Sept7 M3-Pelvis_Anatomy_lecture_5

Question 1

borders of the anal triangle

Answer 1

• ischial tuberosities (imaginary line between them)
• sacrotuberous ligaments
• coccyx

Question 2

ischiorectal (ischioanal) fossa is what

Answer 2

two triangles on either side of the anus mostly filled with fat + levator ani

Question 3

(imp) borders of the ischiorectal fossa

Answer 3

• base (superficial) = skin
• lateral wall = lower part of obturator internus
• medial wall = levator ani
• fossa continuous with the deep perineal pouch (of the UG triangle). nothing separating them. for deep perineal pouch, superficial base was perineal membrane and deep base was also levator ani

Question 4

structures visible in a coronal view of the ischiorectal fossa

Answer 4

• anal canal (middle)
• levator ani (medial wall of the fossa + going oblique and upwards laterally)
• lot of fat below, lat to levator ani (fat pad)
• obturator internus (lateral wall of the fossa)
• pudendal canal (just medial to obturator internus, contains pudendal vessels and n)
• Colle’s fascia (superficial fascia marking start of the superficial base). extends from ischium to anal canal
• skin (base)

Question 5

anal canal structures in coronal view

Answer 5

• levator ani
• anorectal junction (end of smooth features of rectal ampulla. is end of the rectum
• anal columns and sinuses below the ARJ (like prostatic crests on either side of prostate and sinus in middle). are in the anus
• anal valve = narrowing of anal canal at level of the bottom of the anal sinuses and columns
• pectinate line = line between endoderm-derived hindgut (above) and ectoderm-derived anal pit (below)
• anal pecten (region between pectinate line and anocutaneous line)
• anocutaneous line (division between anus and skin)

Question 6

clinical significance of the pectinate line in the anal canal

Answer 6

• internal hemorrhoids are above it and are not painful

- external hemorrhoids are below it and are painful

Question 7

muscles surrounding the rectum

Answer 7

• inner circular layer

- outer longitudinal layer

Question 8

2 anal sphincters and what they cover

Answer 8

internal anal sphincter (more medial): covers upper two thirds of anal canal)
external (more lat): covers lower two thirds of anal canal)
the two overlap in the middle third of the rectum

Question 9

control of anal sphincters (which is voluntary?)

Answer 9

• internal = involuntary. always contracted, SS tone

- external = voluntary (somatic inn in this region is from pudendal n, which gives inferior rectal nerves)

Question 10

internal anal sphincter is what

Answer 10

muscle of inner circular muscular coat around rectum coming down around anal canal

Question 11

external anal sphincter is what

Answer 11

levator ani coming down reaching kink of rectum (of puborectalis sling)

Question 12

3 parts of the external anal sphincter

Answer 12

top to bottom

• deep
• superficial
• subcutaneous

Question 13

bloody supply to the anus

Answer 13

inferior rectal a and v coming from internal pudendal a and v (which come from internal iliac a and v)

Question 14

inn to anus

Answer 14

inferior rectal nerves coming from pudendal n

Question 15

pudendal canal (Alcock canal) def + is where

Answer 15

• a passageway within the obturator fascia (fascia of obturator internus) on lat wall of ischiorectal fossa) for the internal pudendal a and v + pudendal n
• is inferior to the obturator foramen

Question 16

how to see internal pudendal a from the gluteal region

Answer 16

look for ischial spine (look underneath the area of the inferior gluteal a)

Question 17

what internal pudendal a does after swings back in perineum around ischial spine

Answer 17

travels forward to reach the UG triangle (travels on side of ischiopubic ramus, below obturator foramen)

Question 18

diff arteries that come off the internal pudendal a as it goes in the pudendal canal

Answer 18

• start (in the back): gives off inferior rectal a
• end (front): gives off perineal branches that go in deep and sup perineal pouches
• distally becomes the dorsal artery of the penis or clitoris

Question 19

why coccygeus m. is a key point in the pelvis

Answer 19

• points to the ischial spine
• is deep to the SS ligament
• start of the tendinous arch

Question 20

internal pudendal a travels where with respect to coccygeus

Answer 20

below piriformis (medial to it), above coccygeus (lateral to it)

Question 21

PNS divisions

Answer 21

• sensory (afferent): somatic + visceral

- motor (efferent): somatic + ANS (visceral)

