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• Blood is a continuously regenerated connective tissue
• Gases, nutrients, wastes, and hormones move via blood.
• Blood is transported through the cardiovascular system.
• The heart pumps blood.
• Arteries transport blood away from the heart.
• Veins transport blood back to the heart.
• Capillaries facilitate exchange between blood and body tissues.
• Blood components include formed elements and plasma

Formed Elements

• Erythrocytes (red blood cells) carry respiratory gases.
• Leukocytes (white blood cells) defend against pathogens.
• Platelets aid in clot formation to prevent blood loss.

Plasma

• Plasma, the fluid portion of blood, contains plasma proteins and dissolved solutes.
• Blood transports formed elements, dissolved molecules, and ions.
• It carries oxygen and carbon dioxide to/from the lungs.
• Nutrients, hormones, heat, and waste products are transported in blood.
• Leukocytes and plasma proteins protect against pathogens.
• Platelets and plasma proteins protect against blood loss.
• Blood absorbs heat from body cells, especially muscle.
• Heat is released at skin blood vessels.
• Blood regulates body pH.
• It absorbs acid and base from body cells, and it contains chemical buffers.
• Water is added to blood from the GI tract.
• Water is lost through urine, skin, and respiration.
• Fluid is exchanged between blood and interstitial fluid.
• Blood contains proteins and ions that help maintain osmotic balance.
• Blood color ranges from scarlet (oxygen-rich) to dark red (oxygen-poor).
• Blood volume averages 5 L, ranging from 4-6 L.
• Its viscosity relative to water is 4.5-5.5x.
• Plasma concentration is 0.09%.
• Blood temperature is 38°C (100.4°F).
• Blood pH ranges from 7.35-7.45.

Centrifuged Blood

• Whole blood can be separated into parts by centrifuge.
• Erythrocytes are at the bottom, forming a red layer, making up about 44% of the sample.
• The buffy coat is a thin (1%) middle layer of leukocytes and platelets with a gray-white color.
• Plasma is straw-colored and makes up about 55% of the sample.
• Hematocrit is the percentage of the volume of all formed elements.
• With a clinical definition that specifies the percentage of only erythrocytes.
• Adult male hematocrit ranges from 42 to 56%, while females range from 38 to 46%.
• Testosterone increases erythropoietin secretion by the kidney.

Composition of Blood Plasma

• Water makes up ~92%.
• Plasma proteins constitute ~7%; they buffer against pH changes.
• Albumin (~58% of plasma proteins) exerts osmotic force, contributes to viscosity, and transports molecules.
• Globulins (~37%) transport lipids, metal ions, and antibodies.
• Fibrinogen (~4%) participates in blood clotting.
• Regulatory proteins make up (<1%) are enzymes and hormones.
• Other solutes (~1%) include electrolytes that maintain membrane potentials and pH, nutrients for energy, respiratory gases for cellular respiration, and wastes transported to the liver and kidneys for removal.
• Common electrolytes in arterial plasma include sodium, potassium, calcium, and hydrogen.
• Common molecules in blood plasma include glucose, amino acids, lactate, and lipids.

Hemopoiesis

• Hemopoiesis is the production of formed elements in red bone marrow of certain bones.
• Hemocytoblasts are stem cells with a myeloid line that forms erythrocytes, all WBC's except lymphocytes, and megakaryocytes.
• Lymphoid stem cells differentiate into lymphoid line form only lymphocytes.
• Colony-stimulating factors (CSFs) stimulate hemopoiesis.

Erythropoiesis

• Erythropoiesis, the production of red blood cells, requires iron, B vitamins, and amino acids.
• It begins with a myeloid stem cell which responds to multi-CSF to form a progenitor cell.
• The progenitor cell becomes a proerythroblast (a large nucleated cell), then an erythroblast (smaller, produces hemoglobin).
• The erythroblast becomes a normoblast which is smaller and full of hemoglobin without a nucleus.
• A reticulocyte lacks organelles except ribosomes that make hemoglobin.
• Its final stage is an erythrocyte where ribosomes have degenerated.

