HistoLab Skin

Epidermis

stratified squamous keratinizing epithelium

Dermis

a superficial papillary layer of loose connective tissue, underlain by a reticular layer of dense fibrous irregularly arranged connective tissue

Hypodermis

deepest layer of skin, also called subcutaneous tissue, made up of loose connective tissue and adipose tissue.

Epidermis

The stratified squamous keratinizing epithelium of this is made up primarily of keratinocytes. The form and function of these cells changes as they pass from basal to superficial locations.

Stratum basale

Cells of all the layers are generated from the keratinocytes in this layer. Therefore, you may see mitotic figures. The keratinocytes in this and the overlying layers contain melanin granules that have been transferred to them by melanocytes. The cytoplasm of melanocytes does not stain with H&E, giving the appearance of a halo. Special staining methods are required to identify melanocytes definitively.

Stratum spinosum

This is several cell layers in thickness. The cells are attached to each other by intercellular bridges (desmosomes). Because the cells pull apart during preparation, the attachment sites give the cells a spiny appearance.

Stratum granulosum

The cells of this layer are recognizable by their basophilic kerato hyaline granules containing filaggrin and other proteins binding tonofibrils.

Stratum corneum

The superficial keratinized layer is the stratum corneum, which protects the skin against friction, infection, and water loss. It consists of flattened; denucleated squamous.

Papillary layer

loose connective tissue underlying the basal layer of the epidermis containing blood vessels, nerves, and lymphatic vessels. Dermal papillae may contain sensory nerve endings called Meissner’s corpuscles.

Reticular layer

dense, irregularly arranged connective tissue.

Subcutaneous tissue (hypodermis)

This is loose connective tissue containing abundant adipose tissue. It is a good region to examine glands, ducts, blood vessels and nerves.

Eccrine sweat glands

are present in high concentration in the dermis and subcutaneous tissue. They are coiled tubular glands with an acidophilic margin, which corresponds to the layer of myoepithelium. The ducts are straight as they lead through the superficial dermis to the basal aspect of the epidermis. At this point they assume a coiled pathway, which becomes corkscrew like in the stratum corneum.

Pacinian corpuscles

are another type of nerve ending found in the dermis or subcutaneous tissue. They are made up of an axon surrounded by numerous concentric cellular lamellae. These are also found in other regions of the body.

Hair follicles

are well demonstrated in this slide in longitudinal section. The thin epidermis, characteristic of hairy regions, has a lacy or frayed stratum corneum whose appearance is an artifact of sectioning. In life, this layer of the epidermis would be more compact and only the most superficial keratinized cells would be desquamating.

Sebaceous glands

are associated with the hair follicle and their secretions empty into the hair follicle, between the hair shaft and the follicle wall. The arrector pili muscle is a band of Meissner’s corpuscles Eccrine sweat gland smooth muscle that inserts on the hair follicle, deep to the sebaceous glands. Superficially it inserts at the base of the epidermis. Some eccrine sweat glands are dispersed between the hair follicles.