Study Notes on Health, Disease, and Pathophysiology

Chapter 1: Concepts of Health and Disease Pathophysiology

• Pathophysiology: The study of the human body in the disease state.

• Physiology of altered health states: Understanding how different conditions affect normal bodily functions.

Health

• Defined as the degree of wellness or well-being that the client experiences.

• May have different meanings for each patient.

• Goes beyond being free from illness.

• Nurses aim to:

  • Promote and restore health.

  • Prevent illness.

  • Support patients in achieving their optimal wellness level.

Aspects of the Disease Process

Etiology

• Etiology: The study of causes for a particular disease or injury.

  • Idiopathic: Unknown cause.

  • Iatrogenic: Cause results from unwanted or unintended medical treatment.

  • Congenital conditions: Defects present at birth.

  • Acquired defects: Defects caused by events occurring after birth.

• Factors contributing to disease:

  • Biologic (e.g., bacteria).

  • Physical (e.g., trauma).

  • Chemical (e.g., poisons).

  • Social determinants of health: Account for 80% of chronic disease.

Pathogenesis

• Describes the evolution of the disease process, including:

  • Events occurring from initial contact with the causative agent until the disease manifests.

  • Stages:

  • Latent period: Time between exposure and manifestation (silent).

  • Subclinical: Not apparent but diagnosed with antibody tests or cultures.

  • Prodromal stage: Initial manifestations occur, signifying disease onset.

  • Clinical disease: Characterized by clear signs and symptoms.

  • Acute phase: Disease reaches its maximum intensity.

Clinical Course of Diseases

• Acute clinical course: May be brief and intense.

• Subacute: Less severe than acute but prolonged.

• Chronic clinical course: Duration lasts months to years; may involve exacerbations and remissions.

• Convalescence: Recovery period following illness, injury, or surgery.

Morphologic Changes

• Refers to fundamental anatomical and microscopic alterations in cells/tissues due to disease.

  • Gross examination: Observations made with the naked eye.

  • Microscopic examination: Requires microscope.

  • Histology: Study focused on cells and extracellular matrix, crucial for cancer diagnosis.

Lesions

• A lesion represents pathological or traumatic changes in body organs or tissues.

Clinical Manifestations

• Signs and symptoms: Describe structural and functional changes due to disease.

  • Symptoms: Subjective experiences reported by the patient.

  • Signs: Objective findings observed by a healthcare professional.

Syndromes and Complications

• Syndrome: A compilation of signs/symptoms characteristic of a specific disease.

• Complications: Negative extensions or outcomes resulting from disease or treatment.

• Sequelae: Impairments following or caused by disease.

Diagnostics

• Predictive value: The degree to which a test or observation predicts the presence of a disease.

• Diagnosis: The process of identifying a disease based on signs and symptoms presented.

  • Types:

  • Provisional: Based on clinical findings.

  • Histopathological: Conducted by pathologists after examining tissue.

  • Final: Based on provisional diagnosis and investigations.

Disease Classifications

• Acute disorder: Relatively severe but self-limiting.

• Chronic disease: Continuous, long-term process.

• Subacute: Intermediate between acute and chronic.

• Preclinical stage: Disease is not yet clinically evident but expected to progress.

• Subclinical disease: Not clinically apparent and not destined to become apparent.

Chapter 2: Cell and Tissue Characteristics

Cell Composition

Protoplasm

• The intracellular fluid composed of water, proteins, lipids, carbohydrates, and electrolytes.

  • Karyoplasm: Fluid within the nucleus.

  • Cytoplasm: Fluid outside the nucleus but within the cell membrane.

Nucleus

• The control center of the cell responsible for the synthesis of three types of RNA (mRNA, rRNA, tRNA).

Organelles

• Lysosomes: Breakdown excess and worn-out cellular components.

• Mitochondria: Generate energy through cellular respiration.

Cell Communication

• Autocrine signaling: Cell affects its own activity.

• Paracrine signaling: Affects nearby cells.

• Endocrine signaling: Hormones carried in bloodstream affect distant cells.

• Synaptic signaling: Occurs in the nervous system through neurotransmitters.

Movement of Substances Across Cell Membranes

Passive Transport

• Movement driven by chemical or electrical gradients that doesn't require energy.

  • Diffusion: Movement of particles along a concentration gradient.