Leukopoiesis

• Leukopoiesis is the production of leukocytes involving granulocytes, monocytes, and lymphocytes.
• Granulocytes include neutrophils, basophils, and eosinophils.
• Multi-CSF and GM-CSF cause myeloid stem cells to form a progenitor cell, which becomes a myeloblast to further become a granulocyte.
• Monocytes are also derived from myeloid stem cells.
• M-CSF prompts a progenitor cell to become a monoblast, which matures into a monocyte.
• Lymphocytes are stemmed from lymphoid stem cells.
• The stem cells differentiate into B-lymphoblasts and T-lymphoblasts, which mature into B-lymphocytes and T-lymphocytes.
• Some lymphoid stem cells differentiate directly into NK (natural killer) cells.

Thrombopoiesis

• Thrombopoiesis is platelet production.
• A megakaryoblast (produced from myeloid stem cell) forms a megakaryocyte influenced by thrombopoietin.
• The megakaryocyte produces thousands of platelets which creates proplatelets, that extend through blood vessel wall into bloodstream.
• Blood flow "slices" off fragments, producing platelets.
• Erythrocytes (red blood cells) are small, flexible formed elements that lack a nucleus and cellular organelles.
• They are packed with hemoglobin and have a biconcave disc structure.
• A latticework of spectrin protein provides support and flexibility.
• Erythrocytes transport oxygen and carbon dioxide between tissues and lungs.
• Hemoglobin is a red-pigmented protein that is essential for binding to oxygen and carbon dioxide molecules.
• Oxygen binds to the iron of hemogoblin, with binding being fairly weak.
• This allows for rapid attachment and detachment of red blood cells in the lungs.
• Conversely, carbon dioxide binds to globin protein.
• The decreased blood oxygen levels are detected by the kidney, which prompts the organ to secrete EPO into the blood.
• EPO stimulates red bone marrow to increase the rate of which erythrocytes are produced.
• As a result more erythrocytes can enter circulation to be oxygenated and blood oxygen levels increase.

Clinical View on Erythrocytes

• Blood doping is used by some athletes to enhance performance through an increase of oxygenated blood cells
• Done by donating erythrocytes and transfusing those blood cells back into the body prior to competetion to increase EPO levels.
• High levels of EPO increase blood visocity that requires the heart to work harder, which causes cardiovascular damage.
• This causes it been banned from atheltic comptetitions
• As for the lifecycle of blood cell, it is broken down into the liver and spleen during hematopoiesis.
• Hemoglobin is broken down into biliverdin that is further broken down into bilirubin. which is used with other products to excrete fecal matter.

Clinical Conditions

• Anemia is when erythrocytes are lower than normal.
• Symptoms of anemia include include lethargy, shortness of breath, pallor, palpitations.
• Types of anemia includes aplastic anemia due to exposure to poisons, toxins, radiation.
• Congenital hemolytic anemia is due to genetic defects, which causes erythrocytes destroyed early.
• Erythroblastic anemia is due to large numbers of immature cells due to abnormal accelerated cell maturation.
• Hemorrhagic anemia is the loss of blood via injury etc., which causes a blood cell deficieny.
• Pernicious anemia is failure to absorb vitamin B12 due to a lack of a intrinsic factor.
• Sickle-cell disease is a genetic defect relating to oxygen transport of blood.
• ABO group is the classification of surface antigens in erythocytes.
• It has 4 subcategories: type A, type B, type AB, and type O .
• Type A antigen produces B antibodies in plasma.
• Type B antigen produces A antibodies in plasma.
• Type AB antigen produces no antiboties in plasma.
• Type O antigen produces both A and B antibodies in plasma
• The Rhesus or Rh factor is an additional determining antigen of erythocytes
• Antibodies to Rh factor appear after Rh negative person exposed to Rh positive blood.
• If someone receives an incompatible transfusion, agglutination occurs.
• Recipient's antibodies bind to transfused erythrocytes causing a organ hemolytic reaction.

