Final answer:
Keloids are raised hypertrophic scars that occur when the production of collagen during wound healing continues excessively, leading to prominent scar tissue that lacks normal skin structures.
Step-by-step explanation:
Keloids are an overproduction of scar tissue formed when the collagen layout process continues beyond the wound's healing phase, leading to a raised or hypertrophic scar. Unlike atrophic scars that have a sunken appearance, such as those resulting from acne or chickenpox, keloids are notably raised and can grow larger than the original wound. These collagen-rich scars result when fibroblasts produce an excess of tissue, creating a basket-weave pattern that does not regenerate the skin's typical cellular structure.
Consequently, this fibrous tissue lacks accessory skin structures like hair follicles, sweat glands, or sebaceous glands, which are typically found in normal skin.