WORKSHOP ON HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 5. SPECIAL HISTOLOGY

Skin and its appendages

Slide 118. Human scalp.

Staining: hematoxylin and eosin.

Magnification: x80.

The section represents a vertical slice of human scalp Skin.

Under low magnification, we can identify the layers of the skin: the epidermis (1), the papillary layer (2), and the reticular layer (3) of the dermis. The thickness of the epidermis is considerably smaller than that of the finger skin. The papillary layer is less pronounced, whereas the reticular layer is the thickest and is formed by dense irregular Connective Tissue.

The long Hair (4) shown in the slide consists of a shaft (the portion above the skin surface) and a ROOT (the portion embedded in the epidermis and dermis). The shaft is composed of the cortex and cuticle, while the root is composed of the medulla, cortex, and cuticle. Deep within the skin, the root expands to form the hair bulb (5), located at the border of the reticular dermis and hypodermis. Loose connective tissue grows into the root from below, forming the dermal papilla of the hair (6). The hair bulb, as visible in a separate diagram, is surrounded by the internal root epithelial sheath (7), the external root epithelial sheath (8), and the dermal root sheath, or fibrous sheath (hair follicle) (9). The latter is Connective tissue with inner circularly oriented fibers and outer longitudinally oriented fibers. Smooth myocytes—the arrector pili Muscle (10)—insert into the fibrous sheath.

Sebaceous Glands (11) are located near the hair roots. Their short excretory ducts open into the lumen of the root sheath at the level of its upper third.

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Slide 118. Human scalp.