Human Reproduction, Vol.27, No.3 pp. 727–732, 2012
Advanced Access publication on January 16, 2012 doi:10.1093/humrep/der458
ORIGINAL ARTICLE Gynaecology
Vascular architecture of human uterine
cervix visualized by corrosion casting
and scanning electron microscopy
Jerzy A. Walocha 1,*, Jan A. Litwin 2, Tomasz Bereza1,
Wiesława Klimek-Piotrowska 1, and Adam J. Miodoński 3
1
Department of Anatomy, Jagiellonian University Medical College, Kopernika 12, Krakow 31-034, Poland 2Department of Histology,
Jagiellonian University Medical College, Kopernika 7, Krakow 31-034, Poland 3Laboratory of Scanning Electron Microscopy, Jagiellonian
University Medical College, Krakow, Poland
*Correspondence address. E-mail: [email protected]
Submitted on July 29, 2011; resubmitted on December 5, 2011; accepted on December 12, 2011
background: In contrast to the uterine corpus, the vascular architecture of the human cervix has been the subject of only a few
studies, mostly dealing with the ectocervical mucosal vessels. This study presents the vascular system of the cervical wall surrounding the
endocervical canal visualized by the best currently available technique, corrosion casting combined with scanning electron microscopy.
methods: Uteri collected at autopsy (n ¼ 20) were perfused via afferent vessels with fixative followed by Mercox resin and corroded
after polymerization of the resin. The obtained vascular casts of the cervix visualizing all vessels including capillaries were examined in the
scanning electron microscope.
results: The vascular system of the cervix was nearly completely replicated in only two (10%) of the samples. In the wall of the cervix,
four distinct vascular zones surrounding the endocervical canal were observed: (i) the outer zone containing larger vessels, arteries and veins
of 0.3–1 mm diameter; (ii) the zone containing arterioles and venules; (iii) the zone of endocervical mucosal capillaries showing a very high
density, parallel arrangement and relatively few interconnections and (iv) the innermost, subepithelial zone containing small veins running
along the endocervical canal.
conclusions: Despite the loss of the delicate ectocervical mucosal vessels from the cast during the corrosion step, we have successfully visualized the majority of the cervical vasculature. The vascular pattern of the human cervix, especially that of the endocervical mucosa,
may facilitate the adaptation of the cervical vasculature to the extensive remodeling of the cervix during parturition.
Key words: blood vessels / corrosion casting / uterus / cervix
Introduction
The vascular system of the uterus has a unique remodeling capability
associated with the menstrual cycle, implantation and pregnancy
(Rogers, 1996; Osol and Mandala, 2009). This characteristic has stimulated the research in this field from the 19th century to the present,
with the use of various methods of blood vessel visualization
(Manconi et al., 2010). The vascular and microvascular architecture
of the human uterus was also extensively studied (Dalgaard, 1946;
Farrer-Brown et al., 1970a,b,c; Bulletti et al., 1985; Walocha et al.,
2003; Hamid et al., 2006) but the vast majority of the relevant publications dealt with the vasculature of uterine corpus. In contrast, there
are very few studies on the vascular architecture of the human uterine
cervix (Zinser and Rosenbauer, 1960; Gillet et al., 1973; Sekiba et al.,
1979) and they mostly describe the vessels of the ectocervical
mucosa. Hence, the aim of the present study was to visualize the
entire vascular architecture of the human cervix using the best currently available technique, corrosion casting combined with scanning
electron microscopy (SEM).
Materials and Methods
Twenty uteri were obtained at autopsy of women of reproductive ages
(20– 45 years), deceased from causes not related to disorders of the reproductive system. The material was collected no later than 24 h after
death. The study was approved by the Bioethics Committee of the Jagiellonian University (approval KBET/121/8/2007). Each uterus together
with ovaries and cervical portion of the vagina was removed in such a
way that relatively long fragments of uterine and ovarian vessels (arteries
and veins) were retained.
& The Author 2012. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
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Walocha et al.
