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Chapter 1: Structure and Function of the Skin

Amrita Goyal; Kimberly Bohjanen

INTRODUCTION TO CHAPTER

Human skin is the site of many complex structures and dynamic processes as demonstrated in Figure 1-1 and Table 1-1. These processes include barrier and immunologic functions, sensation, vitamin D synthesis, thermoregulation, and protection from ultraviolet (UV) light and trauma.

Figure 1-1.

Cross-section of skin. Diagram showing layers of the skin, appendages, blood vessels, sensory nerve fibers, and sensory receptors.

An illustration depicting a cross-section of the skin.
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Table 1-1.Structure and Function of the Skin
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Table 1-1. Structure and Function of the Skin
Component Structure and Function
Stratum corneum Semipermeable barrier with "bricks" (stacked cornified cells) and "mortar" (ceramides, cholesterol, and fatty acids) like construction.
Stratum granulosum Cells contains keratohyalin granules which are primarily composed of profilaggrin.
Stratum spinosum Contains desmosomes for intercellular adhesion.
Langerhans cells Dendritic cell important in the modulation of the adaptive immune response.
Merkel cells Specialized cell with neuroendocrine function.
Melanocytes Dendritic cells that produce melanin for ultraviolet light protection.
Basal cell layer Contains the stem cells that divide and produce the rest of the keratinocytes in the epidermis.
Basement membrane Interface between the epidermis and dermis.
Ground substance Amorphous gel of mucopolysaccharides that is the substrate for the dermis.
Collagen Network of fibrous proteins for skin tensile strength.
Elastic fibers Fibrous proteins responsible for skin elasticity.
Fibroblasts Cells that produce ground substance, collagen, and elastic fibers.
Mast cells Leukocytes that release histamine and heparin.
Histiocytes/macrophages Leukocytes which phagocytize and present antigen.
Eccrine glands Sweat glands which help in temperature regulation.
Apocrine glands Axillary and anogenital glands responsible for body odor.
Sebaceous glands Component of pilosebaceous unit which produces sebum.
Hair follicle Component of pilosebaceous unit that produces the hair fiber.
Somatic sensory and sympathetic autonomic nerves Supply blood vessels, glands, and hair follicles.
Meissner's corpuscles Specialized nerve receptor for light touch.
Pacinian corpuscles Specialized nerve receptor for pressure and vibration.
Blood vessels Two horizontal plexuses in the dermis which are connected and can shunt blood flow.
Lymphatics Parallel to blood vessels with two plexuses for flow of plasma.
Fat Provides protection from cold and trauma. Essential for storage of energy and metabolism of sex hormones and glucocorticoids.
Fascia Connective tissue layer overlying the muscle beneath the fat.

BARRIER FUNCTION

One of the most important function of human skin is to act as a barrier between us and the external environment.1 It protects against a variety of forms of physical damage, ranging from desiccation to infection, heat loss, and UV damage.2 The skin is a multilayered stalwart against these insults. First, the stratum corneum, with its corneocytes wrapped in cornified cell envelopes, water-impenetrable lipid lamellae, and filaggrin, forms a barrier that protects us from infectious organisms and water loss. Tight junctions help seal the spaces between neighboring cells in the stratum granulosum. Langerhans cells in the ...

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