  • Osmosis: Movement of water across a selectively permeable membrane from low to high solute concentration.

  • Facilitated diffusion: Uses carriers for large substances.

Active Transport

• Requires energy to move ions against their gradient (e.g., Sodium-Potassium ATPase pump).

Cellular Adaptation, Injury, and Death

Reversible Cell Injury

• Hydropic Swelling: Accumulation of water due to cellular injury.

  • First indication of injury, results from malfunctioning sodium/potassium pumps.

  • Example: kidney injury due to high blood pressure.

  • Characteristics include:

  • Large, pale cytoplasm

  • Dilated endoplasmic reticulum

  • Swollen mitochondria

Intracellular Accumulations

• Excess substances leading to injury through toxicity or inflammation. Common in the liver.

Cellular Adaptations

• Types of adaptation:

  • Atrophy: Decrease in cell size/function.

  • Physological (e.g., decrease in uterine size post-pregnancy).

  • Pathological (e.g., cirrhosis of the liver).

  • Hypertrophy: Increase in cell mass/function due to increased demand.

  • Hyperplasia: Increase in cell number (e.g., keloids).

  • Metaplasia: Change in cell type/location due to chronic irritation (e.g., Barrett's esophagus due to acid).

  • Dysplasia: Disorganized cell appearance, potentially pre-cancerous (e.g., endometriosis).

Necrosis and Apoptosis

• Necrosis: Uncontrolled cell death from injury, characterized by inflammation.

  • Types include:

  • Coagulative necrosis: Ischemic injury (e.g., heart).

  • Liquefactive necrosis: Formation of pus.

  • Fat necrosis: Adipose tissue death from trauma.

  • Caseous necrosis: Seen in tuberculosis.

• Gangrene: Massive cellular death due to blood supply interruption.

  • Types:

  • Dry gangrene: Shrinkage and darkening of tissue.

  • Wet gangrene: Rapid spreading, associated with infection.

  • Gas gangrene: Infection by anaerobic bacteria, typically in compound fractures.

• Apoptosis: Programmed cell death, essential for growth and development. Does not cause inflammation.

Chapter 3: Epidemiology

• Epidemiology: Focuses on the patterns of disease in populations, concerning disease occurrence and transmission.

  • Incidence: Number of new cases over time.

  • Prevalence: Total existing cases at a given time.

  • Morbidity: Effects of illness on daily life.

  • Mortality: Causes of death in a population.

Chapter 4: Genetic Control of Cell Function and Inheritance

Mitosis and Meiosis

• Mitosis: Process for replicating somatic cells.

• Meiosis: Process for producing gametes.

Genetic Terms

• Genotype: Genetic makeup, expressed in base pair sequences.

• Phenotype: Observable traits resulting from genotype.

Chapter 5: Genetic and Congenital Disorders

• Genetic control: Stored in chromosomes (23 pairs total: 22 autosomes, 1 sex chromosome).

• Karyotype: Visual representation of chromosomes for diagnosing genetic disorders.

• Congenital disorders: Present at birth, may be inherited or developmental.

  • Teratogenic disorders: Caused by agents affecting development during pregnancy.

  • Multifactorial disorders: Influenced by both genetic and environmental factors.

Chromosomal Disorders

• Down Syndrome (Trisomy 21): Genetic disorder caused by nondisjunction or translocation during meiosis.

• Turner Syndrome: Female phenotype with only one X chromosome.

• Klinefelter Syndrome: Male phenotype with an extra X chromosome.

Developmental Disorders

• Caused by external factors affecting growth during critical periods.

Single Gene Disorders

• Can be dominant or recessive.

  • Cystic Fibrosis: Autosomal recessive disorder affecting the lungs and pancreas.

  • Sickle Cell Anemia: Genetic hemolytic disease arising from single gene mutation.

Chapter 6: Neoplasia

• Neoplasia: Disorder of uncontrolled cell growth and differentiation.

• Cancer is characterized by altered cell differentiation and proliferation.

Chapter 7: Stress and Adaptation

Homeostasis

• Mechanism by which biological systems maintain stability during changes to optimal conditions.

  • Negative feedback mechanisms: Prevents deviations from set points, e.g., blood sugar regulation.

  • Positive feedback mechanisms: Amplifies change, e.g., childbirth contractions.

Stressors and Adaptation

• External and internal stressors can impact health and adaptation.

