Understanding Pathophysiology Concepts

• Pathophysiology studies the body's responses to dysfunctions or diseases and how these changes affect overall health and function.
• Disease is defined as an interruption, cessation, or disorder of a body system or organ structure.
• Key aspects of the disease process include etiology, pathogenesis, morphologic changes, clinical manifestations, diagnosis, and clinical course.

Health

• The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being, not merely the absence of disease or infirmity
• Healthy People 2030 highlights five key environments of social determinants of health: economic stability, education access and quality, healthcare access and quality, neighborhood and built environment, and social and community context.

Aspects of the Disease Process

• Disease is an acute or chronic illness acquired or congenital, causing physiological dysfunction.
• Etiology refers to the causes or factors leading to the onset of a disease, such as biologic agents, physical forces, chemical agents, genetic inheritance, or nutritional imbalances
• Many diseases are multifactorial in origin, examples include: cancer, heart disease, and diabetes
• Risk factors include congenital conditions (defects present at birth) and acquired defects (caused by events after birth).
• Pathogenesis describes how a disease evolves, including cellular and tissue events from initial contact with an etiologic agent to disease expression.
• Morphology refers to the fundamental structure of tissues and cells in relation to disease

Morphology and Histology

• Morphologic changes involve both gross anatomic and microscopic alterations characteristic of a disease
• Histology involves the study of cells and the extracellular matrix of body tissues.
• Lesions represent a pathologic or traumatic discontinuity of a body organ or tissue and can be assessed via imaging methods.

Clinical Manifestations

• Clinical manifestations include the signs and symptoms of a disease.
• Signs are objective findings like elevated temperature or swelling.
• Symptoms are subjective experiences reported by the patient, e.g., pain or dizziness.
• A syndrome is a compilation of signs and symptoms characteristic of a specific disease state.
• Complications are adverse extensions of a disease or outcomes from treatment.
• Sequelae are lesions or impairments that follow or are caused by a disease.

Diagnosis

• Diagnosis involves identifying the nature or cause of a health problem, bacterial pneumonia or hemorrhagic stroke
• The diagnostic process requires careful history, physical examination, and diagnostic tests for validation.
• Validity is the extent to which a measurement tool measures what it intends to measure.
• Reliability is the extent to which repeated observations yield the same result.
• Sensitivity is the proportion of people with a disease who test positive.
• Specificity is the proportion of people without a disease who test negative.
• Predictive value indicates how well an observation or test predicts the presence of a disease.

Clinical Process

• Diseases are classified as acute, subacute, or chronic.
• Acute diseases are usually severe and self-limiting.
• Chronic diseases are long-term with the goal of improving the quality of life and limiting symptoms.
• Subacute diseases have an intermediate severity and duration between acute and chronic.
• The preclinical stage is when the disease is not clinically evident but is destined to progress.
• Subclinical disease is not clinically apparent.
• Carrier status is when a person harbors an organism without showing infection signs or symptoms.

Epidemiology and Patterns of Disease

• Epidemiology studies disease occurrence in human populations, looking for patterns related to age, race, lifestyle, or location.
• Incidence measures new cases of a disease in a population at risk over a specified time.
• Prevalence measures existing cases of a disease in a population at a given time

Morbidity and Mortality

• Morbidity describes the effects of an illness on a person's life.
• Mortality provides data on the causes of death in a population.

Determination of Risk Factors

• Risk factors are conditions that may contribute to the development of a disease.
• Cross-sectional studies compare disease prevalence between different groups.
• Case-control studies compare people with a condition (cases) to those without (controls).
• Cohort studies observe a group of people with shared characteristics over time.

Preventing Disease

• Primary prevention aims to prevent disease by removing risk factors, such as through immunizations.
• Secondary prevention detects disease early through screenings, such as PAP smears.
• Tertiary prevention involves clinical interventions to prevent further deterioration or reduce complications of an existing disease.

Cell and Tissue Characteristics

• Intracellular fluid known as protoplasm mainly consists of water (70-85%), proteins (10-20%), and lipids (2-3%).
• The structural and functional proteins are contained in the protoplasm, as well as phospholipids, cholesterol, and triglycerides
• Protoplasm also include carbohydrates (1%) and intracellular ions.
• Two regions of protoplasm: karyoplasm/nucleoplasm inside the nucleus and cytoplasm outside the nucleus.

