28-07-2012, 10:12 AM
Composition of Blood
Blood 1.ppt (Size: 4.15 MB / Downloads: 62)
Consists of formed elements (cells) suspended & carried in plasma (fluid part)
Total blood volume is about 5L
Plasma is straw-colored liquid consisting of H20 & dissolved solutes
Includes ions, metabolites, hormones, antibodies
Plasma Proteins
Constitute 7-9% of plasma
Three types of plasma proteins: albumins, globulins, & fibrinogen
Albumin accounts for 60-80%
Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure
Globulins carry lipids
Gamma globulins are antibodies
Fibrinogen serves as clotting factor
Converted to fibrin
Serum is fluid left when blood clots
Formed Elements
Are erythrocytes (RBCs) & leukocytes (WBCs)
RBCs are flattened biconcave discs
Shape provides increased surface area for diffusion
Lack nuclei & mitochondria
Each RBC contains 280 million hemoglobins
Leukocytes
Have nucleus, mitochondria, & amoeboid ability
Can squeeze through capillary walls (diapedesis)
Granular leukocytes help detoxify foreign substances & release heparin
Include eosinophils, basophils, & neutrophils
Platelets (thrombocytes)
Are smallest of formed elements, lack nucleus
Are fragments of megakaryocytes; amoeboid
Constitute most of mass of blood clots
Release serotonin to vasoconstrict & reduce blood flow to clot area
Secrete growth factors to maintain integrity of blood vessel wall
Survive 5-9 days
Hematopoiesis
Is formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue
Erythropoiesis is formation of RBCs
Stimulated by erythropoietin (EPO) from kidney
Leukopoiesis is formation of WBCs
Stimulated by variety of cytokines
= autocrine regulators secreted by immune system