Key Concepts in Health and Disease

Posted on May 16, 2025 in Biology

Types of Diseases

Diseases can be categorized in various ways:

  • Infectious and Parasitic Diseases: cholera, influenza.
  • Tumors: benign tumors, cancer.
  • Hemic and Immune System Diseases: anemia, coagulopathy.
  • Mental and Behavioral Disorders: depression, intellectual disability.
  • Nervous System Diseases: meningitis, neuropathies.
  • Diseases of the Sense Organs: blindness, otitis.
  • Respiratory System Diseases: bronchitis, asthma.
  • Digestive System Diseases: caries, appendicitis.
  • Skin Diseases: dermatitis, alopecia.
  • Congenital or Genetic Disorders: cleft lip/palate, certain syndromes.

Contamination

Water Contamination

Domestic and industrial wastewater contains pollutants harmful to health:

  • Organic: wastewater, animal fecal waste, fats.
  • Inorganic: nitrates and phosphates from fertilizers, acids, salts, and toxic metals.
  • Biological: microorganisms.

Food Contamination

A food is contaminated when it contains foreign substances. When ingested, these substances can have harmful effects on health.

Pathogens and Disease Stages

Types of Pathogens

  • Bacteria: anthrax, cholera, pharyngitis, gonorrhea.
  • Viruses: influenza, hepatitis A, hepatitis B, mumps.
  • Metazoa (Parasites): amoebiasis, malaria, trichomoniasis.
  • Fungi: candidiasis, histoplasmosis, athlete’s foot.

Stages of Infection

  • Infection: A microorganism enters the body, penetrates tissues, and reproduces.
  • Incubation Period: The time between infection and the onset of symptoms.
  • Acute Period: The disease fully manifests.
  • Decline Period: Symptoms begin to subside.
  • Convalescence: The patient regains strength until recovery.

The Immune System

Physical Barriers & Inflammation

  • Skin: An almost impenetrable barrier to microorganisms, unless there is a wound.
  • Mucous Membranes: Epithelial tissues lining body cavities open to the exterior, coated with mucus secretion that helps destroy pathogens.
  • Inflammation: The body’s response to a microorganism, foreign particle, or other irritant entering the interior.

B Lymphocyte Response

  1. B lymphocytes circulate in the blood, each recognizing a specific antigen.
  2. When a B lymphocyte encounters its specific antigen, it becomes activated and begins to divide rapidly to increase its numbers.
  3. Activated lymphocytes (plasma cells) release antibodies into the bloodstream, which bind to the antigen.
  4. Microorganisms coated with antibodies are targeted and destroyed by other white blood cells.
  5. When the infection clears, some cells remain as memory cells, ready to respond quickly if the same antigen is encountered again.

T Lymphocyte Response

T lymphocytes recognize viral proteins displayed on the surface of infected cells. These viral proteins function as antigens. T lymphocytes destroy the infected cells, preventing the virus from reproducing.

Immune System Disorders

  • Autoimmune Diseases: The immune system mistakenly recognizes some of the body’s own molecules as foreign.
  • Allergy: The immune system responds to antigens that it would not normally react to under healthy conditions.

Treatments & Specific Conditions

Vaccines

Vaccines aim to immunize people against specific pathogenic microorganisms. This is achieved by injecting a weakened, killed, or fragmented form of the microorganism or its components.

Cancer: Characteristics & Treatments

Cancer cells exhibit:

  • Invasiveness: The ability to penetrate and spread to surrounding tissues.
  • Metastasis: The ability to penetrate blood vessels and lymph nodes, travel through the bloodstream and lymphatic system, and establish secondary tumors in distant parts of the body.

Common cancer treatments include:

  1. Surgery: Removal of the tumor.
  2. Radiotherapy: Using radiation to destroy cancer cells.
  3. Chemotherapy: Using drugs to kill cancer cells.
  4. Hormone Therapy: Using hormones to treat hormone-sensitive cancers.
  5. Immunotherapy: Using agents to strengthen the immune system’s ability to fight cancer.

Heart Attack & Stroke

  • Heart Attack (Myocardial Infarction): A part of the heart muscle is deprived of blood flow, usually due to occlusion of coronary arteries.
  • Stroke (Cerebral Infarction): Blood flow to a part of the brain is interrupted, typically because a blood clot blocks a cerebral artery.