In human corneal transplantation, the donor tissue is –
**Core Concept**
Human corneal transplantation involves the transfer of a donor cornea to replace a diseased or damaged cornea. The donor tissue is prepared and preserved to maintain its viability and integrity for transplantation.
**Why the Correct Answer is Right**
The donor cornea is typically preserved in a state of **endothelial down**. This means that the innermost layer of the cornea, the endothelium, is removed from the donor tissue. The endothelium is a monolayer of cells that plays a crucial role in maintaining corneal hydration and clarity. By removing the endothelium, the donor tissue is rendered hypotonic, which slows down the metabolic processes and helps preserve the corneal stroma and epithelium. This method of preservation allows for longer storage times and improved graft survival rates.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the donor tissue is not typically stored in an **endothelial up** state, which would lead to excessive metabolic activity and tissue damage.
**Option B:** This option is incorrect because the donor tissue is not typically preserved in a **sterile saline** solution, which would not provide adequate preservation of the corneal tissue.
**Option C:** This option is incorrect because the donor tissue is not typically stored at **37°C**, which would promote excessive metabolic activity and tissue damage.
**Clinical Pearl / High-Yield Fact**
In human corneal transplantation, the donor tissue is typically preserved in a state of endothelial down to maintain its viability and integrity for transplantation. This method of preservation allows for longer storage times and improved graft survival rates.
**Correct Answer: C.**