Structure and Function

The diagnosis of skin disease is based on color, morphology, and distribution of cutaneous lesions. The structure of the skin and associated appendages relates directly to these characteristics.

Folliculitis presents with papules or pustules. Follicular accentuation is characteristic of any eruption in darker-skinned races. In patients with miliaria, involvement of the sweat gland ostia results in erythematous papules, pustules, or superficial vesicles in areas of heavy sweating. The vesicles of miliaria crystallina are irregular in shape because the stratum corneum fails to impede the spread of the blister in random directions. This is in stark contrast to spongiotic and subepidermal blisters, which are distinctly round—as in acute dyshidrotic eczema or bullous pemphigoid.

The color of a cutaneous eruption relates to various pigments. Brown pigments include melanin, lipofuscin, and hemosiderin. Brown pigments located deeper in the dermis impart a blue hue because of diffraction of light. This is evident in blue nevi as a result of deep melanin and as a result of lipofuscin present in the sweat within nodular hidradenomas. Red pigment relates to oxygenated hemoglobin and blue to deoxygenated hemoglobin. Dilatation or proliferation of blood vessels and the rapidity of blood flow produce various shades of red and blue. Yellow pigments relate to lipid deposition or carotenoids dissolved in the cytoplasm of epithelial cells and histiocytes. In granulomatous disease, diascopy removes the visible appearance of oxygenated hemoglobin, allowing the observer to see the apple jelly yellow appearance of carotenoids within the cytoplasm. This section of the atlas will focus on the structure of the skin and how that structure translates to clinical manifestations of disease.

Fig. 1.1

In early fetal life, a cuboidal periderm is present, rather than an epidermis. Fetal skin, H&E × 40.

Fig. 1.2

In early fetal life, the spine is composed of cartilage, and mesenchyme is present rather than a dermis. Mesenchyme heals without scar formation. Once dermis forms, scars will occur after injury. Fetal skin, H&E × 40.

Fig. 1.3

Skin in young children is characterized by small adnexal structures and fine dermal collagen bundles that stain deep red in contrast to the thick, pink collagen bundles of an adult. Many plump fibroblasts are present in the dermis, actively synthesizing collagen. Childhood skin, H&E × 20.

Fig. 1.4

Facial skin is characterized by prominent sebaceous follicles, often containing Demodex mites. Facial skin, H&E × 40.

Fig. 1.5

Skin of the ear demonstrates small adnexal structures with an elastic cartilage surrounded by a red perichondrium. Ear skin, H&E × 20.

Fig. 1.6

The structure of the ear canal is similar to other parts of the ear, except for the presence of ceruminous glands, which represent modified apocrine glands. Ear canal skin, H&E × 20.

Fig. 1.7

Scalp skin demonstrates many terminal hair follicles. The inferior segment of each follicle sits within the subcutaneous fat. Scalp skin, H&E × 40.

Fig. 1.8

Axillary skin is rugose and demonstrates large apocrine glands. Axillary skin, H&E × 40.

Fig. 1.9

Breast skin demonstrates numerous smooth muscle bundles. Breast skin, H&E × 20.

Fig. 1.10

Nipple skin demonstrates smaller smooth muscle bundles. The mammary duct resembles a large sweat duct. Breast skin, H&E × 20.

Fig. 1.11

The secretory portion of mammary glands demonstrates columnar epithelium forming complex lumens. Breast skin, H&E × 100.

Fig. 1.12

Prepuce demonstrates a rugose appearance with many smooth muscle fascicles and high vascularity. Prepuce, H&E × 20.

Fig. 1.13

Eyelid anatomy, below the conjunctiva; the densely fibrous tarsal plate contains sebaceous glands (meibomian glands), H&E × 100.

Fig. 1.14

The lid margin; on the cutaneous surface of the lid, a layer of striated muscle is present below the epidermis, H&E × 10.

Fig. 1.15

Volar skin demonstrates a thick stratum corneum and lack of hair follicles, low power, H&E × 40.

Fig. 1.16

Volar skin demonstrating a thick corneum and dermis, H&E × 100.

Sep 3, 2019 | Posted by in Dermatology | Comments Off on Structure and Function
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