Human Health And Diseases

• Early Greeks like Hippocrates and Indian Ayurveda system of medicine asserted that health is a state of body and mind where there was a balance of certain humors. This ‘good humor’ hypothesis was disproved by William Harvey who discovered blood circulation.
• It was believed that person with ‘blackbile’ belonged to hot personality and have fevers.
• Health: State of complete physical, mental and social well being and not merely absence of disease. It increases productivity and brings economic prosperity. It increases longevity and reduces infant and maternal mortality.
• It is affected by

(i)    Mind and mental state

(ii)   Genetic disorders - defects inherited from parents.

(iii) Infections

(iv) Life style (food, water, rest, exercise, habits etc.)

• For achieving good health - balanced diet, personal hygiene, regular exercise, awareness about diseases, immunization, proper disposal of wastes, hygienic food and water resources.
• Disease: When functioning of 1 or more organs of body is affected.
• Infectious : easily transmit from 1 person to another. eg. AIDS (fatal)
• Non-Infectious : don’t transmit easily. eg. Cancer.

Common Diseases In Humans:

• Pathogens: Disease causing organism. eg. bacteria, virus, fungi, protozoans, helminths etc.
• They enter our body, multiply and interfere with normal vital activities causing morphological and functional damage.
• They have to adapt to host’s environment. eg. pathogen entering gut adapt to low pH.

1.     Bacterial Diseases: eg. Dysentery, pIague, diphtheria, typhoid, pnuemonia etc.

(a)   Typhoid: By Salmonella typhi

• They enter small intestine through contaminated food and water.
• Symptoms : Sustained high fever (39⁰ to 40⁰ C), weakness, stomach pain, constipation, headache, loss of appetite, intestinal Perforations .
• Its confirmed by Widal Test.
• Mary Mallon (nicknamed Typhoid Mary) was a typhoid carrier who continued to spread typhoid for many years through food She prepared.

(b)   Pneumonia : By Streptococcus  Pneumoniae and Haemophilus influenzae .

• Droplet infection (by sharing glasses and utensils with infected person). It infects alveoli of lungs (alveoli get filled with fluid leading to respiratory problems).
• Symptoms: Fever, cough, headache, chills, lips and finger nails turn gray to blue.

2.     Viral Diseases:

• Common cold: By Rhino viruses, lasts for 3-7 days.
• Droplet infection (by sneezing or cough of infected person) or transmitted through contaminated objects (book, pen, cups etc.)
• Infect nose and respiratory passage but not lungs.
• Symptoms: Cough, headache, tiredness, nasal congestion and discharge, hoarseness, sore throat.

3.     Protozoan Diseases:

        (a)   Malaria: By Plasmodium (P. vivax, P. malariae and P. falciparum)

• P. falciparum cause malignant malaria (serious or fatal).
• It enters human body as sporozoites (infectious form) through bite of infected female Anopheles mosquito.
• They multiply within liver cells and enter RBC resulting in their rupture which releases toxin haemozoin responsible for chill and high fever recurring every 3-4 days. When Anopheles bites infected person, parasite enters mosquito’s body and multiply to form sporozoites which are stored in salivary gland. On mosquito bite, sporozoites enter human body.
• Malarial parasite require two hosts - human and mosquito to complete its life cycle.
• Fertilisation of male and female gamete of parasite occur in mosquito’s gut.

        (b)   Amoebiasis (Amoebic dysentry) : By Entamoeba histolytica.

• It enters large intestine through faeces. Housefly are mechanical carriers of the parasite, transmitted by drinking water and food contaminated by faecal matter.
• Symptoms: Constipation, abdominal pain, cramps and stools with excess mucous and blood clots.

4.     By helminths:

(a)   Ascariasis: By Ascaris (common round worm)

• Through contaminated water and food.
• Eggs of parasite are excreted along with faeces of infected person.
• Symptoms: Fever, muscular pain, internal bleeding, anemia and blockage of intestinal package.

(b)   Elephantiasis/filariasis: By Wuchereria (filarial worm) - W. bancrofti and W. Malayi.

• Through bite of female mosquito vectors.
• Symptoms : Chronic inflammation of lymphatic vessels/lower limbs, genital organs are also affected resulting in gross deformities.

5.     Fungal Diseases:

• Ringworm: By Microsporum, Trichophyton and Epidermophyton.
• Acquired from soil or by using towels, clothes or comb of infected person.
• Symptoms: Dry, scaly lesions on skin, nails and scalp, heat and moisture help fungi to thrive in skin folds like groin or toes.

