What is the difference between innate and acquired immunity?

Innate immunity is the non-specific, first line of defence that is present from birth — it includes physical barriers (skin), chemical barriers, and non-specific cells (neutrophils, macrophages). Acquired (adaptive) immunity develops after exposure to a specific antigen and is antigen-specific, includes B cells (antibodies) and T cells, and has immunological memory.

What is a vaccine and how does it work?

A vaccine is a biological preparation containing weakened, killed, or partial antigens of a pathogen. When administered, it stimulates the immune system to produce antibodies and memory cells against those antigens, without causing the disease. If the person is later exposed to the real pathogen, the immune system responds quickly and strongly, preventing or reducing the severity of illness.

Samacheer Kalvi 10th Science Chapter 19 Long Answer Questions — Health and Diseases with Answers

Question 1: Define health. Classify diseases and explain the types of diseases with examples.

Answer:

Definition of Health:

WHO Definition (1948): Health is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity."

This definition recognises three dimensions of health:

Physical health: The body functions normally, free from illness or injury
Mental health: Emotional and psychological well-being; ability to think clearly and cope with stress
Social health: Ability to maintain positive relationships and function effectively in society

Classification of Diseases:

Diseases can be classified based on different criteria:

A. Based on Duration:

1. Acute Diseases:

Answer

Develop suddenly, are severe, and last for a short period (days to weeks)
e.g., Common cold, influenza, food poisoning, typhoid

2. Chronic Diseases:

Answer

Develop gradually and persist for a long period (months to years or lifelong)
e.g., Diabetes mellitus, hypertension, tuberculosis, arthritis, cancer

B. Based on Causative Agent:

1. Communicable (Infectious) Diseases:

Answer

Caused by pathogenic microorganisms (viruses, bacteria, fungi, protozoa, helminths)
Can spread from one person to another (directly or indirectly)
e.g.:
Viral: Influenza, HIV/AIDS, Measles, Dengue, Hepatitis
Bacterial: Tuberculosis, Typhoid, Cholera, Tetanus, Pneumonia
Fungal: Ringworm, Athlete's foot, Candidiasis
Protozoan: Malaria, Amoebiasis, Sleeping sickness
Helminthic: Ascariasis (roundworm), Filariasis (elephantiasis)

2. Non-Communicable (Non-infectious) Diseases:

Answer

Not caused by pathogens; cannot spread from person to person
e.g.:
Lifestyle diseases: Diabetes, obesity, hypertension, cardiovascular disease
Genetic disorders: Sickle cell anaemia, haemophilia, Down syndrome
Deficiency diseases: Scurvy (Vitamin C), Rickets (Vitamin D), Night blindness (Vitamin A), Anaemia (Iron)
Degenerative diseases: Arthritis, Alzheimer's disease, Parkinson's disease
Cancer: Abnormal cell growth

C. Based on Organ System Affected:

Cardiovascular disease (heart and blood vessels)
Respiratory disease (lungs)
Renal disease (kidneys)
Neurological disease (nervous system)

D. Based on Cause:

Congenital Diseases:

Present from birth; may be genetic or due to developmental problems during foetal development
e.g., Congenital heart disease, Down syndrome, cleft palate

Hereditary (Genetic) Diseases:

Transmitted through genes from parents to offspring
e.g., Haemophilia, colour blindness, sickle cell anaemia, cystic fibrosis

Acquired Diseases:

Develop after birth; not present at birth
e.g., Tuberculosis, AIDS, diabetes (Type 2)

Degenerative Diseases:

Caused by deterioration of organs or tissues, often age-related
e.g., Osteoarthritis, Alzheimer's, macular degeneration

Question 2: Explain the modes of transmission of communicable diseases and the ways to prevent them.

Answer:

Communicable diseases are infectious diseases that can be transmitted from one individual to another. Understanding transmission is crucial for prevention and control.

Modes of Transmission:

A. Direct Transmission (Person to Person):

1. Droplet Infection (Airborne / Droplet transmission):

Answer

Pathogens are released into the air in tiny droplets from an infected person's respiratory secretions (coughing, sneezing, talking)
These droplets are inhaled by a susceptible person nearby
Range: droplets travel up to 1–2 metres; aerosols can travel farther
Examples: Influenza, Common cold, Tuberculosis, Measles, COVID-19, Chickenpox, Whooping cough

