Anatomy and Physiology?

Question

Keratinocytes
a. are found in both the dermal and epidermal layers of the skin
b. are responsible for the permeability characteristics of the epidermis
c. determine thickness of the skin
d. are special cells of the immune syster

Answer 1

The correct answer is c. Keratinocytes are the keratin-producing cells that form the majority, 90%, of the epidermis. Answer a is wrong due to the fact that keratinocytes are not found in the dermis. Keratinocytes are produced from stem cells that are positioned directly above the dermis. There are 5 layers of epidermis, and the first layer, called the stratum basale, is formed at the junction with the dermis. During keratinocyte production, the cells are pushed upward, not downward, as every 28 days these keratinocytes, producing sqaumous epitheliial cells, are sloughed off of the body. Answer A is Incorrect.
Answer B is also incorrect. In fact, keratinocytes do the exact opposite. When these cells reach the stratum corneum, the outermost region of the epidermis, the keratinocytes become highly flattened, enucleated, and are highly filled with keratin, a structural protein. This outer epidermal layer serves as the body's first defense against the outside world, effectively shileding the body. It protects against viral infection, and also forms an effective barrier against many other infectious agents. This outermost layer also serves as a means to prevent water loss and serves this purpose quite well by minimizing water loss. So, answer B is Wrong.
Answer D is wrong because keratinocytes are not cells of the immune system, also called lymphocytes. Keratinocytes are epithelial cells and are not considered to be immune system cells. Although keratinocytes contribute as a barrier against infection, these cells are not grouped together with the lymphocytes of the immune system. So, answer D is Wrong.

Answer C is CORRECT. The keratinocytes, or the cells forning 90% of the epidermis, are responsible for the thickness of the skin. The evidenced supporting this fact is shown by the layers of the epidermis, which can be 4 or 5 layers, depending upon the location of the skin. The 5 layers of the skin are: 1. stratum basale - forms at the juntion with the dermis; 2- stratum spinosum; 3 - stratum granulosum; 4 -stratum lucidum; 5 - stratum corneum. Layer 4, the stratum lucidum is found only in thick skin, such as the bottom of the feet and the palms of the hand. Other areas of the epidermis do not have this extra layer of skin, and are, therefore, thinner.
Answer C is Correct.

Answer 2

i think the answer is a. The keratinocytes it is the major type of cell of the epidermis.

Answer 3

the answer is
c. determine thickness of the skin

Answer 4

a

Answer 5

Madscientist is spot on.

Answer 6

b