General Concepts of Disease: Principles of Diagnosis
Characteristics of Disease
 Disease: disturbance of body structure or function
 Lesions: well-defined, characteristic structural changes in organs and
tissues as a result of disease
 Organic disease: one caused by a physical or physiological change to some
tissue or organ of the body.
o Associated with structural changes
o Gross examination
o Histologic examination (at the cellular level; could be done using
microscope)
 Ex. Cancer cell
 Functional disease: a medical condition that impairs normal functioning of
bodily processes that remains largely undetected under examination,
dissection or even under a microscope.
o No morphological abnormalities yet body functions are profoundly
disturbed.
 Ex. IBS, Tension headache
 Pathology: the study of disease
o Pathologist: a physician who specializes in diagnosing and classifying
diseases by studying the morphology of cells and tissues
o Clinician: Physician/health care professional that cares for patients
 Symptoms: subjective manifestations such as pain or weakness
 Signs: physical findings or objective manifestations
o Ex. Swelling or redness
 Symptomatic disease: with symptoms and/or signs
 Asymptomatic disease: no signs or symptoms
o Early stages of disease are usually asymptomatic; if not treated will
progress to symptomatic.
 Difference between asymptomatic and symptomatic depends on the extent
of disease.
 Etiology: the cause of the disease
o Etiological agent: agent responsible for causing the disease
 Pathogenesis: Process of development of disease
 Pathogen: any microorganism that causes disease
Classification of Disease
 Classification is based on the similarity of lesions and pathogenesis.
 Diseases with similarities may not necessarily be closely related.
Congenital and hereditary diseases
 Developmental disturbances
 Caused by genetic abnormalities, abnormalities in chromosome number or
distribution, intrauterine injury, interaction of genetic and environmental
factors.
 Congenital disorders are present from birth, and hereditary disorders are
transmitted from parents to their children through the genes.
 Examples:
o Hemophilia= hereditary
o German measles=Congenital
Inflammatory diseases
 Body reacts to injury through an inflammatory process
 Examples:
o Allergic reaction–hay fever
o Bacteria or microbiologic agents–sore throat
o Autoimmune disease–SLE, diabetes type 1
o Unknown etiology
Degenerative diseases
 Tissue or organ degeneration as a result of aging or breakdown
 Examples:
o Arthritis, atherosclerosis
Metabolic disease
 Disturbance in metabolic process in body
o Examples: Diabetes, hypo or hyperthyroidism, fluid and electrolyte
imbalance
Neoplastic diseases
 Uncontrolled cellular growth
 Examples:
o Benign–lipoma
o Malignant–Lung cancer
Health and Disease
 Good health is more than the absence of disease
o It is a condition in which the body and mind function efficiently and
in harmony, as an integrated unit.
 Traditional medicine focuses on curing or ameliorating the disease.
 Modern medicine is focuses on reliving suffering and advance human
welfare but does not guarantee good health
 Good health requires active participation
Principles of Diagnosis
 Diagnosis: determination of nature and causes of illness through methods
such as clinical history, physical examination, differential diagnosis.
 Prognosis: the eventual outcome of disease
 Treatment is
o Specific– directed at the underlying cause
o Symptomatic–alleviates symptoms but does not influence course of
disease
Clinical History
 History of current illness
o Severity, time of onset, and character of patient’s symptoms
 Medical history
o Details of general health and previous illnesses that may shed light
on current problems
 Family history
o Health of patient’s family members; diseases that run in families
 Social history
o Patients occupation, habits, alcohol and tobacco consumption,
general health, current problems
 Review of symptoms
o Symptoms other than disclosed in history of present illness,
suggesting other parts of the body affected by disease
 Gathering information:
o S–site
o O–onset
o C–character
o R–radiation (of pain or discomfort)
o A–alleviating factors
o T–timing
o E–exacerbating factors
o S–severity
o P–Provocative/palliative
o Q–Quality
o R–Region
o S–Severity
o T–Temporal/timing
 Types of diagnostic tests and procedures:
Physical Examination
o Physical examination
 Systematic examination of the patient with emphasis on parts
of the body affected by illness.
 Abnormalities are noted and correlated to clinical history.
o Differential diagnosis
 Considering the various diseases or conditions that may also
explain patient’s symptoms and signs
 Diagnostic possibilities narrowed by tests and procedures
 Opinion of medical consult may be sought
Screening Tests
 Screening tests for the detection of disease
o Detect early asymptomatic disease amenable to treatment to
prevent or minimize late-stage organ damage
 Screen for carriers of some gentic diseases transmitted from parent to child
as either dominant or ressicve trait
 Identifying carriers allows affected persons to make decisions on future
childbearing or management of current pregnancy
o EX. Sickle cell in 8% of the black population
Requirments for Effective Screening
 A signifiganct amount of people need to be at risk for the disease in the
group being screened
 A inexpensive, non-invasive test must be aviable to screen for the disease
that does not yield a high number of false-positive or false-negative results
 Early identification and treamtnet of the disease will favoubly influence the
course
Diagnostic Tests and Procedures
 Clinical lab tests
 Tests of electrical activity to measure impulses associated with bodily
functions and activities
o ECG: measures serial changes in electrical activity of the heart in
various phases of the cardiac cycle
o EEG: measures electrical activity of brain; brain waves
o EMG: measures electrical activity of skeletal muscle during
contraction and at rest
 Radioisotope (radionuclide) studies
o Evaluate organ function by determining rate of uptake and excretion
of substances labelled with a radioisotope.
