Hematologic System
The blood and the blood forming sites, including the bone marrow and the reticuloendothelial system (RES) Includes:
• Bone Marrow
• Blood
• Spleen
• Lymph System
Bone Marrow
Located in pelvis, r
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Hematologic System
The blood and the blood forming sites, including the bone marrow and the reticuloendothelial system (RES) Includes:
• Bone Marrow
• Blood
• Spleen
• Lymph System
Bone Marrow
Located in pelvis, ribs, vertebrae, sternum Soft material that fills the center of bones
• Hematopoiesis – process of regeneration of RBCs
• Stem cells
o Have the ability to self-replicate
o The majority of stem cells are myeloid cells
• Myeloid
o Erythrocytes (RBC)
o Leukocytes (WBC)
o Thrombocytes (Platelets)
• Lymphoid
o Lymphocytes (T or B cells)
• Stroma – the remaining tissue in the marrow that is not involved in hematopoiesis
• Hematopoiesis – the complex process of formation and maturation of blood cells
occurs in the bone marrow
Blood
• Connective tissue that transports, regulates, & protects
o Plasma: fluid portion of blood that contains proteins, electrolytes, gases, nutrients, & wastes – 50%
o Blood cells:
▪ erythrocytes (RBC)
▪ leukocytes (WBC)
▪ thrombocytes (platelets)
o Proteins:
▪ Albumin – oncotic pressure
▪ Globulin
▪ Fibrinogen
Red Blood Cells: Erythrocytes
• Biconcave disk – flexible & thin membrane so O2 & CO2 can easily diffuse across it ; disk shape provides a large surface area that facilitates the absorption and release of O2 molecules
• Types
o Hemoglobin – 95% of cell’s mass
o Reticulocytes – slightly immature erythrocytes
▪ This count will be increased in situations of active bleeding – the body is trying to create new RBCs quickly
• Erythropoiesis
o Process of immature cells being released (takes place in myeloid stem cells in bone marrow)
o Entire process takes 5 days
• Iron stores and metabolism
o Present in the heme portion of the molecule
o Iron is stored as ferritin & released when needed
o Need to investigate reason for low iron level – need to look for causative factors like bleeding or disease process (colon cancer). Not an intake issue – most Americans get enough iron from meat & vegies
• Vitamin B12 and folic acid
o Needed for DNA synthesis in our RBCs (diet derived; vegetarians may have a deficit as this comes from animals / sometimes can be an absorption issue – missing part of intestine lining from abdominal surgery or disease & may be B12 deficient or folic acid deficit)
o The effects of either decreased absorption or decreased intake of vitamin B12 are not apparent for 2-4 years
• Destruction
o Avg life span is 120 days
o Removed through liver & spleen
o Recycled into hemoglobin
An important property of heme is its ability to bind to oxygen loosely and reversibly. Oxygen readily binds to hemoglobin in the lungs and is carried as oxyhemoglobin in arterial blood. Oxyhemoglobin is a brighter red than hemoglobin that does not contain oxygen (reduced hemoglobin); thus, arterial blood is a brighter red than venous blood. The oxygen readily dissociates (detaches) from hemoglobin in the tissues, where the oxygen is
needed for cellular metabolism. In venous blood, hemoglobin combines with hydrogen ions produced by cellular metabolism and
thus buffers excessive acid. Whole blood normally contains about 15
g of hemoglobin per 100 mL of blood
White Blood Cells: Leukocytes
• Granulocytes
• Defined by presence of granulo in cytoplasm
o Eosinophils – stain bright red color
o Basophils – stain deep blue color
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