Integumentary System
Answers
193.The answer is a.(Young, pp 95, 164, 168. Junqueira, pp 79–80,
370–372.)The cyst in the vignette is an epidermoid or sebaceous cyst and
the gland shown in the photomicrograph is a sebaceous gland, located in
the dermis and associated with a hair follicle. Secretion from sebaceous
glands is classified as holocrine (i.e., shedding of the disintegrated cell
along with sebum into the hair follicle). Blockage of sebaceous gland ducts,
presumably from injury, infection or irritation, results in cyst formation.
Sebaceous cysts are prone to infection and can have foul-smelling drainage
with inflammation and pain. The lesion usually consists of an enlarged
sebaceous gland with numerous lobules grouped around a centrally
located sebaceous duct, which has become obstructed causing the cyst.
The photomicrograph represents a microscopic section obtained from
thin skin. The presence of sebaceous glands/hair follicles identifies the
section as thin skin. Sebaceous glands and hair follicles are not found in
thick skin. Another difference between thick and thin skin is the virtual
absence of the stratum lucidum in thin skin. There are two types of sweat
glands: merocrine and apocrine. The merocrine glands release their secre-
tion through exocytosis with conservation of membrane (answer b).In
anal, areolar, and axillary regions, sweat glands are apocrine (answer c);
the apical part of the cell is released with the secretion. Endocrine secretion
occurs into the blood (answer d);autocrine secretion is self-stimulation
(answer e).For example, activated T cells stimulate their own proliferation
by secreting IL-2 and synthesizing IL-2 receptors that bind the IL-2.
194.The answer is e.(Junqueira, pp 95, 97, 260, 360, 366, 368.)The
Merkel cell is a neuroendocrine cell. It is a modified keratinocyte found in
areas in which fine tactile sensation is critical, such as the fingertips. A
Merkel cell is associated with an unmyelinated nerve ending, forming a
Merkel corpuscle (disk), essential for two-point discrimination: the ability
to discriminate two closely placed points as separate. Two point discrimi-
nation is dependent on the size of receptive fields and the density of Merkel
corpuscles. Langerhans cells function in phagocytosis (answer a),antigen
presentation (APCs), cytokine production, and expression of Fc, Ia, and C3
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