  • Factors affecting adaptation include age, health status, culture, and personal experiences.

• General Adaptation Syndrome (GAS):

  • 1. Alarm Stage: Initial reaction to stress.

  • 2. Resistance Stage: Body attempts to adapt.

  • 3. Exhaustion Phase: Resources depleted, leading to potential disease or organ damage.

Neuroendocrine Response

• Cortisol: Primary glucocorticoid, diverts metabolism towards energy production.

• Stress Response: Sympathetic nervous system activation leads to increased heart rate and blood pressure.

Chapter 8: Disorders of Fluids, Electrolyte, and Acid-Base Balance

• Osmosis & Diffusion: Movement of water and solutes across cell membranes.

• Fluid Balance Mechanisms:

  • ADH: Regulates water retention in kidneys.

  • Aldosterone: Regulates sodium and water reabsorption.

Edema and Dehydration

• Edema: Excess interstitial fluid leading to swelling, caused by:

  • Increased hydrostatic pressure.

  • Loss of plasma proteins.

  • Inflammation.

• Dehydration: Insufficient body fluid can be due to inadequate intake or excessive loss, causing:

  • Dry mucous membranes.

  • Decreased blood pressure.

Chapter 9: Inflammation, Tissue Repair, and Wound Healing

• Inflammatory Phase: Initial response with vasodilation and increased permeability.

• Proliferative Phase: New tissue formation.

• Maturational Phase: Tissue remodeling and healing.

Chapter 10: Mechanisms of Infectious Disease

• Incidence: Number of new disease cases in a population over time.

• Prevalence: Total active cases at a specific time.

Chapter 12: Disorders of the Immune Response including HIV and AIDS

Pathogens

• Types:

  • Prions: Infectious proteins.

  • Viruses: Acellular organisms that require a host.

  • Bacteria: Prokaryotic cells that cause infections.

  • Fungi: Multicellular or unicellular organisms.

  • Parasites: Eukaryotic multicellular organisms requiring a host.

Infection Stages

• Stages of Infection:

  • Incubation: Period post-exposure with no symptoms.

  • Prodromal Stage: Initial signs.

  • Acute Stage: Maximum manifestations of the disease.

  • Convalescent Stage: Containment and recovery.

Immune System Function

• Defends against pathogens, removes dead/damaged cells, and differentiates between self/non-self.

  • Innate Immunity: Immediate response; includes skin and immune cells.

  • Adaptive Immunity: Tailored responses involving B and T lymphocytes, including memory function.

  • Humoral Immunity: Antibody-mediated response from B cells.

  • Cell-Mediated Immunity: T-cell mediated response for intracellular pathogens.

Autoimmunity and Immunodeficiency

• Autoimmunity: Immune system's attack on its tissues.

• Primary Immunodeficiency Disorders: Genetic defects leading to increased susceptibility to infections.

• Secondary Immunodeficiency Disorders: Acquired conditions, e.g., malnutrition or HIV.

Characteristics of Down Syndrome

• Small head, flat facial features.

• Slanted eyes and epicanthal fold.

• Large tongue, high arched palate.

• Small hands, single palmar crease.

• Muscles tend to be hypotonic, resulting in loose joints.

• Delayed developmental stages throughout childhood.

• Cognitive impairment can range from mild to major, affecting learning abilities.

• Delayed or incomplete sexual development

  • Males typically infertile.

  • Females have lower rates of fertility compared to the general population.

Developmental Disorders

• Occur due to exposure to drugs, chemicals, or radiation during the childbearing years, which can affect fetal development.

• TORCH infections: An acronym representing maternal infections that can lead to congenital anomalies in the developing fetus:

  • Toxoplasmosis: Caused by a parasite that can affect fetal brain development.

  • Other agents: Includes various infections and agents that may harm development, such as syphilis.

  • Rubella: Viral infection that can result in significant fetal malformations if contracted during pregnancy.

  • Cytomegalovirus: A common virus that can have serious effects on the developing fetus, leading to neurological disorders.

  • Herpes: Can be transmitted to the fetus during birth or pregnancy, possibly causing severe complications.

Cortisol, the stress hormone, diverts metabolism from building tissue to supplying energy to deal with stress.

• Primary glucocorticoid.

• Promotes appetite and food seeking.

• Causes signs and symptoms of stress:

  • Increased blood glucose.

