Human Health and Disease Overview

Overview of Human Health and Disease

• The chapter "Human Health and Disease" is typically studied in three main parts: common diseases, immunity, and substance abuse.
• Health is considered a state of complete physical, mental, social, and physiological well-being, not just the absence of disease.
• Mind maps are useful for revision, and assumes the reader has already studied the chapter in detail.
• The mind map will cover the key theories of health, categories, and factors of disease, and the concepts of immunity.

Historical Perspectives on Health

• The 'Good Humor Theory' stated that health was determined by the balance of "humors" or bodily fluids.
• Key proponents associated with the theory were Hippocrates and the Indian Ayurvedic system.
• William Harvey, known for his discovery of blood circulation, disproved the Good Humor Theory by demonstrating consistent body temperatures.
• His work showed that body temperature was not directly affected by humor imbalances, contrasting old beliefs.

Modern Health Perspective

• Health is defined as a state of complete physical, mental, social, and physiological well-being.
• Health isn't merely the absence of disease or physical fitness.
• Factors affecting health include genetic disorders, infections, and lifestyle habits.
• Healthy living can increase productivity, longevity, and economic prosperity.
• Healthy living can also decrease infant and maternal mortality rates.

Understanding Disease

• Disease is defined as a condition where one or more organs/systems in the body is adversely affected.
• These conditions are characterized by visible signs and symptoms.
• Diseases can be categorized into infectious (transmissible) and non-infectious (non-transmissible).
• Cancer is non-infectious, whereas AIDS is infectious.

Disease Terminology

• Pathogens are disease-causing organisms that negatively affect the host organism.
• Parasites reside within the host's body, multiplying and disrupting vital bodily functions, causing harm.

Modes of Disease Transmission

• Diseases transmitted through air droplets (aerosols) or contact with contaminated objects include:
  • Pneumonia
  • Diphtheria
  • Common cold
  • Smallpox
• Direct contact can spread diseases like tetanus and smallpox (viral).
• Contaminated food and water can transmit:
  • Typhoid
  • Dysentery
  • Polio
  • Amoebiasis
  • Ascariasis
• Insect vectors transmit diseases like malaria (via mosquitoes).
• Diseases spread through body fluids include:
  • Syphilis
  • AIDS
  • Trichomoniasis
• Female Anopheles mosquitoes transmit malaria, while female Aedes mosquitoes transmit dengue and chikungunya.

Measures to Prevent Infectious Diseases

• Maintain personal hygiene for physical health.
• Maintain healthy habits around food consumption such as proper hygiene when handling food and water.
• Good habits include consuming clean drinking water, foods, vegetables, and fruits.
• Maintain public hygiene by properly disposing of waste and periodically cleaning and disinfecting facilities.
• Avoid close contact with infected individuals and control vectors by eliminating breeding sites like standing water.
• Efforts to eliminate infections include using mosquito nets, introducing larvivorous fish, and spraying insecticides.
• Having doors and windows fitted with wire mesh can keep insects away.

Bacterial Diseases: Typhoid

• Typhoid is caused by the pathogen Salmonella typhi.
• The diagnostic test for typhoid is the Widal test.
• Salmonella typhi affects the small intestine, spreading to other organs via the bloodstream.
• Common symptoms include sustained high fever (39-40°C), weakness, stomach pain, constipation, and loss of appetite.
• Severe cases can cause intestinal perforation, internal bleeding, or death.
• Typhoid Mary (Mary Mallon) was a cook and typhoid carrier who spread the disease through contaminated food.

Bacterial Diseases: Pneumonia

• Pneumonia can be caused by Streptococcus pneumoniae or Haemophilus influenzae.
• It affects the alveoli of the lungs, which fill with fluid, leading to breathing problems.
• Symptoms include fever, chills, cough, headache, and, in severe cases, bluish lips/fingernails.
• Transmission occurs through air droplets and can affect people of all ages.

Viral Diseases: Common Cold

• The common cold is caused by the rhinovirus family.
• Transmission occurs through air droplets.
• It affects the nose and upper respiratory tract, but not the lungs.
• Symptoms include nasal congestion, sore throat, cough, headache, and tiredness.
• Common colds typically last 3-7 days, and don't require specific medical treatment.

Helminth Diseases: Ascariasis and Elephantiasis

• Ascariasis (roundworm) is caused by Ascaris lumbricoides, affecting the intestine.
• It can cause internal bleeding, fever, muscle pain, anemia, and intestinal blockage.
• Elephantiasis (filariasis) is caused by Wuchereria bancrofti or Wuchereria malayi.
• It affects the lymphatic vessels, causing chronic inflammation and grotesque deformities.
• This disease impacts the lower limbs and genital organs in particular.

Fungal Diseases: Ringworm

• Ringworm is caused by fungi like Microsporum, Trichophyton, and Epidermophyton.
• It affects the skin, nails, and scalp, thriving in moist and humid conditions.
• The infection presents as dry, scaly, and intensely itchy lesions.
• Ringworm can be spread through soil, towels, combs, clothing, or direct contact.

