A Focus on the Depths of Skin

Glabrous skin – palmo-plantar area

Histologically, an extra epidermal layer is seen between the granular and corneous layers, called layer lucidum. The phones of this layer are nucleated and called transitional cells(18) (Figure 4A). At high-recurrence ultrasonography (HFUS), the epidermis of this anatomical zone is viewed as a bilaminar hyperechoic structure(23), conceivably coming about because of the difference between the epidermis itself and an exceptionally thick and minimal layer corneum. The other skin layers are like the non glabrous skin (Figure 4B).

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Figure 4

Glabrous skin. A: Histology. Thicker corneous layer and nearness of layer lucidum (reference mark). B: HFUS, cross-sectional view. Hyperechoic epidermis with bilaminar appearance (bolt).

Scalp and hair shaft

The hair follicle is a dynamic microstructure joined to the skin, answerable for the creation of hair, in steady self-recovery. Consequently, it presents a cyclic conduct. Times of high mitotic action and cell separation (anagenous stage) are hindered by a renovating stage (catagenous stage), trailed by a calm period (telogen stage), with an ensuing development restart (Figure 5A).

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Figure 5

Scalp. A: Histology, longitudinal segment. B: HFUS, longitudinal view. Epidermis (e), dermis (d), slanted hypoechoic groups comparing to hair follicles (bolts).

At HFUS, the presence of the scalp skin layers is like the skin of other anatomical destinations: hyperechoic line (epidermis), hyperechoic band (dermis) and hypoechoic band (subcutaneous). All the more profoundly, a hypoechoic band relating to the galea is watched and, following, the calvarium showed by a strongly hyperechoic line. Longitudinal hypoechoic structures relating to the hair follicles are seen on the scalp pictures. Contingent upon the period of the hair development cycle, such structures are seen at various skin layers, as follows: in the telogen stage, the bulb is situated in the dermis, while in the anagenous stage, the bulb is situated in the subcutaneous tissue(24) (Figure 5B).

The scalp skin of the frontal locale is more slender than the occipital district, and the hair follicles thickness is variable(24) (Figure 6).

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Figure 6

HFUS, longitudinal view, scalp. Male, 41-year-old patient. Variety of the skin thickness and in the quantity of hair follicles. A: Frontal locale. B: Occipital area. Dermis (marks), hair follicle (jewels).

The anagenous period of the hair follicle begins the terminal hair shaft made out of fingernail skin, cortex and medulla(20) (Figure 7A). HFUS, longitudinal view takes into account separating a trilaminar hyperechoic structure, likely relating to the course of action of keratin layers (Figure 7B).