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What is the primary function of hemoglobin in red blood cells?
What is the primary function of hemoglobin in red blood cells?
Hemoglobin primarily functions to transport oxygen from the lungs to the tissues and facilitate the return transport of carbon dioxide back to the lungs.
Define hematocrit and state the normal range for adult females.
Define hematocrit and state the normal range for adult females.
Hematocrit is the percentage of blood volume that is occupied by red blood cells. The normal range for adult females is 37-47%, with an average of 42%.
What are the three main types of cellular components found in blood?
What are the three main types of cellular components found in blood?
The three main types of cellular components in blood are red blood cells (erythrocytes), white blood cells (leucocytes), and blood platelets (thrombocytes).
Explain the significance of blood viscosity and its relation to flow resistance compared to water.
Explain the significance of blood viscosity and its relation to flow resistance compared to water.
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Where does hematopoiesis primarily occur in adults, and what types of blood cells are predominantly produced?
Where does hematopoiesis primarily occur in adults, and what types of blood cells are predominantly produced?
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What are the two main components of bone marrow and their functions?
What are the two main components of bone marrow and their functions?
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Describe the role of the multipotent uncommitted stem cell in blood cell formation.
Describe the role of the multipotent uncommitted stem cell in blood cell formation.
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How do myeloid and lymphoid stem cells differ in their development?
How do myeloid and lymphoid stem cells differ in their development?
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What is the function of Erythropoietin (EPO) in blood cell production?
What is the function of Erythropoietin (EPO) in blood cell production?
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Identify two types of factors that regulate differentiation and proliferation of bone marrow cells.
Identify two types of factors that regulate differentiation and proliferation of bone marrow cells.
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Study Notes
Blood Composition
- Blood is composed of a fluid called plasma that contains cellular elements including erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).
Blood Characteristics
- The average adult male has 5-6 liters of blood, while the average adult female has 4-5 liters.
- Blood temperature is approximately 100.4°F (37°C).
- Blood is five times more viscous than water, making it more resistant to flow. The viscosity is attributed to red blood cells and other components.
- The pH of blood ranges from 7.35-7.45, which is slightly alkaline.
- Blood color varies from scarlet (oxygenated) to deep red (deoxygenated).
Functions of Blood
- Blood is responsible for transporting nutrients, electrolytes, oxygen, carbon dioxide, waste products, hormones, and maintaining body temperature.
- It also serves as a defense against foreign organisms and provides clotting mechanisms for injury and infection.
- It plays a crucial role in homeostasis.
Hematocrit
- Hematocrit is the percentage of blood occupied by cells.
- The normal range for females is 37-47% (average 42%), while the normal range for males is 40-50% (average 45%).
- Testosterone contributes to the higher hematocrit in males.
- Anemia is characterized by a low number of red blood cells or insufficient hemoglobin.
- Polycythemia is a condition with an abnormally high number of red blood cells, generally over 65%, which can be caused by dehydration or tissue hypoxia.
Blood Cells
- There are three main types of blood cells: red blood cells (RBCs), white blood cells (WBCs), and platelets (PLs).
Formation of Blood Cells
- Most blood cell types require continuous replacement, with a lifespan measured in hours, days, or weeks.
- The process of blood cell formation is called hematopoiesis or hemopoiesis.
Sites of Hematopoiesis
- Hematopoiesis occurs in various locations depending on age and developmental stage.
- During embryonic development, hematopoiesis occurs in the yolk sac (first three months), then shifts to the liver and spleen (fourth to seventh month of gestation), before ultimately transitioning to the bone marrow.
- At birth, the entire bony skeleton contains hematopoietically active marrow.
- During childhood and adolescence, the activity decreases in long bones.
- In adults, hematopoiesis primarily occurs in the flat bones, including the skull, ribs, vertebrae, and pelvis.
Bone Marrow
- The bone marrow is one of the largest organs, comprising about 5% of total body weight.
- It consists of two components: red marrow (cellular component) and yellow marrow (fatty component).
- The red marrow is the site of production for all types of blood cells.
- All blood cells originate from a single type of cell within the bone marrow: the multipotent uncommitted stem cell (MPUCSC).
