Overview
This lecture covers the structure and function of the dermis, subcutaneous (hypodermis) layer, and the biological basis of skin color.
Structure and Function of the Dermis
- The dermis is a thick skin layer beneath the epidermis, made mostly of dense irregular connective tissue.
- It contains many blood vessels that nourish and support the epidermis.
- Nerve cells in the dermis detect touch and pressure (Meissner's and Pacinian corpuscles).
Dermis Layers: Papillary and Reticular
- The papillary layer (top of dermis) is made of areolar connective tissue with many blood vessels and dermal papillae.
- Dermal papillae are projections of the dermis into the epidermis, creating epidermal ridges.
- Epidermal ridges are responsible for fingerprints, which are individual-specific due to genetic and environmental factors.
- The reticular layer (majority of dermis) is made of dense irregular connective tissue, forming tension lines used as guides in surgical incisions.
Subcutaneous Layer (Hypodermis)
- The hypodermis lies beneath the skin and consists of areolar and adipose (fat) tissue.
- Functions of the hypodermis include energy storage, cushioning, insulation, and extensive blood supply.
- Hypodermic needles target this layer for injection.
Skin Color and Pigments
- Melanin is the only skin-produced pigment, protecting against UV light; eumelanin (brown-black) and pheomelanin (red-yellow) types determine skin shade.
- Carotene is a yellow-orange pigment from the diet, accumulating in the stratum corneum and hypodermis.
- Hemoglobin, a blood protein, gives skin a pinkish hue due to its red coloration.
Key Terms & Definitions
- Dermis — Thick connective tissue layer beneath the epidermis.
- Papillary Layer — Upper dermis made of areolar connective tissue, forms dermal papillae.
- Dermal Papillae — Projections that form epidermal ridges (fingerprints).
- Reticular Layer — Deep dermis, dense irregular connective tissue, forms tension lines.
- Hypodermis (Subcutaneous) — Layer beneath skin, made of areolar and adipose tissue.
- Melanin — Skin pigment protecting against UV (eumelanin and pheomelanin types).
- Carotene — Dietary pigment giving yellow-orange color, stored in skin.
- Hemoglobin — Blood protein for oxygen transport, gives skin a pink tone.
- Tension Lines — Natural lines in the dermis guiding surgical incisions.
Action Items / Next Steps
- Review the structure and functions of dermal layers for upcoming exam.
- Understand how each pigment contributes to skin color.
- Prepare lab notes on touch receptors (Meissner's, Pacinian corpuscles).