DISSECTION 31
The Perineum, Urogenital Triangle
References: M1 402-409, 418-434; N 348, 360-368, 376; N361, 378-385, 395; R 327-347, 350-354
AT THE END OF THIS LABORATORY PERIOD YOU WILL BE RESPONSIBLE FOR THE
IDENTIFICATION AND DEMONSTRATION OF THE STRUCTURES LISTED BELOW:
1. Muscles, fasciae, and fascial spaces: superficial perineal compartment, ischiocavernosus,
bulbospongiosus, urogenital diaphragm, sphincter urethrae, deep transverse perineus, fascia
penis, tunica albuginea, inferior fascia of urogenital diaphragm (perineal membrane), deep
perineal compartment.
2. Ligaments, etc.: symphysis pubis, pubic arcuate ligament, fundiform ligament of penis,
suspensory ligament of penis or clitoris.
3. Nerves: dorsal nerve of penis or clitoris.
4. Arteries: internal pudendal artery, deep artery of penis or clitoris, dorsal artery of penis or clitoris.
5. Veins: superficial dorsal vein of penis, deep dorsal vein of penis.
6. Cavernous bodies: crura of penis and clitoris, bulb of urethra and vestibule, corpus cavernosum
penis, corpus spongiosum.
7. Visceral structures: membranous urethra, spongy urethra.
YOU SHOULD ALSO BE ABLE TO DO THE FOLLOWING THINGS:
1. Label on a diagram the fascias, muscles, nerves and vessels of the urogenital diaphragm.
2. Draw a diagram of the pudendal nerve and its branches.
3. Draw a diagram of the internal pudendal artery and its branches.
4. Demonstrate on the cadaver the boundaries and contents of the deep perineal space.
5. Identify on the cadaver the structures enclosed between the superficial perineal fascia (Colles'
fascia) and the inferior fascia of the urogenital diaphragm (perineal membrane).
6. Name the abdominal fascial layers that are continuous with the perineal fascias.
7. Demonstrate the course of lymphatic and venous drainage from the perineum.
8. Explain how urine can spread to the anterior abdominal wall and why it usually does not spread
into the ischiorectal fossa or the thighs when the urethra is injured inferior to the urogenital
diaphragm.
Dissection 31, Perineum, Urogenital Triangle
Examine the tela subcutanea of the urogenital
triangle for superficial branches of pudendal
arteries and nerves. The inner fibrous or deep
layer of the tela of this region is called the
superficial perineal [Colles'] fascia (N360, 363;
N378, 380). Look for the superficial transverse
perineus muscle along the posterior border (base)
of the urogenital triangle. (It may be absent or
unidentifiable.) Incise the superficial perineal
fascia through the median line and across the base
of the triangle, then reflect it laterally to open the
SUPERFICIAL PERINEAL COMPARTMENT (A344,
346, 370-371; G3.44, 54; N361, 364, 376, 384,
385; N379, 381, 395, 404, 405).
Identify and clean the following structures
within this compartment (structures of the female
in parentheses): [N364, 365 (361) N381, 382,
(379)]
Page 2
Cut the crura from their attachments to the
ischiopubic rami, and the bulb from the INFERIOR
FASCIA
OF
THE
UROGENITAL
(PERINEAL MEMBRANE). (In the female, transect
the vagina just superior to the bulb of the
vestibule.) Review the FUNDIFORM LIGAMENT
of the penis and find the SUSPENSORY
LIGAMENT, which attaches the fascia penis to the
SYMPHYSIS PUBIS. Make a cross section through
the body of the penis (G3.48, 51, 49; N364;
N381; A348-350) and identify the following
parts:
DEEP FASCIA, called Buck's
(FASCIA PENIS)
fascia
CORPUS CAVERNOSUM PENIS
CORPUS SPONGIOSUM PENIS
TUNICA ALBUGINEA
of the corpora
ISCHIOCAVERNOSUS MUSCLE
DEEP ARTERY OF THE PENIS
BULBOSPONGIOSUS MUSCLE
SPONGY URETHRA
CRURA OF THE PENIS
CLITORIS)
(CRURA OF THE
BULB OF THE URETHRA (VESTIBULE)
Expose the crura of the penis (or the clitoris)
and the URETHRAL (vestibular) BULB by
reflecting their investing musculature. In the
male, reflect the skin from the dorsum of the
penis. Trace the DORSAL ARTERIES (A347;
G3.51B, 48A; N381, 389; N401, 409) and
NERVES distally to the glans, then proximally to
the site where they emerge from the UROGENITAL
DIAPHRAGM (N385; N405).
This diaphragm
consists of deep fascia, SPHINCTER URETHRAE
and the DEEP TRANSVERSE PERINEUS MUSCLE,
which span the gap between the inferior rami of
the pubic and ischial bones.
