| Anatomy
and Development In the cervix there is a complicated system of
secretory units producing mucus. Often, but not always, a
secretory unit corresponds to a crypt. A crypt is a deep
part, often ramified, of a cleft between folds of the
endocervical mucosa. The cleft-fold architecture of the
endocervix has been known for several centuries and gives
rise to a silhouette reminiscent of the stem of a palm
tree. This has led to the nomenclature "plicae
palmatae" describing the macroanatomical surface of
the cervical canal. There are 20-50 such folds (Fig. 1)
and totally some 200-900 crypts, the number being
dependent on age, parity, previous diseases, etc. The
macro- and microanatomy of the cervix have been carefully
studied by Fluhman (1961), who has drawn special
attention to the cleft-fold structure and the occurrence
of so-called "tunnel clusters", narrow and long
tubular ramifications of crypts.
Fig. 1. Cut-away
schematic drawing of the cervical canal. Crypts and folds
are shown as well as crypts and "grapes". Note
that some crypts open in the clefts under the folds.
The complicated
morphology of the endocervix is the result of a
complicated embryological and postembryonal development
process. We still lack much knowledge in this field. Some
aspects were considered previously (Odeblad 1994a) and some new aspects will be introduced here.
The schematic presentation of Figure 2 may help explain
the situation.
It is supposed that a
secretory unit can originate from a single cell (or a
small cluster of cells) which has been transformed from
an F cell (undifferentiated fetal cell) in the primitive
cervix. This change may have been brought about by a
transformation growth factor. This transformed cell is
supposed to have the potential to develop into mucus
secreting cells and form secretory units of either G, L,
S or P type. When cell(s) start to proliferate, more
space is needed, and the growth can occur either as an
exophytic or an endophytic process. Which of these
processes is "chosen" may largely depend on the
blood supply. If the capillaries also proliferate an
exophytic process may occur. Vessel proliferation may, in
tum, depend on one or several angiogenetic factors (some
10 possible candidates are presently known).
Fig. 2.
Schematic drawing indicating how exophytic and endophytic
growth processes give rise to fold-cleft structures and
to crypts and "grapes". (a) Early embryonic
life; (b) differentiation of a cell in the Mullerian
epithelium; (c) differential cells are multiplying; (d)
late embryonic life and pre-adolescence; (e) adolescence
and adult life of a woman.
An exophytic growth in
early embryonic life may give rise to folds in a
primordial state, which later grow to fully developed
folds and clefts (see Fig. 2). An endophytic growth gives
rise to a primordial crypt. Exophytic processes starting
later in life (in adolescence or later) result in
"grape"-like structures, 0.2-0.7mm in size,
easily visible in the colposcope. Endophytic processes
result in new primordial crypts or in crypt-branching or
formation of tunnel clusters.
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