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Questions and Answers
What is the primary function of erythrocytes in the blood?
What is the primary function of erythrocytes in the blood?
Which cellular component of blood is primarily responsible for immune response?
Which cellular component of blood is primarily responsible for immune response?
What percentage of blood volume is typically occupied by red blood cells?
What percentage of blood volume is typically occupied by red blood cells?
Which of the following statements about platelets is accurate?
Which of the following statements about platelets is accurate?
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How does the hematocrit relate to red blood cells?
How does the hematocrit relate to red blood cells?
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What is the primary role of the plasma component of blood?
What is the primary role of the plasma component of blood?
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Which blood cell type has the longest lifespan in the human body?
Which blood cell type has the longest lifespan in the human body?
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What is a common clinical significance of abnormal blood cell counts?
What is a common clinical significance of abnormal blood cell counts?
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What is the primary role of hemoglobin in red blood cells?
What is the primary role of hemoglobin in red blood cells?
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What distinguishes red blood cells from white blood cells?
What distinguishes red blood cells from white blood cells?
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Which of the following describes the shape of red blood cells?
Which of the following describes the shape of red blood cells?
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What is the main function of leukocytes (white blood cells)?
What is the main function of leukocytes (white blood cells)?
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Which type of leukocyte is classified as agranular?
Which type of leukocyte is classified as agranular?
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What does an elevated white blood cell count typically indicate?
What does an elevated white blood cell count typically indicate?
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How does erythropoietin affect red blood cell production?
How does erythropoietin affect red blood cell production?
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What is the lifespan of red blood cells in the circulation?
What is the lifespan of red blood cells in the circulation?
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What is the primary role of platelets in the blood?
What is the primary role of platelets in the blood?
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What occurs during the vascular spasm stage of hemostasis?
What occurs during the vascular spasm stage of hemostasis?
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Which of the following statements about the lifespan of platelets is correct?
Which of the following statements about the lifespan of platelets is correct?
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What term describes the process by which blood thickens and forms a gel when drawn from the body?
What term describes the process by which blood thickens and forms a gel when drawn from the body?
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What initiates the extrinsic pathway of blood clotting?
What initiates the extrinsic pathway of blood clotting?
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Which of the following is NOT a component of the formed elements of blood?
Which of the following is NOT a component of the formed elements of blood?
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Which group of blood cells is primarily responsible for fighting infections?
Which group of blood cells is primarily responsible for fighting infections?
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How many clotting factors are known to be involved in the clotting process?
How many clotting factors are known to be involved in the clotting process?
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Study Notes
Blood and Internal Environment
- Blood, interstitial fluid, and lymph are all vital for transporting nutrients and removing waste from cells.
- Blood is a liquid connective tissue comprised of formed elements (cellular components) and plasma (liquid extracellular matrix).
Properties of Blood
- Blood consists of 55% plasma and 45% formed elements.
- Plasma is primarily water (91.5%) and solutes (8.5%), including proteins, nutrients, enzymes, hormones, respiratory gases, electrolytes, and waste products.
- Formed elements include erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).
- The hematocrit measures the percentage of total blood volume occupied by red blood cells.
- Blood is more viscous than water and has a temperature of 38°C and a pH of 7.35-7.45.
- It constitutes about 8% of body weight with a volume ranging from 4 to 6 liters.
Functions of Blood
- Blood transports oxygen, carbon dioxide, nutrients, hormones, heat, and waste products.
- It regulates body fluid homeostasis, pH, and temperature.
- Blood protects against blood loss through clotting, combats toxins and microbes through phagocytic WBCs and specialized plasma proteins.
Formation of Blood Cells
- Pluripotent stem cells in red bone marrow have the capacity to develop into many cell types.
- The process of producing blood cells is called hemopoiesis (hematopoiesis).
- Lymphocytes have a lifespan of several years, while other blood cells live for hours, days, or weeks.
- The number of RBCs and platelets is relatively constant, while WBCs vary depending on invading pathogens and antigens.
Red Blood Cells (Erythrocytes)
- Erythropoiesis (production of RBCs) begins in red bone marrow.
- Erythropoietin, a hormone released by the kidneys in response to hypoxia, stimulates erythrocyte differentiation.
- Reticulocytes, immature red blood cells, mature in the circulation within 1-2 days.
- RBCs lack a nucleus and other organelles, allowing for efficient oxygen transport.
- Their biconcave disc shape enhances oxygen transport.
- RBCs have a lifespan of about 120 days and are removed by the spleen and liver.
- Breakdown products from dead cells are recycled and reused.
- RBCs contain hemoglobin:
- Carries oxygen to cells
- Carries 23% of total CO2 to the lungs
- Each hemoglobin molecule contains an iron ion that binds four oxygen molecules.
- Each erythrocyte contains 280 million hemoglobin molecules.
- The normal RBC count is 5 million per microliter of blood.
White Blood Cells (Leukocytes)
- WBCs have a nucleus and organelles but lack hemoglobin, unlike RBCs.
- Classified as granular or agranular based on the presence or absence of granules.
- Granular: neutrophils, eosinophils, basophils
- Agranular: lymphocytes, monocytes
- Most WBCs live for a few days, though some can survive for months or years.
- Their primary function is to combat invading microbes.
- Chemotaxis is the attraction of phagocytes by chemicals released from inflamed tissues.
- Emigration (diapedesis) is the process of WBCs leaving the bloodstream and collecting at sites of invasion.
- Elevated WBC counts usually indicate infection or inflammation.
- Low WBC counts can be caused by various factors.
- A differential WBC count helps identify potential problems.
Platelets
- Platelets are essential for blood clotting.
- They help stop blood loss from damaged vessels by forming a platelet plug.
- Their granules contain chemicals that promote blood clotting.
- Megakaryocytes in red bone marrow splinter into fragments, creating platelets with many vesicles but no nucleus.
- Normal blood contains 250,000 to 400,000 platelets per mm3.
- Platelets have a lifespan of 5 to 9 days and are removed by macrophages.
Hemostasis
- Hemostasis is a sequence of responses that stop bleeding.
- It involves:
- Vascular spasm: Smooth muscle in blood vessel walls contracts to reduce blood loss.
- Platelet plug formation: Platelets clump around damage to stop bleeding.
- Blood clotting (coagulation): Formation of a gel composed of formed elements entangled in fibrin threads.
Blood Clotting (Coagulation)
- Blood remains liquid within its vessels, but coagulates when drawn out.
- Serum is plasma minus clotting factors.
- A blood clot is a network of fibrin fibers trapping formed elements.
- The process of gel formation is called clotting or coagulation.
- Coagulation factors (13 clotting factors including calcium, prothrombin, fibrinogen) participate in clotting.
- Blood clotting occurs in three stages:
- Extrinsic or intrinsic pathway: Leads to the formation of prothrombinase (prothrombin activator)
- Conversion of prothrombin into thrombin:
- Conversion of soluble fibrinogen into insoluble fibrin:
Extrinsic vs. Intrinsic Pathway
-
Extrinsic pathway:
- Starts with trauma to the vascular wall or surrounding tissue.
- Fewer steps and occurs rapidly, within seconds for severe injuries.
-
Intrinsic pathway:
- Initiated by damage within the blood vessel itself.
- More complex with multiple steps.
- Plays a smaller role in initial clotting but contributes to sustained clotting.
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Description
Test your knowledge on the properties, functions, and components of blood. This quiz covers essential aspects including the composition of blood, its role in the body, and the measurement of hematocrit. Perfect for students studying biology or human anatomy.
