The Female Pelvis

Question 1

What are the functions of the pelvis?

Answer 1

• Protect the pelvic organs
• Transmit body weight to our legs
• Mobility (walking and running)
• Maintain upright posture and flexibility
• Childbirth
• Pelvic floor

Question 2

What is the structure of the pelvis?

Answer 2

4 BONES

• 2 INNOMINATE BONES (also known as the hip bone)
  
  • The ilium
  • The ischium
  • The pubis
• 1 SACRUM
• 1 COCCYX

Question 3

What is the ilium?

Answer 3

Forms the upper flattened position of the pelvis.

• The iliac crest: makes up the upper border
• The anterior superior iliac spine: makes up the uppermost point
• Below point: anterior inferior iliac spine
• Iliac bone: forms the upper 2/5 ths of the acetabulum.
• The outer surface of the ilium is rough and is an attachment for the gluteus muscles of the buttocks.
• The inner surface is smooth and concave.

Question 4

What is the ischium?

Answer 4

Is a smaller bone that consists of a large thick area called the ischial tuberosity.
It makes up the inferior position of the innominate bone.

Question 5

What is the pubis?

Answer 5

A small bone situated at the front of the pelvis.

Composed of a body and two rami- the superior and inferior pubic rami.

Question 6

Where do all the innominate bones meet?

Answer 6

ACETABULUM

Question 7

What is the sacrum?

Answer 7

It forms the rear of the pelvis

Situated between the two ilia, forms the posterior wall of the pelvis and is composed of five fused vertebrae

Question 8

What is the coccyx?

Answer 8

Forms the base of the spinal column and pelvis → small triangular bone situated beneath the sacrum. It is hinged with the sacrum and moves backwards during the passage of the fetus.

Question 9

What are the 4 joints that articulate the pelvis bones?

Answer 9

Two sacroiliac joints
The symphysis pubis
The sacrococcygeal joint

Question 10

What are the powerful ligaments of the pelvis?

Answer 10

Sacroiliac ligaments which run in front and behind the sacroiliac joint.
Pubic ligament- present both in front and behind the symphysis pubis.
Sacrotuberous ligament- run from the ischial tuberosities to the sacrum.
Sacrospinous ligament- run from the ischial spines to the sacrum.

Question 11

What is the false and true pelvis?

Answer 11

For obstetric purposes the pelvis can be considered to consist of the false pelvis above the iliopectineal line and the true pelvis below this.
The false pelvis play no role in childbirth.
The shape and diameters of the true pelvis is important in allowing the passage of the fetus.
It consists of:
Brim: roughly oval shaped and has landmarks
Cavity: extends from the brim to the outlet and forms the Curve of Carus.
Outlet: diamond/ovoid shaped and its partly formed of ligaments and also includes landmarks.
The fetus rotates within these sections accommodating to the largest diameters.

Question 12

What are the diameters of the pelvis and why is it important to know it?

Answer 12

Important for the midwife to gain information o:

• Whether there is sufficient room for the passage of the fetus
• Understands why the fetus rotates as it moves through the pelvis
• Predict and difficulties that can develop

BRIM
A/P POSITION: 11CM
OBLIQUE: 12CM
TRANSVERSE: 13CM

CAVITY
A/P POSITION: 12CM
OBLIQUE: 12CM
TRANSVERSE: 12CM

TRANSVERSE
A/P POSITION: 13CM
OBLIQUE: 12CM
TRANSVERSE: 11CM

Question 13

What are the two diameters that are important in a posteriot position?

Answer 13

Sacrocotyloid diameter- 9 cm long

Diagonal conjugate- 12.5 cm long

Question 14

What are the four types of pelvis?

Answer 14

Gynecoid
Android
Anthropoid
Platypoid

Question 15

What are the physiological changes through pregnancy?

Answer 15

The hormones relaxin and progesterone acts on the ligaments of the body allowing more room for the passage of the fetus but also allows movement of the joints and so women may complain about having lower back pain.
Pelvic girdle pain: uncomfortable symptoms caused by stiffness of the pelvis.

Question 16

What are the physiological changes through labour?

Answer 16

The most common position for a cephalic presentation is left occipital anterior (LOA)
The diameter presenting is the SOB
As the fetal head descends into the brim it adapts to the largest diameter so will enter in the transverse position.
In the pelvic cavity, the fetal head rotates 90 to the largest diameter of the pelvic outlet, anterior posterior position. This rotation is facilitated by the muscles of the pelvic floor.
Once the head has delivered, the shoulders rotate to fit the biggest diameter of the pelvis.

Question 17

What are the physiological changes during postnatal period?

Answer 17

Once placenta is out, hormonal influence is rapidly removed and ligaments tighten to restrict movement of the pelvis.