Mechanisms of Disease

Health

Physical, mental, and social well-being—not merely the absence of disease

Disease

An abnormality in body function that threatens health

Etiology

Study of the factors that cause a disease

Idiopathic

Refers to a disease with an unknown cause

Signs and symptoms

Objective and subjective abnormalities associated with a disease

Pathogenesis

Pattern of a disease's development

Epidemiology

the study of occurrence, distribution, and transmission of diseases in human populations

Endemic

diseases are native to a local region

Epidemics

occur when a disease affects many people at the same time

Pandemics

are widespread, perhaps global, epidemics

Why is it hard to discover the cause of disease?

Since it's difficult because many factors affect disease transmission

How can disease be fought?

Through therapy (treatment) and prevention

Pathophysiology

Study of underlying physiological aspects of disease

Pathophysiology Examples

Genetic mechanisms

Infectious mechanisms (pathogenic organisms and particles)

Neoplastic mechanisms (tumors and cancer)

Traumatic mechanisms (physical and chemical agents)

Metabolic mechanisms

Endocrine imbalances

Malnutrition

Inflammatory mechanisms

Autoimmunity

Inflammation

Degeneration

Risk factors

Genetics

Age

Lifestyle

Stress

Environment

Preexisting conditions

Viruses

Microscopic, intracellular parasites that consist of a nucleic acid core with a protein coat

Invade host cells and pirate organelles and raw materials

How are viruses classified

hape, nucleic acid type, and method of reproduction

Prions

Pathogenic protein molecules

Convert normal proteins to abnormal proteins, causing abnormal functions that produce disease; may be passed on to offspring

What do prions cause?

rare, degenerative disorders of the nervous system such as bovine spongiform encephalopathy (BSE)—Mad Cow Disease and variant Creutzfeldt-Jakob disease (vCJD)

Bacteria

Tiny cells without nuclei

Secrete toxins, parasitize host cells, or form colonies

Bacteria Classification

By growth requirements

Aerobic: Require oxygen

Anaerobic: Require no oxygen

Staining properties (depend on composition of cell wall)

Aerobic

Require oxygen

Anaerobic

Require no oxygen

Staining of cell walls

Gram- positive

Gram- negative

Bacilli

Rod-shaped cells

Cocci

Round cells

Curved

spiral rods

Small bacteria

Obligate parasites

Spores

Non-reproducing forms of bacteria that resist unfavorable environmental conditions

Fungi

Simple organisms similar to plants but lacking chlorophyll

Yeast

Small, single-celled fungi

Molds

Large, multicellular fungi

Mycotic infections

Often resist treatment

Protozoa

Large one-celled organisms that have organized nuclei.

They may infest human fluids and parasitize or destroy cells.

Groups of Protozoa (types)

amoebeas, flagellates, ciliates, sporozoa

Amoebas

Possess pseudopodia

Flagellates

Possess flagella

Ciliates

Possess cilia

Sporozoa (coccidia)

Enter cells during one phase of a two-part life cycle; borne by vectors (transmitters) during the other phase

Pathogenic animals

Large complex multicellular organisms, Parasitize or otherwise damage human tissues or organs

Pathogen animals major groups

Nematodes

Platyhelminths

Arthropods

Nematodes

Roundworms, Pinworms & Hookworms

Platyhelminths

Flatworms and flukes

Arthropods

Often vectors of disease

Chain of Infection

infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, susceptible host

Infectious agent

a pathogen, such as a bacterium or virus that can cause a disease

reservoir

where the bacteria/virus lives and grows

Portal of exit

a way for the infectious agent to escape from the reservoir in which it has been growing

Mode of transmission

a way that the infectious agent can be transmitted to another reservoir or host where it can live

Portal of entry

a way for an infectious agent to enter a new reservoir or host

Susceptible Host

a person likely to get an infection or disease, usually because body defenses are weak

Could be due to:

age

predisposed illnesses

immunocompromised

Person-to-person contact

Can be prevented by education

Can be prevented by using aseptic technique

Environmental contact

Can be prevented by avoiding contact

Can be prevented by safe sanitation practices

Opportunistic invasion

Can be prevented by avoiding changes in skin and mucous membranes

Can be prevented by cleansing of wounds

Transmission by a vector

Can be prevented by reducing the population of vectors and reducing contact with vectors

Vaccination

Stimulates immunity

Drug therapy

destroy or inhibit pathogens

Antibiotics

Natural compounds derived from living organisms

Antibiotic resistance

the ability of bacteria to withstand the effects of an antibiotic

Antiviral drugs

Inhibit viral reproduction and slow down progression of viral infections

Inflammatory response

Reduces injury to tissues, thus maintaining homeostasis

Signs and symptoms of the inflammatory response

Redness, heat, swelling, and pain

Inflammation mediators

histamine, prostaglandins, and kinins

Inflammatory response - blood vessels

Some cause blood vessels to dilate, increasing blood volume (redness and heat); white blood cells travel quickly to the injury site

chemotaxis

Some attract white blood cells to injury site

What can inflammation be

local or systemic (bodywide)

Fever

High body temperature caused by a resetting of the body's "thermostat"; destroys pathogens and enhances immunity

Chronic inflammation

can constitute a disease itself because it causes damage to tissues

Neoplasms (tumors)

Abnormal growths of cells

Benign tumors

remain localized

Malignant tumors

spread, forming secondary tumors

Metastasis

Cells leave primary tumor and start a secondary tumor at new location

Benign epithelial tumors examples

Papilloma

Adenoma

Nevus

Nevus

Small, pigmented tumor

Adenoma

Glandular tumor

Papilloma

Fingerlike projection

Benign connective tissue tumors

lipoma

Osteoma

Chondroma

Lipoma

Adipose (fat) tumor

Osteoma

Bone tumor

Chondroma

Cartilage tumor

Carcinomas

malignant epithelial tumors

Carcinomas examples

Melanoma

Adenocarcinoma

Sarcomas

connective tissue cancers

Sarcomas examples

Lymphoma

Osteosarcoma

Myeloma

Fibrosarcoma

Lymphoma

Lymphatic cancer

Osteosarcoma

Bone cancer

Myeloma

Bone marrow tumor/cancer

Fibrosarcoma

Cancer of fibrous tissue

Causes of cancer

Varied and still not clearly understood

Hyperplasia

growth of too many cells

anaplasia

development of undifferentiated cells

Factors that play a role in causing cancer

Genetics

Carcinogens

Age

Enviroment

Viruses

Genetic factors

e.g., oncogenes cancer genes

Carcinogens

Chemicals that alter genetic activity

Age

Changes in cell activity over time or accumulated effects of cell damage

Environment

Chronic exposure to damaging substances

Viruses what do they do

Cause change in genetic "machinery"

Methods of detecting cancers

Self-examination

Diagnostic imaging: Radiography (e.g., mammogram and computed tomography [CT] scan), magnetic resonance imaging (MRI), ultrasonography

Biopsy (e.g., Pap smear)

Blood tests