Maternal Pelvis

Question 1

Innominate Bones

Answer 1

3 fused bones

• ilium
• ischium
• pubis

Question 2

The Ilium

Answer 2

• forms the upper expanded part of innominate bone. It gives rise to female hips
• gluteal muscles are attached to the external aspect
• the inner surface forms the iliac fossa
• the upper ridge is called the iliac crest

Question 3

Function of the pelvis

Answer 3

• provides attachment for trunk and limb muscles

- pelvic girdle contains and protects the bladder, rectum and internal reproductive organs

Question 4

Bones of the Pelvis

Answer 4

-made up of 4 irregularly shaped bones

Question 5

The composition of the pelvis

Answer 5

• made up of bone that is highly vascular, hard mineralised living tissue
• supports and protects muscles and sorts at and minerals such as calcium and phosphorus
• in preg, maternal calcium metabolism is altered to meet fetal needs and skeletal growth

Question 6

The Ischium

Answer 6

• a thickened L shape bone, connected to ilium posteriorly and pubis anteriorly
• the ischial spines protrude from its posterior edge on the internal surface (this determines position of fetal head and acts as a landmark)

Question 7

The Pubis

Answer 7

• forms the anterior aspect of the innominate bone and comprises a body and two rami
• it forms 1/5 of the acetabulum

Question 8

The Sacrum and Coccyx

Answer 8

• shield shaped bone formed from 5 fused vertebrae
• articulates with the innominate bones at the sacroiliac joints
• the coccyx is formed from 4 fused coccygeal vertebrae
• the external anal sphincter is attached to the lowest point

Question 9

Joints of the pelvis

Answer 9

• sacroiliac joints are sinovial joints and include very strong posterior ligaments in order to support the trunk
• movements at these joints is usually slight, but increases in range during pregnancy under the influence of progesterone and relaxin
• symphysis pubis consists of an oval disk of fibrocartilage. Aprox 4cm long, the joint is reinforced by ligaments crossing from one pubis bone to the other

Question 10

Blood and nerve supply to the pelvis

Answer 10

• blood is supplied via the pudendal arteries and veins

- episiotomies are affected by pudendal nerve as need to know not to damage

Question 11

Maternal positions during birth

Answer 11

• upright froward leaning positions during birth increase the pelvis diameter by 30%
• lunges, squats and forward leaning positions as well as seating positions which place the pelvis higher than the knees help the fetus navigate the pelvis

Question 12

The pelvic floor - functions

Answer 12

• supports weight of abdominal and pelvic organs
• muscle responsible - control of micturition, defecation, sexual intercourse
• relaxes to allow expulsion of the fetus

Question 13

The pelvis floor - structure

Answer 13

• the bony pelvis provides protection to the pelvic organs - urethra, vagina, rectum
• the pelvic floor is mainly composed of soft tissues which fill out pelvis

Question 14

Superficial Muscles

Answer 14

(usually damaged during vaginal delivery)

• lie external to the deep muscles
• provide additional strength