Figure 1 Reconstruction of the human cervical vasculature based on adjacent electron micrographs of sagitally dissected cast, showing organization
of the vessels in four zones: zone containing large vessels (1), zone containing arterioles and venules (2), endocervical mucosal capillaries (3) and
endocervical subepithelial veins (4). Cervical glands are marked by asterisks. Bar ¼ 1 mm. Inset: arteriole (A), venule (V) and capillary (C) under
high SEM magnification: note fusiform imprints of endothelial cell nuclei in the arteriole and more rounded/irregular imprints in the venule.
Bar ¼ 10 mm.
Immediately after removal, the uteri were perfused via the afferent arteries with prewarmed (378C), heparinized saline (Heparin, Polfa, Poland,
12 IU/ml) containing 3% dextrane (70 kDa) and 0.025% lidocaine (Lignocaine, Polfa), until the fluid outflowing via the veins was completely transparent (5– 10 min). Next, perfusion was continued using a solution of
0.66% paraformaldehyde/0.08% glutaraldehyde (Sigma) in 0.1 M cacodylate buffer, pH 7.4, supplemented with 0.2% lidocaine. Finally, the vascular
system was injected with 60 – 80 ml of Mercox CL-2R resin (Vilene Comp.
Ltd., Japan) containing 0.0625 mg/ml methyl methacrylate with the polymerization initiator (Vilene Comp. Ltd.) and the uteri were left in a
warm water bath (568C) for 12 h to allow polymerization and tempering
of the resin.
When the polymerization was completed, the uterine tissues were
macerated for 5 – 6 days by repeated soaking in 10% potassium hydroxide
at 378C followed by washing with warm (50– 558C) running tap water.
The obtained vascular casts were washed in several changes of distilled
water, cleaned in 5% trichloroacetic acid for 1– 2 days, washed again in distilled water for 2 – 3 days and freeze dried in a lyophilizer (Liovag G2, Aqua
Fina, Germany).
Parts of the freeze-dried casts corresponding to uterine cervix and a
small fragment of uterine body were excised and examined
macroscopically. In order to facilitate sectioning of the casts, they were
next embedded at 558C in a mixture of polyethylene glycols (PEG
2000/PEG 600, 20:1), cooled to room temperature to solidify PEG
(Walocha et al., 2002) and gently dissected longitudinally in the plane of
the endocervical canal to expose the vasculature of cervix wall. The sectioned fragments were washed with stirred distilled water to remove PEG
and stored in an exiccator containing phosphorus pentoxide until microscopic examination. The fragments were then mounted onto copper
plates using colloidal silver and ‘conductive bridges’ (Lametschwandtner
et al., 1990) and coated with gold. The casts were examined in a JEOL
SEM 35-CF scanning electron microscope at 20– 25 kV. Casts of arteries/arterioles were distinguished from those of veins/venules on the
basis of different imprints of endothelial cell nuclei (Miodoński et al.,
1976; Fig. 1, inset).
Results
Among the 20 corrosion casts prepared, the vascular system of the
cervix was nearly completely replicated in only two specimens
obtained from multiparous women—with exception of the
Human cervical vessels studied by corrosion casting
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Figure 2 An area of sagitally dissected supravaginal portion of the cervix showing a change in the orientation of endocervical mucosal capillaries
from irregular network (left) to parallel vessels running obliquely to the endocervical canal. Note small subepithelial veins (asterisks) running along
the canal, close to its lumen. Bar ¼ 100 mm.
Figure 3 Parallel endocervical mucosal capillaries with very few
interconnections in the vaginal portion of the cervix. Bar ¼ 100 mm.
subepithelial ectocervical vessels. The wall of the cervix showed a high
density of blood vessels. Roundish or oval avascular areas observed in
the mucosal layer represented the corroded cervical glands. In both
the vaginal and supravaginal portions, four distinct vascular zones surrounding the endocervical canal could be observed: (1) the outer zone
containing larger vessels; (2) the zone containing arterioles and
venules; (3) the zone of endocervical mucosal capillaries and (4) the
innermost, subepithelial (pericanalar) zone containing capillaries and
small veins (Fig. 1).
