HSC Ch 7

Human Diseases: A Systemic Approach - Notes

Overview

  • Authors: Zelman, Raymond, Holdaway, Dafnis, Mulvihill

  • Publication: Eighth Edition, Pearson Education, Inc. 2015, 2011

Chapter: Diseases and Disorders of the Blood

Objectives

  • Distinguish between formed elements and plasma.

  • Describe the function of:

    • Red Blood Cells (RBCs)

    • White Blood Cells (WBCs)

    • Platelets

  • Identify the characteristics, diagnosis, and treatments of:

    • Main types of anemia

    • Hemoglobinopathies

    • Main types of clotting disorders

    • Selected inherited disorders of the blood

    • Disorders affecting leukocytes

Blood Composition

  • Blood is composed of:

    • Serum: Aqueous (water) based component.

    • Formed elements: Include RBCs, leukocytes (WBCs), and platelets.

  • Leukocytes (White Blood Cells): Categorized into five types:

    • Neutrophils (polymorphonuclear leukocytes)

    • Lymphocytes

    • Monocytes

    • Eosinophils

    • Basophils

Anatomy and Physiology Review

Plasma

  • Main liquid component of blood.

Erythrocytes (RBCs)

  • Primary role is oxygen transportation.

Hemoglobin

  • Components:

    • Globin: Protein portion.

    • Heme: Contains iron (Fe) for oxygen binding.

  • Hemoglobin composition:

    • Four globin chains: Two alpha (141 amino acids) and two beta (146 amino acids).

Erythropoiesis

  • Process of RBC production.

  • Stimulated by erythropoietin, a hormone released by renal cells when oxygen levels are low.

White Blood Cells (Leukocytes)

Types of WBCs

  1. Neutrophils: Most numerous, phagocytic cells vital for non-specific immune response.

  2. Lymphocytes: Second most common, responsible for specific immunity against antigens.

  3. Monocytes: Exit circulation to become phagocytic in connective tissue.

  4. Eosinophils: Increase in allergic responses.

  5. Basophils: Least common, release histamine and heparin.

Platelets (Thrombocytes)

  • Function: Essential for blood coagulation.

  • Characteristics:

    • Small cytoplasmic fragments from megakaryocytes.

    • Lifespan: Approximately 10 days.

Erythropoiesis Essentials

  • The process of producing red blood cells from progenitor cells in the bone marrow.

  • Stimulated by erythropoietin, a hormone produced by the kidneys.

  • Nutritional requirements include:

    • Iron

    • Folic Acid

    • Vitamin B12

Diagnostic Tests and Procedures

  • Key blood counts measured:

    • RBCs

    • WBCs

    • Platelets

    • Hemoglobin

    • Hematocrit

    • Serum chemistry

    • Enzyme levels

    • Hormone levels

Anemia

  • Defined as an abnormally low number of RBCs.

Causes

  1. Hemorrhage

  2. Excessive destruction of RBCs

  3. Nutritional deficiency

  4. Chronic disease

  • Symptoms typically arise from hypoxia and hemolysis.

Categories of Anemia

  1. Inadequate erythropoiesis factors:

    • Iron deficiency: Most common cause.

    • Folic acid or vitamin B12 deficiency:

      • Vitamin B12 binds to intrinsic factor for gastrointestinal absorption.

      • Pernicious Anemia: Lack of intrinsic factor, common in older adults.

    • Aplastic anemia: Resulting from radiation, viruses, or toxins.

    • Renal failure: Decreased erythropoietin production.

    • Neoplastic involvement (leukemia/metastatic cancer): Crowds healthy bone marrow.

  2. Blood loss from:

    • Trauma

    • Surgical procedures

    • Ulcers

    • Excessive menstruation

  3. Hemolysis: RBC breakdown due to:

    • Drug reactions

    • Mechanical heart valves

    • Hereditary hemoglobin defects.

Types of Anemia

  • Iron-deficiency anemia:

    • Staging involves:

    • First Stage: Subclinical; no anemia present yet.

    • Second Stage: Iron stores depleted.