Question 22

lumbar plexus nerves fct in general

Answer 22

-motor (somatic and ANS) and sensory (somatic and visceral)

Question 23

lumbar plexus nerves, parts of interest

Answer 23

• lumbosacral trunk (L4 and L5) = uppermost part of the sciatic nerve
• obturator n (L2,3,4) (through obturator canal to medial thigh muscles and skin)

Question 24

sacral plexus: where levels S1,2,3,4 come from anatomically

Answer 24

come out of the anterior sacral foramina

Question 25

ventral rami of sacral plexus are where in the pelvis

Answer 25

on top of piriformis | dorsal rami go to the back

Question 26

sciatic n levels + is what two nerves later

Answer 26

L4 to S3. comes out above piriformis in greater sciatic foramen - common fibular n - tibial n

Question 27

pudendal n levels and fct

Answer 27

S2,3,4 - motor (somatic and ANS) - sensory (somatic and visceral)

Question 28

how not to confuse lumbosacral trunk with the S1 level

Answer 28

lumbosacral trunk crosses the ala of the sacrum and NOT the sacral promontory

Question 29

where are the sacral nerves in the pelvis

Answer 29

above piriformis (makes sense bc said before that ventral rami are above piriformis)

Question 30

regions where the pudendal n is travelling

Answer 30

1. pelvis (S2,3,4) 2. gluteal region 3. pudendal canal (start of canal = gives off hemorrhoidal (inferior rectal) n). middle of canal gives off perineal n. 4. deep perineal space 5. dorsum of the penis (where becomes dorsal n of the penis). travels with the deep dorsal arteries (from dorsal penile a) + the deep dorsal veins between Buck's fascia and the tunica albugenia

Question 31

inferior rectal n and a path taken

Answer 31

1. leave the pudendal a and n but stay in the pudendal canal 2. leave the pudendal canal 3. go towards the anal sphincter

Question 32

PSS innervation of the pelvis

Answer 32

pelvic splanchnic nerves - originate from ventral rami of S2,3,4 - travel on each side of pelvis THROUGH inferior hypogastric plexus (a SS structure) (on lat rectal and bladder walls) - after reach lat rectal wall, go to distal third of transverse colon, sigmoid colon, rectum, bladder, genitalia. preganglionic fibers synpase in the walls of the organs * don't synapse in hypogastric plexus*

Question 33

SS innervation to pelvis

Answer 33

sup and inf hypogastric plexi - white rami communicantes go from spinal cord to SS trunk ganglia from T1 to L2 (T5 and below don't synapse there). the chain continues below L2 height until S3 - these two plexi arise from the lowest levels of the SS chain - pregang fibers synapse in the inferior hypogastric plexus**, then go to organs via blood vessels pathway

Question 34

hypogastric nerves def

Answer 34

nerves between the ONE superior hypogastric plexus in the body and the TWO inferior hypogastric plexi (one on each side). so there are TWO hypogastric nerves

Question 35

what SS fibers synapse in the sacral part of the SS chain

Answer 35

postganglionic fibers that start at the SS chain (sacral) and that travel through rami levels S2,3,4 to leave the pelvis via the sacral foramina and reach the sciatic nerve

Question 36

sacral splanchnic nerves def

Answer 36

sympathetic nerves extending from the SS chain ganglia to the inferior hypogastric plexus

Question 37

where to recognize pelvic splanchnic nerves if can find them

Answer 37

back wall of pelvis, on sacrum, exited sacral foramina with the sacral nerves

Question 38

SS inn to the leg is done how

Answer 38

postgang fibers leaving hypogastric plexus reach a sacral nerve (S1) (or postgang fibers leaving SS chain and going to sciatic n) and go to the leg

Question 39

SS inn of the pelvis comes from which nerves and plexus

Answer 39

- SS chain to sacral splanchnic nerves going to hypogastric plexus - SS chain to sup hypogastric plexus to hypogastric nerves to inferior hypogastric plexus

Question 40

superior hypogastric plexus is located where

Answer 40

over the aorta at level of bifurcation

Question 41

sacral sympathetic chain relates to what nearby structure in the pelvis

Answer 41

is below the lateral sacral a

Question 42

how to recognize pelvic splanchnic n vs sacral splanchnic n

Answer 42

- sacral splanchnic n leave the SS chain ganglia | - pelvic splanchnic n come off the sacral n and go out