 Endoscopy
o Examination of the interior of the body using rigid or flexible tubular
instruments equipped with lens and light source
o To perform surgery formerly done though large abdominal incisions
 Ultrasound
o Mapping echo’s produced by high-frequency sound waves
transmitted into body; echoes reflect change in tissue density,
producing images
 X-ray
o High-energy radiation at lower does to produce images to help
diagnose disease
o Can penetrate through tissues at varying degrees depending on
tissue density
o Act on a photographic film or plate (roentgenogram) as the rays
leave the body
 Computed tomographic (CT) scans
o Radiation detectors record amount of x-rays or ionizing radiation
absorbed by body and feed data into a computer that reconstructs
the data into an image
 Magnetic resonance imaging (MRI)
o Computer-constructed images of body on response of hydrogen
protons in water molecules when placed in a strong magnetic field
o Advantages:
 does not use ionizing radiation
 can detect abnormalities in tissues surrounded by bone (such
as spinal cord, orbit, skull)
 bone interferes with scanning because of its density but does
not produce an image in MRI because of its low water content
 Cytologic and histologic examinations
o Papanicolaou (Pap) smear identifies abnormal cells in fluids or
secretions; for recognizing early changes that may be associated with
cervical and other cancers
o Biopsy: tissue samples obtained for histologic examination to
determine abnormal structural and cellular patterns accompanying
disease
Types of Biopsies
o Image-guided
o Fine needle aspiration
o Core needle
Genes, Chromosomes, Cells and Tissues
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Cells group together to form tissues
Tissues form organs
Organs work together to form body systems
Cell: basic structural and functional unit of the body
Tissues: group of similar cells performing the same functions
o Four types: Epithelium, Connective, Muscle, and Nerve
 Organs: groups of tissues
 Organ systems: groups of organs functioning together
 Functioning organisms: integrated organ systems
Basic Structure and Organization of Cells
 Nucleus: contains genetic information; directs metabolic function of
cells
o 2 types of nucleic acid combined with protein
o Membrane is double layered with pores, and separates the
nucleus from cytoplasm
 Deoxyribonucleic acid (DNA): in chromosomes in the
nucleus, contains genetic information
 Ribonucleic acid (RNA): in the nucleoli; component of
messenger, transfer, ribosomal RNA, primarily performs
ribosomal synthesis and assembly.
 Cytoplasm: surrounds nucleus; structures carry out directions of the
nucleus
o A mass of protoplasm surrounded by selectively permeable cell
membrane
o Contains organelles
 Mitochondria
o Rod shaped structures capable of converting food material into
energy to manufacture ATP (adenosine triphosphate) that fuels
chemical reactions in the cell
o Maternal inheritance
 Endoplasmic reticulum
o Interconnected network of tubular channels enclosed by
membranes; communicates with nuclear and cellular membranes
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o Rough endoplasmic reticulum (RER): with ribosomes
o Smooth endoplasmic reticulum (SER): with lipids
Golgi apparatus
o Flattened membrane-like sacs near the nucleus
o For synthesis of large carbohydrate molecules
o Connected with the tubules of the RER
o Proteins from ribosomes ->RER tubules->Golgi apparatus>combine with carbohydrate molecules->form secretory granules
Lysosomes
o Digestive system of the cell
 Cytoplasmic vacuoles with digestive enzymes
 Digestion occurs within phagocytic vacuole to prevent
leakage of enzymes
 Peroxisome: with enzymes that decompose hydrogen
peroxide, H2O2
Centrioles
o Short cylindrical structures adjacent to nucleus
o Move to opposite poles of the cell during division to form the
mitotic spindle
Cytoskeleton
o Form cells structural framework, shape, and cell movements
o Consists of 3 types of protein tubules
 Microtubules-Largest
 Intermediate filaments
 Microfilaments-smallest
o Intermediate filaments are always the same no matter where they
are.
