Immunity Lesson 3: Defense Lines in the Skin

• The text discusses the third lesson on immunity, focusing on how the immune system works, specifically the three defense lines: first, second, and third.
• The first defense line consists of barriers on the skin surface, like the epidermis and dermis, filled with keratin to prevent microorganisms from entering the body.
• The second defense line involves the sweat glands in the dermis that produce sweat to help in excretion, containing water, salts, and nitrogenous waste products.
• Hair follicles in the dermis have sebaceous glands that secrete an oily substance to lubricate and soften hair, preventing it from becoming brittle.
• The third defense line includes specialized immune cells in deeper skin layers and melanocytes that produce melanin to give skin its color.
• The skin also plays a role in immunity by acting as a defensive barrier due to the presence of dead cells filled with keratin in the epidermis, creating a strong defense against microbial penetration.
• Sweat plays a crucial role in immunity as it excretes water, salt, and waste products from the body, contributing to both excretion and sensory functions through nerve endings.

Explore how the immune system functions through the three defense lines present in the skin, including barriers, sweat glands, sebaceous glands, and specialized immune cells. Learn how each defense line contributes to protecting the body against pathogens and maintaining overall health.