Hematology and Related Disorders: Study Notes for Anatomy & Physiology

Hematology and Related Disorders

Introduction

Hematology is the study of blood, its components, and related disorders. Understanding the composition, function, and pathology of blood is essential for students of Anatomy & Physiology, as blood plays a critical role in homeostasis, transport, and immune defense.

Composition of Blood

Main Components

• Plasma: Makes up about 55% of blood volume; consists of 90% water, 8% proteins (mainly albumin, globulins, and fibrinogen), and 2% hormones, electrolytes, and enzymes.

• Cellular Elements: Includes erythrocytes (red blood cells, RBCs), leukocytes (white blood cells, WBCs), and thrombocytes (platelets).

Functions of Blood Elements

• Transport: Delivers nutrients, hormones, oxygen, and other substances to tissues; removes cellular waste (e.g., CO2).

• Regulation: Maintains temperature and distributes heat.

• Protection: Immune defense via WBCs and antibodies; clotting via platelets and fibrinogen.

Plasma Proteins

• Albumin: Maintains blood volume and oncotic pressure.

• Globulins: Transport substances (e.g., bilirubin, steroids, iron); include antibodies.

• Fibrinogen: Essential for blood coagulation.

Blood Cells

Erythrocytes (Red Blood Cells)

• Structure: Flexible, biconcave cells containing hemoglobin (~270 million molecules per cell).

• Function: Transport oxygen via hemoglobin; facilitate CO2 removal with carbonic anhydrase.

• Lifespan: Approximately 120 days in circulation.

Hemoglobin and Oxygen Saturation

• Hemoglobin (Hb): Protein with 2 alpha and 2 beta chains, each containing iron (Fe) for oxygen binding.

• Oxygen Saturation Curve: Shows the relationship between partial pressure of oxygen (PO2) and hemoglobin saturation.

Leukocytes (White Blood Cells)

• Types: Neutrophils (polymorphonucleocytes), lymphocytes, monocytes, eosinophils, basophils.

• Function: Immune defense; neutrophils are first responders to infection.

• Development: Immature forms (bands) indicate increased production during infection.

Thrombocytes (Platelets)

• Function: Initiate clotting, aggregate at injury sites, and promote vasoconstriction.

• Normal Count: Present in circulation of healthy individuals.

Formation and Lifecycle of Blood Cells

Hematopoiesis

• Process: Formation of blood cells from stem cells in bone marrow.

• Regulation: Controlled by cytokines and interleukins.

Erythrocyte Lifecycle

• Production: Stimulated by erythropoietin.

• Destruction: Old RBCs are removed by the spleen and liver.

Laboratory Values in Hematology

Common Laboratory Values

Parameter	Normal Range	Description
Hemoglobin (Hb)	14-16 g/dL (M), 12-15 g/dL (F)	Oxygen-carrying protein in RBCs
Hematocrit (HCT)	40-49% (M), 37-42% (F)	Percentage of RBCs in blood
Mean Corpuscular Volume (MCV)	80-100 fL	Average size of RBCs
Mean Corpuscular Hemoglobin (MCH)	27-33 pg	Average amount of Hb per RBC
White Blood Cell Count (WBC)	4,000-10,000 /μL	Number of WBCs
Platelet Count (PLT)	150,000-400,000 /μL	Number of platelets

Interpreting Abnormal Values

• Low Hb/HCT: Indicates anemia.

• High WBC: Suggests infection or inflammation.

• Low PLT: May indicate bleeding risk.

Hematology Disorders

Anemia

Anemia is defined as a decrease in the number or function of RBCs, resulting in reduced oxygen delivery to tissues. It can be classified by cause and cell morphology.

• Iron Deficiency Anemia

• Megaloblastic Anemias (Vitamin B12 and Folate deficiency)

• Anemia of Chronic Disease

• Hemolytic Anemias

Iron Deficiency Anemia

• Cause: Insufficient iron for hemoglobin synthesis.

• Symptoms: Fatigue, pallor, glossitis, koilonychia (spoon nails), pica (craving non-food substances).

• Lab Findings: Low Hb, low ferritin, microcytic hypochromic RBCs.

