Female pelvis is known as Gynaecoid is regarded as the true female pelvis because its characteristics give rise to no difficulties in child birth, providing the fetus is of normal size.
Allow the movement of the body
Permits to sit and kneel
Adapted for child bearing
Transmits the weight of the trunk to the legs
Provides protection to the pelvic organs
The sacrum distributes the nerves to the various parts of the pelvis
Pelvic is made up of four pelvis bones:
· 2 innominate bones
· 1 coccyx
Innominate bones: composed of three parts:
· Pubic bone
The Ilium :
· Large flared out part
· Upper border: iliac crest on which hands rest when placed on hip
· At the front of iliac crest can be felt a bony prominence known as anterior superior iliac spine
· Short distance below it is anterior inferior iliac spine
· Similar points at the other end of the iliac crest: posterior superior and posterior inferior iliac spines
· The concave anterior surface of the ilium is iliac fossa.
It is the thick lower part
It has large prominence known as ischial tuberosity on which body rests while sitting.
Behind and little above tuberosity is an inward projection called ischial spine. In labor the station of the fetal head is estimated in relation to the ischial spine.
forms the anterior part
it has a body and 2 oar projections : superior and inferior ramus
The 2 pubic bones meet at the symphysis pubis
The 2 inferior rami form the pubic arch
Space enclosed by the body of pubic bone, the rami and the ischium is called obturator foramen.
The innominate bones contain a deep cup to receive the head of femur called as acetabulum. (all three part of the bone contribute to the acetabulum, ie, 2/5th of ilium, 2/5th of ischium, 1 /5th of pubic bone)
Lower border of innominate bones : 2 curves are found
One extends from the posterior inferior iliac spine to the ischial spine, is called greater sciatic notch. It is wide and rounded.
The other lies between the ischial spine and the ischial tuberosity : lesser sciatic notch
Wedge shaped bone consisting of five fused vertebrae
Upper border of the first sacral vertebrae juts forward and is known as sacral promontory
Anterior surface of the sacrum is concave and is called as hollow of sacrum
Laterally sacrum extends into a wing or ala
4 pairs of holes or foramina pierce the sacrum and the through these nerves from the cauda equina emerge to supply the pelvic organs
Posterior surface is roughened to receive attachments of muscles
· The coccyx is a vestigial tail
· Consists of 4 fused vertebrae and forms a triangular bone
· Deflects backward during the process of child birth
1 symphysis pubis
2 sacroiliac joints
1 sacro coccygeal joint
Inter-pubic ligaments at the symphysis pubis
Sacro coccygeal ligaments
The pelvis is anatomically divided in to a false pelvis and true pelvis.
True pelvis- It is a bony canal through which the fetus must pass during birth. It has a brim, cavity and a outlet.
Falsc pelvis - the false pelvis is formed by the iliac portions of the innominate bones and is limited above by the iliac crests. Its only obstetric function is to support the enlarged uterus during pregnancy. Its boundaries are: posteriorly - lumbar vertebrae, laterally-iliac fossa and anteriorly - anterior abdominal wall.
Shape is round
Pelvis tilts forward in the erect posture
Plane of the inlet makes an angle of 55 degree.
High inclination has got obstetrical significances
Sacral angle is more than 90 degree
Axis is downwards and backwards
Landmarks of the pelvic brim:
Sacral ala / wing
Ilio pectinal line
Ilio pubic eminence
Cavity: extends from the brim above to the outlet below.
Anterior wall is formed by pubic bones and symphysis pubis and its depth is 4 cms
Posterior wall is formed by the curve of the sacrum and is 12 cms in length
Because of such a difference it forms a curved canal
Shape: It is almost round.
Pelvic outlet: 2 types- anatomical and obstetrical
Anatomical: it is formed by the lower borders of each of the bones together with the sacro tuberous ligament
Obstetrical outlet: includes the narrow pelvic strait through which thc fetus must pass.