Perineum and Urogenital triangle

Question 1

Describe the shape and location of the perineum.

Answer 1

Diamond shaped

Below the pelvic diaphragm.

Question 2

What are the main components of the perineum ?

Answer 2

Divided into a urogenital triangle anteriorly and an anal triangle posteriorly

Question 3

Identify the main layers of the abdominal wall.

Answer 3

Superficial to deep:

1) Skin
2) Subcutaneous tissue (Superficial fascia,
SF)
− Subcutaneous fatty layer (Camper’s
fascia)
− Deep membranous layer (Scarpa’s fascia)
3) Abdominal muscles with their investing fasciae

Question 4

What is the relation of the perineal and abdominal fascias ?

Answer 4

Abdominal fascia continues as perineal fascia.

Question 5

Describe the composition of the perineal fascia.

Answer 5

The superficial fascia (subcutaneous tissue) of the perineum has 2 layers:

1) Superficial fatty layer
• Continuous with Camper’s fascia of the abdomen
2) Deep membranous layer (Colles’ or perineal fascia)
• Continuous with Scarpa’s fascia of the abdomen

Question 6

Describe the structures lined by the layers of the perineal fascia in males.

Answer 6

MALES

1) Superficial fatty later:
− fuses with the membranous layer of superficial fascia in the penis and scrotum to become dartos fascia (and muscle)
− continuous posteriorly with the ischio-anal fat pad in the anal region

2) Deep membranous layer:
− continuous with the dartos fascia in the penis and scrotum
− attached posteriorly to the posterior margin of the perineal membrane and perineal body.
− fuses with fascia lata

Question 7

Describe the structures lined by the layers of the perineal fascia in females.

Answer 7

FEMALES

1) Superficial fatty later:
− makes up the substance of the
labia majora
− continuous posteriorly with the ischio-anal fat pad in the anal region

2) Deep membranous layer:
− attached posteriorly to the posterior margin of the perineal membrane and perineal body.
− fused with fascia lata

Question 8

What is the perineal membrane. Identify its attachments ?

Answer 8

A layer of the pelvic fascia which spans the urogenital triangle between the ischiopubic rami. Attaches to the perineal body in the midline posteriorly.

Question 9

What is the function of the perineal membrane ?

Answer 9

Provides major support for the urogenital organs + there is an anterior aperture for the passage of nerves and vessels to the penis or clitoris

Question 10

What are the main components of the urogenital triangle ?

Answer 10

Divided by the perineal membrane into:

1) a deep (superior) compartment (pouch)
2) a superficial (inferior) compartment (pouch)

Question 11

Identify all the relevant layers of abdominal/pelvis/perineal fascia involved in creating the perineal pouches.

Answer 11

♦ Deep fascia of the abdominal wall , covers the abdominal wall inner surface, then become pelvic fascia when it gets to pelvis.

♦ Then divides into:

1) Superior fascia of pelvic diaphragm (SFPD, covers superior surface of pelvic diaphragm)
2) Inferior fascia of pelvic diaphragm (IFPD, covers inferior surface of pelvic diaphragm)

♦ IFPD will give another layer, perineal membrane (PM).
Between PM and IFPD, there are a couple of structures: Deep transverse perineal muscle, bulbourethral gland (in males), external urethral sphincter.

♦ Inferior to PM (closer to skin), between PM and Perineal Fascia (membranous layer of perineal superficial fascia): Superficial transverse perineal muscle +
ischiocavernosum and bulbospongiosum muscles covering bulbs of the penis and bulb of the vestibule, and crus of penis or of the clitoris.
——-
1) Superficial perineal pouch: between PF and PM

2) Deep perineal pouch: between PM and inferior fascia of pelvic diaphragm.

Question 12

Identify the structures making up the pelvic diaphragm.

Answer 12

Levator ani muscle and Cocygeus muscle

Question 13

Define perineal body.

Answer 13

Tendinous structure in the midline between the vagina and the anus, where two sides of the pelvic diaphragm muscles merge (origin of Perineal Membrane as well).

Question 14

Where is the superficial perineal pouch located ?

Answer 14

Potential space between the perineal fascia and the perineal membrane, bounded laterally by the ischiopubic rami.

Question 15

Identify the main contents of the superficial perineal pouch (in males).

Answer 15

♠ Root (bulb and crura) of the penis and associated muscles (ischiocavernosus and bulbospongiosus)
♠ Proximal (bulbous) part of the spongy urethra
♠ Deep perineal branches of the internal pudendal vessels and pudendal nerves
♠ Superficial transverse perineal muscles

Question 16

Identify the main contents of the superficial perineal pouch (in females).

Answer 16

♣ Clitoris and ischiocavernosus muscle
♣ Bulbs of the vestibule and the surrounding bulbospongiosus muscle
♣ Greater vestibular glands
♣ Deep perineal branches of the
internal pudendal vessels and pudendal nerves
♣ Superficial transverse perineal muscles

Question 17

Identify the main functions of Ischiocavernosus in the male, and female ?

