Blood physiology.pdf

BLOOD PHYSIOLOGY Dr. Dhelal Qasim Mohammed  Objectives 1.What is the characteristics, component, and the function of the blood 2.What is the volume and the function of the plasma 3.What is hemopoiesis and its site 4.What is the factors that regulate hemopoiesis 5.What is the s...

BLOOD PHYSIOLOGY Dr. Dhelal Qasim Mohammed  Objectives 1.What is the characteristics, component, and the function of the blood 2.What is the volume and the function of the plasma 3.What is hemopoiesis and its site 4.What is the factors that regulate hemopoiesis 5.What is the shape, number and the function of RBC 6.What is the stages and the regulation of RBC The circulatory system is composed of: 1) the heart (pump) 2) blood vessels (conduit) 3) the blood (the circulating material)  The Blood Blood is a viscous fluid which is pumped by the heart through a closed system of blood vessels. It is composed of cells (formed elements) and plasma. The cells are the red blood cells (erythrocyte), white blood cells (leukocyte), and platelets (thrombocyte), which are suspended in the fluid portion, the plasma. General Properties of Whole Blood - Fraction of body weight 8% - Volume Female: 4-5 L Male: 5-6 L - Temperature 38 C - pH 7.35 - 7.45  Functions of the blood 1-Transport of O2, nutrients and hormones to the tissues. 2-It carries CO2 to the lungs and other products of metabolism to the kidneys to be excreted. 3-Blood participates in the regulation of body temperature. 4- Helps to maintain the pH and electrolyte concentrations of interstitial fluid within the ranges required for normal cell functions. 5-Blood also serves essential body protective functions, such as combating invading microorganisms, mediating inflammation, initiating immune responses to foreign materials, and maintaining hemostasis.  PLASMA Plasma is a part of the extracellular fluid of the body. The normal plasma volume is about 5% of the body weight (3500 ml in a 70-kg man). Plasma consists of an aqueous solution of proteins, electrolytes, and small organic molecules.  Plasma Proteins The major types of protein present in the plasma are albumin, globulins & fibrinogen. Their average normal concentrations are: 4.5 g/dl, 2.5 g/dl, and 0.3 g/dl, respectively.  Functions of plasma proteins 1-Proteins exert an osmotic pressure of about 25 mm Hg across the capillary wall. It is called the “colloid osmotic pressure” or “oncotic pressure”. It tends to pull water into the blood. 2-Plasma proteins are responsible for 15% of the buffering capacity of blood helping to keep the blood pH constant. 3-Some of the plasma proteins function in the transport of hormones and different substances in blood. 4-Circulating antibodies in the γ globulin fraction of the plasma proteins play a special role in providing the body with immunity. 5- Fibrinogen and other plasma proteins are concerned with blood clotting. 6- When the tissues become depleted of proteins, the plasma proteins can act as a source for rapid replacement of the tissue proteins.  HEMOPOIESIS Formation of blood cells (hemopoiesis) occurs at different anatomical sites during the course of development from embryonic to adult life. 1-In the early few weeks of embryonic life blood cells are produced in the yolk sac. 2-Later on (after the third month of pregnancy) they are formed mainly in the liver and also in the lymph nodes and the spleen. 3- During the latter part of fetal life and after birth, blood cells are produced by the bone marrow of all bones. 4- By the age of 20 the active red marrow of long bones (except for the upper humerus and femur) has become inactive, yellow and fatty, and produce no more blood cells. 5- Beyond 20 years blood cells are normally formed in the marrow of flat or membranous bones (such as the vertebrae, sternum, ribs and pelvis) and the proximal ends of humerus and femur. Even in these bones, the marrow becomes less productive as age increases.  In certain pathological states, when there is increased demand for blood cell production, red marrow reappears in the shafts of the long bones, replacing the fat. From birth onwards, all blood cells except lymphocytes are normally made only in the bone marrow.  Only in pathological situations, such as in diseases in which the bone marrow becomes destroyed, significant hemopoietic activity occur in the liver, spleen and other sites, when it is referred to as extramedullary hemopoiesis.  Factors Regulating Hemopoiesis- Hemopoietic Growth Factors include erythropoietin, colony-stimulating factors (CSFs), and interleukins (ILs). These growth factors affect their target cells through binding to specific receptors. Erythropoietin is produced mainly by kidney cells, and to lesser extent in liver it is a circulating hormone. The other factors are produced by macrophages, activated T-lymphocytes, fibroblasts, and endothelial cells.  RED BLOOD CELLS (ERYTHROCYTES) Red blood cells (RBCs) are non nucleated, biconcave discs. The red cell membrane is flexible and exhibits a remarkable deformability The average normal RBC count in adult male is 4.5-6.5 million/mm3, and in adult female is 3.8- 5.8/mm3 of blood. At birth, the average RBC count is high The number of RBCs varies with age, sex, and altitude.  ERYTHROCYTE CHARACTERISTICS Most numerous formed element with Very flexible membrane No nucleus Biconcave disk Life span about 120 days Contains hemoglobin  ERYTHROPOIESIS =PRODUCTION OF RBC OCCURS IN THE RED BONE MARROW OF FLAT BONES AND IN SOME LONG BONES  During the reticulocyte stage, the cell passes to the blood and after 1-2 days in blood it becomes mature erythrocyte. The concentration of reticulocytes among all the red cells of the blood is normally 0.5-1.5 % in adults. Reticulocyte count is used as a clinical measurement of erythropoietic activity. The basic substances needed for normal RBC and hemoglobin production are: amino acids (proteins), iron, vitamin B12, folic acid, and vitamin B6.  Factors affecting Erythropoiesis Erythropoietin Protein diet Vitamins e.g. Vit B12,Folic Acid, Vit C, Vit E, Riboflavin etc. Metals e.g. Fe, Cu, Co, Mn etc Hormones e.g. Testosterone, Growth hormone, Cortisol, epinephrine and nor epinephrine,prostaglandine.  Feedback Regulation of Erythropoiesis - Erythropoietin a glycoprotein hormone, is produced by renal cells in response to a decreased renal blood O2 content. -Erythropoietin stimulates erythrocyte production in the red bone marrow.