Question

The superficial layer of transition tissue possess different shapes because of
A. Degree of distention
B. Maturation
C. Environmental change
D. None of the above

Answer 1

Hint: The urinary system is lined by urothelium which can stretch to accommodate urine. Multiple layers are present in this epithelium and help in stretching and accommodation. Stretching increases the volume of the organ. The tight junctions are also present that act as a barrier between blood and lumen.

Complete answer: Epithelial tissue covers the body parts such as the inner lining of the mouth, organs, alimentary canal, urogenital tract etc. The transitional tissue consists of multiple layers of cells which can contract and expand according to the degree of distension needed. It is a type of stratified epithelium. The transitional epithelium is covered by microvilli. The main function of the transitional epithelium is to increase the volume of the organ. It helps in preventing entry of toxic substances and pathogens in the bloodstream acting as a barrier between the lumen and the blood. This barrier occurs because of tight junctions between the cells. Transitional epithelium is mainly made up of three types of layers.
i. Basal layer: Cells of the basal layer are cuboidal or columnar. The basal layer has stem cells which provide constant renewal of epithelium. Cells are rich in tonofilaments which help in the attachment to the basement membrane with the help of desmosomes. These cells are also rich in mitochondria.
ii. Intermediate layer: Cells of this layer are rich in the Golgi apparatus and membrane-bound vesicles. This layer is proliferative and plays the role of rapid regeneration in case of injury or infection. It also transports protein to the superficial layer.
iii. Superficial layer: It acts as an impenetrable barrier between lumen and bloodstream and is a fully differentiated layer.
Hence, the correct answer is option A.

Note: The transitional epithelium is found in the urinary bladder, ureters, urethra and the ducts of the prostate gland. The transitional epithelium lining urinary system is called the urothelium. It is a type of stratified epithelium made up of different layers which can contract and expand according to the degree of distension needed.