✦ Pacinian corpuscles are specialized mechanoreceptors that detect deep pressure and vibration.

✦ They are predominantly located in the hypodermis (subcutaneous layer), which lies beneath the dermis.

✦ Their deep placement allows them to respond to stronger stimuli compared to superficial receptors like Meissner’s corpuscles.

✦ Structurally, they are onion-shaped and contain concentric lamellae that deform with pressure changes.

✦ This unique location and structure make them critical for detecting vibration and heavy touch in the skin and connective tissue.

🖊️ The hypodermis is primarily composed of adipose tissue, which serves as insulation and an energy reservoir.

🖊️ This fatty layer cushions internal organs and helps regulate body temperature.

🖊️ It also anchors the skin to underlying muscles and structures, providing flexibility.

🖊️ Unlike the epidermis, which is epithelial, the hypodermis is classified as connective tissue.

🖊️ Its adipose content is also important in drug absorption when medications are given via subcutaneous injection.

👉 Mammary glands are modified apocrine glands, which release secretions through partial loss of cytoplasm.

👉 Unlike eccrine glands, which are widespread and secrete watery sweat, apocrine glands produce more complex secretions.

👉 In mammals, apocrine modifications allow secretion of milk, which contains proteins, fats, and carbohydrates.

👉 These glands are hormonally regulated and become functional at puberty.

👉 Their classification is based on the mode of secretion, which involves apical budding of the cell.

🔴 Dendritic cells (Langerhans cells) in the epidermis serve an immunological role by acting as antigen-presenting cells.

🔴 They capture and process microbial antigens that breach the skin barrier.

🔴 Once activated, they migrate to lymph nodes to stimulate T-cell responses.

🔴 This makes them essential for cutaneous immunity and defense against infections.

🔴 Other cells like keratinocytes, melanocytes, and Merkel cells have structural, pigmentary, or sensory roles but are not primary immune cells.

✦ The epidermis is composed of keratinized stratified squamous epithelium.

✦ This multilayered structure provides mechanical protection against abrasion, pathogens, and water loss.

✦ The outermost layer (stratum corneum) consists of dead keratinized cells that form a protective barrier.

✦ Keratinocytes in lower layers proliferate and migrate upward, becoming keratinized as they move outward.

✦ This specialization allows the skin to act as a durable external barrier while remaining flexible.