Disease & Disease-Producing Organisms

Chapter 5Anatomy & Physiology I

• Any abnormality of the structure or function of a part, organ or system

• Diseases fall into 7 different, but often overlapping categories

• 7 Predisposing factors increase the probability of a person becoming ill

• The study of disease

Disease

• Infection: • Degenerative diseases• Nutritional disorders• Metabolic disorders• Immune disorders• Neoplasms• Psychiatric Disorders

Categories of Disease

Infection

• Believed to play a part in at least 50% of all human illnesses

• Cause:– Many diseases are

caused by infectious organisms

• Example– cold, AIDS, tuberculosis

etc

Degenerative Diseases• Involve degeneration

(breaking down) of tissues in any system of the body

• Causes– Hereditary– Wear and tear– Infection– No known causes

• Example: – Alzheimer,

osteoporosis, and arthritis

Nutritional Disorders• Caused by:– dietary lack (deficiency) of

essential vitamins, minerals, proteins, or other substances

– Excess alcohol, caloric intake• Example– Scurvy – lack of Vitamin C– Rickets – lack of Calcium– Beriberi- lack of thiamine– Kwashiorkor- lack of protein– Goiter: lack of iodine

Nutritional Excesses

Metabolic Disorders• A disturbance in the buildup, breakdown, or excretion

of substances• Causes– Disruption in the reactions of cellular metabolism– Hormone imbalance regulate many metabolic activities– Hereditary errors of metabolism

• Examples– diabetes, – gout (a disorder of the joints), >> uric acid– digestive disorders, and – hereditary dysfunctions.

Immune Disorders• Caused by– Immune deficiencies: The decreased ability of the

body to fight infection and disease. Caused by genetic or infection• Example: AIDS

– Hypersensitivity – overactive immune system• Allergies–Animals, pollen, medicine, nuts etc

• Autoimmune disorders–Example: rheumatoid arthritis, multiple

sclerosis (MS), and systemic lupus erythematosus (SLE)

Neoplasms

• The word neoplasm means “new growth” and refers to cancer and other types of tumors.

• An abnormal and uncontrolled growth of tissues– Benign– Metastatic

Psychiatric Disorders

• A health condition that changes a person’s thinking, feelings, or behavior (or all three) and that causes the person distress and difficulty in functioning

Predisposing Factors

• May not cause a disease, but does increase the probability of a person becoming ill

• Age: measles is more common in children, Alzheimer in elders

• Gender: heart disease to men, diabets to women• Heredity: diabetes, allergies, and certain forms of cancer.• Living conditions & habits: sleep, exercise, diet, drugs,

alcohol, and tobacco • Emotional disturbance: stress, anxiety, anger, sensitivity• Physical & chemical damage – Injuries & chemical exposure• Preexisting illness: high blood pressure or diabetes,

increases one's chances of contracting another disease.

• Pathophysiology:– Is the study of close relationship of each

disease's pathologic and physiologic aspects and the understanding of these fundamentals in treatment.

The Study of Disease

Disease Terminology • Etiology – study of the

cause of disease• Epidemiology: the study of

diseases in populations. Epidemiology statistics include:

• Incidence – The number of new disease cases, occurence and tendency to affect certain groups of individuals more than other groups

• Morbidity – the proportion of a population with a specific disease

• Mortality – the proportion of a population that dies from a given disease

Disease Terminology Cont.• Diseases are classified

based on severity and duration as:– Acute – relatively severe

but last a short time– Chronic – may be less

severe but likely to be continuing or recurring

– Subacute – between acute and chronic diseases

Disease Terminology Cont.• Based on origin:• Idiopathic – disease without known cause• Iatrogenic – disease caused by adverse effects

from medical treatment• Communicable – disease that can be transmitted

from one person to another– Epidemic – many people from a certain region

acquire a certain disease at the same time– Endemic – a disease found to a lesser extent, but

continuously in a particular region– Pandemic – a disease prevalent throughout the world

Example of Endemic Disease: The Goiter Belt in the US

• Medical process – History, including signs and symptoms

• Sign – objective evidence (observed by physician or other healthcare professional

• Symptoms – subjective evidence (conditions noted by the patient). For example: imaging studies, blood tests, and study of tissues removed in biopsy.