  • Stronger sympathetic system effect on the heart.

• Decreases nonessential activities:

  • Hormone production.

  • Metabolic rate.

  • Bone formation.

  • Reproductive functions.

  • Red and white blood cell production.

  • Immune system depression.

  • Anti-inflammatory effect.

Corticotropin-releasing factor (CRF): Central to the endocrine component of the neuroendocrine response to stress.

General Adaptation Syndrome (GAS)

• Fight or Flight Sympathetic Response:

  • Rapid response to trauma; emergency epinephrine and norepinephrine released.

  • Sympathetic nervous system manifestations of the stress reaction:

  • Both attach to adrenergic receptors.

  • Norepinephrine:

    • Causes vasoconstriction; increases BP.

    • Reduces gastric secretion.

    • Increases night and far vision.

  • Epinephrine:

    • Enhances cardiac contractility; increases HR and cardiac output.

    • Causes bronchodilation.

    • Increases glucose release from the liver.

Renin-Angiotensin Aldosterone System Activation

• Kidney releases renin activated by sympathetic system and decreased blood flow.

• ANG1: weak vasoconstriction (ACE transformation to ANG2).

• ANG2: stronger vasoconstriction, stimulates adrenal cortex to release aldosterone.

  • Na/K ATP in nephrons activated:

  • Kidney absorbs Na and H2O.

  • Excretes K.

  • Increased BP and blood volume.

Other Responses in GAS

• Endorphin Release:

  • Endogenous opioids that elevate pain threshold and produce euphoria and sedation.

• Oxytocin:

  • Produced during childbirth and lactation, associated with bonding and attachment.

  • Moderates the stress response, producing a calming effect.

Immune Response

• Endocrine-immune interactions suppress the immune response, hallmark of the stress response:

  • Increased corticosteroid production.

  • Thymus atrophy.

  • Decreased immune cell production and activity.

Types of Stress

• Physiological Stress:

  • Stress-induced changes in bodily function; regulatory sensors detect stress.

  • Body alters functioning to re-establish balance; negative feedback stops the reaction when balance is restored.

• Psychological Stress:

  • Events of psychological or social origin that challenge homeostasis (e.g., adverse childhood events, social isolation, climate change).

  • Directly affects the CNS; stress response activated without detected imbalance.

• Acute Stress:

  • Activates neural pathways for arousal, attention, aggression.

  • Life-threatening potential, detrimental for those with limited coping abilities.

  • Effects include increased alertness and cognitive functioning.

Chronic Stress Effects

• Sustained or intermittent stress leads to elevated sympathetic system and cortisol:

  • Long-term stress affects various body systems:

  • Consistently elevated BP and suppressed immune function.

  • Contributes to infertility, accelerates aging, rewires the brain (increased susceptibility to anxiety, depression, dementia, PTSD).

Adaptation to Stress

• Physiological Reserve: Body's ability to increase function when adapting to stress (e.g., carrying more oxygen).

• Factors affecting adaptation:

  • Time: Gradual changes improve adaptation efficiency.

  • Health Status: Both physical and mental health influence the ability to adapt.

  • Age: Extremes of age decrease adaptation capacity.

  • Genetics: Inherited resistance or mutations aiding adaptation (e.g., sickle cell mutation for malaria resistance).

  • Hardiness: Emotional reactions and coping mechanisms play a role in stress perception.

  • Social Factors: Nutrition, sleep, and environmental factors impact physiological responses.

Relaxation Programs

• Help control automatic stress responses, reduce epinephrine and cortisol levels.

• Techniques like relaxation, meditation, and mindfulness can control sympathetic responses.

Stress Responses

• Freeze Response: Immobility and inhibited speech during overwhelming threats, often misinterpreted as noncompliance.

• Fawn Response: Compliance and prioritizing others' needs to reduce perceived threats, linked to chronic trauma, may lead to inadequate care responses.

Key Trauma-Informed Principles

• Assume stress responses reflect adaptive strategies.

• Create psychological safety through predictable structures and respectful communication in clinical settings.

Abnormalities in Body Fluid can occur in:

• Blood volume

• Concentration

• Electrolyte composition of the body fluid

  • Can cause clinical problems or death

• Occur as a result of different pathologic conditions.

Hypotonic Solution

• Water moves from outside the cell (low solutes) to inside the cell (high solutes), causing it to swell.