The Nucleus

• The nucleus, which contains DNA, is the control center of the cell.
• Cellular division and managing genetic information is its main function.
• The instructions on how to make proteins(needed for cellular function and survival) is contained in the nucleus
• Protein synthesis depends on the production of RNA
• mRNA (messenger RNA) carries genetic instructions.
• rRNA (ribosomal RNA) is part of ribosome structure.
• tRNA (transfer RNA) transports amino acids.
• A nuclear envelope encloses the nucleus with nuclear pores exists for molecular exchange
• Cells in bones (osteoclasts) have more than one nucleus.

The Cytoplasm and Organelles

• The cytoplasm exists otside the nucleus
• The aqueous solution is referred to as cytosol, it is a region of the protoplasm
• Organelles are suspended in the cytoplasm
• Water, electrolytes, proteins, fats, and glycogen (called cytosol) are contained in the Cytoplasm
• Melanin is pigments that can accumulate within the cytoplasm

Organelles

• Ribosomes are the sites of protein synthesis, made of rRNA and proteins and exists in the cytoplasm or attached to the rough ER.
• Endoplasmic Reticulum (ER): Tubular channels aid in the transport of proteins and lipids.
• Rough ER: synthesizes proteins using ribosomes and makes digestive enzymes found in lysosomes and proteins that are secreted, such as insulin
• Smooth ER: synthesizes lipids, involved in detoxification and calcium storage, smooth ER does not have ribosomes
• Golgi Complex: Modifies, sorts, and packages proteins from the ER, it is a network of smooth membranes located near the nucleus

Lysosomes and Peroxisomes

• Lysosomes digest worn-out cell parts and foreign materials, lysosomes allow the cell to autodigest
• Peroxisomes detoxify free radicals and degrades peroxides
• Proteasomes degrade misfolded proteins and regulate protein quality.
• Mitochondria produce ATP through cellular respiration.
• The cytoskeleton, is a network of microtubules, microfilaments, intermediate filaments, and thick filament, maintains cell shape and movement.

Membranes

• A thin-membrane(cell membrane) separates intracellular components from the extracellular environment
• Cells come together to form tissues and organs
• Semi-permeable membrane exists for the plasma membrane with a selective transport system
• Plays role in cell recognition, cellular mobility, maintaining cell shape.

Lipids

• Phospholipids and glycolipids and cholesterol help to give the membrane its structural integrity
• Proteins (integral and surface): convert chemical energy to electrical energy, electrical energy into mechanical energy such as the synthesis of ATP
• Integral proteins span the lipid bilayer and include ion channels.
• Peripheral proteins are on either side of the membrane
• Glycocalyx participates in cell-to-cell recognition and adhesion.

Cell Membrane Function

• Provides receptors for hormones and other biologically active substances to regulate organ and body system function
• Ligands like neurotransmitters, antigens, lipoproteins, infectious agents, and drugs bind with membrane receptors Electrical events in nerve and muscle cells depend on the cell membrane function
• Cell membrane function also include: regulation of cell growth and proliferation

Microtubules

• Formed from tubulin and maintain cell shape and participate in intracellular transport
• Form basic structure for cytoplasmic organelles and contain cilia, flagella, centrioles, and basal bodies.

Microfilaments

• Thin threadlike cytoplasmic structures, categorized into thin, intermediate, and thick type, that produce muscle contraction and support asymmetric cell shapes

Cell Communication

• It is very important to maintain a stable internal environment or the ability to maintain homeostasis
• Signals help cells to regulate growth, division, and coordinate the function of tissues and proteins.
• Autocrine signaling affects its own activity by the chemical a cell releases into the extracellular fluid.
• Paracrine signaling acts on nearby cells
• Endocrine signaling acts on cells through hormones carried in the bloodstream.
• Synaptic signaling is the process where neurotransmitters act only on adjacent nerve cells in the nervous system

Cell Receptors and Ligands

• Ion Channel–Linked Receptors Rapid synaptic signaling between electrically excitable cells, transmission of impulses in nerve and muscle cells
• G-Protein–Linked Receptors, are the on–off switch for signal transduction
• Enzyme-Linked Receptors are the receptors for certain protein hormones, activate an intracellular domain with enzyme activity

Intracellular Receptors

• Ligands move directly across the membrane to bind to the intracellular receptor.
• First messengers: Neurotransmitters, protein hormones and growth factors, steroids, and other chemical messengers
• Second messengers: Intracellular mechanisms
• Protein kinases

The Cell Cycle and Cell Division

• Main stages of cell cycle (life cycle of a cell): Mitosis: cell division stage (cytokinesis) the daughter cell receives chromosomes identical to the parent cell, Interphase: is the non dividing phase
• Types of cell division: Mitotic cell division: occurs in somatic cells, Meiosis: occurs in gamete-producing cells

Cell Metabolism and Energy Sources

• Energy metabolism converts fats, proteins, and carbohydrates into energy (ATP).
• Catabolism breaks down nutrients and body tissues to produce energy
• Anabolism builds more complex molecules from simpler ones.
• Anaerobic (wo oxygen) glycolytic pathway occurs in the cytoplasm
• Aerobic (w oxygen) pathway occurs in the mitochondria.

