Question

*explain the features of the epidermis--include type(s) of tissue it’s composed of: (p. 185-6)

● if the epidermis has no direct blood supply, how are epidermal cells supplied with nutrients?

● what happens as the older epidermal cells are pushed up to the surface away from their nutrient source?

*explain the features of the dermis- include type(s) of tissue it’s composed of: (p. 190-1)

● a tattoo is created when ink is injected into the dermis--why will the tattoo be permanent?

Explanation:

1. Epidermis features and nutrient - supply: The epidermis is composed of stratified squamous epithelium. Since it has no direct blood supply, epidermal cells receive nutrients via diffusion from the underlying dermis. As older epidermal cells are pushed to the surface away from the nutrient source, they become keratinized and eventually slough off.
2. Dermis features and tattoo permanence: The dermis is composed of dense irregular connective tissue (collagen and elastic fibers). Tattoos are permanent because the ink is injected into the dermis. Dermal cells do not shed as frequently as epidermal cells, and the immune system's macrophages engulf the ink particles but do not completely remove them, keeping the ink in place.

Answer:

1. The epidermis is composed of stratified squamous epithelium. Epidermal cells get nutrients by diffusion from the dermis. Older cells pushed to the surface become keratinized and slough off.
2. The dermis is composed of dense irregular connective tissue. Tattoos are permanent because ink in the dermis is not easily removed as dermal cells do not shed rapidly and macrophages retain ink particles.