Clinical note: Sebaceous glands become much more active after puberty and can become affected by acne vulgaris, in which blocked ducts or hair follicles produce small white lesions (comedones) caused by build-up of sebum and dead cells. The disease is normally self-limiting, but comedones can become sites of bacterial infections. Sometimes there is marked scaring left in the wake of the inflammation.

On slides 36 and 89 identify the

• Secretory portions and darker-staining ducts of merocrine (“eccrine”) sweat glands (Figs. 18-16a and 18-17).
• Myoepithelial cells surrounding the secretory units (better shown on slide 89).
• In the ducts, note the unusual stratified cuboidal epithelium lining the ducts and the lack of myoepithelial cells.

Examine the micrograph of apocrine sweat glands (Fig. 18-16b) and look for such structures on slide 17 and slide 25.

• Compare the lumen size and overall histological appearance of apocrine sweat glands to the more common merocrine/eccrine sweat glands.

Summarize the histological and functional differences between merocrine and apocrine sweat glands.

Examine the structure of nails and their association with other parts of a digit as shown on the demo slide (Fig. 18-14).

How does the structure of a nail and nail bed compare with that of a hair follicle?

Next is the cardiovascular system.