St A - Pelvis; Walls, Floor and Neurovascular Supply

Question 1

Describe how the pelvis is divided?

Answer 1

Into a greater (false) pelvis and lesser (true) pelvis which are divided by the pelvic brim.

Question 2

Describe the bony landmarks of the Ilium

Answer 2

Iliac crests, iliac fossa (in greater pelvis), anterior superior iliac spine and the posterior iliac spine

Question 3

What are the bony landmarks of the ischium?

Answer 3

Question 4

What are the bony landmarks of the pubis?

Answer 4

Question 5

Name the joints of the pelvis

Answer 5

• Sacroiliac joint, - Hip joint (synovial), - Pubic Symphysis (secondary cartilaginous)

Question 6

What makes up the pelvic inlet (pelvic brim, superior pelvic aperture, linea terminalis)

Answer 6

Inferior - Pubic symphysis, pubic crest, pectineal line. Laterally - Arcuate line of ilium, - Sacral ala and sacral promontory

Question 7

Name the pelvic ligaments that make up the greater and lesser sciatic foramen

Answer 7

Sacrotuberous ligament - From sacrum to ischial tuberosity, Sacrospinous ligament - from sacrum and sacrotuberous ligament to ischial spine.

Question 8

Name the pelvic gateways and what passes through them

Answer 8

Greater sciatic foramen - Sciatic nerve, gluteal neurovascular bundle and pudendal nerve. Obturator canal - Obturator neurovascular bundle, Gap between inguinal ligament and pelvic bone - femoral neurovascular bundle, Lesser sciatic foramen - Pudendal nerve, internal pudendal vessels.

Question 9

What are the barders of the pelvic outlet?

Answer 9

Posterior - Tip of coccyx, Lateral - Ischial tuberosities and inferior margin of sacrotuberous ligament, Anterior - Pubic arch

Question 10

Describe some of the major differences between the male and female pelvis

Answer 10

Pelvic inlet - wide in women and narrow in men. Sub-pubic angle - Wide in women and narrow in men.

Question 11

What makes up the boundaries of the pelvic walls?

Answer 11

Antero-inferior wall - formed by pubic symphysis, body and rami of pubis. Postero-superior wall - sacrum and piriformis. Lateral Wall - Obturator internus with obturator fascia

Question 12

What is inferior to rhe pelvic floor?

Answer 12

The perineum which is divided into deep and superficial compartments anteriorly by the perineal membrane

Question 13

What forms the pelvic floor/diaphragm?

Answer 13

Levator ani and coccygeus (S4-5)(ischiococcygeus) muscles and their fascia

Question 14

Name the three part sof levator ani

Answer 14

• Puborectalis (important in faecal continence), - Pubococcygeus (subdivided into puboperineus and then pubovaginalis or puboprostaticus) - Iliococcygeus

Question 15

What is the urogenital hiatus and anal hiatus made up of?

Answer 15

It is the gap between the medial boarders of levator ani

Question 16

What is the function of levator ani?

Answer 16

• Supports pelvic organs, - Augments the external anal sphincter which maintains faecal continence, - Augments urethral sphincter which maintains urinary continence, - Forms vaginal sphincter, - Actively contracted in coughing, sneezing and forced expiration

Question 17

When the pelvic muscles meet in the midline, what does this form?

Answer 17

• Anococcygeal body (raphe below anus) - Perineal body (central tendon of perineum)

Question 18

What is the function of the perineal membrnae?

Answer 18

It supports the pelvic floor anteriorly. It is a thick triangular fascial sheet that fills the space between the arms of the pubic arch

Question 19

What is the roof of the pelvic cavity?

Answer 19

The peritoneum

Question 20

Describe features of the prevertebral (pre-aortic) plexuses

Answer 20

Prevertebral plexus is formed around the abdo aorta with preganglionic and postganglionic sympathetic fibres, preganglionic parasympathetic fibres and visceral afferent fibres. Condensations of the prevertebral plexus forms the coeliac, renal, superior mesenteric, inferior mesenteric and superior hypogastric plexuses.

Question 21

What are the pelvic autonomic nerves?

Answer 21

• Sacral sympathetic trunks (lumbar and Sacral splanchnic nerves) - Parasympathetic fibres from S2-4 via (Pelvic splanchnic nerves). These nerves will converge onto a superior or inferior hypogastric plexus and then onto periarterial plexus

Question 22

Describe the location of the superior hypogastric plexus

Answer 22

It is found in front of the inferior part of the abdominal aorta and its bifurcation.

Question 23

Describe features of the inferior hypogastric plecus

Answer 23

• Lies on either side of rectum at the base of the bladder and vagina. - It is formed by sympathetic fibres from hypogastric nerves (from SHP) and PSNS fibres from pelvic splanchnic nerves.

Question 24

Visceral fibres conducting unconscious (reflexive) sensations travel with what?

Answer 24

Parasympathetic fibres

Question 25

Describe how visceral afferents conducting pain travel

Answer 25

Either with SNS or PSNS depending on their relation to the pelvic pain line. If organs are touching the peritoneum then fibres run with sympathetic fibres so pain is perceived as suprapubic. If organs are not touching the peritoneum then they run along parasympathetics so pain is perceived in S2, S3 and S4 dermatome

Question 26

What provides somatic innervation to the perineum and what is it’s clinical relevance?

Answer 26

Supplied by the pudendal nerve. It curves posterior to the ischial spine so a local anaesthetic injection here using the ischial spine as a landmark can numb the perineum.

Question 27

Describe the arterial supply of the pelvis

Answer 27

The internal iliac artery, branches include; anterior and posterior trunks. Umbilical artery, obturator artery, middle rectal artery, internal pudendal artery, superior and inferior gluteal arteries and lateral sacral artery

Question 28

Describe the venous drainage of the pelvis

Answer 28

Extensive venous plexus which drains to the internal iliac or internal pudendal vein. Then joints external iliac vein to form common iliac vein which meets its opposite to form the IVC (L5)

Question 29

Describe the lymphatic drainage of the pelvis

Answer 29

Tends to parallel venous drainage and are very interconnected. There are pararectal, gonadal, sacral, external and internal iliac, common iliac and superficial and deep inguinal which drain to para-aortic lymphnodes.