Anatomy of the Pelvis

Question 1

The Pelvis

Answer 1

• Pelvic bones create a point of attachment for the lower limbs and transmit weight from the trunk to these limbs
• Support the pelvic organs

Question 2

Size & Shape

Answer 2

The size and shape of the female pelvis in relation to the fetal skull is an important determinant of successful childbirth

Question 3

Pelvic Girdle

Answer 3

• Pair of innominate bones (hip)
• These join anteriorly at the symphysis pubis
• Meet posteriorly with the sacrum to form the sacroiliac joint

Question 4

Joints of the pelvic girdle

Answer 4

• Sacroiliac Joint
• Pubic Symphysis
• Hip (coxal)

Question 5

Ligaments

Answer 5

• Ligaments are dense bands of fibrous tissue that keep boney landmarks in place
• Contain elastin and collagen
• Softening of ligaments is stimulated by hormones such as relaxin, oestrogen and progesterone
• Joint laxity may lead to backache and joint instability

Question 6

Bones of the Pelvic Girdle

Answer 6

• Ilium
• Ischium
• Pubic bones
• Sacrum
• Sacral Promontory
• Coccyx

Question 7

True & False Pelvic

Answer 7

• The true and false pelvis’ are separated by the pelvic brim
• The true pelvis is surrounded by almost completely all bone

Question 8

The Pelvic Brim

Answer 8

• Pelvic brim - the infants head passes through in late-stage pregnancy
• Pelvic cavity - the rounded shape of this cavity encourages the rotation of the baby’s head
• The ischial spines reduce the dimensions. The infants head is considered engaged when it reaches the ischial spines as well as when the fetal head is flexed and the widest diameter of the fetal head have passed into the brim

Question 9

The Pelvic Outlet

Answer 9

• Described as the anatomical or obstetric outlet
• Suprapubic arch, ischial spines, sacrospinous ligaments and lower border of the sacrum
• The sacrococcygeal joint is flexible which allows the coccyx to move posteriorly out of the way during child birth

Question 10

Pelvic Measurements

Answer 10

BRIM - anteroposterior = 11cm

          - oblique                 = 12cm
          - transverse            = 13cm

CAVITY - anteroposterior = 12cm

          - oblique                 = 12cm
          - transverse            = 12cm

OUTLET - anteroposterior = 13cm

           - oblique                = 12cm
           - transverse           = 11cm

Question 11

Types of Pelvis Shapes

Answer 11

GYNACOID - is the most typical type of pelvis possessed in females

ANDROID - male type feature, small inlet and is heart shaped. ischial spines prominent

ANTHROPOID - side walls ofter flare out, generally lard pelvis, the delivery may occur without rotation

PLATYPELLOID - reduced the anteroposterior diameter. the fetus may have difficulty entering the brim but not after that