Prevention and Control of Diseases:

• Maintaining personal hygiene (keeping body clean, consuming clean drinking water, food, vegetables, fruits) and public hygiene (proper disposal of waste and excreta, cleaning and disinfecting water reservoirs, tanks).
• Close contact with infected person should be avoided.
• Avoid stagnation of water in and around residential areas, use mosquito net, clean coolers, spraying insecticides in ditches, doors and windows should be provided with wire mesh to prevent mosquito entry, introducing fish like Gambusia in ponds that feed on mosquito larvae.
• Use of vaccines and immunisation programmes enabled to eradicate small pox and control polio, diphtheria, pneumonia, tetanus.
• Antibiotics and other drugs enable treatment of diseases.
• Disease transmitted through food and water: typhoid, amoebiasis, ascariasis.
• Air borne diseases: pneumonia and common cold.
• Insect vector diseases: dengue and chikungunya.

Immunity: Ability of host to fight against disease causing organisms.

1.     Innate Immunity: Non specific type of defence present at birth.

• Provide barriers to foreign agents.
• Physical barrier: Skin, mucus coating of respiratory, urogenital and gastrointestinal tracts traps microbes.
• Physiological barrier: Acid in stomach, saliva in mouth, tears from eyes.
• Cellular barrier: leucocytes like polymorpho-nuclear leucocyte (PMNL), monocyte, natural killer in blood and macrophage phagocytose and destroy microbes.
• Cytokinine barrier: Virus infected cell secrete protein - interferons.

2.     Acquired Immunity: Pathogen specific, characterised by memory.

• Primary response: Body encounters pathogen for first time, low intensity.
• Secondary/Anamnestic response: Subsequent encounter with same pathogen, high intensity as body has memory of first encounter.
• These are carried out by 2 lymphocytes M-Iymphocytes and T-Iymphocytes.
• b N lymphocyte: Produce army of proteins (antibodies) in response to pathogen into our blood.
• T lymphocyte: Don’t produce antibodies but help b N lymphocyte to produce them

• Antibody mediated immunity: Also called humoral immune response as antibodies are found in blood.
• Each antibody molecule has 4 peptide chains - 2 small (light chains) and 2 longer (heavy chains). So its represented as H₂ L₂· eg. IgA, IgM, IgE, IgG.

(b)   Cell mediated immunity: By T-Iymphocytes.

• Responsible for graft rejection - organs to be transplanted can’t be taken from just anybody. Tissue matching, blood group matching are essential and person has to take immuno  suppressants all his life.
• Body is able to differentiate self from non-self.

3.     Active Immunity: Host is exposed to antigens (may be in form of living or dead microbes or other proteins) which produce antibodies in the host.

• Slow and takes time to give full effective response.
• When microbes gain access to body during infection, active immunity is induced.
• This is how immunisation (deliberately injecting microbes) works.

4.     Passive Immunity: When readymade antibodies are given against foreign agents directly into the body.

• eg. (i) Foetus receives antibodies (IgG) from mother through placenta during pregnancy.

(ii)   Yellowish fluid colostrum secreted during lactation has antibodies Ig A to protect infant.

Vaccination and Immunisation : Based on property of memory of immune system.

• In vaccines, preparation of antigenic proteins of pathogens or inactivated/weakened pathogen are introduced in body. Antibodies produced in body against these antigens neutralise pathogenic agents during infection.
• Vaccines generate memory and b and T cells recognise pathogen quickly and produce antibodies in response.
• Passive immunisation: Preformed antibodies are injected or antitoxin (preparation containing antibodies to the toxin) are injected in response to deadly microbes to which quick immune response is required.
• eg. in tetanus and snake bite.
• Recombinant DNA technology has allowed production of antigenic polypeptides of pathogen in bacteria or yeast. eg. hepatitis B vaccine from yeast.

Allergies: Exaggerated response of immune system to certain antigens.

• Allergens: Substance to which immune response is produced. eg. dust, pollens, animal danger etc. Antibodies produced to these are Ig E type.
• Symptoms: Sneezing, watery eyes, running nose, difficulty in breathing.
• Its due to chemicals like histamine and serotonin from mast cells.
• Treatment: Use of drugs like anti- histamine, adrenalin and steroids.
• to determine the cause of allergy, patient is exposed to small dose of allergens to study reactions.
• Modern day protected environment has led to lowering immunity and more sensitivity to allergens.