Relatively large arteries and veins, 0.3– 1 mm in diameter, located in
the outermost zone of the cervix wall gave off arteriolar and venular
branches observed in the successive zone, characterized by a slightly
lower density of blood vessels. The arterioles and venules entered
Figure 4 Endocervical mucosal capillaries showing a bent course:
from perpendicular to nearly parallel to the endocervical canal
(beyond the micrograph). Vaginal portion of the cervix.
Bar ¼ 100 mm.
the next zone where they supplied/drained an extremely dense
mucosal capillary plexus. Near the internal os, the plexus was irregular
but towards the vaginal portion of the cervix it assumed a pattern of
parallel capillaries running increasingly obliquely to the axis of the
endocervical canal (Fig. 2) and showing relatively few interconnections
(Fig. 3). In deeper areas of the mucosa, these capillaries first ran for a
short distance perpendicular to the endocervical canal and then bent
to assume an oblique orientation (Fig. 4). In the vaginal portion of the
cervix, the capillaries were nearly parallel to the long axis of the endocervical canal. As compared with the endocervical mucosal capillaries,
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the endometrial capillary network of the uterine body was less dense
and the capillaries showed an irregular arrangement (Fig. 5).
The mucosal capillaries were drained by small veins, 100–200 mm
in diameter, running along the axis of the endocervical canal and
located directly beneath its lumen, in the subepithelial region. The
veins followed such a course for some distance and then turned
towards deeper regions of the wall (Fig. 6) and joined larger veins
located in its outermost zone. The veins were surrounded by a
single layer of irregular capillaries forming a plexus of variable
Walocha et al.
density (Fig. 7). Collectively, the subepithelial veins were observed
along the whole length of the endocervical canal with the exception
of its last segment close to the external os (Fig. 1) and their
number, depending on canal segment, ranged from one to four
(Fig. 8).
The cervical glands were surrounded by a dense capillary plexuses,
either irregular (Fig. 9) or, especially in the case of dilated glands (retention cysts), sometimes composed of parallel capillaries following
the course of the gland (Fig. 10). Larger vessels, mostly arterioles
and venules, were also observed in the direct vicinity of the glands.
Discussion
Figure 5 Spiral artery and endometrial mucosal capillaries in the
uterine body. Note lesser density of capillaries and their irregular arrangement. Bar ¼ 100 mm.
In our previous study on vascularization of the uterine myomata
(Walocha et al., 2003), we obtained acceptable vascular corrosion
casts in 20% of postmortem specimens of the uterine corpus. For
some reason, successful replication of the vascular system in postmortem specimens of the cervix is more difficult, because in the
present study only 10% of these were nearly completely replicated.
Unfortunately, during the corrosion step, the delicate and highly
fragile mucosal microvasculature of the ectocervix exposed on the
surface of the cast was lost. This weakness of the present study is
ameliorated by the fact that the ectocervical mucosal vasculature
was described in detail by other authors (Zinser and Rosenbauer,
1960; Gillet et al., 1973; Sekiba et al., 1979).
Indeed, the studies dealing with angioarchitecture of the human
uterine cervix published so far have been focused mostly on the ectocervical mucosal vessels, because of the significance of this region in
the development of cervical cancer, the most common and severe
pathology of the cervix. Moreover, vascular abnormalities of this
region can also be observed by routine colposcopic examination
(Joshi et al., 2008; O’Connor, 2008). Two detailed papers published
in the 1960s and 1970s employed a gelatin and ink injection technique
followed by light microscopy of cleared specimens (Zinser and Rosenbauer, 1960; Gillet et al., 1973). The corrosion casting method combined with SEM is the best currently available technique for
morphological examination of vascular networks (Lametschwandtner
et al., 1990), because it offers high resolution and a
quasi-three-dimensional image of the vessels without interference
Figure 6 Subepithelial vein (asterisks) running along the endocervical canal (L, lumen). Bar ¼ 1 mm.