Leukocytes

• Leukocytes defend against pathogens.
• They contain a nucleus and organelles, but not hemoglobin.
• Leukocytes are motile and flexible, reside mostly in tissues, and undergo diapedesis (squeezing through blood vessel walls) and chemotaxis (attraction to chemicals at infection sites).
• Five leukocyte types are divided into two classes: granulocytes and agranulocytes.
• Granulocytes have granules seen with a light microscope, which include neutrophils, eosinophils, and basophils.
• Agranulocytes have granules not visible with a light microscope and include lymphocytes and monocytes.
• Neutrophils (polymorphonuclear leukocytes) are the most numerous, have a multilobed nucleus and pale granules and phagocytize infectious pathogens.
• Eosinophils are 1-4% of leukocytes, have a bilobed nucleus, reddish granules, and phagocytize antigen-antibody complexes and allergens.
• Basophils are 0.5-1% of leukocytes with a bilobed nucleus and blue-violet granules that contains histamine and heparin.
• Histamine release causes an increase in blood vessel diameter and capillary permeability.
• Heparin release prevents blood clotting.
• Monocytes have a C-shaped nucleus, are 2-8% of blood leukocytes and reside in tissues.
• They transform into large phagocytic cells, macrophages, to phagocytize bacteria, viruses, and debris.
• Lymphocytes reside in lymphoid organs and structures, are 20-40% of blood leukocytes, and have a dark-staining round nucleus.
• The three categories of lymphocytes include T-lymphocytes that manage the immune response.
• Includes B-lymphocytes which become plasma cells and produce antibodies, and NK (natural killer) cells which attack abnormal and infected tissue cells.
• Leukopenia is a reduced number of leukocytes that increases risk of infection.
• Leukocytosis is an elevated leukocyte count and may be caused by recent infection or stress.
• Differential count measures the amount of each type of leukocyte and whether any are immature; useful for clinical diagnoses.
• Leukemia is malignancy in leukocyte-forming cells which causes an increase in leukocytes.
• Acute leukemia is a rapid progression of forming of leukocyctes, while chronic leukemia is slow progression.
• Platelets are small, membrane-enclosed cell fragments without a nucleus that break off of megakaryocytes in red marrow.
• Plays a role in blood clotting and they circulate for 8 to 10 days.
• Normally a healthy body has 150,000 to 400,000 platelets, while 30% are stored in the spleen.

Hemostasis

• Hemostasis, the stoppage of bleeding, occurs in three overlapping phases: vascular spasm, platelet plug formation, and coagulation.
• Vascular spasm: blood vessel constriction in response to blood vessel injury, limiting blood leakage and lasting minutes.
• Platelets and endothelial cells release chemicals that stimulate further constriction.
• Platelet plug formation is a inhibited form of activation
• Blood vessels are smooth with endothelial walls coated with prostacyclin.
• This platelet plug activates when the wall is damaged, collagen fibers appear, and collagen sticks to fibren.
• Serotonin and thromboxane A₂ cause prolonged vascular spasms.
• Adenosine diphosphate (ADP) and thromboxane A2 attract other platelets and facilitate their degranulation (positive feedback).
• Procoagulants stimulate coagulation, and Mitosis stimulating substances trigger repair of blood vessel
• Blood clotting, which involves the network of fibrin protein, meshes traps erythrocytes.
• Clotting requires calcium, clotting factors, platelets, and vitamin K.
• Initiate clotting with intrinsic and extrinsic pathways.
• Positive feedback ensures clot formation continues once its initiated, that stops when blood vessel is filled to begin healing.
• The sympathetic increases vasoconstriction and heart rate.
• Actinomyosin (protein within platelets) serum is squezzed out of developing clot making it smaller during the healing window.
• Fibrin starts within two days after clot formation and continues by degradation of fibrin strands.

Clinical Conditions of Blood

• Hemophilia disorders, such as types Hemophilia A and hemophilia B.
• Hemophilia A and hemophilia B occur in X-linked recessive pattern and are most common.
• Males exhibit full-blown disease; females typically carriers Occurs from deficiency of factor VIII, factor IX, or factor XI (more rare) Thrombocytopenia results from a platelet deficiency can be caused by break down and decease production.
• May occur in bone marrow infections or cancer.
• Can be caused by aspirin, ibuprofen, warfarin, ginkgo.
• Hypercoagulation is the increase tendancy of bloodclots that cna lead to a thrombus known as embolis
• If it gets lodged it the lungs this is called pulmonary embolism.
• It has drug-related, environmental, and genetic causes.

Hemotopoiesis

• Hemotopoiesis occurs in most bones in youg children, however is stricted to selected ones during adulthood. This causes older individuals more likely to become anemic and produce active leukocytes.
• As for certian types of leukemia , it is more prevelant for elderly people.