Overview
This lecture covers the structure and function of the dermis, focusing on its two main layers, sensory structures, clinical relevance, and the role of skin pigments in determining skin color and as diagnostic tools.
Structure and Layers of the Dermis
- The dermis is divided into the superficial papillary layer and the deeper reticular layer.
- The papillary layer is made of areolar tissue, containing tactile (Meissner’s) corpuscles for light touch sensation.
- Dermal papillae are wavy projections in the papillary layer that interlock with the epidermis.
- Capillaries in the papillary layer nourish the epidermis.
- The reticular layer consists mainly of dense irregular connective tissue, providing strength and elasticity.
- Collagen fibers in the reticular layer resist stress from multiple directions; elastic fibers allow stretch and recoil.
Sensory Structures and Other Components
- Tactile corpuscles in the papillary layer detect light touch.
- Lamellated (Pacinian) corpuscles in the reticular layer sense deep pressure and vibration.
- The reticular layer contains arterial blood vessels, sweat glands, hair follicles, and sebaceous glands.
Skin Markings and Clinical Significance
- Dermal papillae create epidermal ridges, which form fingerprints.
- Sweat pores in epidermal ridges leave unique fingerprint patterns.
- Cleavage lines (tension lines) in the reticular layer align with collagen fiber direction.
- Surgical incisions made parallel to cleavage lines heal faster and with less scarring.
Skin Pigmentation and Diagnostic Use of Skin Color
- Melanin is the main pigment determining skin color, with variations in shade.
- Carotene, a yellow-orange pigment from food, can accumulate in the skin.
- Hemoglobin in blood gives skin a pinkish hue due to dermal blood flow.
- Erythema is redness from increased blood flow (exercise, trauma, infection).
- Pallor is paleness from reduced blood flow (cold or shock).
- Cyanosis is a blue tint indicating low blood oxygen and requires urgent attention.
Key Terms & Definitions
- Dermis — The inner, connective tissue layer of skin beneath the epidermis.
- Papillary layer — Upper dermal layer of areolar tissue with tactile corpuscles and dermal papillae.
- Reticular layer — Deeper dermal layer with dense irregular connective tissue, providing strength.
- Tactile (Meissner’s) corpuscles — Sensory receptors for light touch in the papillary layer.
- Lamellated (Pacinian) corpuscles — Sensory receptors for deep pressure/vibration in the reticular layer.
- Dermal papillae — Projections of the papillary layer creating epidermal ridges (fingerprints).
- Cleavage lines — Natural orientation of collagen fibers in the dermis important for surgical healing.
- Melanin — Pigment responsible for skin color.
- Carotene — Yellow-orange skin pigment from dietary sources.
- Hemoglobin — Blood pigment that can impart a pinkish hue to skin.
- Erythema — Reddening of the skin due to increased blood flow.
- Pallor — Paleness of skin from reduced blood flow.
- Cyanosis — Bluish skin color indicating low oxygen levels.
Action Items / Next Steps
- Review functions and distinguishing features of the papillary and reticular layers.
- Memorize key terms and definitions.
- Prepare answers for review questions provided in the lecture.