What type of tissue lines the urinary bladder?
A simple squamous epithelium
B dense connective tissue
C transitional epithelium
D pseudostratified columnar epithelium
The correct answer and explanation is:
The correct answer is C. Transitional epithelium.
Transitional epithelium is a specialized type of epithelium found in the urinary system, particularly lining the urinary bladder, ureters, and part of the urethra. Its primary function is to allow for the stretching and expansion of these organs as they fill with urine. This ability to stretch is crucial for accommodating varying volumes of urine in the bladder, as the bladder must expand significantly to hold urine before it is excreted.
The unique feature of transitional epithelium is that it appears to have multiple layers of cells when the bladder is empty, but as the bladder fills and stretches, the cells flatten and the number of layers decreases. This gives the tissue the flexibility to adapt to the changes in the bladder’s volume.
The cells of transitional epithelium are dome-shaped when the bladder is relaxed, but they can become flattened when the bladder is distended. This distinctive feature differentiates it from other types of epithelial tissue, such as simple squamous or pseudostratified columnar epithelium.
In contrast, simple squamous epithelium (option A) is a single layer of flat cells, commonly found in areas where passive diffusion or filtration occurs, such as in the lungs and blood vessels. Dense connective tissue (option B) consists of collagen fibers and provides structural support, but it is not a lining tissue. Pseudostratified columnar epithelium (option D) appears stratified but is actually a single layer of cells, often found in the respiratory tract. However, it does not have the ability to stretch like transitional epithelium.
Thus, transitional epithelium is perfectly suited for the urinary bladder, where it must handle the significant stretching that occurs during bladder filling and emptying.