CHAPTER 3
Epithelium and Glands
45
D. Cui
Connective tissue
Basal cuboidal cell
Dome-shaped cell
Basement membrane
B
Figure 3-17B.
Transitional epithelium (relaxed).
The
relaxed
,
normal
transitional epithelium
is composed of
four to six layers of cells. The cells located basally are smaller,
low columnar or cuboidal cells. By contrast, the cells located
in the most superF cial layer are larger and exhibit a rounded,
dome shape
that bulges into the lumen.
D. Cui
Connective tissue
Basement membrane
Flattened top cell
C
Figure 3-17C.
Transitional epithelium (distended).
A presentation of
transitional epithelium
in the
distended
state
is shown. These cells change shape according to the degree
of distention of the bladder. When the transitional epithe-
lium is stretched, the top dome-shaped cells become
attened
squamous cells
and the epithelium becomes thinner.
SYNOPSIS 3-2
Pathological Terms for Epithelial Tissue
Metastasis
: The spread of a malignant neoplasm from its site of origin to a remote site, usually through blood and
lymphatic vessels (±ig. 3-2C).
Dyslipidemia
: A general term describing a disorder of lipoprotein metabolism causing abnormal amounts of lipids and
lipoproteins in the blood; certain dyslipidemias constitute a major risk factor for the development of atherosclerosis, such
as hypercholesterolemia (±ig. 3-3C).
Osteomalacia
: Abnormal bone mineralization producing weak, soft bones; may be caused by vitamin D deF ciency or
kidney disorders, including renal ±anconi syndrome (±ig. 3-6C).
Metaplasia
: The reversible process by which one mature cell type changes into another mature cell type, as in squamous
metaplasia of respiratory or glandular epithelia (±igs. 3-9C and 3-14C).
Microabscess
: Collection of neutrophils and neutrophil debris within the parakeratotic scale in the skin disease psoriasis
(±ig. 3-13C).
Micropustule
: Collection of neutrophils within the epidermis, abutting the parakeratotic scale in the skin disease psoriasis
(±ig. 3-13C).
Parakeratosis
: Persistence of the nuclei of keratinocytes into the stratum corneum of the skin or mucous membranes;
parakeratotic scales containing neutrophils are seen in the skin disease psoriasis (±ig. 3-13C).
Connective
Connective
tissue
tissue
Connective
Connective
tissue
tissue
Transitional
epithelium
Lumen
Dome shaped
Dome shaped
surface cells
surface cells
Connective
tissue
Connective
tissue
Dome shaped
surface cells
A
Figure 3-17A.
Transitional epithelium, urinary blad-
der.
H&E,
3
155; inset
3
250
Transitional epithelium
has the special
characteristic of
being able to change shape to accommodate a volume
change in the organ it lines. In the relaxed state, tran-
sitional epithelium contains four to six cell layers, and
each surface cell appears dome
shaped, often contain-
ing two nuclei (these cells are “binucleate”). This picture
illustrates transitional epithelium in a relaxed state (in
most slides, this tissue is unstretched and the surface cells
appear dome shaped). The
lumen
of the bladder appears
as a white space. The transitional epithelium lining the uri-
nary tract including the bladder, ureter, and major calyces
of the kidney is also referred to as
urothelium
. The
black
dashed line
indicates the thickness of the epithelium.
Transitional Epithelium (Stratif
ed Epithelium)
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