Epidermis___The_outermost_layer_of_the_skin__composed_of_stratified_

Epidermis

• Definition: The outermost layer of the skin, made of stratified squamous epithelium, serving to protect and prevent water loss.

Stratum Basale

• Description: The deepest layer of the epidermis.

• Components:

  • Basal Cells: Actively divide to produce new skin cells.

  • Melanocytes: Produce melanin, the pigment providing skin color and UV protection.

  • Merkel Cells: Assist in touch sensation.

Stratum Spinosum

• Function: Layer above the stratum basale where keratinocytes strengthen.

• Characteristics: Formation of desmosomal connections between cells.

Stratum Granulosum

• Role: Middle layer where keratinocytes begin to die.

• Significance: Accumulates keratohyalin granules, contributing to the skin’s waterproof barrier.

Stratum Lucidum

• Description: A thin, transparent layer of dead keratinocytes.

• Location: Found only in thick skin (e.g., palms and soles), enhancing protection.

Stratum Corneum

• Characteristics: The outermost layer made of flattened, dead keratinocytes.

• Function: Forms a protective barrier due to keratin content.

Key Cell Types in the Epidermis

• Keratinocytes:

  • Primary cells that produce keratin, providing strength and water resistance.

• Melanocytes:

  • Located in the stratum basale, responsible for melanin production.

• Merkel Cells (Tactile Disc):

  • Sensory receptors in the stratum basale that respond to light touch.

Dermis

• Definition: The layer of skin beneath the epidermis, composed of connective tissue, blood vessels, nerves, and accessory structures.

Papillary Layer

• Structure: Superficial layer made of loose connective tissue.

• Function: Contains dermal papillae that interlock with the epidermis, increasing surface area for exchange.

Dermal Papillae

• Description: Fingerlike projections extending into the epidermis.

• Components: Contains capillaries and touch receptors.

Tactile Corpuscle

• Role: Sensory receptor in dermal papillae that detects light touch.

Reticular Layer

• Structure: Deeper layer composed of dense irregular connective tissue.

• Contains: Blood vessels, glands, and sensory receptors.

Gland Types in the Dermis

• Sebaceous Gland:

  • Oil-producing gland in the reticular layer; secretes sebum for moisture.

• Sweat Gland:

  • Responsible for sweat production, helping to regulate body temperature and eliminate waste.

Additional Sensory Structures

• Lamellated Corpuscle:

  • Deep pressure receptor in the reticular layer that detects vibrations and pressure.

• Free Nerve Ending:

  • Unencapsulated nerve endings that detect pain, temperature, and some touch sensations.