vascular spasms  Blood vessels constrict to diminish blood flow and loss Coagulation  Formation of a network of fibers that seals the blood vessel  Involves a clotting cascade

Coagulation Clotting cascade  Involves 12 clotting factors  Requires the presence of Ca2+ and platelet factor 3 (PF3) produced by aggregating platelets  Summary of events: An initial inactive clotting factor, found in the plasma, is activated by exposed collagen This activates the next factor and so on….. Until thrombin converts fibrinogen into fibrin

Clotting Cascade Intrinsic Pathway  Initiated when Hageman factor is activated by exposed collagen Extrinsic Pathway  Factor X is activated by thromboplastin released by damaged tissues

Clotting Cascade Role of Thrombin  Converts fibrinogen to fibrin  Activates stabilizing factor (XIII)  Enhances conversion of more thrombin from prothrombin  Enhances platelet aggregation

Coagulation Clot retraction  Platelets trapped in the clot contract and squeeze serum out Vessel repair  Platelets attract fibroblasts that repair blood vessel Clot dissolution  Thrombin and tissue plasminogen activator (tPA) converts plasminogen into plasmin which breaks down fibrin tPA Plasminogen Plasmin Fibrin breaks down

Clotting disorders  Thromboembolism – clots forming in intact vessels Imbalance in clotting – anticlotting mechanisms Slow moving blood Release of thromboplastin from damaged tissue  Hemophilia – deficiency in one of the clotting factors (usually VIII), excessive bleeding  Thrombocytopenia – deficiency in platelets  Impaired liver  Lack of vitamin K

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