Protozoan Diseases: Amoebiasis and Malaria

• Amoebiasis (amoebic dysentery) is caused by Entamoeba histolytica impacting the large intestine.
• Symptoms include abdominal pain, cramps, and stools with mucus and blood clots.
• Malaria is caused by Plasmodium species (vivax, malariae, and falciparum).
• Plasmodium falciparum is the most fatal.
• Malaria parasites affect red blood cells (RBCs) by converting hemoglobin into hemozoin, a toxic substance.
• Symptoms include chills and recurring high fever every 3-4 days.
• If untreated, malaria can lead to fatal complications.
• House flies are mechanical carriers of Amoebiasis.

Malaria Life Cycle - Simplified

• Malaria involves two hosts: a primary host (female Anopheles mosquito) and a secondary host (humans).
• Parasites undergo:
  • Sexual reproduction in the mosquito.
  • Asexual reproduction in humans.
• Sporozoites from the mosquito's saliva enter the human bloodstream during a bite.
• Sporozoites invade liver cells, multiply, and then infect RBCs.
• In RBCs, parasites transform hemoglobin to hemozoin which causes recurrent fever.
• Gametocytes develop in RBCs and are ingested by a mosquito during a blood meal.
• Fertilization happens in the mosquito's gut, forming sporozoites, which migrate to its salivary glands.

Understanding Acquired Immunodeficiency Syndrome (AIDS)

• AIDS is a fatal, incurable infectious disease caused by Human Immunodeficiency Virus (HIV).
• It was first reported in 1981 in the USA and has affected millions over the years.
• HIV compromises the immune system making hosts susceptible to various infections.
• The disease is acquired during an individual's lifetime.
• Because AIDS involves groups of symptoms, it is classified as a syndrome which is non-congenital.
• HIV structure consists of outer glycoproteins (gp120, gp41), protein capsid (p17 & p24), and two single-stranded RNA molecules.

HIV Transmission

• HIV is contracted through:
  • Sexual contact
  • Contaminated blood transfusions
  • Infected needles
  • Intra-uterine transfer via the placenta
• High-risk individuals are:
  • Those with multiple sexual partners
  • Infants born to HIV-positive mothers
  • Recipients of repeated blood transfusions
  • Drug addicts

HIV Replication

• HIV infects macrophages and helper T cells (CD4+ T cells), weakening the immune system.
• HIV attaches to CD4 receptors, injects RNA, performs reverse transcription with reverse transcriptase enzyme to make viral DNA.
• Viral DNA integrates into the host DNA from integrase enzyme.
• Infected cells produce new viruses, causing a progressive decrease in T helper cells.
• This leads to immune deficiency.
• Infected macrophages act like HIV factories and continue spreading the infection.
• Early detection is critical.
• The HIV virus reproduces within CD4+ T (helper) cells, causing a gradual decrease in their numbers.

HIV Treatment

• It can take several months or years for AIDS signs and symptoms to appear after HIV infection.
• ELISA (Enzyme-Linked Immunosorbent Assay) is used for AIDS testing.
• No treatment exists, but antiretroviral drugs can prolong life and reduce mortality by slowing HIV replication.

Understanding Cancer

• Cancer is a non-infectious disease and a leading cause of death globally.
• Two cell types need to be understood: Normal and Cancerous Cells.
• Normal cells are regulated and controlled whereas cancerous cells are not.
• Contact inhibition is present in normal cells, which prevents continuous division and growth.
• No contact inhibition in cancer cells, leading to masses and tumors.
• While normal cells are not prone to spread, cancer cells spread.
• Tumors can be benign (non-cancerous) or malignant (cancerous). Benign tumors do not spread, malignant tumors spread.
• Malignant tumors exhibit metastasis throughout the body via the blood.

Cancer Agents

• Cancer is caused by mutations typically, and results with new cell growth. Agents causing cancer are classified into categories:
• Radiation: Can come from X-rays and Gamma Rays.
• Non-ionizing: Can come from UV rays.
• Chemical: Can come from cigarette smoking.
• Biological can come from viruses.

Cancer Detection

• Cancer can be detected and identified via early, successful testing that is crucial. Key processes include:
• Biopsy (tissue sampling).
• Blood and bone marrow tests.
• Radiography (X-rays).
• CT and MRI scans.

Cancer Treatment

• Techniques for treatment of cancer can involve radiation and surgical removal
• Treatment options include:
  • Surgery
  • Radiation therapy
  • Chemotherapy
• Immunotherapy uses substances like alpha-interferons to stimulate the immune system to fight against tumor cells.
• Often affects other parts resulting in loss of hair.

