Final answer:
A sebaceous gland cell releases its secretory product through complete rupture and destruction, making it a 4. holocrine gland. Holocrine glands are a type of exocrine gland that contribute to skin and hair lubrication.
Step-by-step explanation:
A sebaceous (oil) gland cell of the skin must completely rupture to release its secretory products, which is characteristic of a holocrine gland. In holocrine secretion, the entire glandular cell accumulates the secretory products and is destroyed upon rupture, hence becoming part of the secretion itself. After the cell releases its contents and is lost, new cells differentiate from the surrounding tissues to replace the ones that have been destroyed.
This process is distinct from other types of exocrine glands, such as merocrine and apocrine glands, which do not involve the complete destruction of gland cells for secretion. Sebaceous glands in particular are well-known examples of holocrine glands and are vital for providing lubrication and protection to the skin and hair.