Pelvis

Question 1

differentiate between the abdomen, pelvic cavity and perineum

Answer 1

• abdominal cavity superior until it meets the iliac crests
• then pelvic cavity: greater and lesser pelvis separated by the pelvic brim
• then perineum

Question 2

What bones form the pelvis?

Answer 2

• hip bones (ischium, ilium, pubis)
• sacrum
• coccyx

Question 3

What are the joints of the pelvis?

Answer 3

• pubic symphysis (secondary cartilaginous)
• sacroiliac joint (bilateral and posterior - synovial)
• hip joint (ball and socket joint - synovial)

Question 4

What forms the pelvic inlet?

Answer 4

• pubic symphysis
• pubic crest
• pectineal line
• arcuate line of ilum
• sacral ala and sacral promontory

Question 5

What are the ligaments of the pelvis?

Answer 5

• sacrotuberous ligament: from posterior-inferior iliac spine, sacram and coccyx to ischial tuberosity
• sacrospinous ligament: from sacrum, cocyx and sacrotuberous ligament to ischial spine
• both form greater and lesser sciatic foramina

Question 6

What forms the pelvic outlet?

Answer 6

• pubic symphysis
• ischiopubic ramus
• ischial tuberosity
• sacrotuberous ligament
• coccyx

Question 7

Describe some differences between the male and female pelvis

Answer 7

Females:

• thin and light
• shallow greater pelvis
• wide and shallow lesser pelvis
• inlet is oval and rounded and wide
• outlet is large
• wide pubic arch

Males:

• thick and heavy
• deep greater pelvis
• narrow and deep lesser pelvis
• inlet is heart shaped and narrow
• outlet is small
• narrow pubic arch

Question 8

What forms the different pelvic walls

Answer 8

Antero-inferior:

• pubic symphysis
• body and rami of pubis

Postero-superior:

• sacrum
• piriformis (divides the greater sciatic foramen)

Lateral:
- obturator internus with fascia

Question 9

Where is the perineum found?

Answer 9

inferior to the pelvic floor and divided into 2 compartments (superficial and deep) anteriorly by perineal membrane

Question 10

What muscles form the pelvic diaphragm?

Answer 10

• levator ani (pubococcygeus, puboredctalis, iliococcygeus)

- coccygeus

Question 11

What are the origins and innervations of the levator ani muscles?

Answer 11

• pubis
• ischial spine
• tendinous arch (formed from thickening of internal membrane of obturator internus)
• innervated by S3-4

Question 12

Describe the anatomy and role of puborectalis

Answer 12

• originates from one side of pubis, slings round to attach to other side of pubis
• extends muscle fibres medially around anus region
• important in faecal continence

Question 13

What are the divisions of pubococcygeus?

Answer 13

• puborectalis
• puboperineal
• pubovaginalis (female) or puboprostaticus (male)

Question 14

What is the functions of the pelvic diaphragm (levator ani)?

Answer 14

• supports pelvic organs
• makes anorectal angle more acute and augments external anal sphincter for faecal continence
• augments urethral sphincter for urinary continence
• forms vaginal sphincter
• actively contracted coughing/sneezing/forced expiration

Question 15

Where are the pelvic diaphragm muscles anchored?

Answer 15

• all meet in midline to form anococcygeal body (raphe of ligament) and perineal body (central tendon of perineum)

Question 16

What is the lowest point in the pelvic cavity?

Answer 16

• rectouterine/rectovesical pouch

Question 17

Describe the prevertebral plexuses

Answer 17

• prevertebral plexuses are formed around abdominal aorta by:
• sympathetics (T1-L2/3)
• parasympathetics (vagus or S2-4)
• condense around origins of branches of abdo aorta to form:
• coeliac plexus
• renal plexus
• superior and inferior mesenteric plexus
• superior hypogastric plexus

Question 18

Describe the pelvic autonomic nerves

Answer 18

• sacral sympathetic trunks (motor and sensory, 4 pairs sympathetic ganglia, lumbar and sacral splanchnic nerves)
• parasympathetic fibres from S2-4 (nervi erigentes, motor and sensory)
• hypogastric plexuses (superior and inferior hypogastric plexuses)
• periarterial plexuses (postsynaptic, sympathetic, vasomotor fibres to arteries - superior rectal/ovarian/internal iliac)

Question 19

Where is the superior and inferior hypogastric plexuses found?

Answer 19

• superior: lies in front of inferior part of abdo aorta and its bifurcation
• inferior: lies on each side of rectum, in base of bladder and vagina

Question 20

What is the superior hypogastric plexus formed as?

Answer 20

• continuation of aortic plexus
• sympathetic fibres from L3 and L4 sympathetic ganglia
• parasympathetic fibres from pelvic splanchnic nerves

Question 21

What is the inferior hypogastric plexus formed as?

Answer 21

• sympathetic fibres from hypogastric nerves (from superior hyogastric)
• parasympathetics from pelvic splanchnic nerves

Question 22

Describe what different visceral afferents travel with

Answer 22

• visceral afferents conducting unconscious sensation travel with parasympathetic fibres
• visceral afferents conducting pain travel with: * sympathetics T11-12 (if organ touches peritoneum) - suprapubic pain
• parasympathetics S2-4 (any organ below peritoneum) - perineum pain

Question 23

Where is the pelvic pain line?

Answer 23

• inferior limit of peritoneum

- middle of sigmoid colon

Question 24

Where does the pudendal nerve originate and travel?

Answer 24

• originates S2-4
• travels through greater sciatic foramen
• curves posterior to ischial spine and sacro-spinous ligament
• runs forwards into perineum inferior to levator ani

Question 25

Describe the arterial supply of the pelvis

Answer 25

- common iliac artery => internal iliac artery opposie sacroiliac joint at level T5 disc - internal iliac divides into anterior and posterior trunks - supplies buttock, medial thigh, posterior pelvic and abdo walls, pelvic viscera and perineum

Question 26

Describe the venous drainage of the pelvis

Answer 26

- venous plexuses of pelvic viscera that drain into internal iliac or internal pudendal vein - internal iliac drains to the artery - joins external iliac vein to form common iliac vein

Question 27

Describe the lymphatic drainage of the pelvis

Answer 27

- parallel with venous drainage - common, external, internal iliac and sacral lymph nodes - interconnected