chp 17

• Regulation of Blood Pressure

  • Blood pressure regulation involves various organs and systems, not solely blood pressure itself.

• Blood Temperature

  • Blood temperature is typically higher than the average body temperature.

  • Example: During sweating or physical activity, blood is diverted from major organs to prevent temperature elevation in those organs, causing a flushing effect.

• Role of Hormones in Regulation

  • Hormones play a role in various physiological regulations, which will be discussed further.

Functions of Blood

• Delivery Mechanisms

  • Blood is responsible for transporting:

  • Oxygen

  • Nutrients

  • Hormones

  • Waste products for excretion.

• Thermoregulation

  • Blood steps in to protect organs by adjusting its flow based on temperature.

• pH Maintenance

  • Blood maintains a very strict pH range of approximately 7.35 to 7.45, vital for enzyme function.

  • Bicarbonate ions are used as buffers to stabilize blood pH levels.

• Protection

  • Blood provides protection through:

  • The presence of white blood cells, critical for the immune response.

  • Platelets that aid in clot formation to prevent blood loss.

Blood Composition

• Connective Tissue Characteristics

  • Blood is classified as connective tissue consisting of:

  • Cells (formed elements)

  • Proteins

  • Ground substances (plasma).

• Cellular Components

  • Formed elements include:

  • Red Blood Cells (Erythrocytes)

    • Function: Carry oxygen through hemoglobin.

  • White Blood Cells (Leukocytes)

    • Function: Immune response after pathogen detection.

  • Platelets

    • Function: Clotting process to prevent blood loss.

• Plasma Composition

  • Plasma constitutes approximately 55% of blood volume and contains:

  • Water

  • Proteins

  • Hormones and other solutes.

• Centrifuge Application and Blood Separation

  • Upon centrifugation, blood separates into:

  • Upper Layer (Plasma): Least dense, at the top, mostly water and solutes.

  • Middle Layer (Buffy Coat): Contains white blood cells and platelets.

  • Lower Layer (Formed Elements): Most dense, including red blood cells.

Blood pH and Volume

• Importance of pH in Blood

  • Tight pH range indicates severe issues if altered (e.g., pH of exactly 7 indicates imminent danger).

• Average Blood Volume

  • Comprises about 8% of total body weight, varying slightly with gender and physiological conditions.

Hemoglobin and Color Variation

• Hemoglobin Structure and Function

  • Hemoglobin contains iron in heme groups, which binding to O2 gives blood its characteristic bright red color when oxygenated, and a darker hue when deoxygenated (like maroon).

Formed Elements: Detailed Overview

• Red Blood Cells (Erythrocytes)

  • Mature erythrocytes lack nuclei and organelles, focusing on carrying hemoglobin.

  • Lifespan: Approximately 120 days.

  • Diameter: Around 7.5 micrometers, suitable for capillary passage.

  • Hemoglobin Content: Approximately 250 million hemoglobin molecules per RBC.

• Hematopoiesis

  • Formation of blood components occurs in the red bone marrow from stem cells.

  • Specific processes include:

  • Erythropoiesis: Specifically focuses on the formation of erythrocytes.

Leukocytes and Their Functions

• White Blood Cells (Leukocytes)

  • Types include:

  • Granulocytes: Neutrophils, Eosinophils, Basophils.

  • Agranulocytes: Lymphocytes, Monocytes.

• Functions

  • Respond to infections and produce an immune response.

  • Exhibit movement through blood and tissues via amoeboid motion and chemotaxis:

  • Positive chemotaxis: Movement towards attractive chemicals.

  • Negative chemotaxis: Movement away from harmful chemicals.

Types of Leukocytes with Characteristics

• Granulocytes

  • Neutrophils: Most common (70-80%), involved in phagocytosis with multiple lobes.

  • Eosinophils: Combat parasites and allergies, with a bilobed structure and red-staining granules.

  • Basophils: Least numerous, contribute to inflammatory responses and secrete histamine.

• Agranulocytes

  • Lymphocytes: Key players in adaptive immunity, with a large nucleus and types including B cells and T cells.

  • Monocytes: Differentiates into macrophages in tissue; larger than other leukocytes and effective at engulfing pathogens.

Platelets and Their Role

• Platelets (Thrombocytes)

  • Formed from megakaryocytes, they aid in hemostasis by forming plugs in damaged blood vessels.

  • Lifespan: Averages about 10 days.

  • Contain granules with proteins for the clotting process, including serotonin and platelet-derived growth factor.

Blood Typing: Antigens and Antibodies

• Blood Type Classification

  • Blood types are classified primarily on the presence of antigens on red blood cell surfaces: A, B, AB, and O, demonstrating dominance and recessive patterns of inheritance.

• Universal Donor and Recipient

  • Universal Donor: O negative is termed universal as it lacks A/B antigens.

  • Universal Recipient: AB positive can accept blood from any type without immune complications.

• Rh Factor

  • Rh positive indicates the presence of D antigen, while Rh negative indicates absence.

  • Potential risks arise in pregnancies if the mother is Rh negative carrying an Rh positive fetus, requiring special care to prevent hemolytic disease of the newborn.

Clinical Implications and Disorders

• Leukemia and Leukopenia

  • Leukemia: Characterized by uncontrolled proliferation of abnormal leukocytes, can lead to anemia and immunodeficiency.

  • Leukopenia: A decreased level of white blood cells often caused by drugs or stress hormones affecting their production.

• Common Anemias

  • Various forms result in fatigue, weakness, and reduced oxygenation of tissues depending on the underlying cause.

• Blood Imaging and Smears

  • Blood smears reveal types of leukocytes like neutrophils and lymphocytes for diagnostic purposes.

Conclusion and Further Studies

• Encourage review of material on hematopoiesis, regulation, and pathology of blood components in preparation for upcoming discussions.