Understanding Health, Diseases, and the Immune System

Twins and Multiple Births

Twins originate from the same egg and sperm that then divides into two embryos. These embryos share the same genetic material. On the other hand, fraternal twins develop from two separate eggs and two sperm cells. Genetically, they are like siblings but born at the same time.

Puberty

Puberty is the life stage where a person develops secondary sexual characteristics and achieves reproductive capability. It's the initial phase of adolescence, marking the transition from childhood to adulthood.

Diseases and Health

Causes of Diseases

Degenerative diseases involve the progressive destruction of tissues. Affected organs gradually deteriorate, as seen in Alzheimer's disease.

Health

Health is a state of complete physical, mental, and social well-being.

• Physical Health: Means the body's systems are functioning correctly.
• Mental Health: Refers to a person's emotional and psychological balance.
• Social Well-being: A state where basic human needs are met.

Disease Classifications

• Endemic: A disease present in a specific region or population (e.g., malaria).
• Epidemic: A disease that spreads rapidly, affecting many people simultaneously (e.g., the flu).
• Pandemic: A disease affecting a vast geographical area (e.g., AIDS).

Types of Pathogens

• Viruses: Not considered true living organisms as they require a host cell to reproduce.
• Bacteria: Unicellular prokaryotic microorganisms that cause diseases like salmonella.
• Fungi: Multicellular and unicellular eukaryotic microorganisms that cause diseases like athlete's foot.
• Protozoa: Unicellular eukaryotic microorganisms that cause diseases like malaria.

Immune Responses

Non-Specific Immune Response

This response is carried out by phagocytes, a type of white blood cell. It's the same for all pathogens. When pathogens enter the body:

1. Capillaries in the area dilate, increasing blood flow.
2. Capillary permeability increases, causing blood to leave the vessels and flow to the injured area, leading to swelling.
3. Monocytes that have left the blood vessels become phagocytes.
4. Phagocytes wrap their cellular projections around pathogens, ingesting and destroying them.

Specific Immune Response

Lymphocytes (T and B cells) recognize antigens entering the body.

1. T and B cells recognize the antigen, bind to it, and become activated.
2. Activated T and B cells divide.
3. T cells become cytotoxic T cells, which destroy cells containing antigens.
4. B cells become plasma cells, which produce antibodies that neutralize the antigen.