Auto Immunity: eg. Rheumatoid arthritis is a auto - immune disease.

• Higher vertebrates have evolved memory based acquired immunity based on ability to differentiate foreign organisms from self cells.
• Due to genetic reason, body attacks self cells resulting in auto immune disease.

Immune system: Lymphoid organs + tissue + cells + antibodies (soluble molecules).

• It recognises foreign antigens, plays important role in allergic reactions, auto immune disease and organ transplantation.
• Lymphoid organs: Origin, maturation and proliferation of lymphocyte occur.
• Primary Lymphoid Organs: eg. Bone marrow and thymus.
• Immature lymphocyte differentiate to antigen sensitive lymphocytes.
• Provide micro - environment for development and maturation of T-lymphocytes.
• Bone marrow: Main lymphoid organ, all blood cells are produced here.
• Thymus: Lobed organ near heart beneath breast bone, size reduces with age and becomes very small size at puberty.

• Secondary Lymphoid Organs: eg. Spleen, Lymph nodes, Tonsils, Peyer’s patches of small intestine, Appendix.
• Provides sites for interaction of lymphocytes with antigens which proliferate to become effector cells.
• Spleen: Large bean shaped organ consisting of lymphocytes and phagocytes, acts as filter of blood by trapping blood borne micro-organisms. Its a large reservoir of RBC.
• Lymph nodes: Small solid structures at different points on lymphatic system which trap microbes which get into lymph and tissue fluid, antigens in it activate lymphocytes and cause immune response.
• Mucosal-associated lymphoid tissue (MALT): Lymphoid tissue lining major tracts (respiratory, digestive and urinogenital tracts), 50% of lymphoid tissue.

AIDS: Acquired Immuno Deficiency Syndrome (not congenital-acquired during lifetime)

• Syndrome - group of symptoms.
• First in 1981, it has killed more than 25 million persons in last 25 years.
• Cause: Human Immuno Deficiency Virus (HIV), member of retrovirus having envelope enclosing RNA genome
• Transmission: Sexual contact with infected person, transfusion of contaminated blood, sharing infected needles, from infected mother to her child by placenta.
• It doesn’t spread merely by physical contact.
• Incubation period: Few months to (5 - 10) years.
• After entering body, virus enters macrophages where RNA genome replicates to form viral DNA by enzyme reverse transcriptase.
• Viral DNA incorporates into host’s cell DNA and direct infected cells to produce virus particles. Macrophages produce more virus, so called HIV factory.
• HIV enters helper T lymphocytes (T_H), replicates and produce virus, which attack other helper T cells. This leads to decrease in T -helper cells.
• Symptoms: Fever, diarrhoea, weight loss, immuno deficient, decrease in T-cells cause infections from Tozoplasma (parasite), Mycobacterium, virus, fungi.
• Diagnosis: Enzyme linked immuno sorbent assay (ELISA).
• Treatment: Anti retroviral drugs, prolong life but can’t prevent death.
• National AIDS Control Organisation (NACO), WHO, other Non-Governmental Organisation (NGOs) has started programmes to prevent spreading of HIV infection.

Cancer: One of the most dreaded disease.

• Contact Inhibition: Cell growth and differentiation is highly controlled, contact with other cells inhibit uncontrolled growth, absent in cancer cells.
• Cancerous cells just divide to give rise to masses of cells - tumors.
• Benign tumors: Remain confined to original location, don’t spread, cause little damage.
• Malignant tumors: Mass of proliferating cells (neoplastic/tumor cells) grow rapidly, invade and damage other cells, starve normal cells by competing for vital nutrients, most feared property - metastasis (cells sloughed from such tumors reach distant sites, lodge and start new tumor).
• Causes: Agents are carcinogens (may be physical, chemical or biological).
• Ionising radiation: X-rays and gamma X-rays; non- ionising - UV cause DNA damage leading to neoplastic transformation.
• Chemical carcinogens: Tobacco smoke cause lung cancer.
• Oncogenic viruses: Cancer causing virus have genes - viral oncogenes. Cellular oncogenes/proto oncogenes are present in normal cells which when activated lead to oncogenic transformation of cells.

