Skin Structure and Layers

Overview

This lecture covers the structure and layers of thin skin, including its main tissue components, key cellular layers, and associated skin appendages.

Skin consists of three main layers: epidermis (epithelial), dermis (connective tissue), and hypodermis (fat/loose connective tissue).
Thin skin features a stratum corneum (outermost keratinized layer) that is thinner than the rest of the epidermis.
Thick skin (palms/soles) has a thicker stratum corneum for added protection.

The epidermis is a stratified, keratinized squamous epithelium with multiple layers for protection.
The deepest layer is the basal (or stratum germinativum), composed of columnar cells aligned at the base.
Above the basal layer is the stratum spinosum (prickle cell layer), named for its "prickly" appearance.
The stratum granulosum contains cells with keratohyalin granules.
The stratum lucidum is a thin, clear layer found in certain areas (not all skin).
The stratum corneum is the uppermost, keratinized layer lacking nuclei.
Melanocytes, which produce pigment, are found in the basal and sometimes higher layers.

The papillary dermis is loose connective tissue with finger-like projections (papillae) interfacing with the epidermis.
The reticular dermis is dense connective tissue with thick collagen bundles for strength in all directions.
Skin appendages like hair follicles and sweat glands are located in the dermal layers.
The hypodermis (subcutaneous layer) consists of loose connective tissue and fat for cushioning and insulation.

Eccrine sweat glands are small, tubular structures found in clusters; their ducts are double-layered cuboidal epithelium.
Myoepithelial cells surround eccrine glands, aiding in sweat expulsion.
The skin contains blood vessels (arteries, veins, capillaries) and nerves, which are visible in tissue sections.

Epidermis — outermost skin layer, stratified squamous epithelium, keratinized.
Dermis — middle skin layer, mainly connective tissue (collagen, elastic fibers).
Hypodermis (Subcutis) — deepest layer, mainly fat and loose connective tissue.
Stratum corneum — outer keratinized, anuclear epidermal layer.
Stratum basale (germinativum) — deepest epidermal layer, columnar cells.
Stratum spinosum — prickle cell/spiny layer above basal layer.
Stratum granulosum — granular layer with keratohyalin granules.
Stratum lucidum — clear, thin layer (only in certain skin).
Papillary dermis — superficial dermis with papillae.
Reticular dermis — deep, dense dermal layer.
Eccrine sweat glands — glandular clusters producing sweat.
Myoepithelial cells — contractile cells aiding gland secretion.
Melanocytes — pigment-producing cells in the epidermis.