• Syndrome – a characteristic set of signs and symptoms that accompany a disease; PMS, AIDS

– Diagnosis – a conclusion as to the nature of the illness– Prognosis – prediction of probable outcome of disease– Therapy – course of treatment

Treatment and Prevention of Disease

Methods of disease prevention or treatment that can be used along with or

instead of traditional modern medical practices

Treatment: Complementary and Alternative Medicine

Alternative Medicine

• Naturopathy: healthy life style• Chiropractic: correcting

misalignment for treatment of musculoskeletal disorder

• Acupuncture: insert needle to relief pain

• Biofeedback: electronic devices monitor changes and feed info back to a person

• Herbal medicine

Disease Prevention

• Modern medicine’s major focus is on treating patients who currently have a disease

• Wellness movement focuses on preventing the occurrence of disease by promoting health

• Health – an optimal physical, mental and emotional state of being, not merely the absence of disease

• Health-promoting practices– Massage– Diet– Exercise– Stress management

Infectious Disease• Invasion of the body by disease-producing

microorganisms• Microorganisms – – Aka microbes, germs– A tiny living thing too small to be seen by the naked eye– Most are harmless, many are beneficial, a few cause illness

(are pathogenic)• Parasite – a living organism that lives on or in a living

host at the host’s expense• Pathogen – disease-producing organism

Types of Infection• Infection – pathological state resulting from

the invasion of the body by pathogenic microorganisms

• Local – infection restricted to a small area• Systemic – infection throughout the whole

body• Opportunistic infection – an infection that

takes hold because the body has been weakened by disease or injury

Modes of Transmission• Direct Contact– Touching – Sexual activity

• Indirect Contact– Touched objects

• Vector – an insect or animal that transmits a pathogen from one host to another (mosquito)

• Atmosphere

Portals of Entry & Exit

• Skin• Respiratory

tract• Digestive

system• Urinary

system• Reproductive

system

The Common Cold• 1 billion Americans “catch” a cold

every year• Leading cause of doctor visits &

missed days of work & school• Caused by over 200 different

types of viruses• One sneeze can send hundreds of

thousands of particles several feet, where they live for 3-6 hours

• To prevent– Avoid close contact– Wash hands– Do not touch your face– Clean surfaces frequently

• Microorganisms- simple, microscopic, usually single-cell, forms of life. The group includes bacteria, viruses, fungi, protozoa, and algae. Book: table 5.1

• Microbiology – The study of these microscopic organisms • Bacteria – single-celled organisms which grow in many

environments• Viruses- composed of nucleic acids & protein; can only multiply

inside of living cells• Fungi – plantlike organisms

– Single celled – yeasts– Filamentous - molds

• Protozoa – single-celled animals – Aka parasites– Includes worms

Microbiology

Microorganisms

• Most are harmless to humans and are essential to all of life on earth

• Normal flora – population of microorganisms that normally grow on or within our bodies – Beneficial – If normal flora are destroyed it can cause

overgrowth of normally harmless bacteria, rendering them pathogenic

Bacteria

• Single celled organisms• One of the most primitive

forms of life on earth• Their genetic material is not

enclosed by membrane• Do not have a true nucleus • Lack most organelles

Bacteria Cont.

• Classification– Aerobic – require oxygen to grow– Anaerobic – grow in the absence of oxygen– Facultative anaerobes – use oxygen if present but are also

able to grow without oxygen – e. coli• Endospores – resistant forms of bacteria that can

tolerate long periods of dryness or other adverse conditions. Endospores can be become airborne– Resistant to ordinary methods of disinfection– Particularly dangerous – tetanus, botulism, anthrax

Bacteria Movement

–Flagella: helps them to swim rapidily–Pili – short “hairs”

that help bacteria to glide across solid surfaces & anchor it to surfaces

Bacteria Cont.

