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BLOOD ANATOMY AND PHYSIOLOGY
Functions of the Blood o Blood is unique o Only fluid tissue in the body Carrier of gases, nutrients, and waste products: Oxygen – enters the blood in the lungs and is transported to cells Carbon dioxide – produced by cells, transported in the blood to the lungs, from which it is expelled Ingested nutrients, ions, and water – carried by the blood from the digestive tract to cells Waste products – moved to the kidneys for elimination Clot formation: Clotting proteins help stem blood loss when blood vessel is injured Transport of processed molecules: Most substances are produced in one part of the body and transported in the blood to another part Protection against foreign substances: Antibodies help protect the body from pathogens Transport of regulatory molecules: Hormones and enzymes that regulate body process are carried form one part to another within the blood Maintenance of body temperature: Warm blood is transported from the inside to the surface of the body Heat is released from the blood pH and osmosis regulation: Albumin is also an important blood buffer Contributes to the osmotic pressure of blood Acts to keep water in the blood stream Components of Blood o Blood is a complex connective tissue in which living blood cells o Formed elements, are suspended Physical Characteristics and Volume o Blood is a sticky , opaque fluid with a characteristic metallic taste Color: Color of blood varies from: o Scarlet ( oxygen-rich ) o Dull red ( oxygen-poor ) Weight: Blood is heavier than water 5x thicker or more viscous pH: Slightly alkaline pH between 7.35 and 7. Temperature : 38 degree Celsius or 100.4 degrees Fahrenheit Always slightly higher than body temperature
Plasma o Approximately 90% water o Liquid part of the blood Fresh Frozen Plasma Dissolved substances: Examples are : o Nutrients o Salts ( electrolytes ) o Respiratory gases o Hormones o Plasma proteins , and o Various wastes and products of cell metabolism Plasma proteins: Most abundant solutes in plasma Except for antibodies and protein-based hormones Most plasma proteins are made by liver Composition: Varies continuously as cells remove or add substances to the blood Composition of plasma is kept relatively constant by various homeostatic mechanisms of the body Formed Elements o Disc-shaped red blood cells o Variety of gaudily stained spherical white blood cells o Some scattered platelets that look like debris Erythrocytes o Red blood cells o Function primarily to ferry oxygen in blood to all cells of the body
Multilobed granules and very fine granules Respond to acidic and basic stains Avid phagocytes at sites of acute infection Particularly partial to bacteria and fungi Eosinophils: Blue red nucleus Resembles an old-fashioned telephone receiver and sport coarse Lysosome-like , brick-red cytoplasmic granules Number increases rapidly during allergies and infections by parasitic worms or entering via the skin Basophils: Rarest of the WBCs Contain large, histamine-containing granules that stain dark blue Histamine – inflammatory chemical that makes blood vessels leaky and attracts other WBCs to the inflammatory site Agranulocytes: Second group of WBCs Lack visible cytoplasmic granules Nuclei are closer to the norm – that is spherical Spherical , oval or kidney-shaped Include lymphocytes and monocytes Lymphocytes: Large , dark purple nucleus Occupies most of the cell volume Tend to take up residence in lymphatic tissues Play an important role in the immune response Monocytes: Largest of the WBCs When migrate into the tissue they transform into macrophages with huge appetites o Very important in fighting chronic infections Platelets: Not cells in the strict sense They are fragments of bizarre multinucleate cells called megakaryocytes o Pinch off thousands of anucleate platelet “ pieces ” that quickly seal themselves off from surrounding fluids Platelets are needed for the clotting process Hematopoiesis o Blood cell formation or hematopoiesis o Occurs in red bone marrow or myeloid tissue
Hemocytoblast: All the formed elements arise from a common type of stem cell Descendants of hemocytoblast: Forms two types of descendants : o Lymphoid stem cell – produces lymphocytes o Myeloid stem cell – produce all other classes of formed elements Formation of Red Blood Cells o Because they are anucleate , RBCs are unable to: Synthesize proteins Grow , or Divide Life span: RBC become more rigid and begin to fragment or fall apart in 100 to 120 days (as they age) Lost RBCs: Replaced more or less continuously by the division of hemocytoblasts in the red bone marrow Immature RBCs: Divide many times Begin synthesizing huge amounts of hemoglobin Reticulocyte: Young RBC Still contains some rough endoplasmic reticulum ( ER ) Mature erythrocytes: 2 days of release they have rejected the remaining ER Become fully functioning erythrocytes Entire developmental process from hemocytoblast to mature RBC takes 3 to 5 days Erythropoietin: Controls the rate of erythrocyte production Normally a small amount of erythropoietin circulates in the blood at all times RBCs are formed at a fairly constant rate Control of RBC production: REMEMBER !! It is not the relative number of RBCs in the blood that controls RBC production Control is based on their ability to transport enough oxygen to meet the body’s demands Formation of White Blood Cells and Platelets o Stimulated by hormones Colony stimulating factors and interleukins: Not only prompt red bone marrow to turn out leukocytes Marshal up an army of WBCs to ward off attacks by enhancing the ability of mature leukocytes to protect the body Thrombopoietin: Accelerates the production of platelets But little is known about how that process is regulated Hemostasis o The multistep of hemostasis begins when a blood vessel is damaged and connective tissue in the vessel wall is exposed to blood
Rh+ ( Rh positive ) – their RBCs carry the Rh antigen Anti-Rh antibodies: Not automatically formed and present in the blood of Rh- ( Rh negative ) individuals Hemolysis: Rupture of RBCs Not occur with the 1st^ transfusion because it takes time for the body React and start making antibodies Blood Typing o Importance of determining the blood group of both the donor and the recipient Blood typing of ABO blood groups: Serum containing anti-A or anti-B antibodies is added to a blood sample diluted with saline Agglutination will occur between the antibody and the corresponding antigen Cross matching: Involves testing for agglutination of donor RBCs Blood typing for Rh factors: Done in the same manner as ABO blood typing
