Blood

Composition of Blood Blood is composed of two main elements 1. Plasma – liquid portion 55% 55% 2. Formed elements – various blood cells 45% 45%

Blood Volume About 8% of total body weight in averaged sized adults 4-5 liters in a female and 5-6 liters in a male Direct measurement and indirect measurement

Formed Elements of Blood Red Blood Cells (RBCs) = erythrocytes White blood Cells (WBCs) = leukocytes Platelets = thrombocytes

Hematocrit Packed Cell Volume (PCV) Volume % of red blood cells in whole blood Anemias – decreased red blood cells Physiological polycythemia – increased red blood cells

Red Blood Cells Erythrocytes No nucleus 7.5 μm in diameter Biconcave disk (increases surface area) Doesn’t contain ribosomes, mitochondria or other organelles

Hemoglobin 200 – 300 million molecules per cell Composed of four protein chains and a red pigment called a heme Each heme has an iron molecule that allows it to bond to four oxygen molecules

Formation of Red Blood Cells In adults, erythrocytes begin maturation in the red bone marrow from nucleated cells known as hematopoietic stem cells Divide by mitosis Entire maturation process takes about 4 days 200 Billion RBCs per day

Erythropoiesis

Destruction of Red Blood Cells Average life span of 105 – 120 days Often break apart as they age and are destroyed by macrophages—mostly in the liver and spleen (phagocytosis) Iron returned to marrow Iron returned to marrow Bilirubin excreted as bile Bilirubin excreted as bile Amino acids released a globin for new proteins Amino acids released a globin for new proteins

Destruction of Red Blood Cells

White Blood Cells 5 Types of White Blood Cells Granulocytes GranulocytesNeutrophilsEosinophilsBasophils Agranulocytes AgranulocytesLymphocytesMonocytes

Neutrophils Small cytoplasmic granules stain light purple and give the cytoplasm a coarse appearance. Polymorphonuclear leukocytes – nuclei have multiple lobes Highly mobile and phagocytic Migrate out of blood vessels

Eosinophils Large, numerous cytoplasmic granules that stain orange Nuclei with two lobes Involved in allergic reactions Weak phagocytes

Basophils Large but sparse cytoplasmic granules Least numerous of WBCs Motile Contain histamine and heparin

Lymphocytes Smallest WBCs Large spherical nuclei T Lymphocytes – directly attack infected or cancerous cells B Lymphocytes – produce antibodies

Monocytes Largest WBC Dark, kidney bean shaped nuclei Motile and highly phagocytic (engulf bacteria and viral infected cells)

Platelets Small and nearly colorless Irregular spindles or oval disks Function in blood clotting