Blood The only fluid tissue in the human body Classified as a connective tissue –Living cells = formed elements –Non-living matrix = plasma

Physical Characteristics of Blood Color range –Oxygen-rich blood is scarlet red –Oxygen-poor blood is dull red pH must remain between 7.35–7.45 Blood temperature is slightly higher than body temperature

Blood Plasma Composed of approximately 90% water Includes many dissolved substances (the other 10%) –Nutrients (amino acids, glucose, fatty acids) –Electrolytes ( K+, Na+, Ca++, Cl-) –Respiratory gases (CO 2, O 2, N 2 ) –Hormones –Waste products( urea, lactic acid) –Proteins*

Plasma Proteins Albumin – 60% - regulates osmotic pressure Fibrinogen – 4% - help to stem blood loss when a blood vessel is injured Gamma Globulins (antibodies) - help protect the body from antigens

Formed Elements Erythrocytes = red blood cells Leukocytes = white blood cells Platelets = cell fragments

They are shaped like biconcave discs about 7.5µm in diameter and 2.0µm thick at the edges. The shape increases surface area making gas diffusion in and out more efficient.

Erythrocytes (Red Blood Cells) The main function is to carry oxygen Anatomy of circulating erythrocytes –Biconcave disks about 7.5µm in diameter and 2.0µm thick at the edges. –Essentially bags of hemoglobin –Anucleate (no nucleus) – can’t reproduce –Contain very few organelles – no mitochondria. Produce ATP by anaerobic means Outnumber white blood cells 1000:1

Fate of Erythrocytes Unable to divide, grow, or synthesize proteins RBC counts: Males – 6,000,000 per mm 3 Females – 5,000,000 per mm 3 Average of 30 trillion RBCs in circulation at all times Wear out in 100 to 120 days When worn out, are eliminated by phagocytes in the spleen or liver. Iron is recycled Your body must make RBCs at the rate of 3 million per second to keep up.

Hemoglobin Iron-containing protein Binds strongly, but reversibly, to oxygen Each hemoglobin molecule has four oxygen binding sites Each erythrocyte has 250 million hemoglobin molecules

Control of Erythrocyte Production Rate is controlled by a hormone (erythropoietin) Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood Homeostasis is maintained by negative feedback from blood oxygen levels Polycythemia – Too many Red Blood cells. Caused by living in high altitudes or bone marrow cancer. Increases blood viscosity

Anemia. Reduced oxygen carrying ability of blood. Can be caused by too few RBCs or not enough Hemoglobin. 1.Nutritional A) Not enough iron in plasma headed for bone marrow (16g/mL for men, 14 g/mL women) B) Not enough folic acid and vitamin B 12 – necessary for DNA replication needed to make any cells, and thus more Red Blood Cells cells (RBCs).

2. Pernicious Body can not absorb vitamin B12 necessary to make new cells. 3. Aplastic Bone marrow can not function properly 4.Renal Kidneys can not make enough erythropoietin

Leukocytes (White Blood Cells) Crucial in the body’s defense against disease These are complete cells, with a nucleus (they have DNA) and organelles Able to move into and out of blood vessels (diapedesis) Can move by ameboid motion Can respond to chemicals released by damaged tissues

Leukocyte Levels in the Blood Normal levels are between 4,000 and 11,000 cells per cubic millimeter Abnormal leukocyte levels –Leukocytosis Above 11,000 leukocytes/mm 3 Generally indicates an infection –Leukopenia Abnormally low leukocyte level Commonly caused by certain drugs

5 types of WBCs subdivided into 2 groups 3 types are called Granulocytes – Have cytoplasmic granules. All have short life spans averaging 12 hours. 1. Neutrophil – Most abundant WBC. –54%-62% of WBCs. –Mobile phagocytic cell that engulfs bacteria.

2. Eosinophil 1% - 3% of WBCs. Bilobed nucleus. Cytoplasmic granules stain red. Weakly phagocytic. Engulfs parasitic worms. (tapeworms, flatworms)

3. Basophils <1% of WBCs. Stains dark blue. Release Histamine, a vasodilator.

Agranulocytes Lack cytoplasmic granules 4. Monocytes Largest WBC. Have much longer life spans. (weeks not hours) 3% to 9% of the WBCs. Phagocytic – engulf large invaders.

Monocyte engulphing a cell

5. Lymphocytes 25% to 33% of the WBCs Produce antibodies that act against specific foreign substances. Very long life spans.

Platelets - Thrombocytes Anucleate cell fragments. Function to seal up small breaks in damaged blood vessels and help initiate coagulation. Normal count of 300,000 per mm 3

Hemostasis – stoppage of bleeding Platelet plug formation – Platelets stick to connective tissue exposed when the vessel is injured and to each other forming a platelet plug. Blood vessel spasm – Platelets release serotonin, causing smooth muscle in the wall of the blood vessel to contract and narrow.

Non-activated platelet activated platelet – shape changed and sticky

Coagulation – Blood clot formation 1. Damaged tissues release TF (tissue factor) when in the presence of Ca ++ and PF3 (an enzyme found on platelets) form Prothrombin Activator. 2. Prothrombin (present in the plasma) is converted to Thrombin by Prothrombin Activator and Ca Thrombin acts as an enzyme and converts molecules of fibrinogen into long strands of Fibrin. Ca ++ must be present.

4. Fibrin threads cling to the edge of the damaged tissue forming a mesh that catches blood cells and platelets forming a clot. Normally blood clots in 3 – 6 minutes. A blood clot in a vessel is a Thrombus. If it breaks loose and is carried away by blood flow it is an Embolus.

RBC caught in a meshwork of fibrin

Blood Types Blood types are determined by the presence of certain proteins (agglutinogens) found on the cell membrane of RBCs and proteins (agglutinins) dissolved in the plasma ABO blood group – based on the presence or absence of 2 major agglutinogens on the RBC membrane. Agglutinogen A & Agglutinogen B

4 Possible combinations Agglutinogen A only – Type A blood Agglutinogen B only – Type B blood Agglutinogen A & B – Type AB blood Neither – Type O blood A person with type A blood has anti-B agglutinin in the plasma.

Type A blood has Anti-B agglutinin in the plasma Type B blood has Anti-A agglutinin in the plasma Type AB blood has neither Type O blood has both The agglutinogen of one type will react with the agglutinin of the same type. Example – Agglutinogen A and Agglutinin Anti-A cause Red Blood Cell clumping (Agglutination)

Transfusions Cells in the transfused blood must not be agglutinated by the agglutinins in the recipients plasma. Type O – Universal Donor Type AB – Universal Recipient

Rh Factor Rh+ blood has Agglutinogen D on the cell membranes. Rh- blood lacks the protein. Rh+ blood lacks anti-Rh agglutinins. Rh- blood forms anti-Rh agglutinins only in response to the presence of Rh+ blood.

Erythroblastosis Fetalis Occurs when an Rh- mother gives birth to a second Rh+ baby. When an Rh- mother gives birth to the first Rh+ baby some blood mixing can occur causing the mother to produce anti-Rh agglutinin. This agglutinin will cross the placenta of the 2 nd Rh+ fetus causing the fetal blood to agglutinate.