Layers of the Epidermis Quiz

Structure of the Skin

• The skin is composed of two main layers: the epidermis and the dermis.
• The epidermis is the outer layer, capable of being hard and tough, and is made up of stratified squamous epithelium.
• The epidermis is avascular, meaning it lacks blood vessels, and is composed of five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

Epidermis Layers

• Stratum basale (stratum germinativum): the deepest layer of the epidermis, where cells undergo mitosis and daughter cells are pushed upward to become the more superficial layers.
• Stratum spinosum: cells become increasingly flatter and more keratinized.
• Stratum granulosum: cells contain granules and are dying.
• Stratum lucidum: a thin, clear layer found only in thick, hairless skin of the palms of hands and soles of feet.
• Stratum corneum: the outermost layer of the epidermis, composed of dead cells filled with keratin, which prevents water loss from the skin.

Dermis

• The dermis is the layer of connective tissue that underlies the epidermis.
• It has two layers: the papillary layer and the reticular layer.
• The papillary layer is the upper dermal region, containing projections called dermal papillae that indent the epidermis above.
• The reticular layer is the deepest skin layer, containing blood vessels, sweat and oil glands, and deep pressure receptors.

Cells of the Epidermis

• Keratinocytes: the most common cell type in the epidermis, producing a fibrous protein called keratin.
• Melanocytes: cells that produce melanin, found mostly in the stratum basale.
• Epidermal dendritic cells: cells that alert and activate immune cells to a threat.
• Merkel cells: cells associated with sensory nerve endings, serving as touch receptors.

Integumentary System

• The integumentary system includes the skin, hair, nails, and associated glands.
• Body membranes are classified into epithelial membranes, connective tissue membranes, and synovial membranes.
• Epithelial membranes, including the cutaneous membrane (skin), mucous membranes, and serous membranes, cover body surfaces, line body cavities, and form protective sheets around organs.