Stem Cells
- The MPUCSC differentiates into committed stem cells, which further develop into specific blood cell types: red blood cells, white blood cells, and platelets.
Hematopoiesis
- Developing blood cells are retained within the marrow until they mature sufficiently to function. Once mature, they are released into the bloodstream.
Blood Cell Formation Stages
- The formation of blood cells begins with pluripotent stem cells, which represent 1% of red marrow cells. Pluripotent stem cells can differentiate into either myeloid or lymphoid stem cells.
- The myeloid stem cell lineage continues with progenitor cells (colony-forming units, CFUs), which are specialized to form specific cell types.
- The next generation of cells are blast cells, which have recognizable histological characteristics.
- Blast cells develop within several divisions into mature cell types.
- Lymphoid stem cells develop into lymphocytes in the lymphatic tissue after leaving the red marrow.
Hemopoietic Growth Factors
- Hemopoietic growth factors regulate the differentiation and proliferation of blood cells.
- Erythropoietin (EPO), produced mainly by the kidneys, stimulates red blood cell formation.
- Thrombopoietin (TPO), a hormone produced by the liver, stimulates platelet formation.
- Cytokines, local hormones produced in bone marrow, like IL-1, IL-3, IL-4, IL-5, IL-6, IL-9, IL-11, and colony-stimulating factors (CSFs), contribute to the regulation of proliferation of various bone marrow cells.
Medical Uses of Growth Factors
- Recombinant DNA technology has led to the production of several growth factors for medical applications:
- Recombinant erythropoietin (EPO) is used effectively to treat decreased red blood cell production in patients with end-stage kidney disease.
- Other products, such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF), are used to stimulate white blood cell production in cancer patients undergoing chemotherapy.
- Thrombopoietin helps prevent platelet depletion during chemotherapy.
Erythropoiesis and Erythrocytes
- Erythrocytes (red blood cells) have a lifespan of 120 days.
- They are non-nucleated, biconcave discs.
- Red blood cell production is regulated by erythropoietin (EPO).
- Erythropoiesis requires iron, vitamin B12, folate, and other essential elements for development.
Erythropoiesis
- Erythropoiesis is the process of red blood cell formation.
Development of Mature Red Cells
- Mature red cells develop through a series of stages, beginning as pluripotent stem cells and ultimately becoming non-nucleated, specialized cells.
Contents of Red Blood Cells
- Red blood cells lack a nucleus and are therefore unable to reproduce.
- They also lack mitochondria, relying on anaerobic glycolysis for energy production.
- Red blood cells contain hemoglobin, which is responsible for oxygen transport.
- The normal red blood cell count is between 4.8-5.8 million/mm3 in males and 4.2-5.2 million/mm3 in females.
Control of Erythropoiesis
- Erythropoietin (EPO) stimulates erythropoiesis.
- EPO secretion is triggered by hypoxia (low oxygen levels), which can be caused by anemia, hemorrhage, high altitude, lung disease, or heart failure.
Role of the Kidneys in RBC Formation
- The kidneys play a critical role in erythropoiesis by producing EPO.
Tissue Oxygenation and RBC Formation
- Low tissue oxygen levels stimulate the production of EPO, leading to increased red blood cell formation.
Erythropoietin
- EPO is a glycoprotein hormone, with 90% produced by the renal cortex and 10% by the liver.
- EPO stimulates the proliferation and differentiation of early red blood cell committed stem cells.
- EPO can be measured in plasma and urine.
- High levels of EPO are indicative of anemia, high altitude exposure, or heart failure.
Control of Erythropoiesis (Continued)
- Other essential hormones, including androgens (male sex hormones), thyroid hormone, cortisol, and growth hormone, are crucial for red cell formation.
- Deficiencies in any of these hormones can lead to anemia.
Erythropoietin (Continued)
- Erythropoietin functions to stimulate the self-replication and proliferation of erythrocyte stem cells, stimulate differentiation into proerythroblasts, stimulate hemoglobin synthesis, and stimulate maturation of red blood cells.
- Human erythropoietin can be produced through recombinant DNA technology (CRF).
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Description
Explore the fascinating composition and characteristics of blood, including its cellular elements and vital functions in the human body. This quiz will test your knowledge on blood's role in transporting nutrients and protecting against infections, as well as its physiological properties.