  • Anemia of Chronic Disease

  • Anemia of Renal Failure

  • Megaloblastic Anemia

  • Vitamin B12-Deficiency Anemia (pernicious anemia)

  • Folic Acid-Deficiency Anemia

  • Hemolytic Anemia

Hemoglobinopathies

  • Sickle Cell Anemia:

    • A genetic disorder marked by abnormal hemoglobin (HbS) leading to hemolysis.

  • Thalassemia: Inherited disorder affecting protein chain synthesis.

Hereditary Hemolytic Anemias

  • Types include:

    1. Abnormal Hemoglobin: e.g., Sickle Cell Anemia

    2. Abnormal Shape: e.g., Hereditary Spherocytosis

    3. Abnormal Hemoglobin Synthesis: e.g., Thalassemia

    4. Enzyme Defects: e.g., Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency.

  • Sickle Cell Anemia Details:

    • Genetic change: Valine replaces glutamic acid in the alpha chain.

    • Sickle Cell Trait: Heterozygous for HbS.

    • Sickle Cell Anemia: Homozygous for HbS.

    • Sickle shape RBCs under low oxygen, causing pain and organ damage.

Hereditary Spherocytosis

  • Genetically determined abnormality in RBC shape leading to increased diameter and trapping in the spleen, with decreased lifespan.

G6PD Deficiency

  • Genetics: X-linked recessive, mostly affecting Black males.

  • Description: Deficiency of unstable red cell enzyme leading to hemolysis under stress,

    • Provides some malaria protection.

Polycythemia Vera

  1. Absolute Polycythemia: Increased RBC mass without clear causative factor.

  2. Primary Polycythemia: Increased RBC production, can lead to leukemia.

  3. Secondary Polycythemia: Bone marrow compensates for oxygen deprivation from conditions like:

    • Pulmonary Fibrosis

    • Emphysema

  • Issues may induce a hypercoagulable state requiring intervention (e.g., blood removal or medication).

Diseases of Hemostasis

Thrombocytopenia

  • Definition: Decreased platelets, affecting blood clotting.

  • Purpura: Characteristic skin rash from blood leakage into skin.

  • Petechiae: Small pinpoint spots.

  • Ecchymosis: Larger hemorrhages.

  • Types:

    • Primary thrombocytopenia: Offer no specific underlying disease.

Disorders of Hemostasis

  • Idiopathic Thrombocytopenic Purpura (ITP): Autoimmune condition leading to decreased platelet counts.

  • Characterized by easy bruising, bleeding gums, internal bleeding.

Hemostasis and Coagulation

  1. Key requirements for effective hemostasis:

    • Responsive blood vessels to injury (vasoconstriction).

    • Sufficient number of platelets.

    • Adequate coagulation factors and inhibitors.

  2. Coagulation involved:

    • Two pathways (intrinsic & extrinsic) lead to thromboplastin formation, converting prothrombin into thrombin, which then changes fibrinogen into fibrin.

Vitamin K

  • Vital for the production of specific coagulation factors by the liver; deficiencies due to:

    • Bile flow obstruction from gallstones or tumors.

    • Long-term antibiotic use disrupting intestinal flora that produce Vitamin K.

    • Liver failure impacting factor synthesis.

Coagulation Defects

  • Types include:

    • Thrombus

    • Impaired synthesis of coagulation factors (e.g., due to vitamin K deficiencies).

Hemophilia

  1. Hemophilia A:

    • X-linked recessive disorder, deficiency of clotting factor VIII.

  2. Von Willebrand's Disease:

    • Inherited bleeding disorder marked by deficiency in von Willebrand factor (vWF), a mendelian dominant trait.

    • Deficiency leads to reduced factor VIII levels.

Disseminated Intravascular Coagulation (DIC)

  • Depletes platelets and leads to coagulopathy, often triggered by:

    • Sepsis and blood infections.

    • Endothelial damage.

    • Shock states, obstetrical complications, and some cancer types.

Disorders of White Blood Cells

  • Significant conditions include:

    • Neutropenia

    • Eosinophil Abnormalities including:

    • Idiopathic hypereosinophilic syndrome

    • Eosinophilia-Myalgia syndrome