9. Pelvic diaphragm. Nerves and arteries of the pelvic cavity

Question 1

What is the false pelvis?

Answer 1

The posterior abdominal wall, iliacus covering the iliac bones

Question 2

What is the true pelvis?

Answer 2

aka lesser pelvis, pelvic cavity

Inferior to arcuate lines on the iliac bones (equivalent to pelvic brim or pelvic inlet)

Question 3

____ _____ lines the pelvic lateral wall, while _________ ___ forms the muscular pelvic floor

Answer 3

Obturator Internus lines the pelvic lateral wall, while Levator Ani forms the muscular pelvic floor

Question 4

What is the perineum?

Answer 4

The diamond-shaped perineum is the (pudendal) region below the pelvic floor
Contains the genitalia and urethra anteriorly, and the anal canal and ischio-anal fossae posteriorly

Question 5

Which two structures rest on the elevator ani (the pelvic floor)?

Answer 5

The bladder and prostate

Question 6

Perineal membrane seperates what?

Answer 6

Deep and Superficial compartments of the Perineum anteriorly

Question 7

Inlet / brim of pelvis formed by?

Answer 7

Pubic symphysis and crest
Superior pubic ramus / pectineal line
Arcuate line of ileum
SI join
Sacral ala 
Promontory (S1)

Question 8

Pelvic outlet formed by…

Answer 8

Pubic symphysis and ischiopubic rams
Ischial tuberosity
To sacrotuberous ligament
Sacrum and coccyx

Question 9

Changes to female pelvis?

Answer 9

Must accommodate childbirth

• -> Lighter
• -> More rounded
• -> Wider
• -> Oval inlet

Question 10

Changes to male pelvis

Answer 10

Heavier
Heart shaped inlet
Narrowed outlet (due to more acute sub-pubic angle and encroached upon by the ischial spines)

Question 11

Ligaments of the pelvis?

Answer 11

Sacrospinous

• From ischial spine to adjacent sacrum and coccyx
• Triangular shape

Sacrotuberous

• Broader
• From ileum, sacrum and coccyx to ischial tuberosity

Both enclose the greater and lesser sciatic foramina

Question 12

What are the 3 passages through the pelvis floor?

Answer 12

Greater sciatic foremen
-Superior gluteal nerve and vessels

Lesser sciatic foramen

• Sciatic nerve + Inferior gluteal vesels
• Pudendal nerve + internal pudendal vessels

Obturator canal
-Obturator nerve and vessels

Question 13

Muscles that make up the pelvic walls?

Answer 13

Piriformis

Obturator interns

Question 14

Piriformis, attachments?

2 roles?

Answer 14

From sacrum to greater trochanter
Forms the posterior pelvic wall
Divides the greater sciatic foreman

Question 15

Obturator internus, attachments?

2 roles?

Answer 15

From obturator membrane and adjacent bone, passing to greater trochanter

Forms

• the lateral pelvic wall
• its overlying obturator fascia gives origin to the pelvic floor muscle – levator ani

Question 16

What forms the pelvic floor?

Answer 16

Coccygeus

Levator ani

Question 17

Divisions of elevator ani?

Answer 17

1. Iliococcygeus
2. Pubo-coccygeus, divided into pubo:
   - Rectalis (posteriorly)
   - Vaginalis or prostaticus
   - Urethralis (anteriorly around the urogenital opening)

Question 18

Nerve supply of iliococcygues and pubo-urethralis?

Answer 18

By direct branches from S3,4

Question 19

Function of the tendinous arch of the obturator internus?

Answer 19

Origin for levator ani

Question 20

Position of coccygeus muscle?

Answer 20

Overlies the sacrospinous ligament and blends with levator ani posteriorly

Question 21

Importance of the levator ani as a bowl of the pelvic floor?

Answer 21

For the support of the viscera and maintenance of the urinary + faecal continence.
Weakness may result in incontinence and prolapse

Question 22

Where does each side of the levator ani meet?

