4th stage نسائية Lec-1 د



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4th stage

نسائية

Lec-1

د.ولدان

23/11/2015

ANATOMY OF NORMAL PELVIS & FETAL SKULL

Knowlage of the anatomy of normal female pelvis, fetal skull & soft tissues is essential to understand mechanism of labour.



THE PELVIS

Normal female pelvis is the rounded gynaecoid pelvis occurs only in 40% of white women. There are three other types:

android

Anthropoid & plattypelloid pelvis.



THE PELVIC BRIM OR INLET

The pelvis is divided into true & false pelvis which are separated by pelvic brim.

The plane of pelvic brim is bounded in front by the symphysis pubis [the joint separating the two pubic bones] on each side by the upper margin of pubic bone, iliopectineal line & ala of sacrum. Posteriorly by promontary of the sacrum.

The anteroposterior diameter of brim [true conjugate] is 11cm & the transverse diameter is 13.5cm.



THE PELVIC MID CAVITY

Can be described as an area bounded in front by the middle of symphysis pubis ,on each side by pubic bone, obturator fascia & inner aspect of ischial bone & spines. Posteriorly bounded by the junction of second & third pieces of sacrum.

The cavity is roomy circular with anterioposterior & transverse diameters both measure 12cm.

THE PELVIC OUTLET

Is roughly diamond shaped & bounded infront by the lower margin of symphysis pubis, on each side by the descending ramus of pubic bone , ischial tuberosity & sacrotuberous ligament & posteriorly by the last piece of the sacrum.



In gynaecoid pelvis the subpubic arch is wide & tuberosities are far apart. The anterior-posterior diameter is 13.5cm & the transverse diameter is 11cm.



THE PELVIC FLOOR

It forms part of birth canal, it is formed by the two levator ani muscles which with their fascia form amusculofascial gutter during the second stage of labour with the opening of the vagina looking forward between sides of the gutter



THE PELVIC AXIS

Is an imaginary curve line shows the path which the centre of fetal head follows during its passage through the pelvis, it is obtained by taking several anteroposterior diameters of the pelvis & joining their centers.







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