2. Direct Contact:

Answer

Physical contact between an infected person and a healthy person
Skin contact: Fungal infections (ringworm, athlete's foot), impetigo, scabies
Sexual contact: HIV/AIDS, Syphilis, Gonorrhoea, Hepatitis B (Sexually Transmitted Infections/STIs)
Blood contact: HIV, Hepatitis B and C (sharing needles, blood transfusion with infected blood)
Mother to child (Vertical transmission): HIV, Rubella, Hepatitis B can pass from mother to foetus/newborn via placenta, during birth, or through breast milk

B. Indirect Transmission:

3. Vehicle-borne Transmission (Contaminated food and water):

Answer

Pathogens survive in food or water and infect individuals who consume them
Faecal-oral route: Contaminated water/food → ingestion
Examples: Cholera (Vibrio cholerae in contaminated water), Typhoid (Salmonella typhi), Hepatitis A, Polio, Amoebiasis, Food poisoning

4. Vector-borne Transmission:

Answer

A vector is an arthropod (mosquito, fly, tick) that carries the pathogen from an infected host to a healthy host
Mechanical vector: Housefly (Musca domestica) carries pathogens on its body/legs — spreads cholera, typhoid, dysentery
Biological vector: Pathogen completes part of its life cycle inside the vector
Anopheles mosquito → Malaria (Plasmodium parasite)
Aedes mosquito → Dengue fever, Chikungunya, Zika virus
Culex mosquito → Filariasis (elephantiasis) (Wuchereria bancrofti)

5. Contact with Contaminated Objects (Fomites):

Answer

Pathogens survive on inanimate objects (fomites) — doorknobs, handkerchiefs, clothing, utensils — and are transferred to a new host by touch
e.g., Cold and flu viruses on surfaces; ringworm from contaminated towels

6. Soil and Animal Transmission (Zoonoses):

Answer

Zoonosis: Disease transmitted from animals to humans
e.g., Rabies (dog/bat bite), Plague (rat fleas), Anthrax (soil/cattle), Avian influenza (birds), Leptospirosis (rats)
Soil-borne: Tetanus (Clostridium tetani spores in soil enter through wounds)

Prevention of Communicable Diseases:

1. Personal Hygiene:

Answer

Regular handwashing with soap (especially before eating and after using the toilet)
Covering nose and mouth while coughing/sneezing
Safe sexual practices (condom use)
Not sharing personal items (towels, razors, needles)

2. Environmental Sanitation:

Answer

Safe drinking water (chlorination, boiling, filtration)
Proper sewage disposal
Food safety and hygiene
Control of vector breeding sites (drain stagnant water, use mosquito nets, insecticides)

3. Vaccination:

Answer

Immunisation against diseases like Polio, Measles, Tuberculosis (BCG), Hepatitis B, Typhoid, Influenza

4. Quarantine and Isolation:

Answer

Isolating infected individuals to prevent spread to others

5. Health Education:

Answer

Public awareness about transmission and prevention

Question 3: Describe the human immune system. Differentiate between innate and acquired immunity.

Answer:

The immune system is the body's defence mechanism against pathogens (bacteria, viruses, fungi, parasites) and foreign substances (antigens). It can distinguish between self (the body's own cells) and non-self (foreign substances).

A. Innate (Non-specific) Immunity:

Innate immunity is the first line of defence, present from birth. It is non-specific (responds to any pathogen in the same general way) and does not have immunological memory.

Components of Innate Immunity:

Physical (Mechanical) Barriers:

Skin: Intact skin is an impermeable barrier. Sebum (oily secretion) has antimicrobial properties (lactic acid and fatty acids lower pH).
Mucous membranes: Line the respiratory, digestive, and urogenital tracts. Mucus traps pathogens. Cilia sweep mucus (and trapped pathogens) upward (mucociliary escalator in the trachea).
Tears: Contain lysozyme (enzyme that breaks bacterial cell walls).
Saliva: Contains lysozyme and antibodies (IgA).
Earwax (cerumen): Traps dust and microorganisms.
Stomach acid (HCl): Very low pH kills most swallowed microorganisms.

