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Chapter 22 Disease and the Body’s Immune System Disease • A disease is any condition which interferes with the normal functioning of the body. • Scientists refer to any organism which causes disease as a pathogen. • Pathogens include microscopic creatures such as bacteria, fungi, protozoans, and viruses…even some larger creatures like parasitic worms… The Fight Against Disease • Before 1870, one third of children died before adulthood… • Now, with preventive drugs and treatment, less than one in one hundred die… • Emphasis on the fight against disease has changed to adults…who are now living longer and longer lives… Classification of Diseases • Diseases are classified as infectious (caused by a pathogen) noninfectious (caused by other factors – aging, genetic, poor nutrition and others) • Both of these can be classified as acute (severe but lasting only a short time) chronic (long-lasting or often occurring) Types of Infectious Diseases • Infectious diseases may be further classified as communicable (transferred from person to person) noncommunicable (not transferred from person to person) Example: colds – passed from person to person tetanus – not passed from person to person Noninfectious Diseases Types of noninfectious diseases 1. Degenerative Diseases – organs gradually lose their ability to function properly over time… Examples: Heart disease, Alzheimer’s, Parkinson’s, osteoporosis Noninfectious Diseases 2. Immunological diseases – The immune system malfunctions and overreacts to a foreign material, attack the body, or fail to function properly. Most common: Allergies Most severe: autoimmune diseases (body attacks itself) Example: rheumatoid arthritis, and lupus Noninfectious Diseases 3. Hormonal Diseases – malfunctions of the endocrine system Example: Diabetes 4. Congenital Diseases – Present at birth Sometimes referred to as birth defects Many are inherited – hemophilia, sickle-cell anemia Some are infectious – passed from mother to baby Many are genetic – Down’s syndrome Noninfectious Diseases 5. Psychosomatic Diseases – caused by the mind 6. Nutritional Diseases – caused by improper diet results in a deficiency disease caused by malnutrition Example: scurvy, rickets, anemia Noninfectious Diseases 7. Diseases caused by harmful substances Infectious Disease • Organisms responsible for disease: 1. bacteria 2. viruses 3. protozoans 4. fungus’ – myotic diseases 5. worms – helminthic diseases The Bacteria • Single celled organisms • They are a prokaryotic cell – lack a membrane bound nucleus • Varying structures: – Most have a cell wall – Some have a slimy outer layer – Some have capsules – Some have flagella allowing them to move The Bacteria • Basic bacterial shapes – there are three basic shapes: – Cocci – round shape (tiny spheres) – Bacilli – rod shaped – Spirilla – spiral shaped The Bacteria • Examples of pathogenic cocci: – Staphylococcus aureus: this causes staph infections – Streptococcus pneumonia: causes bacterial pneumonia – Streptococcus pyogenes: causes “strep throat” The Bacteria • Examples of pathogenic bacilli: – Mycobacterium – leprosy and tuberculosis – Salmonella – food poisoning and typhoid fever – Escherichia coli – food poisoning The Bacteria • Examples of spirilla that are pathogenic: – Syphilis – Lyme disease Heterotrophic and Autotrophic Bacteria • Autotrophic means it is a “self feeder” – it produces its own food… • They contain chlorophyll… • Heterotrophic means it needs an outside source for food… • Some heterotrophic bacteria are extremely harmful… • Some are helpful, they assist your body in its maintenance…like E. coli… Reproduction of Bacteria • They produce asexually by binary fission.. • One cell splits into two… • Sometimes, some bacteria does exchange DNA before splitting… Bacteria and Disease • Pasteur’s germ concept of disease… – He said that every infectious disease is caused by a specific germ. Pathogenic activities of bacteria • Pathogenic bacteria cause problems in several ways… • They steal a cell’s nutrients – vitamins and minerals • Many produce harmful substances – toxins that damage or kill infected cells of the individual. • Turn the bodies tissues into battlegrounds…cells near the infected area are often killed between the battle of the immune system and the bacteria. Viruses • What is a virus? – A virus is a tiny capsule of genetic information. – It is a genetic “program” that reprograms the machinery of a living cell to produce a new virus particle instead of a cell’s normal products. Viruses • Structure: – Unlike living cells, a virus consists of only a short string of DNA or RNA surrounded by a rigid structure called a capsule… – Some viruses also have a lipid envelope… Viruses • Replication: – New viruses are manufactured and assembled by infected cells… – The cells own factories build new viruses after the virus changes the DNA code of that cell… – A typical virus is essentially a capsule of “blueprints” for new viruses… – Because a virus is incapable of reproducing on its own, virologists are uncertain whether or not to classify viruses as living things… Protozoa • Diseases caused by protozoa: – Single celled animals – Malaria is an example – caused by the organism Plasmodium – it is common in tropical regions… – 150 million new cases occur each year… – Other diseases: amoebic dysentery, African sleeping sickness… Fungi • Fungal diseases are called “mycotic diseases” • Examples: Athlete’s foot and ringworm • Most cases of dandruff are fungal • Most fungal diseases are characterized by red, inflamed, flaking skin… Roundworms, Tapeworms, Flukes • The body can be invaded by parasitic worms.. • Examples of Diseases: trichinosis & hookworm Spread of Infectious Diseases • Modes of transmission: – Droplet transmission – saliva (sneezes) – Droplet is the most common form of transmission – A person can be a carrier and display no sign of disease… – Disease can be transferred by a vector…like a mosquito… – Some diseases are transferred by contaminated substances… Spread of Infectious Disease • Venereal Diseases: – Diseases that are spread through sexual contact… – STD’s is what they are referred to today… – In 1995, it was estimated that 1 in six teenagers had an STD… Spread of Infectious Disease • Incubation and infection: – A person is said to have an infection the moment the pathogen enters the body… – There is an interval of time from the initial infection and the sign of disease…this is called the incubation period… Preventing Disease • Wash your hands!!! • God instructed the Israelites to wash after touching any possible infectious object… • Avoid unnecessary contact… • Avoid the contamination… • Eliminate vectors… • Vaccinations The Immune System • The most important parts of the immune system are the white blood cells… • They search out and destroy any organism or substance they do not recognize… • They are assisted by the lymphatic system…which transports white blood cells around the body and cleans the fluids of pathogens… The End