The Epidermis

Question 1

Stratum basale

Answer 1

1). deepest epidermal layer
2). attached to basal lamina
3). large stem cells(basal cells) replace superficial keratinocytes that are lost or shed at the epithelial surface
4). melanocytes inject melanin into keratinocytes
5). Merkel cells:
A). They are sensitive to touch, and when compressed, merkel cells release chemicals that stimulate sensory nerve endings, providing information about objects touching the skin.

Question 2

Stratum Spinosum

Answer 2

1) . Each time a basal cell divides, one of the daughter cells is pushed into the next, more superficial layer, where it begins to differentiate into a keratinocyte.
2) . keratinocytes are bound together by maculae adherens attached to tonofibrils of the cytoskeleton
3) . Langerhan cells and melanocytes are often present
4) . These cells play an important role in initiating an immune response against pathogens that have penetrated the superficial layers of the epidermis and epidermal cancer cells.

Question 3

Stratum Granulosum

Answer 3

1). keratinocytes produce keratohyalin and keratin
2). keratin fibers develop as cells become thinner and flatter
3). forms sheets of a lipid rich substance:
A). this substance will form a complete water resistant layer around the cells of the more superficial layers of the epidermis
B). This water resistant layer will prevent the diffusion of nutrients and wastes into and out of the cells, thereby causing cells in the more superficial epidermal layers to die.
4). Gradually the cell membranes thicken, the organelles disintegrate, and the cells die.

Question 4

Stratum Lucidum

Answer 4

1) . only in the thick skin of the palms and soles
2) . the cells in this layer lack organelles and nuclei and are flattened, densely packed, and filled with keratin filaments that are oriented parallel to the surface of the skin

Question 5

Stratum corneum

Answer 5

1) . consists of numerous layers of flattened, dead cells
2) . dehydrated cells lack organelles and nucleus, but still contain large amounts of keratin filaments
3) . relatively dry, which makes the surface unsuitable for the growth of many microorganisms
4) . water resistant but not waterproof
5) . permits slow water loss by insensible perspiration