Epidermis and Cell Types

Question 1

Stratum Corneum

Answer 1

Top layer of the epidermis, 25-30 layers of dead flattened keratinocytes. the cells are extremely thin, flat, plasma membrane-enclosed packages of keratin that no longer contain a nucleus or any internal organelles.

Question 2

Stratum Lucidum

Answer 2

Present only in the thick skin of areas such as fingertips, palms, and soles. 2nd layer. consists of 4-6 layers of flattened clear, dead keratinocytes.

Question 3

Stratum Granulosum

Answer 3

3rd layer of the epidermis. consists of 3-5 layers of flattened keratinocytes that are undergoing apoptosis (cell death). A distinctive feature is darkly staining granules. Marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata.

Question 3

Stratum Spinosum

Answer 3

4th layer of the epidermis. Mainly consists of numerous keratinocytes arranged in 8-10 layer. Cells in the more superficial layers become flattened. Macrophages, projections of melanocytes, and keratinocytes are present in this layer.

Question 4

Stratum Basale

Answer 4

the deepest layer of the epidermis, made of a single row of cuboidal or columnar keratinocytes. some cells in this layer are stem cells. large nuclei. also known as stratum germinativum.

Question 5

Melaninocytes

Answer 5

8% of epidermal cells. These produce the pigment melanin. their long projections extend between the keratinocytes and transfer melanin granules to them. Usually found at the bottom. Melanin is a yellow-red or brown-black pigment that protects against UV rays.

Question 6

Langerhans Cells

Answer 6

Also known as intraepidermal macrophages. come from red bone marrow and rise to the surface. they participate in immune responses, they are easily damaged by UV light. role is to help other cells of the immune system recognizing a microbe and destroying it.

Question 7

Merkel Cells

Answer 7

Also known as tactile epithelial cells. Least numerous of the epidermal cells. located in the deepest layer of the epidermis. they conact the flattened proccess of a sensory neuron. (a structure known as a merkel disc.) These detect touch sensations.

Question 8

Keratinocytes

Answer 8

90% of epidermal cells. arranged in 4-5 layers and produce the protein keratin. they also produce lamellar granules, that release a water-repellant sealant that decreases water entry.

Question 9

Stem Cells

Answer 9

unspecialized cells that can develop into many different types of cells in the body. they function in repair, self renewal, and differentiation. 2 types: embryonic(turn into any cell) and adult(can only turn into a specialized cell)