The Pelvis, Perineum, Rectum and Anal Canal

Question 1

[17-minute video]: Cadaveric study of the Male Pelvis

Answer 1

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Question 2

[2-minute video]: The Uterine Artery

Answer 2

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Question 3

Click on Answer for diagrams of the urinary bladder.

Answer 3

[Diagram] [Diagram 2] [Diagram 3]

Question 4

Click on Answer to view diagrams of the branches of the internal iliac artery and the pudendal artery.

Answer 4

✪ Internal iliac artery: [Diagram 1] [Diagram 2] [Diagram 3] [Diagram 4]
✪ Pudendal artery: [Diagram 5]

Question 5

Click on Answer for sagittal section images of the MRIs/CTs of the male and female pelvis.

Answer 5

Male: [Image 1] [Image 2] [Image 3]

Female: [Image 1] [Image 2] [Image 3]

Question 6

List the anterior muscular relations of the pelvic surface of the sacrum.

Answer 6

iliacus [attached to the alae], piriformis [attacehd to the middle three pieces of the sacrum], coccygeus [attached to the last piece of the sacrum]

Question 7

List the neurovascular and visceral relations of the pelvic surface of the sacrum.

Answer 7

(a) median sacral artery [terminates as glomus coccygeum]
(b) left and right sympathetic chains [fuse to form a ganglion known as ganglion impar]
(c) lateral sacral arteries
(d) ventral rami of upper four sacral nerves
(e) obturator nerve, iliolumbar artery, lumbosacral trunk [all related to the ala of the sacrum, mnemonic: OIL (from lateral to medial)…you may add S for sympathetic chain]
(f) anterior to the last three pieces of the sacrum is the rectum [Diagram]

Question 8

List the structures that pass through the sacral hiatus.

Answer 8

(a) filum terminale
(b) 5th sacral nerve
(c) coccygeal nerve

Question 9

State four differences between the male sacrum and the female sacrum.

Answer 9

(a) the femal sacrum is shorter and wider; the male sacrum is longer and narrower
(b) the sacral promontory is more prominent in the male sacrum than in the female sacrum
(c) the female sacrum is sharply curved at S3, whereas the male sacrum is nearly straight
(d) the articular surface in the femal sacrum reaches S2, whereas in the male it reaches S3

Question 10

List the contents of the sacral canal.

Answer 10

(a) filum terminale
(b) cauda equina [roots of sacral and coccygeal nerves]
(c) dura and arachnoid mater [they end at S2]
(d) branches of the lateral sacral arteries
(e) internal vertebral venous plexus
(f) fat

Further notes:
The lateral sacral arteries are branches of the posterior division of the internal iliac artery.

Question 11

Name the 4 muscles of the pelvic walls.

Answer 11

(a) piriformis
(b) obturator internus
(c) levator ani
(d) coccygeus
[Diagram]

Question 12

State the contents, extents and formation of the pudendal canal.

Answer 12

Contents:
(a) pudendal nerve [which divides within the canal into the dorsal nerve of penis and the perineal nerve]
(b) internal pudendal vessels

Extents:
from the lesser sciatic foramen to the posterior limit of the deep perineal pouch

Formation:
It is formed either by the splitting of the obturator fascia or by separation between the fascia lunata or the obturator fascia.

Question 13

Name two branches of the external iliac artery and state the structures they supply.

Answer 13

deep circumflex iliac artery: supplies transversus abdominis and the internal oblique muscles
inferior epigastric artery: supplies rectus abdominis

Question 14

The perineal body is the site of convergence of which muscles?

Answer 14

✓ bulbospongiosus
✓ external anal sphincter
✓ superficial transverse perineal muscles
✓ deep transverse perineal muscles
✓ levator ani muscle
[Diagram] [Diagram 2]

Question 15

State the peritoneal relations of the rectum.

Answer 15

The upper one third of the rectum is covered by peritoneum anteriorly and laterally.
The middle third of the rectum is covered with peritoneum only anteriorly.
The lower third of the rectum is not covered by peritoneum at all.