• Largest group of pathogens to humans

• Can divide every 20 minutes or every 24 hours

• Cause damage to humans in 2 ways– Produce toxins– Growing in human

tissues

• Physical barriers – skin, mucus membranes

• Immune system

Human defence mechanism

• Cocci– Diplococci– Streptococci– Staphylococci

• Bacilli• Curved rods– Vibrios– Spirilla– spirochetes

Shape & Arrangement of BacteriaThree groups of bacteria based on their shape

Cocci & Bacilli• Cocci – round – Diplococci – in pairs – causes

gonorrhea, and meningitis – Streptococci – in strings – strep

throat– Staphylococci – in clusters -

pneumonia and fever.• Bacilli – straight rods– All endospore-forming bacteria

are bacilli– TB, typhoid fever, Legionnaire’s

disease

Curved Rods

• Vibrios – short curved rods, like a comma – cholera

• Spirilla – resemble a corkscrew

• Spirochetes – similar to spirilla but capable of waving & twisting motions. Casues syphilis

Obligate Intracellular Parasites

• Bacteria that are much smaller than normal• Also include viruses, which are not bacteria• They only grow within the cells of their hosts • Chlamydia• Ricksettia – Transmitted through insect bites– Rocky Mountain spotted fever, typhus

Viruses• Extremely small in comparison to bacteria: seen by electron

microscope• Have some characteristics of living matter but not all

– Contain genetic material & are able to reproduce• Contain only DNA OR RNA

– Generally made of genetic material surrounded by a protein coat– Are not cellular– Do not have enzyme systems

• Can only grow within a host’s cell (obligate)

Virus size comparison. A chlamydia and a staphylococcus are shown for reference

Viruses

Classifying and naming Viruses

• Classified according to:– type of nucleic acid they have: DNA or RNA– whether that nucleic acid is single stranded (ss) or double

stranded (ds).– The diseases they cause: common cold, hepatitis, measles – where they were isolated : West Nile– the symptoms they cause: yellow fever– the host : Chickenpox, HIV, Swine influenza

Other Agents Smaller than Viruses

• Prions (proteinaceous infectious )-made solely of proteins– Slow growing and hard to destroy– Mad cow disease

• Viroids – Composed solely of RNA with no protein coat– So far have only been discovered to cause plant

diseases

Fungi

• Types – Yeast – single celled– Molds – long &

filamentous• Simple plant-like

organisms– Do not contain

chlorophyll – Grow in dark, damp

places• Very few cause

diseases

Mycotic (Fungal) Infections

• Diseases caused by fungi are called mycotic

• Can affect skin– Ringworm – tinea

corporis or capitis– Athlete’s Foot

• Can affect those with compromised immune systems– Candidiasis

Protozoa• Single-celled animal-like

organisms• Amebas – a “blob” that can move• Ciliates – tiny hairs propel this

organism• Flagellates – a tail propels this

organism• Sporozoa – cannot propel

themselves– Obligate parasites, unable to grow

outside host– Carried by mosquitos– malaria

Protozoa Movement

Parasitic Worms (Helminths)

• Roundworms– Ascaris – intestinal; hard to

control & eliminate– Pinworm – intestinal; hard to

control & eliminate– Hookworms – intestinal; suck

blood & cause anemia; larvae enter body through foot

– Trichinea – live in muscles of animals & people; enter body through undercooked meat

– Filaria – live in lymphatic system

Hookworm

Roundworms Ascaris & Filaria

Filaria Infection

Parasitic Worms (Helminths) Cont.

• Flatworms – Tapeworms – can

be 50 feet long in intestines, spread through undercooked meat

– Flukes – can infect many body parts

Tapeworm

Microbial Control

• Infectious diseases are increasing– Increased population, travel, food processing

• Public health measures help control microbes– Sewage/garbage disposal– Water purification– Prevention of food contamination– Milk pasteurization

Aseptic Techniques & Methods

• Sterilization – kills EVERY living microorganism on an object

• Disinfection – kills all pathogens (except spores) but does not necessarily kill harmless microbes

• Antisepsis – pathogens not necessarily killed but prevented from multiplying

Universal Precautions to Control Infection

• Healthcare workers MUST use barriers for any contact with moist substances, non-intact skin, & mucous membranes –REGARDLESS of whether or not blood is visible & REGARDLESS of a patient’s diagnosis

• Soiled linen and trash are treated as contaminated

• Needles are not recapped after blood draws• Handwashing – goal of 100% compliance

Handwashing

• The single most important measure to prevent the spread of infection in ALL settings

• Gloves are not a substitute for handwashing

Areas Missed During Handwashing

Antimicrobial Agents

• Antibiotics– Penicillin– Danger of opportunistic infections developing due

to loss of normal bacteria– Danger of resistant strains of pathogens developing

• Antiviral agents – very few and they have a limited range of effectiveness– Viruses mutate rapidly to become resistant– Antiviral agents are often used in combinations

Antibiotics