Iron Physiology

• Functions: Hemoglobin synthesis, mitochondrial function, neurotransmitter production.

• Storage: In hemoglobin (RBCs), myoglobin, enzymes, liver (ferritin), and plasma (transferrin-bound).

Iron Absorption and Regulation

• Absorption: Occurs in duodenum via enterocytes; regulated by hepcidin and ferroportin.

• Transport: Iron is carried in blood by transferrin.

• Storage: Stored in liver as ferritin.

Types of Iron Deficiency

• Absolute Iron Deficiency: Total body iron is low due to blood loss, poor intake, or absorption issues.

• Functional Iron Deficiency: Iron stores are adequate but unavailable due to increased hepcidin (often in chronic disease).

Common Causes of Iron Deficiency

• Blood loss (menstruation, GI bleeding)

• Poor dietary intake

• Malabsorption (celiac disease, gastritis)

• Increased requirements (pregnancy)

Megaloblastic Anemias

• Vitamin B12 Deficiency: Impaired DNA synthesis; requires intrinsic factor for absorption in ileum. Causes include pernicious anemia (autoimmune destruction of gastric mucosa), malabsorption, and dietary deficiency.

• Folate Deficiency: Also impairs DNA synthesis; often due to poor intake, malabsorption, or increased demand.

• Symptoms: Macrocytic anemia, neurologic changes (in B12 deficiency), glossitis, and pancytopenia.

Hemolytic Anemias

• Definition: Increased destruction of RBCs, either intravascularly or extravascularly.

• Causes: Sickle cell disease, thalassemias, G6PD deficiency, autoimmune reactions, toxins.

Sickle Cell Disease

• Genetics: Mutation in beta chain of hemoglobin (valine replaces glutamic acid).

• Pathophysiology: RBCs become sickle-shaped, aggregate, and occlude vessels, causing hypoxia and organ damage.

• Clinical Presentation: Pain crises, anemia, asplenia.

Thalassemias

• Definition: Defective synthesis of alpha or beta globin chains.

• Symptoms: Microcytic, hypochromic anemia; bone deformities; iron overload.

G6PD Deficiency

• Definition: Enzyme deficiency leading to oxidative damage and hemolysis.

• Triggers: Certain drugs, infections, fava beans.

Polycythemia

• Definition: Increased RBC mass.

• Types: Primary (polycythemia vera), secondary (due to hypoxia or increased erythropoietin), and relative (due to plasma loss).

Summary Table: Anemia Types and Lab Findings

Type	Hemoglobin	Iron	Ferritin	TSAT	MCV	RBC Color	Reticulocytes
Iron Deficiency	Low	Low	Low	Low	Microcytic	Hypochromic	Low
Anemia of Chronic Disease	Low	Normal	Normal/High	Normal/Low	Normocytic/Microcytic	Normal/Hypochromic	Low
Megaloblastic (B12/Folate)	Low	Normal	Normal	Normal	Macrocytic	Normochromic	Low

Treatment Approaches

• Iron Deficiency: Oral iron supplementation (ferrous sulfate); absorption enhanced with vitamin C; IV iron for intolerance or severe deficiency.

• Vitamin B12 Deficiency: Parenteral or oral supplementation.

• Folate Deficiency: Oral supplementation.

Key Terms and Definitions

• Hemoglobin (Hb): Oxygen-carrying protein in RBCs.

• Hematocrit (HCT): Percentage of blood volume occupied by RBCs.

• MCV: Mean corpuscular volume; average size of RBCs.

• Reticulocyte: Immature RBC; indicates bone marrow activity.

• Ferritin: Protein for iron storage.

• Transferrin: Iron transport protein in plasma.

• Hepcidin: Hormone regulating iron absorption and release.

Important Equations

• Oxygen Content of Blood:

$\text{O}_2\ \text{content} = (1.34 \times [\text{Hb}] \times \text{SaO}_2) + (0.003 \times \text{PaO}_2)$

• Transferrin Saturation (TSAT):

$\text{TSAT} = \frac{\text{Serum Iron}}{\text{Total Iron Binding Capacity}} \times 100\%$

Additional info: Some content was inferred and expanded for clarity and completeness, including definitions, normal ranges, and clinical context.