Physiology of The Blood Dr. Miada Mahmoud Rady EMS/474 Hematological Emergencies / lecture 1.

Learning Objectives By the end of this chapter you should be able to: Describe the physiology of blood and its components Discuss the Pathophysiology and signs and symptoms of specific hematological disorders. Outline the general assessment and management of patients with hematological disorders.

Introduction The hematopoietic system consists of organs and tissues involved in the production of blood components. Hematologic disorder: Any disorder of the blood , it could be either : Hemolytic disorders : involves breakdown of red blood cells Hemostatic disorders : Bleeding and clotting abnormalities.

Blood Components

Blood and Blood Components Blood composed of cell and formed elements surrounded by plasma : Plasma : Accounts for 55% of total blood volume. 92% water and 6% to 7% proteins. Formed elements Account for 45% of total blood volume. 99% of which are RBCs.

Function of The Blood Delivery of the various substances essential for cellular metabolism and function as oxygen , nutrient and hormones . Removal of carbon dioxide and waste product resulting from metabolic processes. Defense against invading microorganisms and injury. Acid‐base balance.

Blood Forming Organs Bone marrow : Blood cells are formed within red bone marrow which is present : At birth in all bony cavities of the bodies . In adult its primarily found in membranous bone e.g. Vertebrae, pelvis, sternum, ribs and head of long bone. Cells producing blood cells are known as hematopoietic stem cells .

Give 6 types of blood cells Lymphoid stem cell Stem cells Myeloid stem cell Give 6 types of blood cells RBCS , Platelet , and 4 types of WBCS Lymphoid stem cell Remaining 3 types of WBCS T-lymphocytes B-lymphocytes Natural killer cells

Blood Forming Organs Lymph nodes : Produce lymphocytes and antibodies. Spleen Stores large quantities of blood. Produces lymphocytes, plasma cells, antibodies. Liver Blood‐forming organ only during intrauterine life. Plays important role in coagulation process.

Blood Cells Red blood cells : Bright red in color. Shape : a biconcave disk with a flattened center. Most abundant cell accounting for 45% of total volume . Primarily responsible for tissue oxygenation. Life span of RBCs is about 120 days. Number of RBCs is about 4.2 to 6.2 million cells/mm2

Normal RBCS

Normal and abnormal RBCS

Blood Cells White blood cells : Primarily responsible for body defense ; – Destroy foreign substances (e.g., bacteria and viruses) and Clear bloodstream of debris. Normal WBC count is about 5,000 to 11,000 cells/mm2 Leukocyte production increases in response to infection , inflammation and stress.

Blood Cells Platelets : Platelets (thrombocytes) are small, sticky cell fragments. Play an important role in blood clotting and hemostasis . Normal count 150,000 to 450,000 cells/mm2. Average life span: 5 to 11 days.

Blood Groups and Blood Group Testing System developed to ensure compatibility and prevent medical problems during blood component transfusion. Two commonly used system : ABO system : named according to the antigen located on membrane of the RBCS and include A , B , AB and O. Rh system : also named according to the antigen located on membrane of the RBCS into Rh positive and Rh negative.

Rh isoimmunization

Hemostasis Hemostasis is the process that allows the body to stop bleeding. It consists of three steps : Vascular spasm. Platelet plugging. Coagulation.

Hemostasis Vasoconstriction (immediate response) : Narrowing of the blood vessel to cut off flow at the affected site. Platelet plugging: Platelets stick to collagen and become activated. Activated platelets release chemicals to draw additional platelets to the injury site which causes a plug to form, helping to stop the bleeding.

Coagulation : Involves a dozen clotting factors that are activated when the body is injured Each requires the presence and activation of the preceding factor to work.

Summary

Home work Give short account on the various component of the blood and its cells? Enumerate the stages of hemostasis?

Any Question ?