There are three types of gland on the basis of lost part of cell during secretion.
1.merocrine
2.apocrine
3.holocrine
In merocrine no part of cell loss during secretion whereas ,in apocrine only apical part loss during secretion and in holocrine complete cell loss after secretion.
In mammary gland apical part of the cell lost during secretion of milk so these are apocrine glands.

Apocrine type

Mammary glands are classified as apocrine type glands. Here is an explanation of why they are classified as apocrine glands:

Definition of Apocrine glands:
- Apocrine glands are a type of gland where the secretory cells accumulate their secretory products at the apical surface of the cell.
- The secretory products are then released along with portions of the cytoplasm, resulting in a mixture of cell fragments and secretory substances.

Characteristics of Apocrine glands:
- The mammary glands secrete milk, which is a complex mixture of proteins, fats, and sugars.
- The secretion of milk involves the apical portion of the secretory cells accumulating the milk components before they are released into the mammary ducts.
- This process of milk secretion from mammary glands aligns with the characteristics of apocrine glands.

Comparison with other gland types:
- Holocrine glands release their secretory products by the entire cell rupturing, which is not the case in mammary glands.
- Merocrine glands release their secretory products through exocytosis without any loss of cellular material, which is also different from the process in mammary glands.

Therefore, based on the mechanism of milk secretion and the characteristics of apocrine glands, mammary glands are classified as apocrine type glands.