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14.1 Characteristics of Blood

• Blood Overview:

  • The only type of connective tissue with a liquid matrix (plasma).

  • Functions:

    • Transports vital substances

    • Regulates homeostasis processes

    • Maintains interstitial fluid stability

    • Distributes heat.

• Blood Volume:

  • Varies with body size, fluid concentration, electrolyte levels, and adipose tissue amount.

  • Adults: 4-5 liters (female) and 5-6 liters (male), representing about 8% of body weight.

• Blood Components (Formed Elements):

  • Formed primarily in red bone marrow and include:

    • Red Blood Cells (RBCs)

    • White Blood Cells (WBCs)

    • Platelets (cell fragments).

14.1.1 Blood Composition

• Components in Centrifuged Blood:

  • Plasma: 55% (closest to the top, straw-colored fluid).

  • Formed Elements: 45% (settle at the bottom).

    • Red Blood Cells (RBCs): 95.1% of formed elements

    • White Blood Cells (WBCs): about 0.1%

    • Platelets: about 4.8%.

14.2 Formed Elements

• Hematopoiesis:

  • Formation of blood cells from hematopoietic stem cells in the red marrow.

  • Two types of stem cells:

    • Lymphoid stem cells:

      • Give rise to lymphocytes.

    • Myeloid stem cells:

      • Give rise to all other formed elements, including RBCs, other WBCs, and platelets.

14.2.1 Red Blood Cells (RBCs)

• General Characteristics:

  • Also known as erythrocytes, biconcave discs, lack nuclei and mitochondria.

  • Composed of hemoglobin:

    • Oxyhemoglobin (with O2) and Deoxyhemoglobin (without O2).

• Production and Lifespan:

  • RBCs produced in red bone marrow, live for about 120 days, and generate ATP through glycolysis.

14.2.2 Red Blood Cell Count

• Definition:

  • RBC Count: Number of RBCs per cubic millimeter or microliter of blood.

• Typical Ranges:

  • Males: 4,700,000 - 6,100,000/μL

  • Females: 4,200,000 - 5,400,000/μL

  • Children: 4,500,000 - 5,100,000/μL.

14.2.3 Erythropoiesis

• Definition:

  • Process of RBC formation regulated by erythropoietin (EPO) from kidneys and liver.

• Regulation:

  • Negative feedback mechanism ensures that oxygen levels stimulate RBC production.

• Nutritional requirements for erythropoiesis include:

  • Vitamin B12 and folic acid (DNA synthesis)

  • Iron (hemoglobin synthesis).

14.2.4 Types of Anemia

• Conditions leading to Anemia:

  • Hemorrhagic anemia: Blood loss through hemorrhage.

  • Hemolytic anemia: Destruction of RBCs due to infections or transfusion reactions.

  • Aplastic anemia: Bone marrow failure.

  • Iron-deficiency anemia: Low hemoglobin concentration.

  • Sickle cell anemia: Abnormal hemoglobin shape leads to short-lived RBCs.

14.3 Plasma

• Description:

  • Clear, straw-colored liquid representing 55% of blood volume.

  • Composed of 92% water and various solutes including nutrients, gases, hormones, and plasma proteins (e.g., albumins, globulins).

14.3.1 Plasma Proteins

• Major Plasma Proteins:

  • Albumins: Maintain osmotic pressure.

  • Globulins: Transport lipids, fat-soluble vitamins, and constitute antibodies for immunity.

  • Fibrinogen: Essential for blood coagulation.

14.4 Hemostasis

• Definition:

  • Stoppage of bleeding involving:

  • Vascular spasm.

  • Platelet plug formation.

  • Blood coagulation (clotting).

14.4.1 Vascular Spasm

• Rapid contraction of blood vessel smooth muscle triggered by injury, reducing blood loss.

14.4.2 Platelet Plug Formation

• Platelets adhere to rough surfaces or injured tissue, aided by von Willebrand factor, forming a temporary plug.

14.4.3 Blood Coagulation

• Major event in hemostasis, involving the transformation of fibrinogen into fibrin threads, regulated by clotting factors and vitamin K.

14.5 Blood Groups and Transfusions

• ABO Blood Group:

  • Blood types based on the antigens present on RBCs, crucial for safe transfusions to prevent agglutination.

• Rh Factors:

  • Important in blood type compatibility, especially in maternal-fetal cases.

14.5.1 Universal Donor and Recipient

• Type O: Universal donor (lacks A and B antigens).

• Type AB: Universal recipient (no anti-A or anti-B antibodies).

14.5.2 Rh Incompatibility

• Can occur during pregnancies if an Rh-negative mother becomes sensitized by Rh-positive fetal blood, potentially causing hemolytic disease of the newborn.

Practice Questions on Blood Characteristics and Functions

1. What percentage of blood volume does plasma constitute?

   • Answer: Plasma constitutes 55% of blood volume.

2. What is the primary function of red blood cells (RBCs)?

   • Answer: The primary function of RBCs is to transport oxygen throughout the body.

3. What is erythropoiesis?

   • Answer: Erythropoiesis is the process of RBC formation, regulated by erythropoietin (EPO).

4. What nutritional requirements are essential for erythropoiesis?

   • Answer: Vitamin B12, folic acid, and iron are essential for erythropoiesis.

5. Define hemostasis and its main processes.

   • Answer: Hemostasis is the process of stopping bleeding, involving vascular spasm, platelet plug formation, and blood coagulation.

6. What type of blood is considered the universal donor?

   • Answer: Type O blood is considered the universal donor because it lacks A and B antigens.

7. What happens during Rh incompatibility in pregnancies?

   • Answer: Rh incompatibility can occur if an Rh-negative mother becomes sensitized by Rh-positive fetal blood, which may lead to hemolytic disease of the newborn.

8. What are the main types of anemia and their causes?

   • Answer: Types include hemorrhagic anemia (blood loss), hemolytic anemia (RBC destruction), aplastic anemia (bone marrow failure), iron-deficiency anemia (low hemoglobin), and sickle cell anemia (abnormal hemoglobin shape).

9. What is the role of albumins in blood plasma?

   • Answer: Albumins help maintain osmotic pressure in the blood.

Creating Practice Questions for Study

Importance of Practice Questions

• Reinforcement of Knowledge: Helps solidify understanding of material.

• Assessment of Understanding: Allows students to gauge their grasp of concepts.

• Preparation for Tests: Familiarizes students with the format and style of questions that may appear on assessments.

Tips for Creating Effective Practice Questions

1. Focus on Key Concepts: Identify vital topics and concepts to include.

2. Vary Question Types: Use multiple-choice, short answer, and true/false formats to enhance engagement.

3. Clear and Concise: Ensure questions are straightforward and easy to understand.

4. Provide Answers: Include an answer key for immediate feedback and self-assessment.

5. Adjust Level of Difficulty: Create a mix of easy, moderate, and challenging questions to cater to all learners.

Example Practice Questions Structure

1. What is [Key Concept]?

   • Answer: [Concise response]

2. Explain how [Process or Function] works.

   • Answer: [Brief explanation]

3. List the main components of [Topic].

   • Answer: [Key components]

By implementing these strategies, you can create effective and comprehensive practice questions that enhance learning and retention.