The integumentary system serves as the first line of defense against pathogens, comprising skin, hair, feathers, and scales. These structures act as innate immune defenses, protecting animals from injuries, diseases, and parasites. One crucial component that helps prevent the entry of pathogens is the __________, which acts as a physical barrier.

The integumentary system’s first line of defense is the skin, which forms a tough outer layer that blocks bacteria, viruses, and parasites from entering the body. The epidermis, the topmost layer of the skin, is made of tightly packed cells that create a physical barrier. It also produces antimicrobial peptides that kill microbes that touch the surface. For example, the skin’s keratinized cells seal wounds and prevent infection, keeping the body safe from everyday germs.