Study Guide: Hematology and Immunology – Blood and Lymphatic System

Hematology and Immunology

Overview

Hematology is the medical specialty focused on the anatomy and physiology of blood, while immunology deals with the lymphatic system and the body's immune response. These systems are essential for transporting nutrients, defending against pathogens, and maintaining homeostasis.

Anatomy of the Blood

Hematopoiesis

Hematopoiesis is the process of blood cell formation, occurring in the red marrow of long and flat bones. All blood cells originate from stem cells and mature through various stages before entering the bloodstream.

• hemat/o-: means blood

• -poiesis: means formation

• Stem cells differentiate into myeloid and lymphoid lineages, producing erythrocytes, leukocytes, and thrombocytes.

Erythrocytes (Red Blood Cells)

Erythrocytes are the most numerous blood cells, responsible for transporting oxygen and carbon dioxide via hemoglobin. They lack a nucleus, cannot divide, and have a lifespan of about 120 days.

• Produced as erythroblasts, released as reticulocytes

• Removed by the spleen, which recycles iron and amino acids

• Production stimulated by erythropoietin when levels are low

Leukocytes (White Blood Cells)

Leukocytes are divided into granulocytes and agranulocytes, each with distinct functions in immunity.

• Granulocytes: Neutrophils, Eosinophils, Basophils

• Agranulocytes: Lymphocytes, Monocytes

Neutrophils

Most common leukocyte (54-62%), granulocyte with neutral-staining granules and multi-lobed nucleus. They are phagocytes, ingesting bacteria.

Eosinophils

Granulocytes (1-3%), granules stain pink with eosin, nucleus has two lobes. They release chemicals to destroy foreign cells and parasites.

Basophils

Least common granulocyte (0.5-1%), granules stain blue with hematoxylin, multi-lobed nucleus. They release histamine to increase blood flow.

Lymphocytes

Agranulocytes (25-33%), round nucleus, little cytoplasm. Includes B cells (produce antibodies) and T cells (cell-mediated immunity).

Monocytes

Largest leukocyte (3-7%), kidney-shaped nucleus, few granules. They mature into macrophages and perform phagocytosis.

Thrombocytes (Platelets)

Thrombocytes are cell fragments essential for blood clotting. They originate from megakaryocytes in the bone marrow.

• thromb/o-: blood clot

• -cyte: cell

Plasma

Plasma is the liquid component of blood, making up 55% of its volume. It transports nutrients, wastes, and suspends formed elements.

• Contains albumin, electrolytes, and clotting factors

• Serum is plasma without clotting factors

Anatomy of the Lymphatic System

Lymphatic Vessels and Nodes

Lymphatic vessels begin as capillaries, collect tissue fluid (lymph), and transport it to lymph nodes for filtration. Lymph nodes are grouped in areas prone to infection or cancer.

Lymphoid Tissues and Organs

Lymphoid tissues (tonsils, adenoids, Peyer patches, appendix) and organs (thymus, spleen) are involved in immune responses. The thymus matures T lymphocytes, and the spleen recycles erythrocytes and stores blood.

Physiology of Blood Clotting

Clotting Process

Blood clotting involves vessel constriction, platelet aggregation, and activation of clotting factors. Fibrin strands form a mesh that traps erythrocytes, creating a clot.

• Clotting factors: fibrinogen, prothrombin (liver), thromboplastin (tissue), calcium, others

• Heparin limits clot size

Immune Response

Allergic Reaction

An allergy is a hypersensitivity to allergens, causing local or systemic reactions. Severe systemic reactions can lead to anaphylaxis.

Leukocyte Functions

Leukocytes coordinate the immune response by attacking pathogens and cancer cells. Neutrophils and monocytes are phagocytes, while eosinophils and basophils release chemicals to destroy invaders.

Lymphocyte Types

• NK (Natural Killer) cells: destroy cancer and viral-infected cells

• B cells: produce antibodies

• T cells: cytotoxic (kill infected cells), helper (stimulate response), memory (remember pathogens), suppressor (limit response)

Immune Response Physiology

• Monocytes engulf pathogens and release chemicals

• Interferon stimulates antiviral substances and NK cells

• Interleukin stimulates B, T, and NK cells, produces fever

• Tumor necrosis factor destroys endotoxins and cancer cells

• Antibodies coat pathogens, attract leukocytes, and mark for destruction

• Complements drill holes in pathogen cell walls

Blood Diseases

Erythrocyte Diseases

• Anemia: Reduced erythrocyte count or hemoglobin, causing pallor and fatigue

• Iron deficiency anemia: Microcytic, hypochromic erythrocytes

• Sickle cell anemia: Abnormal, sickled erythrocytes block capillaries, cause pain and clots

Leukocyte Diseases

• HIV: Attacks helper T cells, impairs immune function

• Leukemia: Overproduction of immature leukocytes

Thrombocyte and Blood Clotting Disorders

• Deep Vein Thrombosis (DVT): Blood clot in deep vein, causes erythema, warmth, swelling

• Embolus: Thrombus breaks free, travels to lungs

Lymphatic System Disorders

• Lymphadenopathy: Enlarged lymph nodes due to infection or cancer

• Hodgkin lymphoma: Presence of Reed-Sternberg cells

Laboratory and Medical Procedures

Blood Cell Tests

Blood smears are used to examine blood cells under a microscope for diagnostic purposes.

Blood Chemistry Analysis

Automated analyzers perform multiple blood tests to assess chemical and cellular components.

Blood Transfusion

Blood is collected from donors, stored, and transfused to patients as needed. One unit equals 500 mL (about 1 pint).

Phlebotomy

Phlebotomy is the process of drawing blood for laboratory testing, typically using a tourniquet and vacuum tube.

Summary Table: Blood Cell Types

Cell Type	Appearance	Function
Erythrocyte	Red, biconcave, no nucleus	Transport O2 and CO2
Neutrophil	Granules, multi-lobed nucleus	Phagocytosis of bacteria
Eosinophil	Pink granules, two-lobed nucleus	Destroy parasites, allergic response
Basophil	Blue granules, multi-lobed nucleus	Release histamine
Lymphocyte	Round nucleus, little cytoplasm	Antibody production, cell-mediated immunity
Monocyte	Large, kidney-shaped nucleus	Phagocytosis, become macrophages
Thrombocyte	Cell fragment	Blood clotting

Key Medical Terminology

• hemat/o-: blood

• erythr/o-: red

• leuk/o-: white

• thromb/o-: clot

• -cyte: cell

• -poiesis: formation

Important Equations

Blood volume calculation:

$\text{Blood Volume} = \text{Body Weight (kg)} \times 70 \text{ mL/kg}$

Hematocrit calculation:

$\text{Hematocrit} = \frac{\text{Volume of RBCs}}{\text{Total Blood Volume}} \times 100\%$

Additional info: Academic context was added to clarify cell functions, disease mechanisms, and laboratory procedures for completeness.