The Human Immune System

• Immunity is the body's ability to fight disease-causing organisms.
• It consists of lymphoid organs, tissues, cells, and molecules like antibodies.
• Immunity is categorized as inherited and acquired.
• An innate characteristic inherited at birth:
  • Not specific and without memory
• Acquired via the development of an immune system:
  • Occurs after birth, is specific, and has memory, providing long-term immunity.
• B lymphocytes and T lymphocytes both assist the Acquired Immune System:
  • In fighting invaders
  • Remembering antigens

Primary and Secondary Lymphoid Organs

• Primary lymphoid organs are the thymus and bone marrow.
• The thymus matures T cells, while bone marrow matures B cells.
• Secondary lymphoid organs are the spleen, lymph nodes, tonsils, appendix, and Peyer's patches.
• Secondary Lymphoid tissues generate all lymphoid factors.
• Lymphocyte Interactions generate the cell immune system.
• Malts support mucosa lining on various organs in the system.

Immune Responses

• The primary response is the initial encounter with an antigen, which is slower and of lower intensity.
• The secondary response is much faster and more intense due to memory cells.
• Both B and T lymphocytes mediate these responses.

Antibody Structure

• An antibody consists of four polypeptide chains: two heavy and two light chains.
• Antibodies have antigen-binding sites between the heavy and light chains.
• There are 16 bonds made of disulfide within each antibody.
• General Structure:
  • Two heavy chains
  • Two light chains
  • Held together from four chains
• Known as immunoglobulin.
• Examples:
  • IgG
  • IgA
  • IgM
  • IgE
  • IgD

Organ Transplantation

• Organ transplantation requires blood group and tissue matching to minimize the risk of rejection.
• If a perfect match isn't possible, immunosuppressants are administered.
• T lymphocytes are responsible for graft rejection
• Immunosuppressants are used to prevent rejection

Lymphoid Organs: Bone Marrow

• Bone marrow is the primary lymphoid organ that produces lymphocytes.
• Both Blood and cells are generated at Bone Marrow.

Lymphoid Organs: Thymus

• The thymus is a bilobed organ located near the heart and beneath the breastbone.
• It is large at birth but decreases in size with age.

Lymphoid Organs: Spleen

• The spleen is a bean-shaped organ containing lymphocytes and phagocytes.
• It acts as a filter for the blood, removing blood-borne microorganisms and acting as the reservoir for red blood cells.

MALT: Mucosa-Associated Lymphoid Tissue

• Mucosa-associated Lymphoid Tissue represents about 50% of lymphoid tissue in the human body associated with mucosa lining

Active & Passive Immunity

• In Active Immunity, the body produces antibodies following and being exposed to a pathogen.
• Often occurs through natural means like developing antibodies and creating its own memory.
• Or vaccination.
• In Passive Memory is Ready Made Antibodies.
• Antibodies are transferred to protect the body system vs infections
• For example a snake-bite is a very dangerous situation. At that time, Passive immunity is a great defense for help and support with a fast recovery.

Vaccinations and Immunizations

• Vaccines generate memory cells in the body, preparing it to fight off future infections more effectively and creating memory cell activity.
• Recombinant DNA technology is used to make vaccines, such as the hepatitis B vaccine produced using yeast.

Allergies

• Allergies are the exaggerated response of the immune system to certain environmental antigens (allergens).
• Allergens include dust, pollen and mold.
• Common symptoms are:
  • Sniffling
  • Watery eyes
  • Runny nose
  • Red and itchy eyes
• The body produces IgE antibodies, which stimulate histamine and serotonin.
• Testing is generally implemented to expose a small quantity and record whether any action occurs.
• Treatment involves antihistamines and steroids, which reduce allergic symptoms.

Autoimmunity

• Autoimmunity is the state where the body attacks its own cells and causes autoimmunity which can be genetic.
• Ex:
  • Rheumatoid, or the arthritis disease.

Drug Abuse

• Drug abuse involves the misuse of substances outside the intended purpose, with the potential to cause physical, mental, and behavioral issues.

Types of Drugs

• Opioids bind to receptors in the CNS and GI tract:
  • Examples are morphine, heroin, and codeine, act as pain relievers and depressants.
• Cannabinoids affect the brain and cardiovascular system. and stem cells.
  • Derived from Cannabis sativa, they include marijuana, hashish, and charas.
• Stimulants stimulate the CNS, derived from Erythroxylum coca, used to keep users alert and awake.
• Hallucinogens alter perceptions and thoughts, causing hallucinations: the effects are synthetic or naturally occurring.
• Those who seek performance enhancement use drugs and sports:
  • Some include steroids for promoting strength.
  • Side effects can cause: mental issues.

Negative Impacts

• Commonly affects systems and cells:
  • Tobacco and Brain system
  • Tobacco used through chewing, smoking, sniffing creates and releases a chemical response like Nicotine.
• Other effects include:
  • Respiratory, Circulation effect.
  • Side effects like bronchitis and or increase of the rate for different cancers.
  • Peer pressures can influence consumption with outside interaction.
  • Addicks can lead and develop to different mental or financial stress ofr friends or family.

Detections and Solutions

• Signs of distress:
  • Are noticeable, and include unattendance of school
  • Also isolation of contact etc.
  • The solutions depend on the signs:
  • A better path to educate and counsel.
  • Prevent the pressure of interaction to peer problems
  • Or also seek for help.