Identify the
SUPERFICIAL and DEEP DORSAL VEINS of the
penis (A347; G3.51A, 48A; N364, 385; N381,
405), and trace the deep vein to its passage
through the space between the PUBIC ARCUATE
LIGAMENT and the anterior portion of the
urogenital diaphragm. This fibrous part of the
diaphragm is called the transverse perineal
ligament (A366; G3.51B; N385; N405).
DIAPHRAGM
On one side, open the DEEP PERINEAL
by careful removal of the
inferior fascia of the urogenital diaphragm and
identify the main components within it, as follows
(A366, 369; G3.51B; N385; N405):
COMPARTMENT
the DEEP TRANSVERSE PERINEUS MUSCLE
the
MEMBRANOUS
SPHINCTER MUSCLE
URETHRA
and
its
the INTERNAL PUDENDAL ARTERY and its
branches:
the DEEP ARTERY
(CLITORIS),
OF
THE
PENIS
the DORSAL ARTERY OF THE PENIS
(CLITORIS)
Remove muscle where necessary to trace the
deep and dorsal arteries of the penis from their
origin from the internal pudendal, through the
deep compartment. Review the internal pudendal
artery and its branches.
Identify the superior fascia of the urogenital
diaphragm and review the transverse perineal
ligament. Note that the ischiorectal (ischioanal)
fossa, on each side of the midline, is prolonged as
an anterior recess which lies between the
urogenital and the pelvic diaphragms.
Dissection 31, Perineum, Urogenital Triangle
Page 3
STUDY QUESTIONS
1.
With which abdominal fascia is
the superficial perineal fascia
(Colles' fascia) continuous?
1.
The deep (membranous) (Scarpa's) layer of the
tela subcutanea (superficial fascia).
2.
Where does the superficial perineal
fascia attach firmly to deep fascia?
2.
Along the ischiopubic rami and to the posterior
border of the urogenital diaphragm.
3.
What is the superficial perineal
space?
3.
The space bounded superiorly by the inferior
fascia of the urogenital diaphragm and inferiorly
by the Colles' fascia. It contains the root
structures of the penis or clitoris and associated
muscles.
4.
What is the deep space or
compartment of the urogenital
diaphragm?
4.
The area between the inferior and superior
fascias of the urogenital diaphragm.
5.
What name is given to the most
anterior non-muscular part of the
urogenital diaphragm?
5.
Transverse perineal ligament.
6.
What structures pass through the
gap between the transverse perineal
ligament and the arcuate ligament
of the pubis?
6.
Dorsal vein(s) of the penis to join prostatic
plexus.
7.
What is the crus of the penis?
7.
The posterior attached portion of the corpus
cavernosum penis.
8.
What is the bulbospongiosus?
8.
The striated muscle of the corpus spongiosum in
the male and the vestibular bulb in the female.
9.
What is the innervation of the
bulbospongiosus?
9.
Perineal branches of the pudendal nerve.
10. What is the central tendon of
the perineum?
10. Often called the perineal body, it is a common
attachment for the external anal sphincter, the
bulbospongiosus and the superficial and deep
transverse perineus muscles.
Dissection 31, Perineum, Urogenital Triangle
Page 4
11. What occupies the deep space of
the urogenital diaphragm in the male?
11. The deep transverse perineus muscle and
sphincter urethrae, membranous urethra,
bulbourethral glands, dorsal nerve of penis,
internal pudendal vessels, and origin of branches,
deep and dorsal arteries of the penis and
branches to bulb and urethra which pierce the
inferior fascia of the UG diaphragm.
12. What other name is given to the
inferior fascia of the urogenital
diaphragm?
12. Perineal membrane.
13. What is the lymphatic drainage
of the penis or clitoris?
13. Lymph from the penis or clitoris drains to nodes
directly in front of the pubic symphysis and
bilaterally to inguinal nodes.
14. Where is the major vestibular
gland?
14. The major vestibular gland is located in the
superficial perineal space posterior to the bulb of
the vestibule and deep to the bulbospongiosus
muscle (A368, G3.54).
15. List the nerves that supply the
vulva.
15. The vulva is supplied by the ilioinguinal nerve
(anterior labial branches), the genitofemoral
nerve (genital branch), perineal branch of
posterior femoral cutaneous nerve, and the
perineal nerve (posterior labial branches).
16. Name the structures that are
incised in a
16.
a) median episiotomy.
a. skin, vaginal mucosa, central tendon of
perineum
b) mediolateral episiotomy.
b. skin, vaginal mucosa, bulbospongiosus
muscle, superficial transverse perineus
muscle, inferior fascia of urogenital
diaphragm, deep transverse perineus muscle
Dissection 31, Perineum, Urogenital Triangle
17. Draw a diagram showing
the pudendal nerve and
the internal pudendal
artery and their major
branches in the
perineum.
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17.
LJ:bh
revised
06/19/09