Answer 22

In the midline to form the:

1. anococcygeal raphe (boday and ligament)
2. perineal body (/Central tendon of the perineum) just anterior to the anal canal and posterior to the vagina in the female

Question 23

What forms a sling around the recto-anal junction?

Answer 23

Puborectalis

Question 24

Levator ani:
Attachments?
Nerve supply?
Function?

Answer 24

Nerve supply: S3 and 4

Attachments:

• Posterior aspect of the pubic bone
• Tendinous arch of the obturator fascia
• -> Ischial spine

Function:
Supports the pelvic viscera
Makes the recto-anal angle more acute aiding rectal continence
Augments the external anal and urethral spincters
Forms a vaginal sphincter

Question 25

Name the pelvic lymph nodes?

Answer 25

Lumbar (caval/aortic)
Inferior mesenteric
Common iliac
Internal iliac
External iliac
Superficial inguinal
Deep inguinal
Sacral 
Pararectal
Obturator

Question 26

What makes up the somatic pelvic nerve supply?

Answer 26

Lumbosacral plexus: Made up of ventral rami of L 4,5 and S1,2,3,4.
Gives of the pudendal nerve (S2,3,4) to the pelvic floor and voluntary sphincters
PLUS direct branches from S3 and S4 to pelvic floor muscles

Question 27

What makes up the autonomic pelvic nerve supply?

Answer 27

Sympathetic trunk, bilateral and extending into the pelvis give:

• Sacral Splanchnics
• Superior hypogastric plexus, which sends branches to the pelvic plexuses

Parasympathetic pelvic splanchics from S2,3,4

These are lateral and posterior to rectum and mesorectum

Question 28

The thoracic sympathetic trunk gives which splanchnics?

Answer 28

The thoracic sympathetic trunk gives:

Greater splanchnic nerve derived from T 5 to 9 (Foregut)

Lesser splanchnic nerve derived from T 10 and 11 (Midgut)

Least splanchnic nerve derived from T 12 (Hindgut)

Question 29

Relationship between splanchinc nerves and pelvis?

Answer 29

The splanchnic nerves form the pre-aortic (vertebral) plexus and synapse in ganglia at the coeliac trunk, SMA and IMA
The pre-aortic plexus passes into the pelvis as the superior hypogastric plexus that divides to become the (inf hypogastric) pelvic plexus.
This pelvic plexus is augmented by sacral splanchnics from the sympathetic trunk in the pelvis

Question 30

What happens to the sympathetic trunks are they reach the pelvis?

Answer 30

Pass anteior to the sacrum and fuse as the ganglion impar opposite the coccyx
They carry pre-ganglionic nerves that arise in spinal cord segments T10-L2 and emerge that withe equivalent spinal nerves to pass as white rami communicantes to the sympathetic trunks which then give sacral splanchnic nerves to the pelvic plexus

Question 31

Other name for pelvic plexus?

Answer 31

Inferior hypogastric

Question 32

Which splanchnic nerves contribute to the pre-aortic plexus?

Answer 32

Lesser and least splanchnic (T10-12)

Question 33

What “boosts” the pelvic plexus?

Answer 33

Sacral splanchincs

Question 34

What is the position of the pelvic plexus?

Answer 34

In fascia lateral to:

• Rectum
• Seminal vesicles
• Prostate
• (Cervix and vaginal fornices)
• Posterior aspect of bladder

In angle between internal iliac and inferior vesical arteries

So is at risk of surgical injury

Question 35

Branches and supply of the internal iliac artery?

Answer 35

Branch of the common iliac opposite the SI joint at the level of the L5

Divisions: Into anterior and posterior trunks to supply…

• The buttock
• The medial thigh
• The posterior pelvic and abdominal walls
• The pelvic viscera (reuctum, anal canal, uturus, vagina, bladder, urethra) **
• The perineum

**The ovary and testis are supplied by gonadal arteries from the Ao at L2

Question 36

Collateral circulation of the internal iliac artery?

Answer 36

Its gluteal branches contribute to important anastomoses around the hip that may form a collateral circulation for the lower limb