The Structure of Skin: Layers, Cells & Histology

 The skin is the largest organ of the body, functioning as a physical barrier while supporting immune defence, thermoregulation, and sensory input. Structurally, it consists of three main layers, each with unique cell types and functions.

📌 The Three Layers of Skin

🔹 Epidermis (Outer Layer)

- Composition: Stratified squamous epithelium

- Cell Types:

• Keratinocytes – The major structural cells, forming the protective keratinised barrier
• Melanocytes – Produce melanin for pigmentation and UV protection
• Langerhans cells – Antigen-presenting immune cells involved in skin surveillance

- Key Feature: The stratum corneum consists of dead, keratin-filled cells, constantly shedding and renewing (approx. every 28 days).

🔹 Dermis (Middle Layer)

- Composition: De- Dense irregular connective tissue

- Structures Inside:

• ✅ Blood vessels – Nourish the epidermis (which lacks its own blood supply)
• ✅ Nerve endings – Responsible for pain, pressure, temperature, and touch
• ✅ Sweat glands – Thermoregulatory eccrine glands, and apocrine glands linked to hair follicles
• ✅ Collagen & elastin fibres – Provide strength and elasticity

🔹 Hypodermis / Subcutaneous Layer (Deepest Layer)

- Composition: Loose connective tissue & adipose

- Functions:

• ✅ Fat storage for energy reserve & insulation
• ✅ Shock absorption, protecting muscles & bones
• ✅ Houses major blood vessels & lymphatics

💡 Key Takeaway: The skin is a highly specialised, multilayered organ, each layer contributing to protection, sensation, and homeostasis.