 Identification and characterization of intermediate filament
provide diagnostic information
 EX. Cancer cells metastasising and moving elsewhere. We
can identify the cells origin based on the intermediate
filaments
 Reinforce cells interior and keep its shape by holding the
organelles in proper position
Tissues: group of similar cells performing the same functions
o Four types: Epithelium, Connective, Muscle, and Nerve
Epithelium
 Covers the exterior of the body
 Lines interior of the body surfaces communicating with the outside:
GUT, urinary. Tract, and vagina
 Forms glands and parenchymal (functional cells) of the excretory or
secretory organs (liver and kidneys)
 Contains no blood vessels but is nourished by diffusion
 Functions:
o Protection
o Absorption
o Secretion: mucus, sweat, oil, enzymes, hormones
 Types:
A) Simple squamous
B) Cuboidal
C) Columnar
D) Pseudostratified columnar
E) Transitional
F) Stratified squamous
 Exocrine glands: discharge secretions through a duct
o Pancreas is both and exocrine and endocrine gland
 Endocrine glands: discharge secretions directly into the bloodstream
o Ex. Thyroid and adrenals
 Endothelium: Layer of simple squamous epithelium (vessels and heart)
 Mesothelium: layer of simple squamous epithelium lining pleural,
pericardial, and peritoneal cavities
Basement membrane
o Located between the epithelium and connective tissue
o Composed of collagen fibers and proteins
Connective
 Collagen fibers
o Connect and support tissues
o Contain collagen; long and flexible, strong but do not stretch
 Elastic fibers
o Responsible for distensibility of arteries
o Contain elastin, not as strong but stretches
 Reticulin fibers
o Form supporting framework of organs
o Similar to collagen but thin and delicate
Muscle
 Smooth muscle
o Located in the walls of hollow internal organs
 Gastrointestinal, biliary, and reproductive tracts
 Blood vessels
o Functions automatically under conscious control
 Skeletal muscle
o Moves skeleton
o Under conscious control
 Cardiac muscle
o Found only in heart
o Resembles skeletal, but with features common to both smooth and
skeletal
Nerve
 Neurons: nerve cells, transmit nerve impulses
 Neuroglia: supporting cells
o More numerous than neurons
o Astrocytes: long, star-shaped cells, numerous highly branched
process
o Oligodendroglia: small cells, little cytoplasm, surround nerve cells
o Microglia: phagocytic cells
Organ
 Groups of different tissues integrated to perform a specific function
o One tissue performs primary function; others preform secondary
 Parenchymal cells: primary functional cells of an organ
 Parenchyma: functional part of an organ
o Ex. Nephrons–kidney & Neurons–brain
 Stroma: tissue that forms the supporting framework of an organ
Movement of Material In and Out of Cells
 Oxygen and nutrients must enter the cell and waste products must be
eliminated by crossing through a selectively permeable membrane
 Diffusion: solutes move from concentrated to a diluted solution
 Osmosis: water molecules move from dilute to concentrated solution
 Phagocytosis: ingestion of particles too large to pass across cell membrane
o Cytoplasm flows around the particle and cytoplasmic processes fuse
to engulf particle within a vacuole into the cytoplasm
 Pinocytosis: ingestion of fluid rather than solid material
Changing Conditions
 Atrophy: reduction in cell size in response to diminished function,
inadequate hormonal stimulation, and reduced blood supply
 Hypertrophy: increase in cell size without increase in cell number
o Ex. Muscles of weight lifter
o Heart of person with high blood pressure
 Hyperplasia: increase in both cell size and number in response to increased
demand
o Glandular tissues of breast during pregnancy in preparation for
lactation
o Enlargement of thyroid gland to increase output of hormones
 Metaplasia: change of one type of cell to another
o Ex. Lining of a chronically inflamed bladder
 Dysplasia: cell development and maturation are disturbed and abnormal
o Individual cells vary in size and shape
o Ex. Chronic inflammation of the epithelial cells of uterine cervix may
progress to cervical epithelial dysplasia and neoplasia
 Increases enzyme synthesis
 Adaptive response as in inactivating/detoxifying drugs or chemicals through
SER enzymes
Cell injury, death, & necrosis
 During normal conditions potassium is actively transported into Sal,
sodium is moved out
 Apoptosis is a naturally occurring death in the cell
 Changes resulting from cell injury
o Self swelling: sodium diffuses into self together with water
molecules
o Fatty change: accumulation of fat droplets within the cytoplasm
due to impairment of enzyme systems that metabolize fat(liver)
 Cell necrosis: cell damage + cell death
o All necrotic cells are dead but not all dead cells are in necrotic
o Cell necrosis is when the cell encounters a pathogen or substance
that destroys it
 Cell aging
o Genetic and environmental factors play a role in cell longevity
o Aging of cells may be caused by damage to cellular DNA, RNA, and
cytoplasmic organelles
o The more efficient the cells repair process the greater the
likelihood of survival
o As cell ages, it’s enzyme systems gradually declined, and cell is
less able to protect itself from injury
o Telomerase, also called terminal transferase, is a
ribonucleoprotein that adds a species-dependent telomere repeat
sequence to the 3' end of telomeres. A telomere is a region of
repetitive sequences at each end of eukaryotic chromosomes in
most eukaryotes