Cellular Innate Immunity:

Neutrophils: Most abundant WBCs; first responders; phagocytose (engulf and destroy) bacteria and fungi
Macrophages: Derived from monocytes; phagocytose pathogens and present antigens to lymphocytes; produce cytokines (chemical signals that coordinate immune response)
Natural Killer (NK) cells: Kill virus-infected cells and tumour cells
Mast cells and Basophils: Release histamine and other chemicals in allergic and inflammatory responses
Dendritic cells: Phagocytose pathogens and present antigens to T cells — bridge between innate and acquired immunity
Complement System: A series of proteins in blood that are activated by pathogens — can directly lyse (burst) bacteria, tag pathogens for destruction (opsonisation), and attract phagocytes

Inflammatory Response:

When tissues are damaged or infected, mast cells and macrophages release histamine and other mediators
Signs of inflammation: Redness (vasodilation → increased blood flow), heat (increased metabolism), swelling (increased vascular permeability → fluid leakage into tissues), pain (prostaglandins stimulate nerve endings)
Inflammation recruits more phagocytes to the site of infection

Fever:

Elevated body temperature in response to infection (pyrogens released by macrophages act on the hypothalamus)
Mild fever helps by: inhibiting bacterial/viral replication, enhancing immune cell activity, increasing antibody production

B. Acquired (Adaptive) Immunity:

Acquired immunity develops in response to a specific antigen encountered during the organism's lifetime. It is antigen-specific, has immunological memory, and is much more powerful than innate immunity.

Characteristics:

Specificity: Each lymphocyte recognises and responds to one specific antigen
Diversity: Millions of different lymphocyte clones, each specific for a different antigen
Memory: After the first exposure (primary response), memory cells remain and allow a faster, stronger response (secondary response) upon re-exposure
Self-tolerance: Does not attack the body's own cells (normally)

Two Types of Acquired Immunity:

1. Humoral Immunity (Antibody-mediated):

Answer

Mediated by B lymphocytes (B cells)
B cells mature in bone marrow
When a B cell encounters its specific antigen, it is activated (with help from T helper cells), proliferates, and differentiates into:
Plasma cells: Produce antibodies (immunoglobulins) specific to that antigen
Memory B cells: Long-lived cells that remain and respond quickly if the same antigen is encountered again
Antibodies (Immunoglobulins — IgG, IgM, IgA, IgE, IgD):
Y-shaped proteins with antigen-binding sites
Neutralise pathogens (block their ability to infect cells)
Tag pathogens for destruction by phagocytes (opsonisation)
Activate complement system
Effective against: extracellular bacteria, viruses in the blood, toxins

2. Cell-mediated Immunity:

Answer

Mediated by T lymphocytes (T cells)
T cells mature in the thymus
Three main types:
T Helper cells (CD4+ T cells): Coordinate the immune response by releasing cytokines; activate B cells and cytotoxic T cells
Cytotoxic T cells (CD8+ T cells / killer T cells): Directly kill cells infected with viruses, bacteria, or cancer cells by releasing perforin and granzymes
Regulatory T cells (Tregs): Suppress the immune response to prevent autoimmunity
Memory T cells: Long-lived; respond rapidly upon re-exposure
Effective against: intracellular pathogens (viruses inside cells), cancer cells, transplant rejection

Summary Comparison:

Feature	Innate Immunity	Acquired Immunity
Specificity	Non-specific	Highly specific
Speed of response	Immediate (hours)	Slow (days to weeks for first response)
Memory	No	Yes (immunological memory)
Components	Skin, mucus, phagocytes, NK cells	B cells, T cells, antibodies
Effectiveness	Moderate	Very high
Present at birth	Yes	Develops after antigen exposure

Question 4: Describe lifestyle diseases with special reference to diabetes, hypertension, and cancer.

Answer:

Lifestyle diseases (also called non-communicable diseases or diseases of affluence) are diseases that are primarily caused by unhealthy lifestyle choices including poor diet, physical inactivity, tobacco use, excessive alcohol consumption, and chronic stress. They are not caused by pathogens and cannot be spread from person to person.

1. Diabetes Mellitus:

Definition: A group of metabolic disorders characterised by persistent high blood glucose levels (hyperglycaemia) due to deficiency or ineffectiveness of insulin.

Types:

Type 1 Diabetes (Insulin-Dependent Diabetes Mellitus/IDDM):
Autoimmune destruction of insulin-producing beta cells in the pancreas
Body produces no insulin
Usually diagnosed in childhood or young adulthood
Must be treated with daily insulin injections
Not primarily a lifestyle disease (autoimmune cause)

Type 2 Diabetes (Non-Insulin-Dependent Diabetes Mellitus/NIDDM):
Body cells become resistant to insulin OR pancreas produces insufficient insulin
Most common form (90% of all diabetes cases)
Strongly linked to obesity, sedentary lifestyle, unhealthy diet, and ageing
Can often be managed with diet, exercise, and oral medications; may eventually require insulin

Risk Factors for Type 2: Obesity, physical inactivity, unhealthy diet (high sugar and refined carbohydrates), family history, age over 45 years.