Question 16

State the anterior relations of the upper two-thirds of the rectum [peritoneal] in the male and female.

Answer 16

Male: rectovesical pouch and coils of the small intestine and sigmoid colon within it
Female: rectouterine pouch and coils of the small intestine and sigmoid colon within it
[Diagram 1]: rectovesical pouch
[Diagram 2]: rectouterine pouch

Further notes:
The pouch of Douglas (cul-de-sac) represents the caudal extension of the peritoneal cavity. It is the rectovaginal pouch in the female and the rectovesical pouch in the male.

Question 17

State the anterior relations of the lower two-thirds of the rectum in the male and female [ampulla/non-peritoneal].

Answer 17

Male: base of the urinary bladder, terminal parts of the ureters, seminal vesicles, ampullae of vas deferens, prostate [all these structures are separated from the rectum by well-defined rectovesical fascia of Denonvilliers]
Female: Vagina (lower part) (It is separated from rectum by an ill-defined rectovaginal fascia)
[Diagram 1]: male
[Diagram 2]: female

Question 18

State the boundaries of the perineum.

Answer 18

Anteriorly: pubic symphysis
Posteriorly: tip of the coccyx
Laterally: inferior pubic rami and ischial rami anteriorly, ischial tuberosity in the middle, and the sacrotuberous ligament posteriorly
Superiorly: the pelvic floor
Inferiorly: skin and fascia

Question 19

List the fascia of the urogenital triangle.

Answer 19

(a) superficial fascia
(b) perineal membrane
(c) pelvic fascia

Question 20

State the contents of the superficial perineal pouch in the male.

Answer 20

(a) root of the penis [bulb and two crura]
(b) bulbospongiuosus
(c) ischiocavernosus
(d) superficial transverse perineal muscle
(e) scrotal vessels and nerves

Question 21

State the contents of the superficial perineal pouch in the female.

Answer 21

(a) root of clitoris [formed by bulb of vestibule and 2 crura]
(b) greater vestibular glands
(c) bulbospongiosus
(d) ischiocavernosus
(e) superficial transverse perineal muscle
(f) labial nerves and vessels

Question 22

State the contents of the deep perineal pouch in the male.

Answer 22

(a) urethra
(b) bulbourethral glands
(c) external urethral sphincter
(d) deep transverse perineal muscle

Question 23

State the contents of the deep perineal pouch in the female.

Answer 23

(a) urethra
(b) vagina
(c) external urethral sphincter
(d) deep transverse perineal muscle

Question 24

State the roof and floor of the:
(a) superficial perineal pouch
(b) deep perineal pouch

Answer 24

(a) roof: perineal membrane, floor: superficial fascia
(b) roof: pelvic fascia, floor: perineal membrane

Question 25

Describe the arterial supply of the uterus.

Answer 25

The uterus is supplied mainly by two uterine arteries and partly by two ovarian arteries.
The uterine artery gives off several branches:
(1) Close to the cervix after crossing the ureter, it gives rise to ureteric, vaginal, and cervical branches. The cervical branches form circular anastomosis around the isthmus.
(2) Along the side of body of the uterus it gives off arcuate (coronary) branches which run transversely on the anterior and posterior surfaces of the body of uterus and anastomoses with their counter parts along the midline.
(3) Along the fallopian tube it gives off tubal branches and few ovarian twigs.
[Diagram]

Question 26

State the parts of levator ani.

Answer 26

(a) Puborectalis aka. puboanalis [It originates from the posterior surface of the pubic bones (also known as puboanalis). It encircles the rectum (anorectal junction) and is partly interwoven with the external anal sphincter. It forms the puborectal sling posterior to the rectum.]
(b) Pubococcygeus [It originates from the pubic bone lateral to the origin of puborectalis muscle and inserts into the tendinous center of the perineum, anococcygeal body and tailbone.]
(c) Iliococcygeus [It extends laterally from the fascia of the obturator internus muscle to the tailbone.]
[Diagram]