Case 4 - anatomy of the perineum

Question 1

where is the perineum?

Answer 1

The perineum is a space located inferior to the pelvic diaphragm

Question 2

perineum is diamond shaped - what are the boundaries of the perineum?

Answer 2

The perineum is diamond shaped and has the following boundaries:

Anterior boundary – pubic symphysis
Posterior boundary – coccyx
(sacrotuberous ligaments contribute to the posterior boundary)
Lateral boundary – ischial tuberosities
(ischiopubic rami contributes to lateral boundary)

Question 3

name the superficial perineal muscles

Answer 3

Bulbospongiosus
Ischocavernosus
Superficial transverse perineal

Question 4

role of bulbiospongiosus muscle in males

Answer 4

Empties the urethra of urine
Possible role in maintaining
erection (by preventing venous
return)
bulbospongiosus muscle is involved in the expulsion of semen during ejaculation by contracting and forcefully pushing the semen out of the urethra

Question 5

describe the position of bulbospongiosus muscle in males

Answer 5

bulbospongiosus is centrally positioned overlying the
bulb of the penis; united by a
median fibrous raphe

Question 6

describe the position of bulbospongiosus muscle in females

Answer 6

In females, bulbospongiosus is positioned overlying the bulb of the vestibule and greater vestibular glands.
Bulbospongiosus is NOT united by a median fibrous raphe , instead the Bulbospongiosus is separated by the vagina

Question 7

role of bulbiospongiosus muscle in females

Answer 7

The role of the Bulbospongiosus in females:

Narrows the vaginal opening, expresses secretions of the greater vestibular glands

Contributes to the erection of the clitoris

Question 8

describe the position of ISCHOICAVERNOSUS muscle in males

Answer 8

ISCHOICAVERNOSUS covers the crus of the penis

Question 9

role of the ISCHOICAVERNOSUS in males

Answer 9

ISCHOICAVERNOSUS maintains an erection and stabilises the erect penis

Question 10

role of the ISCHOICAVERNOSUS in females

Answer 10

Increases pressure in the clitoris

Question 11

describe the position of ISCHOICAVERNOSUS muscle in females

Answer 11

Covers the crus of the clitoris

Question 12

what about the anal triangle contain?

Answer 12

Anal canal and external anal
sphincters are located in the
mid-line of the anal triangle

anal triangle contains faecal continence

Question 13

describe the location of the ischiorectal fossae

Answer 13

there are 2 ischiorectal fossae and these are located lateral to the anal canal and sphincter

Question 14

how is the pelvic diaphragm located in regards to the anal triangle?

Answer 14

Pelvic diaphragm is located directly above the anal triangle

Question 15

what is the perineal body?

Answer 15

It’s a Junction between the anal and urogenital triangle

Question 16

Pudendal nerve enters the pudendal canal (which is on the lateral wall of the ischiorectal fossa) and gives off the following nerves:

Answer 16

Inferior rectal nerves
Perineal nerve
Dorsal nerve of the clitoris/penis

Question 17

what does the Inferior rectal nerves supply

Answer 17

these supply the external anal sphincter and surrounding skin

Question 18

what does the Perineal nerves supply

Answer 18

supplies sensory and motor innervation to the structures in the urogenital triangle

Question 19

what does the Dorsal nerve of the clitoris/penis supply

Answer 19

supplies the corpus cavernosa; this nerve runs deep to the perineal membrane (in males)

Question 20

What is the normal function of the greater vestibular glands?

Answer 20

Produce mucus that provides lubrication for the vagina

Question 21

which vessel supplies the main erectile tissues (penis/clitoris)?

Answer 21

Deep artery of the penis/clitoris

Question 22

the perineal membrane covers what?

Answer 22

The perineal membrane covers the urogenital triangle

Question 23

what is the perineal membrane the site of anchorage for?

Answer 23

the site of anchorage for the erectile external genitalia.

Question 24

In obstetrics, the perineal body is called simply “the perineum”. It is of great clinical importance because it is at risk of damage during childbirth.
What might be the consequence of a damaged perineal body?

Answer 24

Bowel and urinary incontinence & sexual dysfunction.

Question 25

What are the ischiorectal fossae filled with?

Answer 25

fat

Question 26

What muscular structure forms the roof of the ischiorectal fossae?

Answer 26

Pelvic diaphragm (levator ani)

Question 27

What muscular structure forms the lateral walls of the ischiorectal fossae?

Answer 27

Obturator internus

Question 28

What is the distribution of the pudendal nerve and its branches?

Answer 28

It passes out of the pelvic cavity via the greater sciatic foramen, loops over the sacrospinous ligament, enters the perineum through the lesser sciatic foramen, passes in the pudendal canal (lateral wall of ischiorectal fossa) and gives off: the inferior rectal nerve, the perineal nerve, and the dorsal nerve of the penis (in males) or the dorsal nerve of the clitoris (in females).

Question 29

Where is the best place to deliver anesthetic to treat a pudendal nerve block?

Answer 29

Near the ischial spines, behind the sacrospinous ligament, via a transvaginal approach where the pudendal nerve is most accessible. (this case is about a woman)

Question 30

What landmarks would an obstetrician use to deliver the anesthetic for the pudendal nerve block accurately?

Answer 30

An obstetrician would use the ischial spines as the key landmark, palpated through the vaginal wall, along with the ischial tuberosity which is located posteromedial to the ischial spine as a reference point for needle insertion; this allows for precise placement of the anesthetic near the pudendal nerve located behind the sacrospinous ligament