Pathogens enter the body through various routes: air (respiratory tract), contaminated food/water (digestive tract), skin contact, insect bites, or sexual contact.
3. Describe the modes of transmission of communicable diseases.
Answer
Communicable diseases spread through:
1. Direct contact:
Answer
Person-to-person physical contact
Example: Ringworm, chickenpox, STDs
2. Indirect contact — through contaminated objects (fomites):
Colostrum (mother's first milk) to baby; antiserum injection (anti-snake venom)
5. What are vaccines? How do they work? Give examples.
Answer
Vaccines are biological preparations that provide immunity against specific diseases by stimulating the immune system without causing the actual disease.
How vaccines work: 1. Vaccine is introduced into the body (injection, oral, or nasal) 2. It contains weakened/killed pathogens, or their antigens (surface proteins) 3. The immune system recognises these antigens as foreign and mounts an immune response 4. B lymphocytes produce antibodies and memory cells are formed 5. On future exposure to the actual pathogen, memory cells enable a rapid, strong immune response → disease is prevented or quickly overcome
Airborne — droplets from coughing, sneezing, speaking of infected person
Primarily affects
Lungs (pulmonary TB)
Symptoms
Persistent cough (often with blood), fever, night sweats, weight loss, fatigue
Diagnosis
Mantoux test, sputum culture, chest X-ray
Treatment
DOTS (Directly Observed Treatment Short course) — 6-month antibiotic regimen
Prevention
BCG vaccine, early detection, good ventilation, avoiding crowding
📚 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 definition emphasises that health has three components — physical (body functioning well), mental (emotional and psychological well-being), and social (ability to interact and contribute to society).
