254
UNIT 3
Organ Systems
CLINICAL CORRELATION
Figure 13-11C.
Molluscum Contagiosum.
H&E,
3
53
Molluscum contagiosum
is a viral skin infection, caused
by the molluscum contagiosum virus, a member of the
poxvirus family. The disease is characterized by fl
esh-
colored, dome-shaped, pearly papules with a dimpled
center. Lesions are typically 1 to 5 mm in diameter
and common on the trunk, arms, and legs. The disease
is common in childhood, and usually self-limited in
immunocompetent patients. In adults, the disease usu-
ally indicates cellular immunodeF
ciency. The papules
are usually nonpainful, but may itch or be complicated
by secondary infection. The diagnosis is mainly based
on the clinical appearance of the lesions. This slide
shows lobules of keratinocytes with large eosinophilic
intracytoplasmic inclusions called
molluscum bodies
within the stratum granulosum and stratum corneum.
The treatment may include laser therapies, cryotherapy,
or curettage, or there may be no treatment at all.
Molluscum
bodies
C
Figure 13-11A.
Nail, f
nger.
H&E,
3
17
The
nail
is a translucent, hard, keratinized
sheet resting on the tip of each digit. It includes
many components: (1) the
nail plate
, the nail
itself, which is hard keratin; (2) the
nail root
,
also called the
nail matrix
, seen as the
lunula
in the living state; (3) the
nail bed
, a layer of
epidermis beneath the nail plate; (4) the
epony-
chium
, also called the
nail cuticle
, which is the
junction zone between the skin of the F
nger
and the nail plate and which forms a protec-
tive seal; (5) the
perionychium
(
nail wall
), the
skin that surrounds the edge of the nail; and
(6) the
hyponychium
, the junction seal between
the nail plate and the skin of the F ngertip. All
of the sealed areas at the edges of the nail plate
protect the delicate nail matrix and nail bed
from dehydration and infection.
Nail
lunula
Nail
lunula
Eponychium
Nail root
(matrix)
Finger tip
(thick skin)
Nail bed
Nail
plate
Hyponychium
Eponychium
(nail cuticle)
Thin skin
Nail
groove
Perionychium
Nail
matrix
Nail
plate
A
Figure 13-11B.
Nail root (matrix) and nail bed.
H&E,
3
69
The
nail root
is a cellular layer and is also called the
matrix
or
germinal matrix
. It contains many layers of epithelial cells, which
are responsible for the production of the
nail plate
. These cells
proliferate and become fl
attened and highly keratinized and are
pushed forward by newly formed cells. As they differentiate, the
cells F
nally lose color and shape and become part of the nail plate.
The nail plate is similar to the hair shaft, but the pattern of kera-
tin formation is different. The nail bed (equivalent to the epider-
mis) rests under the nail plate. The nail bed extends from the nail
matrix to the hyponychium.
Nail
Nail
matrix
matrix
Nail
matrix
Nail plate
Nail plate
Nail plate
Eponychium
Eponychium
Eponychium
Nail bed
Nail bed
Nail bed
B
Normally, the
nail bed
is smooth and allows for healthy nail
growth and a smooth appearance. If a nail bed is infected by
bacteria
or
±ungus
, the nail bed becomes rough, and an accumu-
lation of organic waste materials can react with the nail plate
and cause the nail to become thickened and distorted.
previous page 269 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online next page 271 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online Home Toggle text on/off