The Female Pelvis and the Reproductive Organs

Chapter 1 The Female Pelvis and the Reproductive Organs



The female pelvis


The normal pelvis is comprised of four pelvic bones:



image two innominate bones


image one sacrum


image one coccyx.




The innominate bones (Fig. 1.1)


Each innominate bone is composed of three parts:



image the ilium


image the ischium


image the pubic bone.


image

Fig. 1.1 Innominate bone showing important landmarks.



The ilium




image At the front of the iliac crest is a bony prominence known as the anterior superior iliac spine; below it is the anterior inferior iliac spine.


image Two similar points at the other end of the iliac crest are called the posterior superior and the posterior inferior iliac spines.


image The concave anterior surface of the ilium is the iliac fossa.



The ischium


The ischium is the thick lower part.



image The ischial tuberosity is the prominence on which the body rests when sitting.


image Behind and a little above the tuberosity is an inward projection, the ischial spine.


In labour the station of the fetal head is estimated in relation to the ischial spines.



The pubic bone




image This has a body and two oar-like projections: the superior ramus and the inferior ramus.


image The two pubic bones meet at the symphysis pubis and the two inferior rami form the pubic arch, merging into a similar ramus on the ischium.


image The space enclosed by the body of the pubic bone, the rami and the ischium is called the obturator foramen.


image The innominate bone contains a deep cup, the acetabulum, which receives the head of the femur.


On the lower border of the innominate bone are found two curves:



image One extends from the posterior inferior iliac spine up to the ischial spine and is called the greater sciatic notch. It is wide and rounded.


image The other lies between the ischial spine and the ischial tuberosity and is the lesser sciatic notch.



The sacrum


This is a wedge-shaped bone consisting of five fused vertebrae. The first sacral vertebra juts forward and is called the sacral promontory.



The coccyx


The coccyx consists of four fused vertebrae, forming a small triangular bone.



The pelvic joints


There are four pelvic joints:



image The symphysis pubis is formed at the junction of the two pubic bones, which are united by a pad of cartilage.


image Two sacroiliac joints join the sacrum to the ilium and thus connect the spine to the pelvis.


image The sacrococcygeal joint is formed where the base of the coccyx articulates with the tip of the sacrum.


In the non-pregnant state there is very little movement in these joints, but during pregnancy endocrine activity causes the ligaments to soften, which allows the joints to give.



The pelvic ligaments


Each of the pelvic joints is held together by ligaments:



image interpubic ligaments at the symphysis pubis


image sacroiliac ligaments


image sacrococcygeal ligaments.


Two other ligaments are important in midwifery:



image the sacrotuberous ligament


image the sacrospinous ligament.


The sacrotuberous ligament runs from the sacrum to the ischial tuberosity, and the sacrospinous ligament from the sacrum to the ischial spine. These two ligaments cross the sciatic notch and form the posterior wall of the pelvic outlet.



The true pelvis


The true pelvis is the bony canal through which the fetus must pass during birth. It has a brim, a cavity and an outlet.




The pelvic brim


The fixed points on the pelvic brim are known as its landmarks (see Fig. 1.2 and Box 1.1).


image

Fig. 1.2: Brim or inlet of female pelvis (see Box 1.1).



Box 1.1 Landmarks of the pelvic brim (commencing posteriorly)



See Figure 1.2 for numbers




• Sacral promontory (1)


• Sacral ala or wing (2)


• Sacroiliac joint (3)


• Iliopectineal line: the edge formed at the inward aspect of the ilium (4)


• Iliopectineal eminence: a roughened area formed where the superior ramus of the pubic bone meets the ilium (5)


• Superior ramus of the pubic bone (6)


• Upper inner border of the body of the pubic bone (7)


• Upper inner border of the symphysis pubis (8)



Diameters of the brim


Three diameters are measured (Figs 1.3 and 1.4):



image anteroposterior


image oblique


image transverse.

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Related posts:

  1. The Placenta
  2. Trauma During Birth, Haemorrhage and Convulsions
  3. Obstetric Emergencies
  4. Problems of Pregnancy

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Jul 11, 2016 | Posted by in MIDWIFERY | Comments Off on The Female Pelvis and the Reproductive Organs

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