Question

As a student in an esthetic program, Hannah is tasked with building a three-dimensional model of the layers of the skin. Her model must include captions describing each skin layer and connect skin histology and physiology to esthetics. Hannah visits a craft store to purchase supplies from which she will construct her model.

Hannah takes a break from her model building to jot down some important notes about the stratum corneum. Specifically, she indicates that this layer _____, with the cells undergoing _____ approximately every 28 days.

a) Sheds, Mitosis
b) Regenerates, Apoptosis
c) Divides, Differentiation
d) Thickens, Proliferation

Answer 1

The stratum corneum sheds dead keratinocytes, renewing itself approximately every 28 days through a natural process where new cells are pushed up from lower layers.

Step-by-step explanation:

The stratum corneum is the outermost layer of the epidermis, which is exposed to the external environment. It is composed of dead keratinocytes that have undergone a process of keratinization, where the cells fill with keratin and lose their nuclei, becoming flattened and hard. This layer serves as a waterproof barrier protecting underlying layers and helps prevent penetration by microbes and dehydration of tissues. The cells in the stratum corneum are shed periodically in a process called desquamation, and they are continually replaced by newer cells that are pushed up from the lower layers, particularly the stratum granulosum. The replacement of the entire stratum corneum takes place approximately every 28 days, making the skin fresh and healthy. Therefore, Hannah's notes should indicate that the stratum corneum sheds, with the cells undergoing this renewal process approximately every 28 days.