Cell Structure And Organelles

Step 1: Classify Glands based on Mode of Secretion:

• Merocrine (Eccrine): Cells release secretion via exocytosis with no loss of cytoplasm (e.g., Salivary glands, most sweat glands).
• Apocrine: The apical portion of the cell containing the secretory product is pinched off and lost (e.g., Mammary glands, some sweat glands).
• Holocrine: The entire cell disintegrates to release the secretion (e.g., Sebaceous/Oil glands).
• Endocrine: Ductless glands releasing hormones into blood (not applicable to milk).

Step 2: Identify Mammary Gland Type:
Mammary glands secrete milk and lipids. The lipid secretion involves the pinching off of the apical cytoplasm. Hence, they are modified sweat glands of the Apocrine type.
Step 3: Final Answer:
Option (D) is correct.

Concept: The epithelium lining the vagina must resist mechanical friction while remaining moist.
Explanation: The vagina is lined by stratified non-keratinized squamous epithelium. The stratified layers provide protection, and the lack of keratin keeps the surface moist. Keratinized epithelium is found on dry surfaces like skin.

Mesothelium is the epithelium lining body cavities (pleura, pericardium, peritoneum). It is a simple squamous epithelium, which allows smooth movement of organs. Cuboidal, columnar, and transitional types are found in ducts, intestine, and urinary tract, respectively.