The Pelvic Floor can be differentiated into a Pubic and Sacral Segment, contrasted
as follows :—
Loose in its attachments.
Drawn up during labour.
Driven down in prolapsus uteri.
Passes down with viscera in genu-pectoral
posture, when vagina is distended by
air, and is therefore intestinal.
Firm in its attachments.
Driven down during labour.
Always remains in position (posterior vaginal wall excepted) in prolapsus uteri.
Remains in position in genu-pectoral posture, with vagina distended by air, and
is therefore vertebral.
Three vertical "lines of cleavage" exist in the pelvic floor :—
1. Vaginal, i.e., between vaginal walls. All in front is drawn up in labour, and goes
down with viscera in genu-pectoral posture ; all behind is driven down during labour,
and remains in situ in genu-pectoral posture after
vagina is distended with air. (Figs. 4 and 5.);
2. Recto-vaginal\ between anterior wall of
rectum and posterior wall of vaginar All in
front comes down in prolapsus uteri; all behind
remains in situ} (Fig. 10.);
3. Rectal, between the anterior and posterior walls of rectum. All in front of this is lifted
up in the " bimanual," and when rectum is distended with air. (Fig. 19.)
The first line is therefore the physiological
line of cleavage, the second is the pathological,
and the third the instrumental. (Fig. 22.)
The Sims speculum pulls back the sacral
segment, while, by posture of patient, the pubic
segment sags down.
The Hodge and ring pessaries are kept
in position by the pubic segment pressing them
against the oblique sacral one. In retroversion
of the uterus, and in prolapsus uteri, they keep the posterior vaginal wall its proper
length and render it rigid, so that it runs round the top bar of the pessary like a pulley,
and is reflected down on the cervix making it tense. It thus pulls the cervix back and
keeps it so.