Movement of Substances Across the Cell Membrane

• Passive Transport (w/o the required use of energy)
• Diffusion is the act of moving from an area of high concentration to low
• Facilitated Diffusion is the act of moving from an area of high concentration to low but it assisted by a transport protein since the molecules are too large Water diffusion from area higher to lower concentration is Osmosis
• Active Transport (requires energy)
• Primary active transport involves the direct use of the energy source in the transport of a substance
• Secondary active transport use the energy from the transport of one substance for the cotransport of a second substance. Classified into 2 groups: Symport/Cotransport: substances are transported in the same direction, Countertransport/antiport: substances and transported in the opposite direction
• Endocytosis: cells surround and take in materials from their surroundings (engulfed)
• Phagocytosis (cell eating) involves the engulfment and then killing or degrading of microorganisms or other particulate matter
• Exocytosis facilitates the secretion of intracellular substances into the extracellular spaces (reverse of endocytosis)

Membrane Potential

• Ion channels are integral proteins that span the cell membrane
• Protein subunits undergo conformational changes to form open channels for ion movement.
• Electrical potentials result from ion distribution across membranes.
• Resting membrane potential is the voltages generated by ions diffusing across the membrane.
• Equilibrium potential is when no net ion movement occurs because diffusion and electrical forces are balanced.

Organization of Cells into Tissues

• Cells with similar origin or function form tissues that associate with other tissues to form organs.
• The 4 Types of Tissue:
  • Epithelial
  • Connective
  • Neural
  • Muscle

Epithelial Tissue

• Covers the body’s outer surface and internal enclosed cavities (including blood vessels), forms the secretory portion of glands and their ducts
• Free, lateral, and basal surfaces are 3 distinct surfaces
• Epithelial Tissue is considered Avascular
• The Types of Epithelial Tissues: Squamous, cuboidal, columnar, Simple, stratified, pseudostratified

Connective Tissue

• Connects and binds or supports various tissues
• Types of Connective tissue: loose(areolar), adipose, reticular, and dense

Muscle Tissue

• Primary function is contraction, responsible for movement of the body and its parts and for changes in the size and shape of internal organs
• Actin is for thin filaments
• Myosin is for thick filaments
• Muscle aid with Locomotion and movement of skeletal structures, with the Pumping blood through the heart, and with Contraction of blood vessels and visceral organs
• Cardiac (main part of the heart)
• Smooth (involuntary muscle, spontaneous or is stimulated by the autonomic nervous system)(found in the iris of the eye, the walls of blood vessels, surrounding hollow organs (stomach urinary bladder), hollow organs (ureters and common bile duct)
• Skeletal (most abundant, attached to bones, and skeletal muscle contractions are responsible for the force and movements of the skeleton

NERVOUS TISSUE

• Neurons: function in communication
• Neuroglial cells: support the neurons

Cell Junctions and Cell-to-Cell Adhesion

• Tight Junctions Seal the surface membranes of adjacent cells together
• Adhering Junctions Represent a site of strong adhesion between cells
• Gap Junctions involve the close adherence of adjoining cell membranes within the formation of channels linking the cytoplasm of the two cells

Extracellular Matrix (ECM)

• Classes of extracellular macromolecules Glycosaminoglycans (GAGs), which are usually found linked to protein as proteoglycans
• Fibrous proteins—the fibrous adhesive proteins that are found in the basement membrane
• Type of fibrous proteins: Collagen, elastin, fibronectin, and laminin
• Proteins and polysaccharides of the ECM are secreted locally and organized into a supporting mesh.
• Varies in amount and type based on tissue and function.

Test your knowledge of pathophysiology with questions covering the focus of pathophysiology, key components of health according to the WHO, disease processes, and the nature of defects such as autoimmune diseases and cancer. This quiz assesses understanding of disease mechanisms and their impacts on health.