Flashcards in Lecture 24 RH Deck (41):
Where do the iliac arteries come from? At what level does the aorta split?
1) Abdominal aorta branches at level of L4/5 disk and divides into 2 branches; one to the right and the other to the left.
2)Both branches are called common iliac arteries.
3)Common iliac arteries further branch into internal and external iliac arteries.
*Number here denotes steps along the path of the arteries
Where do the veins of the pelvis go and what are they called?
Veins accompany major arteries and are named similar to the arteries. IVC is the point where they meet at L5.
What is the iliopectineal line?
rim of the pelvis is the iliopectineal line which separates the true (greater) pelvis from the false (lesser) pelvis.
Where do the common iliac arteries split into the internal and external iliac arteries?
at the iliopectineal line.
What structures does the internal iliac artery supply?
pelvic wall (somatic/parietal branches)
What are the other arteries that supply the pelvis?
Branches from outside of the pelvis
Superior rectal (from inferior mesenteric artery) to sigmoid colon and upper rectum.
Median sacral artery
Which vein is unusual in the pelvis?
inferior rectal vein is part of portosystemic anastomosis and drains into liver rather than IVC
What is interesting about the parietal branches of the internal iliac artery?
Parietal branches of internal iliac are variable in how they form.
What are the parietal branches of the internal iliac artery?
Anterior and posterior branches.
What does the posterior iliac artery divide into and what does each branch supply?
Iliolumbar: Supplies body wall of iliolumbar region.
Lateral sacral: Supplies lateral sacral region
Superior gluteal: supplies superior gluteal region.
What does the anterior iliac artery supply?
Obturator artery: supplies the obturator region
Internal Pudendal: Supplies the perineal region (including skin), the external genitalia, and the pelvic floor
Where does the superior gluteal artery go and how?
Superior gluteal artery goes to the gluteal region and goes through the greater sciatic foramen following piriformis superiorly.
*The superior gluteal nerve also exits at this region.
What are the visceral branches of the internal iliac artery?
3 major visceral branches:
Uterine: It is tortuous due to enlargement during pregnancy.
What are some organs supplied by end arteries?
What is the clinical significance of end organs/arteries?
Vasoconstrictor drugs are harmful if injected into end organs.
What are the principles underlying veins in the pelvis?
Veins form many plexuses in the pelvic region.
No valves are present.
Where do veins of the pelvis drain into?
They drain to tributaries of internal iliac vein which also communicate with internal venous plexus
How do cancer cells spread from the prostate?
cancer cells can spread via venous system
What is the problem with the prostate venous plexus regarding cancer cells?
Prostatic venous plexus normally drains to tributaries of the IVC. Sacral veins also drain to IVC through holes in the sacrum. As a result, cancer cells could potentially spread to the vertebral column via these veins and through the vertebral column it could spread to other parts of the body.
What is the significance of the communication between the inferior mesenteric vein and the liver?
inferior mesenteric vein could potentially take cancer cells to the liver
What are portosystemic anastomoses and what is a potential problem that could result from it?
Varices of veins going to the liver could result from blockage of the liver. These varices could potentially fall below anal canal to the exterior. This problem is what causes haemorrhoids.
What is the result of distension of blood vessels in rectum + anal canal?
varices in upper part of anal canal generate pressure (discomfort).
Varices in lower part of anal canal generate pain due to somatic innervation of anal canal.
How does lymph drain the perineum?
Superficial lymph nodes drain the perineum (anal and urogenital triangles). Superficial lymph nodes drain into deep lymphnodes of the inguinal region (inguinal nodes) and the deep lymph nodes pass near the vertebral column to the left brachiocephalic vein.
What lymphatics drain the pelvic viscera?
pelvic viscera drain directly to deep lymph nodes of abdominal region.
What is the principle underlying lymphatic drainage of the testis and the scrotum?
Testis and scrotum are drained by vessels that drain the area of their embryological origins.
Testis to nodes on posterior abdominal wall.
Scrotum drains to inguinal nodes.
What is a sign of cancer of abdominal viscera or the testis?
Enlargement of the left supraclavicular node (sentinal node).
What are the somatic nerves of the pelvis?
Main parietal branches are the obturator nerve and the pudendal nerve.
What does the sacral plexus supply?
Sacral plexus (S2 - 4) supplies muscles of the pelvis and gluteal region
What is the course of the pudendal nerve before it branches?
Pudendal nerve arises at sacral plexus.
Pudendal nerve enters pelvic cavity via the greater sciatic foramen and then exits via the lesser sciatic foramen.
it then enters fossa in the ischioanal fossa.
What are the branches of the pudendal nerve?
Inferior rectal nerve
Penneal + muscular branches
Posterior scrotal nerve
Dorsal nerve of clitoris/penis (also contains cavernous nerves)
What does the inferior rectal nerve supply?
External anal sphincter, perianal skin, and anal canal below pectinate line.
Does a pudendal nerve block paralyse pelvic floor?
No because nerves have already come off at the location of the block.
How is the correct location for a pudendal block found?
Clinician looks for fatty tissue around pudendal canal. Finger is put into vagina to feel for the ischial spine (lesser sciatic foramen)
What are the kinds of plexuses found in the pelvis?
Superior hypogastric plexus (sympathetic)
Pelvic splanchnic nerves (Parasympathetic)
Inferior hypogastric plexus (mixed)
What is the role of sympathetics and parasympathetics of the pelvis?
Sympathetics contract sphincters and constrict arteries.
Parasympathetics cavernous nerves to smooth muscles in walls of viscera (eg peristalsis and dilation of arteries)
Why is there an overlap of neurovascular supply and lymph drainage in perineal structures?
Area which has smooth muscle/epithelial lining is derived from endoderm. They form an interface with the ectoderm structures including skin and skeletal muscle.
Overlap of lymph drainage, blood supply, and nerve supply exist in perineal structures.
Where do reflex arcs related to the pelvis take place?
All the main reflexes associated with pelvis and perineal region are related to 3 spinal segments S2,3,4. This includes Micturition, Defaecation, and Erection.
Relaxation of involuntary internal urethral sphincter occurs at the level of T12/L1 via sympathetic fibers.
Relaxation of voluntary external urethral sphincter is controlled by S2,3,4
Which nervous system control dilation and constriction of blood vessels in the pelvis
Dilation = parasympathetic
Constriction = Sympathetic
What is the pelvic pain line?
Line between inferior part of the coccyx and the pubic symphysis called the pelvic pain line. Above this line visceral afferents follow sympathetic fibers and go to T1-L2, below line are pain fibers that follow parasympathetic nerves to S2 - S4.