Tactile System

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The tactile system from the skin (body’s largest organ) has sensory receptors at different layers — epidermis (top layer) and dermis (middle layer) — which together sense touch, pressure, pain, temperature, and other stimuli. Large nerves from the hypodermis (bottom layer) extend to the dermis into the epidermis, allowing touch and pressure signals to transmit to the brain. More about the three layers of tissue make up the skin:

• Epidermis: The outer, visible layer of skin also has specialized cells (Merkel cells) acting as touch receptors for light touch. Free nerve endings transmit pain. The epidermis makes new skin (new cells replace 40,000 dead skin cells shed daily) every 30 days. It protects the body (Langerhans cells are part of the body’s immune system); provides skin color (contains the pigment melanin — its amount determines skin, hair, and eye colors; more melanin makes darker skin).
• Dermis, also called Corium: The middle layer, making up 90% of skin’s thickness, detects light touch (especially the fingertips), pressure deep in the tissue, detects cold/heat, and its nerve endings send sensations to the brain. The dermis contains two proteins. Collagen makes skin cells strong and resilient; elastin keeps skin flexible and helps stretched skin regain its shape. Other functions: grows hair (roots of hair follicles attach to the dermis), responds not only to temperature and pain, but itchiness and texture/softness, makes oil (oil glands help keep skin soft and smooth and keep it from absorbing too much water), produces sweat (sweat glands help regulate temperature), and supplies blood (blood vessels provide nutrients to the epidermis, keep skin layers healthy).
• Hypodermis, also called Subcutaneous Tissue: The bottom fatty layer contains sensory nerves that also help sense pain, temperature, pressure, and proprioception (body position).