Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Diagram 1.
Source:
https://www.mdpi.com/1422-0067/24/23/16657
Diagram 2.
Source:
https://igcse-biology-2017.blogspot.com/2017/06/328-understand-how-division-of-diploid.html
Human skin is the largest organ in the body, acting as the first barrier against the external environment. When the skin is injured - whether from a scrape, cut, or burn - it triggers a rapid and coordinated healing process that depends heavily on mitosis and cell differentiation. The outer layer of the skin, the epidermis, is constantly renewed through cell division, but during wound repair, mitosis accelerates dramatically as the body works to restore structure and function.
Immediately after an injury, damaged cells release chemical signals that recruit immune cells to remove pathogens and debris. Beneath the wound surface, basal stem cells in the epidermis begin dividing rapidly through mitosis. These new daughter cells migrate upward, eventually differentiating into the specialized keratinocytes that rebuild the protective outer layer. In deeper wounds that reach the dermis, fibroblasts divide and differentiate into cells that produce collagen to rebuild connective tissue.
Mitosis plays a critical role in increasing the number of replacement cells, but the healing process would not succeed without differentiation, the process by which unspecialized cells become specialized for specific tasks. Keratinocytes harden and form new skin layers, fibroblasts produce extracellular matrix, and endothelial cells create new blood vessels during angiogenesis. Together, this coordinated sequence restores both the structure and function of the skin.
Scientists measure wound healing using metrics such as mitotic index (percentage of dividing cells), wound closure time, changes in cell type proportions, and collagen production rates. Data consistently show that wounds with higher early mitotic activity close faster and form more functional tissue. Environmental factors - such as temperature, hydration, and infection - can alter mitosis and differentiation, affecting overall healing success.
Without rapid mitosis and precisely regulated differentiation, the body could not replace lost skin, defend against pathogens, or maintain homeostasis. Wound healing demonstrates how these processes work together to ensure survival.
Table 1.
Days After Injury | Mitotic Index % | Wound Closure % |
|---|---|---|
1 | 4 | 5 |
3 | 12 | 28 |
5 | 19 | 56 |
7 | 11 | 82 |
10 | 6 | 97 |
Graph of Information - Figure 1.
Table 2.
Cell Type | Day 3 % | Day 7 % | Day 10 % |
|---|---|---|---|
Basal Stem Cells | 38 | 22 | 12 |
Keratinocytes | 29 | 48 | 62 |
Fibroblasts | 21 | 24 | 21 |
Endothelial Cells | 12 | 16 | 18 |
Graph of Information - Figure 2.
According to Table 1, on which day does the mitotic index reach its highest percentage?
Using Table 1 and Figure 1, describe the relationship between mitotic index and wound closure percentage from Day 1 to Day 10 after injury.
Using information from the reading and Diagram 1, explain how cells, tissues, and organ-level responses interact during the inflammation and proliferation stages of wound healing.
Explain how mitosis and differentiation together support the formation of new skin tissue after injury.
Respond using Claim, Evidence, and Reasoning.
Based on Diagram 2, why do daughter cells produced during mitosis contain identical sets of chromosomes?
Using Table 2 and Figure 2, describe how changes in the percentages of basal stem cells and keratinocytes from Day 3 to Day 10 provide evidence of differentiation.