Hypertonic Solution

• Water moves out from inside (low) to outside (high), causing cells to shrink.

Body Fluids

• Extracellular fluids: Contained outside the cell, rich in Na+, Cl, HCO3, and proteins.

  • Interstitial fluid: Between cells.

  • Vascular compartment: In blood vessels, rich in protein.

• Intracellular fluids: Contained inside the cells, rich in K+, Mg2+, inorganic and organic phosphates, and proteins. Low in Na+ and Cl.

Fluid Movement

• When solutes are in the capillaries, they will pull fluid into the capillary.

• If there are more solutes or osmotic pressure in the interstitial space, it will pull water towards it.

• Hydrostatic pressure: The pressure of blood or fluid pushing from the bottom.

• Hydrostatic pressure pushes fluid away; high pressure in capillaries forces fluid out.

Balancing Water and Electrolytes

• Thirst: Triggered by osmoreceptors in the hypothalamus due to sodium imbalance.

• Antidiuretic hormone (ADH): Reabsorbs water from the kidney tubules when dehydrated.

• Aldosterone: Reabsorbs sodium and water.

• Atrial natriuretic peptide (ANP): Synthesized by myocardial cells for regulation of fluid, sodium, and potassium.

Renal Function in Fluid Balance

• Fluid balance: Regulates the amount and makeup of body fluids.

• Acid-Base balance: Secretes and reabsorbs H+ and HCO3, responding to pH levels.

Controlling Blood Osmolarity

• High osmolarity: More solutes compared to fluid, triggers thirst and ADH release.

• Low osmolarity: Lack of thirst and decreased ADH release.

Edema - Fluid Excess

• Excessive fluid in interstitial space, causing swelling or tissue enlargement.

• May impair tissue perfusion and trap drugs in interstitial tissue.

Causes of Edema

• Increased hydrostatic capillary pressure: Due to higher blood pressure or volume.

• Loss of albumin: Decreased plasma osmotic pressure leads to edema, especially seen in malnutrition or liver disease.

• Increased capillary permeability: Inflammatory response.

• Obstruction of lymphatic circulation.

Fluid-Deficit Dehydration

• Insufficient body fluid due to inadequate intake or excessive loss.

• More severe in infants and older adults.

Causes of Dehydration

• Vomiting, diarrhea, excessive sweating, diabetic ketoacidosis, insufficient intake in older adults.

Effects of Dehydration

• Dry mucous membranes, decreased skin turgor, lower BP, fatigue, confusion, decreased urine output.

Sodium

• Normal level: 135-145 meq/L.

• Regulates extracellular fluid volume and osmolarity. Losses can cause hyponatremia or hypernatremia, affecting overall health.

Potassium

• Normal level: 3.5-5 meq/L. Essential for cardiac function and muscle contraction. Imbalances can lead to severe complications.

• Hyperkalemia can lead to dysrhythmias, while hypokalemia can cause muscle weakness and decreased cardiac function.

Calcium

• Normal level: 9-11 mg. Essential for muscle contraction and blood clotting. An imbalance can cause neuromuscular excitability or decreased nerve firing.

Phosphorus and Magnesium

• Important for various biochemical processes in the body, with normal levels 1.5-2.5 for magnesium.

This information serves to highlight the importance of proper fluid and electrolyte balance in maintaining physiological homeostasis and the clinical implications of imbalances.

The immune system performs three primary functions:

• Defends against invasion or infection by pathogens.

• Removes dead or damaged cells.

• Recognizes abnormal cells.

The immune system has the capacity to recognize and destroy abnormal cells originating from host tissues, with any molecule capable of being recognized as non-self being considered an antigen. Specificity and memory enable the immune system to distinguish between self and non-self, targeting responses to invaders, a function referred to as immunocompetence.

Defense Mechanisms

The immune system employs three defense mechanisms:

1. Physical and chemical barriers to infection (e.g., skin, mucous membranes, GI acid).

2. Inflammatory Responses.

3. Immune response, which occurs when barriers are breached, involving either innate or adaptive immunity.

Aging and the Immune System

In older adults:

• The immune system becomes less able to distinguish self from non-self, leading to a higher incidence of autoantibodies and autoimmune disorders.

• There is a decline in immune responsiveness which affects adaptation to environmental stresses.

• Macrophages destroy bacteria, cancer cells, and antigens more slowly, contributing to increased cancer rates in older adults.

