L8.3 Vessel/Nerves/Lymphatics of the pelvis

Question 1

Where does the abdominal aorta divide; and what are the branches

Answer 1

• L4/5
• Common iliac → crosses the pelvic prim
• Ex iliac → becomes artery of the lower limb
• Int iliac → branches which supply pelvic structures
  
  • Somatic/parietal branches: Wall of pelvis
  • Visceral branches

Question 2

Ovarian/testicular A

Answer 2

• Branches just below the renal A

Question 3

SUP rectal A & Median sacral A

Answer 3

• SUP rectal A
  
  • Continuation of the IMA
  • Is an unpaired A
  • (INF rectal V accompanies A - unusual as it is part of the portosystemic system (drains back into liver))
• Median sacral A (just know it’s there)

Question 4

Pathway of veins

Answer 4

V accompant major A (IVC at L4/5)

Question 5

Parietal branches of the internal iliac (has many variations)

Answer 5

• 2 main branches:
• POS parietal→ supply body wall
  
  • Iliolumbar
  • LAT sacral
  • SUP gluteal (N goes above piriformis)
• ANT parietal & visceral
  
  • Obturator
  • INF gluteal
  • Internal pudendal → supplies most of perineum and external genitalia
    
    • Has branch of INF rectal A

Question 6

Visceral branches of the internal iliac A

Answer 6

• SUP vesical (via umbilical)
• INF vesical (in males)
• Middle rectal
• Uterine A & Vaginal A anastomose extensively
  
  • Uterine A is tortuous which allows extension (allows supply even during enlargement of the uterus during pregnancy

Question 7

Examples and implications of end organs

Answer 7

• i.e. Clitoris/penis
• Dorsal A of the penis (end A)
  
  • Within corpus spongiosum & cavernosum → also have end arteries
• Vasoconstrictor drugs are not injected into end A

Question 8

SUP rectal V and the portal venous system

Answer 8

• Drains into IMV
• Communicates with branches of Int iliac V below (MID & INF rectal V) which drains into IVC
• IMV is part of the portal system → Cancer metastase into liver

Question 9

Venous plexus of the pelvis

Answer 9

• V follows A
• Veins form plexuses and do no have valves
  
  • Vesical → drains bladder
  • Prostatic → prostate
  • Uterovaginal
  • Rectal
• Drain to tribuatries of Int iliac vein
• Communications b/w veins (setting up potential pathway of cancer cells)
• Cavernous vessels & N run alongside prostate to erectile tissue
  
  • Removal of prostate → commonly damage erectile N

Question 10

Venous plexus of the prostate

Answer 10

• Prostatic venous plexus provides a pathway for metastasis of cancer
  
  • LAT parts of prostate is a common site of origin of cancer cells
  • Able to communicate with veins that pass through sacral forminae (e.g. ANT sacral veins)
    
    • Cancer able to metastase through foraminae into vertebral canal
    • Secondaries may be able to appear in bones/brain…

Question 11

Implications of the port-systemic anastomoses

Answer 11

• SUP rectal (portal) and MID + INF V (systemic)
  
  • Elevation in portal pressure (liver pressure)
    
    • May result in distension (varices) of communicating veins May result in descending of these dilated veins through the anal canal
      
      • Known as hemorrhoids
      • Varices in upper part: Generates pressure and discomfort
      • Varices in lower part: Painful

Question 12

Lymph drainage of the pelvis

Answer 12

• SUP lymph nodes → deep lymph nodes
• SUP inguinal nodes drains skin of perineum → to deep inguinal nodes
  
  • Along POS wall back to circulation
• Pelvic viscera drains directly into deep nodes
  
  • Nodes along iliac vessels adjacent to abdominal aorta
  • para-aortic nodes

Question 13

Lymph drainage of the testes

Answer 13

• Drains into pre-aortic lymph nodes
• Drains into POS ab wall (cannot be palpated - implications for testicular cancer)
  
  • Lymph drained by thoracic duct
  • First sign of cancer may be identified from the sentinel node

Question 14

Lymph drainage of the scrotum

Answer 14

• Drains into inguinal nodes
• Cancer of scrotum identified with enlargement of inguinal nodes

Question 15

Somatic N of the pelvis

Answer 15

Somatic N (S2, 3, 4) supplies muscle of the pelvis

• Gives off parietal branches
• Obturator
• Pudendal N (supplies perineum)

Question 16

Pathway and branches of the pudendal N

Answer 16

• Pudendal N briefly appears in pelvic cavity → then immediately exists LSF
  
  • Supplies pelvic floor from below (prevents compression of the N)
  • Through pudendal canal (in the Ischioanal fossa)
    
    • Perineal + muscular branches
    • POS scrotal
    • Dorsal N of clitoris/penis

Question 17

What structures may be damaged during the pudendal N block

Answer 17

• Structures endangered
  
  • Pudendal canal (Int pudendal A maybe damaged)

Question 18

Visceral N of the pelvis

Answer 18

• INF hypogastric plexus (Mixed)
  
  • Plexi going into INF hypogastric plexus:
    
    • SUP hypogastric plexus
      
      • Contains SNS fibres (T11-L1)
    • Pelvic splanchinic N
      
      • Contains PNS (S2-4)
• SNS → contract sphincters/constrict arteries
• PNS → found in cavernous N (responsible for dilation of BV and peristaltic activity)

Question 19

Junctional zones in the perineum

Answer 19

• Interface b/w area of SM and epithelial lining derived from endoderms and ectoderm
• Have sites of overlap of NS, BS, lymph drainage

Question 20

Reflex defaecation

Answer 20

• Faeces collected in ampulla → defaecation inhibited by contraction of int & ex sphincter (SNS)
• Stretch anal canal stimulates afferent fibres (pass to S2-4 PNS)
  
  1. PNS → contracts rectal wall
  2. Inhibition of SNS → involuntary relaxation of Int anal sphincter
  3. Pudendal N voluntarily relaxes external sphincters

Question 21

Reflex erection

Answer 21

• PNS stimulation (nervi erigentes S2-4)
  
  • → dilate dorsal A (supplying erectile tissue in crura)
  • → Compression of veins (bulbospongiosus & restriction of venous drainage)
• SNS mediates ejaculation (T12-L1)
• PNS - responsible for dilation → erection
• SNS - responsible for ejaculation

Question 22

Pelvic pain line

Answer 22

• Located around mid S. Colon
• Below pelvic pain line → with PSN (S2-4)
• Above pelvic pain line → with SNS (T1-L2)