Symptoms: Excessive urination (polyuria), excessive thirst (polydipsia), excessive hunger (polyphagia), fatigue, blurred vision, slow-healing wounds, frequent infections.

Complications: Diabetic retinopathy (blindness), diabetic nephropathy (kidney failure), diabetic neuropathy (nerve damage), cardiovascular disease, foot ulcers and amputation.

Prevention/Management: Healthy weight, regular exercise, balanced low-sugar diet, regular blood glucose monitoring, medication.

2. Hypertension (High Blood Pressure):

Definition: A condition in which the force of blood against arterial walls is persistently elevated. Normal blood pressure is 120/80 mmHg. Hypertension is defined as blood pressure greater than 140/90 mmHg.

Systolic pressure (first number): Pressure when the heart beats
Diastolic pressure (second number): Pressure when the heart rests between beats

Types:

Primary (Essential) Hypertension: No identifiable cause; accounts for 90–95% of cases; develops gradually over years
Secondary Hypertension: Caused by an underlying condition (kidney disease, thyroid disorder, hormone abnormalities)

Risk Factors: Excess dietary salt, obesity, sedentary lifestyle, smoking, excessive alcohol, chronic stress, age, family history.

Symptoms: Often called the "silent killer" — usually has no symptoms until very advanced. May cause headaches, vision problems, chest pain in severe cases.

Complications:

Heart attack (myocardial infarction)
Stroke (cerebrovascular accident)
Heart failure
Kidney damage
Retinopathy (damage to blood vessels in the eye)

Prevention/Management: Reduce salt intake (less than 5g/day), regular exercise, healthy weight, limit alcohol, quit smoking, stress management, antihypertensive medications (if needed).

3. Cancer:

Definition: Cancer is a group of diseases characterised by uncontrolled, abnormal cell division and the ability to invade or spread to other parts of the body (metastasis).

Characteristics of Cancer Cells (vs Normal Cells):

Divide uncontrollably (no contact inhibition)
Do not respond to normal growth-stopping signals
Are immortal (do not undergo apoptosis/programmed cell death normally)
Can invade neighbouring tissues
Can spread to distant organs through the blood and lymphatic system (metastasis)

Causes of Cancer (Carcinogens):

Chemical carcinogens: Tobacco smoke (lung, mouth, throat cancer), alcohol (liver, mouth cancer), asbestos (mesothelioma), benzene (leukaemia)
Physical carcinogens: UV radiation (skin cancer — melanoma, basal cell carcinoma), X-rays and other ionising radiation
Biological carcinogens: Certain viruses — Human Papillomavirus/HPV (cervical cancer), Hepatitis B and C viruses (liver cancer), Epstein-Barr virus (lymphoma); Helicobacter pylori bacteria (stomach cancer)
Genetic factors: Inherited mutations (BRCA1/BRCA2 genes → breast and ovarian cancer)

Types of Cancer (based on tissue of origin):

Carcinoma: Cancer of epithelial tissue (most common — skin, lung, breast, colorectal, prostate)
Sarcoma: Cancer of connective tissue (bone, muscle, cartilage)
Leukaemia: Cancer of blood-forming cells (bone marrow) — excessive abnormal WBCs
Lymphoma: Cancer of lymphocytes in lymph nodes and other lymphoid tissue

Warning Signs of Cancer (CAUTION mnemonic): Change in bowel/bladder habits, A sore that doesn't heal, Unusual bleeding/discharge, Thickening/lump in breast or elsewhere, Indigestion/difficulty swallowing, Obvious change in a wart/mole, Nagging cough/hoarseness.

Treatment:

Surgery: Remove the tumour
Radiation therapy (Radiotherapy): X-rays or gamma rays to kill cancer cells
Chemotherapy: Drugs that kill rapidly dividing cells
Immunotherapy: Use the immune system to fight cancer (checkpoint inhibitors, CAR-T cell therapy)
Targeted therapy: Drugs that target specific molecules in cancer cells (e.g., Imatinib for chronic myeloid leukaemia)
Hormone therapy: For hormone-sensitive cancers (breast, prostate)

Prevention:

Avoid tobacco and alcohol
Protect skin from UV radiation (sunscreen, avoid prolonged sun exposure)
HPV vaccination (prevents cervical cancer)
Regular screening (mammography, colonoscopy, Pap smear)
Healthy diet, exercise, and maintaining healthy weight

📚 Samacheer Kalvi 10th Science Guide — Buy Online

Frequently Asked Questions

According to the World Health Organization (WHO), health is 'a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.' This holistic definition was adopted in 1948.