Detection and diagnosis:

• Bone Marrow Test: Increased cell count (eg. leukemia).
• Biopsy: Piece of suspected tissue cut into thin sections is stained and examined (histopathological study).
• Radiography: Use of X-rays.
• Computed Tomography (CT): Use X-rays to generate 3 D image of internal objects.
• Magnetic Resonance Imaging (MRI): Use strong magnetic fields and non-ionising radiations to detect changes in tissue.
• Antibodies against cancer specific antigens detect cancers.
• Techniques of molecular biology detect genes susceptible to cancers.

Treatment: Surgery, immunotherapy, radiotherapy, chemotherapy.

• Radiotherapy: Tumor cells are irradiated lethally.
• a - interferon: Biological response modifiers which activates immune system and destroys tumor.
• Some drugs have side effects like hair loss, anaemia etc.

Drugs and Alcohol Abuse:

1.     Opioids: Bind to opioid receptors in CNS and gastrointestinal tract.

• Heroin: Commonly called smack, chemically diacetylmorphine, white, bitter crystalline, odourless compound, by acetylation of morphine (extracted from latex of poppy plant papaver somniferum), depressant.
• Taken by snorting and injection

2.     Cannabinoids: Interact with receptors in brain.

• From inflorescences of plant Cannabis sativa, used to produce marijuana, hashish, charas and ganja.
• Effects cardiovascular system.
• Taken by inhalation and oral ingestion.

3.     Coca alkaloids: (Cocaine) stimulating action on CNS.

• From coca plant Erythroxylem coca (native to South America).
• Interferes with transport of neuro transmitter dopamine.
• Produce sense of euphoria, increased energy, hallucination in excessive dosage.
• Cocaine/coke/crack is snorted, abused by sportspersons.

• Other plants Atropa belladona and Datura.

Medicinal drugs: barbiturates, amphetamines, benzodiazepines.

• Help to cope up mental illness like depression and insomnia.
• Morphine: Effective sedative and painkiller.
• When they are taken for other purpose- drug abuse.
• Smoking: Increases carbon monoxide (CO) in blood and reduces concentration of haembound oxygen, cause oxygen deficiency.
• Increases chances of cancers of lung, urinary bladder and throat, bronchitis, emphysema, coronary heart diseases, gastric ulcers etc.
• Tobacco: Contains nicotine (alkaloid which stimulate adrenal gland to release adrenaline and nor-adrenaline into blood increasing BP and heart rate). It increases risk of cancer of oral cavity. It is smoked, chewed or used as snuff.

Adolescence and Drug Abuse:

• Adolescence: Period during which child becomes mature in attitudes and belief; its a bridge linking childhood and adulthood (12 -18 years of age). Its a vulnerable phase of mental and psychological development.
• First use may be out of curiosity and experimentation but becomes a way to escape problems.
• Causes: Pressure to excel in academics, unstable family structure, internet, TV etc.

Addiction and Dependence:

• Addiction: Psychological attachment to certain effects - euphoria and temporary feeling of well being.
• It drives people to intake them even when not needed - self destructive. So, tolerance level of receptors increase, leading to greater intake.
• Dependence: Tendency of body to manifest a characteristic and unpleasant withdrawal syndrome if regular dose is disrupted. It leads to anxiety, nausea, shakiness, sweating and social adjustment problems.

Effect of Drug! Alcohol Abuse:

• It leads to reckless behaviour, vandalism, violence, respiratory failure, heart failure or cerebral hemorrhage, damage CNS, liver (cirrhosis).
• Warning signs: Drop in academic performance, isolation, depression, aggression, loss of interest in hobbies, fluctuation in weight, appetite, change in sleeping pattern etc.
• Intravenous drugs may cause AIDS and Hepatitis B.
• Sportsperson misuse narcotic analgesics, anabolic steroids, diuretics to increase muscle strength, promote aggressiveness, hence increase athletic performance.
• Effects on female: Masculisation, aggressiveness, mood swings, depression, abnormal menses, hair growth on -face, enlargement of clitoris, deepening of voice.
• Effects on male: Acne, aggressiveness, mood swings, depression, reduction of size of testicles, decreased sperm production, kidney and liver dysfunction, premature baldness, breast enlargement, enlargement of prostate gland.

Prevention and Control:

• Avoid undue peer pressure.
• Educate and counsel them to accept disappointments and failures.
• Seek help from parents and peers.
• Look for danger signs to initiate remedial steps.
• Seeking professional and medical help.