BIOS 251 Week 4 Case Study: Tissue – Graded An A+

BIOS 251 Week 4 Case Study: Tissue – Graded An A+ Describe the five different layers of the skin. The five layers of the skin are known as the epidermis, which is divided further into five different layers. The layers are stratum corneum, stratum lucidum, spinosum, granulosum, and stratum basale. All five of these layers contain different characteristics and responsibilities for the skin. - Stratum corneum is the most superficial layer and is the one that is visible, so an individual can see this layer with their eyes. In the article Skin 1: the structure and functions of the skin by writer Sandra Lawton she states that within this layer it is made up of dead skin cells that are filled with keratin, a tougher protein (Lawton, 2021). The components of this layer not having a nucleus or water present make it waterproof. - In the article previously stated by Sandra Lawton states that Stratum lucidum is the next layer which contains dead keratinocytes due to the further distance from the surface and inability for rich blood supply (Lawton, 2021). This is the layer that is most found in palms of the hands or soles of the feet where the skin is thickest. - The Spinosum and Granulosum layers are the next layers. In the book Anatomy and Physiology: Unity of Form and Function by Kenneth Saladin he states that these layers both contain cells that are spiny-shaped due to having the responsibility of the skin's strength and flexibility (Saladin, 2019). - Stratum basale is the deepest layer of skin. This layer is the basal layer which is the innermost layer of the epidermis. The stratum basale is located near the blood supply of the dermis and its cells are the only ones capable of mitosis while containing keratinocytes. This layer moves upwards as the cells age until they have reached the outermost layer of the skin: the stratum corneum. Describe the four different cell junctions. The four different cell junctions include that of tight junctions, adherens junctions, desmosomes, and gap junctions. These each contain their own function and characteristics. - Tight junctions connect nearby cells and close off the intercellular gap, forcing things to move through the cell rather than between them. - Adherens junctions link microfilaments and connect two cells together. - Desmosomes in the book Anatomy and Physiology: Unity of Form and Function by Kenneth Saladin states that desmosomes are a “patch that holds cells together... not continuous and cannot stop chemicals from going around them,” (Saladin, 2019). They're well known for being able to withstand mechanical tension between cells. Half- desmosomes connect basal cells to the basement membrane and are a form of desmosome. - Gap junctions are junctions that merge to form connexons, a ring-like structure. These junctions allow for material transport as well as communication between all cells. What is the purpose of the plakophilin gene? The plakophilin gene is responsible for the production of a protein known as plakophilin 2. In the article Plakophilin-2 is required for transcription of genes that control calcium cycling and cardiac rhythm the several authors state that Plakophilin 2 is a protein that is found in the desmosomes of cellular junctions that helps aid structural integrity (Cerrone, et. al., 2017). This explains that the plakophilin gene is all about structure and sticks to that. It won't shy away from what it is known to do. How would mutations in the plakophilin gene disrupt cell-to-cell interactions? Mutations in the plakophilin gene disrupt cell to cell interactions in that the Plakophilin 2 is a desmosome junction protein. In the article previously stated by Cerrone, et. al., the authors state “Desmosomes serve as a link between myocytes and intermediate cells,” (Cerrone, et. al., 2017). Myocytes are what generates tiny electrical impulses that tell the heart to beat and sends that to intermediate cells which are cells that vary in sizes and shapes. According to an article by Cerrone and multiple authors stated previously that the plakophilin gene protein “Participates in intercellular coupling and interacts with voltage-gated sodium channel complexes,” (Cerrone, et. al., 2018). Desmosome connections become weaker when the plakophilin 2 gene is mutated, and mechanical stress can induce structural anomalies in places like the heart, leading to sudden cardiac arrest. How would mutation in the plakophilin gene lead to hyperhidrosis? Overactive sweat glands can produce hyperhidrosis, which is defined as abnormally excessive amounts of sweating that is not always connected to heat or a form of exercise. In the article Hyperhidrosis by the Mayo Clinic states that sweat glands are found in epithelial cells, which are joined by cellular junctions such as desmosomes, a mutation in the plakophilin 2 gene could affect communication between these cells (Mayo Clinic, 2020). Desmosome junctions normally prevent material from passing between cells, but a mutation in plakophilin 2 could make these junctions weak, allowing water to pass through, making heavy sweating easier to seep through the skin. References Cerrone, M., Montnach, J., Lin, X., Zhao, Y.-T., Zhang, M., Agullo-Pascual, E., Leo-Macias, A., Alvarado, F. J., Dolgalev, I., Karathanos, T. V., Malkani, K., Van Opbergen, C. J. M., van Bavel, J. J. A., Yang, H.-Q., Vasquez, C., Tester, D., Fowler, S., Liang, F., Rothenberg, E., … Delmar, M. (2017, July 24). Plakophilin-2 is required for transcription of genes that control calcium cycling and cardiac rhythm. Nature News. Retrieved September 22, 2021, from Lawton, S. (2021, August 16). Skin 1: The structure and functions of the skin. Nursing Times. Retrieved September 22, 2021, from Mayo Foundation for Medical Education and Research. (2020, August 18). Hyperhidrosis. Mayo Clinic. Retrieved September 22, 2021, from Saladin, K. (2019). Anatomy and Physiology: The Unity of Form and Function (9th ed.). McGraw-Hill.