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Human cervical vessels studied by corrosion casting
Figure 9 Cervical gland surrounded by irregular capillary network.
Bar ¼ 100 mm.
Figure 7 Subepithelial endocervical vein covered by capillary
network. Note that venules (asterisk) joining the vein drain mucosal
capillaries. L, lumen of the endocervical canal. Bar ¼ 100 mm.
Figure 10 Dilated cervical gland (possibly developing retention
cyst) surrounded by parallel capillaries. Bar ¼ 1 mm.
Figure 8 Four subepithelial veins close to the lumen of endocervical canal (astersisks). Bar ¼ 100 mm.
from the non-vascular tissue. There has been only one study of the
human cervical vessels using this technique (Sekiba et al., 1979) but
it visualized exclusively ectocervical mucosal vasculature under
normal and pathological conditions. The present study demonstrates
for the first time almost the entire vascular system of the human cervical wall, especially the vasculature of the endocervical mucosa which
was only fragmentarily described by Gillet et al. (1973).
The cervical blood vessels are arranged in four distinct zones
around the endocervical canal. The existence of such zonation was
also demonstrated by magnetic resonance imaging (DeSouza et al.,
1994) which revealed the outer zone of larger blood vessels and
another high signal area corresponding to the zone of numerous
mucosal capillaries. These zones were separated by a low signal
stromal zone, in our material corresponding to the zone containing
arterioles and venules, which indeed shows lower general density of
blood vessels. The zones observed in the cervix are a continuation
of the uterine body wall layers: the zone of larger blood vessels corresponds to the vascular layer of the myometrium, while the other
three zones belong to the mucosal layer. In the zone of arterioles
and venules, relatively straight or wavy arterioles supplying the
mucosal capillaries are an equivalent of spiral (coiled) arterioles
which are characteristic of the endometrium.
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In our study, two findings are quite surprising: the extremely high
density of endocervical mucosal capillaries and the presence of small
veins located in the direct vicinity of the endocervical canal. Even
though the injection of the resin might cause some dilatation of thinwalled capillaries and a slight artifactual increase in the diameter of
their casts, still the density of mucosal vessels revealed in our specimens is enormous. The density of the endometrial capillary network
in the uterine body is lower (albeit still considerable) and it gradually
increases in the transition zone between the isthmus and the cervix.
Such high density and regular arrangement of the endocervical capillaries may be related to the extensive remodeling of the cervix during
parturition (Word et al., 2007), to which the vascular system must
adapt. Since the mucosal capillaries are largely parallel, the dilatation
of the cervix could result in the increase in intercapillary distance
and such ‘spreading’ of capillaries might be possible because they
show relatively few interconnections. Owing to their initial high
density, the capillaries would still retain sufficient blood supply to
the stretched mucosa. Moreover, a rich blood supply to the endocervical region could facilitate development of such cervical pathologies as
placenta previa or lobular endocervical glandular hyperplasia/minimal
deviation adenocarcinoma).
Small subepithelial veins running along the endocervical canal have
not been described in previous papers dealing with the cervical vasculature. We observed them in two cast specimens and it seems that
such veins are a frequent feature of the human cervix. Such a vascular
pattern suggests bidirectional draining of endocervical mucosal capillary plexus: centrifugal, by the venules/veins located in the middle
and peripheral zones of the cervical wall and centripetal, by the subepithelial veins. This unusual double draining system could be
related to the extreme density of mucosal capillaries, as it provides efficient evacuation of blood from the capillary plexus. The endocervical
subepithelial veins can also contribute to formation of cervical varices,
a rare complication of pregnancy, which may cause bleeding or thrombosis (Hurton et al., 1998; Sammour et al., 2011).
Authors’ roles
J.A.W. was involved in study design, data collection and analysis and
manuscript preparation. T.B. and W.K.-P. performed experiments,
J.A.L. participated in data analysis and manuscript preparation,
A.J.M. was involved in study design and data analysis. All authors
approved the final version of the manuscript.
Funding
The study was supported by the statutory funds from the Jagiellonian
University Medical College.
Conflict of interest
None declared.
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