Structure and Function of the Skin

Environmental Agents that are Harmful to the Skin
Solid matter
Liquids
Gases
Sunlight
Microorganisms
Functions of the Skin
Prevent body fluids from leaving the body
Protect the body from potentially damaging environmental agents
Serve as an area for heat exchange
Provide protection against invading microorganisms
Role of Receptors in the Skin
Relay the following sensations to the CNS for localization and discrimination:
Pressure
Temperature
Pain
Layers of the Skin
Outer epidermis
Avascular layer composed of 4 to 5 layers of stratified squamous keratinized epithelial cells formed in the deepest layer of the epidermis
These cells migrate to the skin surface to replace cells lost during normal shedding
Basement membrane
Thin adhesive layer cementing the epidermis to the dermis
Layer involved in blister formation
Layers of the Skin (cont.)
Inner dermis
Connective tissue layer that separates the epidermis fro the underlying subcutaneous fate layer
Contains blood vessels and nerve fibers that supply the epidermis

Five Layers of the Epidermis
Stratum germinativum, or basal layer
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

Cells of the Epidermis
Keratinocytes
Melanocytes
Merkel’s cells
Langerfhan’s cells
Papillary Dermis
Definition
A thin, superficial layer that lies adjacent to the epidermis
Composition
Consists of collagen fibers and ground substance
This layer is densely covered with conical projections called dermal papillae
Papillary Dermis (cont.)
Function
Minimize the separation of the dermis and the epidermis
Nourish the epidermal layers of the skin

Reticular Dermis
Definition
The thicker area of the dermis that forms the bulk of the dermal layer
Composition
Complex meshwork of three-dimensional collagen bundles interconnected with large elastic fibers and ground substance
A viscid gel that is rich in mucopolysaccharides
Immune Cells Found in the Dermis
Macrophages
T cells
Mast cells
Fibroblasts
Skin Appendages
Hair
Nails
Sebaceous and sweat glands
Types of Sweat Glands
Eccrine sweat glands
Simple tubular structures that originate in the dermis and open directly to the skin surface
Numerous (several million) and vary in density
Located over the entire body surface
Transport sweat to the outer skin surface to regulate body temperature
Types of Sweat Glands (cont.)
Apocrine sweat glands
Less numerous than eccrine sweat glands
Larger and located deep in the dermal layer
Open through a hair follicle, even though a hair may not be present
Found primarily in the axillae and groin
Secretions of the Sebaceous Glands
Lipids, including triglycerides
Cholesterol
Wax
Nails
Definition
Hardened keratinized plates
Function
Protect the fingers and toes and enhance dexterity