Pelvic Cavity & Sacrum

Question 1

Pelvic Cavity Function

Answer 1

• contain and support the urinary bladder, rectum, anal canal, and reproductive tracts
• contains most of the reproductive tract in women and part of the reproductive tract in men.

Question 2

Sacrum

Answer 2

• formed by the fusion of the 5 sacral vertebrae
• the base of the sacrum articulates with vertebra L5
• the apex articulates with the coccyx

Question 3

Lumbosacral joints

Answer 3

Formed between L5 & the sacrum

consists of:
* 2 facet joints (zygapophysial joints)
* an intervertebral disc that joins the bodies of L5 and S1

Stabilized by: (stability in all directions-minimal movement)
* iliolumbar ligament
* lumbosacral ligaments
* anterior longitudinal ligament (not as much)

Question 4

Sacro-iliac joints

Answer 4

Synovial joints between the L-shaped articular facets on the lateral surfaces of the sacrum & facets on the iliac parts of the pelvic bones
* transmit forces from the lower limbs to the vertebral column.

Stabilized by:
* Anterior sacroiliac ligament: thickening of the fibrous membrane of the joint capsule
* Interosseous sacro-iliac ligament: largest, strongest ligament
* Posterior sacro-iliac ligament: covers the interosseous sacro-iliac ligament

Question 5

Pubic symphysis joint

Answer 5

lies anteriorly between the adjacent surfaces of the pubic bones
* joint’s surfaces is covered by cartiliage

Stabilized by: (small, back up protection, during pregnancy)
* superior pubic ligament
* inferior pubic ligament

Question 6

Muscles of the lateral pelvic wall

Answer 6

2 muscles:
* obturator internus
* piriformis

Both originate in the pelvic cavity but attach peripherally to the femur

Question 7

Sacral & Coccygeal Plexuses

Answer 7

• situated on the posteriorlateral wall of pelvic cavity
• formed by the ventral rami of S1 to Co, with a significant contribution from L4 & L5 which enter the pelvis from the lumbar plexus
• Nerves from these plexuses contribute to the innervation of the lower limb & muscles of the pelvis & perineum. Cutaneous branches supply skin over the medial side of foot, the posterior aspect of lower limb, and most of the perineum.

Question 8

Sacral plexus

Answer 8

• formed by the anterior rami of S1 to S4, & the lumbosacral trunk (L4 and L5). The plexus is formed in relation to the anterior surface of the piriformis muscle, which is part of the posteriorlateral pelvic wall
• sacral contributions to the plexus pass out of the anterior sacral foramina & course laterally & inferiorly on the pelvic wall.
• has dorsal and ventral divisions except S4 has only ventral devisions

Question 9

Sacral plexus branches

Answer 9

• branches of the sacral plexus include the sciatic nerve and gluteal nerves, which are major nerves of the lower limb & the pudental nerves which is a nerve of the perineum. Numerous smaller branches supply the pelvic wall, floor, & lower limb.
• most nerves originating from the sacral plexus leave the pelvic cavity by passing through greater sciatic foramen inferior to piriformis muscle, and enter gluteal region of lower limb

Question 10

Coccygeal plexus

Answer 10

the small coccygeal plexus has a minor contribution from S4 & is formed mainly by the anterior rami of S5 & Co, which originate inferiorly to the pelvic floor.