Answer 17

MALE:
♠ Covers the crus of penis
♠ Maintains erection of penis

FEMALE:
♣ Covers the crus of clitoris
♣ Maintains erection of clitoris

Question 18

Identify the main functions of bulbospongiosum in the male, and female.

Answer 18

MALE:
♠ encloses bulb of penis
♠ compresses bulb of penis to expel last drops of urine/semen
♠ assists erection

FEMALE: 
♣ encloses bulb and greater vestibular gland
♣ “sphincter” of vagina
♣ assists in erection of clitoris
♣ compresses greater vestibular gland

Question 19

Where is the deep perineal pouch located ?

Answer 19

Potential space between the perineal membrane, the inferior fascia of the pelvic diaphragm, and the inferior portion of the obturator fascia.

Question 20

Identify the main contents of the deep perineal pouch in males.

Answer 20

♂ Anterior recess of ischio-anal fossa
♂ Membranous urethra
♂ external urethral sphincter
♂ deep transverse perineal muscles
♂ bulbo-urethral glands
♂ dorsal neurovascular structures of the penis

Question 21

Identify the main contents of the deep perineal pouch in females.

Answer 21

♀ Anterior recess of ischio- anal fossa
♀ the proximal part of the urethra
♀ inferior part of the external urethral sphincter muscle
♀ Compressor urethra
♀ Urethrovaginal sphincter
♀ deep transverse perineal muscles
♀ dorsal neurovascular structures of the clitoris

Question 22

What is the ischioanal fossa ? Identify the main boundaries of the ischioanal fossa.

Answer 22

Large fascia-lined, wedge-shaped spaces, between:
− Skin of the anal region (inferiorly)
− Levator ani (pelvic diaphragm) (superiorly)
− Obturator internus and ischium (lateral)
− Anal canal (medially)
(no posterior wall, open, so L and R ischioanal fossas can communicate with each other posterior to anal canal)

Question 23

Identify the contents of the ischioanal fossa.

Answer 23

− fatty tissue that allows for changes in the position and size of the anal canal and anus during defecation
− the inferior rectal vessels and nerves that supply the external anal sphincter
− the perforating branches of S2 and S3
− the perineal branch of the S4 nerve.
− Pudendal nerve and internal pudendal vessels*

Question 24

What is the clinical significance of the ischioanal fossa ?

Answer 24

Site of infection and abscess that may require surgical intervention

Question 25

State any other names given to the Pudendal Canal.

Answer 25

Alcock’s canal

Question 26

Describe the anatomical location of the pudendal canal.

Answer 26

A horizontal passageway within the obturator fascia, along the lateral wall of the ischio-anal fossa

Question 27

Identify the main contents of the pudendal canal.

Answer 27

− pudendal nerve
− the internal pudendal artery
− the internal pudendal vein

Question 28

Describe the arterial blood supply, and veinous drainage of the perineum.

Answer 28

The internal pudendal vessels supply the:
• perineum
• urethra
• posterior 2/3 of scrotum or labia
• cavernous tissue of penis or clitoris
• skin of shaft and glans of penis or clitoris

The external pudendal branch of femoral vessels supply the:
• anterior 1/3 of scrotum or labia

VEINOUS DRAINAGE
Veins mirror the arteries

Question 29

Where does the internal pudendal arise from ? (main supply of perineum)

Answer 29

“Arises from the anterior trunk of the internal iliac”

Question 30

Describe the lymphatic drainage of the perineum.

Answer 30

♦ Superficial structures (such as the penis, scrotum and labia) drain into the superficial inguinal lymph nodes

♦ Deep structures (such as the corpora cavernosa, corpus spongiosum, bulb of penis and vestibule, proximal vagina and urethra) drain into the internal iliac lymph nodes

Question 31

Describe the nerve supply of the perineum.

Answer 31

♪ Somatic motor for control of striated muscles (external urethral and external anal sphincters, bulbospongiosus and ischiocavernosus)
♪ Sensation (urethra, glans of penis and clitoris)
♪ Autonomic both sympathetic and parasympathetic, afferent and efferent
♪ Derived from S2, S3, S4 pudendal nerves + pelvic plexuses (R and L pelvic plexuses) (a.k.a. inferior hypogastric plexus)

Question 32

Which parts of the urethra are most likely to be ruptured ?

Answer 32

Membranous and proximal spongy (bulbar)

Question 33

What would happen if the membranous urethra was ruptured ?

Answer 33

If membranous urethra is ruptured, urine:
− will escape into deep perineal pouch
− May pass through urogenital hiatus and distribute extraperitoneally around bladder

Question 34

What would happen if the proximal spongy (bulbar) urethra was ruptured ?

Answer 34

Urine (or blood):
− escapes through the rupture into the superficial perineal pouch
− descends into the scrotum
− rises onto the anterior abdominal wall deep to the superficial fascia.

“Blue swimming trunks”: Bruising trapped under Scarpa’s and Colles’ (perineal) fasciae ONLY in the front (laterally, membranous layer has fused with fascia lata so cannot go posteriorly. Also fused with PM and Perineal body so will not go posterior to that)