• T cells exhibit slower responses to antigens. Antibody levels may remain stable, but their binding affinity decreases, contributing to increased incidences of pneumonia, flu, endocarditis, and heightened mortality risk.

Immune Components

• B cells: Form antibodies providing humoral immunity. They present antigens to T cells and release cytokines, primarily developing into plasma cells that manufacture antibodies.

• T cells: Develop from bone marrow stem cells and mature in the thymus, mediating cell-mediated immunity through different functions among helper, regulator (suppressor), and cytotoxic T cells.

• Natural killer cells: Induce apoptosis in infected or abnormal cells.

• Polymorphonuclear leukocytes: Include neutrophils (first line against bacteria), lymphocytes (viral infections), eosinophils (for larger organisms), and basophils (involved in allergic reactions).

• Mast cells: Trigger allergic responses.

Innate vs Adaptive Immunity

• Innate Immunity: Always present, does not require prior exposure, non-specific, immediate response involving NK and phagocytic cells.

• Adaptive Immunity: Requires prior exposure; it is antigen-specific and has memory, involving B and T cells.

Inflammation in Immunity

Inflammation is part of innate immunity, characterized by vasodilation, increased vascular permeability, and leukocyte movement to neutralize and destroy invaders, with manifestations including fever, redness, and pain.

Hypersensitivity Types

• Type I: IgE-mediated reactions causing immediate allergic responses.

• Type II: Antibody-mediated reactions against cell surface antigens.

• Type III: Immune complex reactions due to antibodies against soluble antigens.

• Type IV: Cell-mediated delayed responses without antibodies.

Immune Disorders

Various conditions arise from alterations in immune function, which can range from autoimmunity, hypersensitivity, deficiencies, to the impact of aging on immune responsiveness.

1. IgG

   • The major antibacterial and antivirus antibody.

   • Crosses the placenta, providing protection to infants.

   • Presents stronger and higher levels of response.

2. IgA

   • Found in body secretions (e.g., saliva, tears).

   • Protects against gastrointestinal and respiratory invaders.

3. IgM

   • The first antibody response in primary immunity.

   • Major antibody associated with B cells.

4. IgE

   • Initiates inflammatory and allergic responses.

5. IgD

   • Found on the surface of B cells.

   • Acts as an antigen receptor to stimulate B cells.

Major Histocompatibility Complex Molecule Class 1

• A group of genes that encode cell surface proteins responsible for antigen presentation to T lymphocytes.

  • Regulates adaptive immune responses.

Key Features

• Present on all nucleated cells.

• Present endogenous (intracellular) antigens.

• Recognized by CD8 cytotoxic T cells.

• Critical for identifying virus-infected or malignant cells.

How It Works

1. A cell is infected.

2. Viral proteins are broken down inside the cell.

3. Peptides are loaded onto MHC I.

4. The MHC I-peptide complex moves to the cell surface.

5. CD8 T cells recognize the abnormal peptide and destroy the cell.

Molecule Class 2

Key Features

• Present only on professional antigen-presenting cells (APCs):

  • Dendritic cells.

  • Macrophages.

  • B cells.

• Present exogenous (extracellular) antigens.

• Recognized by CD4 helper T cells.

• Coordinate broader immune activation.

How It Works

1. APC engulfs a pathogen.

2. Pathogen is digested in lysosomes.

3. Peptides are loaded onto MHC II.

4. The complex is displayed on the cell surface.

5. CD4 T cells activate and coordinate the immune response.

Why is MHC Important?

• Essential for self vs non-self recognition.

• Central to organ transplantation compatibility.

• Highly polymorphic (many genetic variants).

• Associated with autoimmune diseases (e.g., HLA-B27 and ankylosing spondylitis).

Immune System Components

• BLAST:

  • B - cell (bone marrow).

  • L - Lymphocytes.

  • A - Antigens.

  • S - Suppressor cells (T-regulator cells suppress humoral response).

  • T - cells (thymus for cellular immunity).

Humoral Response

• Humoral Immunity:

  • Antibody proteins that attack specific antigens mediated by B lymphocytes.

  • B lymphocytes become plasma cells that secrete antibodies to destroy viruses and bacteria, preventing invasion.

  • B lymphocytes can become memory cells that remain to fight future infections without the requirement for a T helper cell to activate them.