PASS 610 - Exam 3 - Perineum & External Genitalia
Questions with Correct Answers
An episiotomy is an incision made in the perineum to enlarge the distal end of the birth canal
and to prevent serious damage to the perineal structures. This procedure is often performed
when there is a risk of tearing the birth canal due to a breech or forceps delivery. When
performing a median episiotomy, a cut is made immediately posterior to the vagina, through
the perineal body. If this cut went too far, the physician might cut through the external anal
sphincter or the rectum. So, external anal sphincter is the correct answer.
It's important to remember that episiotomies are often made in the posterolateral direction,
not on the midline. If the incision tears further during the delivery, a median incision is more
likely than a posterolateral incision to extend posteriorly through the external anal sphincter,
and the rectum. Consequently, a posterolateral incision is considered safer by some.
The bulbospongiosus muscle, ischiocavernosus muscle, and sphincter urethrae are anterior to
the area that is cut during an episiotomy. The sacrospinous ligament extends from the sacrum
to the ischial spine--it is deep to the perineum and should not be involved with this procedure.
During a prostatectomy, the surgeon attempts to protect the prostatic plexus of nerves which
contains nerve fibers that innervate penile tissue to cause erection. From which nerves do these
fibers originate?
A) Deep perineal
B) Dorsal nerve of the penis
C) Genitofemoral
D) Pelvic splanchnics
E) Pudendal✔✔D) Pelvic splanchnics
Erection is mediated by parasympathetic nerves, and the pelvic splanchnic nerves are the
parasympathetic nerves that innervate the smooth muscle and glands of all pelvic viscera. So,
the pelvic splanchnic nerves are the nerves contributing the fibers to the prostatic plexus which
innervate penile/clitoral erectile tissue to cause erection.
, None of the other listed nerves carry parasympathetic fibers which could innervate the penis
and cause erection. Additionally, none of these other nerves contribute to the prostatic plexus,
which is an extension of the inferior hypogastric plexus. The deep perineal nerve is the a branch
of the perineal nerve that innervates all the muscles of the urogenital triangle. The dorsal nerve
of the penis/clitoris is a branch of the pudendal nerve that provides sensory innervation to the
skin of the shaft of the penis/clitoris. The genitofemoral nerve provides motor innervation to
the cremaster muscle and sensory innervation to the skin of the anterior scrotum/labium majus
and the upper medial thigh. Finally, the pudendal nerve is the major nerve of the perineal
region. Its branches include the inferior rectal nerve, perineal nerve, and the dorsal nerve of the
penis/clitoris.
If the venous drainage of the anal canal above the pectinate line is impaired in a patient with
portal hypertension, there may be an increase in blood flow downward to the systemic venous
system via anastomoses with the inferior rectal vein, which is a tributary of the:
A) External iliac
B) Inferior gluteal
C) Inferior mesenteric
D) Internal iliac
E) Internal pudendal✔✔E) Internal pudendal
The rectal venous plexus is one of the four portal/systemic anastomoses. Blood from the portal
system can flow into the venous system at this junction. This means that portal blood, from the
superior rectal vein, could flow through the rectal venous plexus, into the inferior rectal vein
and into the systemic venous drainage. Now, you just need to figure out what the inferior rectal
vein drains into. And it drains into the internal pudendal vein, so that's the answer. See Netter
plate 370 for a picture illustrating this concept
The boundaries of the perineum include all the following except:
A) Ischiopubic rami
B) Ischial tuberosity
C) Tip of the coccyx
D) Sacrotuberal ligament
Questions with Correct Answers
An episiotomy is an incision made in the perineum to enlarge the distal end of the birth canal
and to prevent serious damage to the perineal structures. This procedure is often performed
when there is a risk of tearing the birth canal due to a breech or forceps delivery. When
performing a median episiotomy, a cut is made immediately posterior to the vagina, through
the perineal body. If this cut went too far, the physician might cut through the external anal
sphincter or the rectum. So, external anal sphincter is the correct answer.
It's important to remember that episiotomies are often made in the posterolateral direction,
not on the midline. If the incision tears further during the delivery, a median incision is more
likely than a posterolateral incision to extend posteriorly through the external anal sphincter,
and the rectum. Consequently, a posterolateral incision is considered safer by some.
The bulbospongiosus muscle, ischiocavernosus muscle, and sphincter urethrae are anterior to
the area that is cut during an episiotomy. The sacrospinous ligament extends from the sacrum
to the ischial spine--it is deep to the perineum and should not be involved with this procedure.
During a prostatectomy, the surgeon attempts to protect the prostatic plexus of nerves which
contains nerve fibers that innervate penile tissue to cause erection. From which nerves do these
fibers originate?
A) Deep perineal
B) Dorsal nerve of the penis
C) Genitofemoral
D) Pelvic splanchnics
E) Pudendal✔✔D) Pelvic splanchnics
Erection is mediated by parasympathetic nerves, and the pelvic splanchnic nerves are the
parasympathetic nerves that innervate the smooth muscle and glands of all pelvic viscera. So,
the pelvic splanchnic nerves are the nerves contributing the fibers to the prostatic plexus which
innervate penile/clitoral erectile tissue to cause erection.
, None of the other listed nerves carry parasympathetic fibers which could innervate the penis
and cause erection. Additionally, none of these other nerves contribute to the prostatic plexus,
which is an extension of the inferior hypogastric plexus. The deep perineal nerve is the a branch
of the perineal nerve that innervates all the muscles of the urogenital triangle. The dorsal nerve
of the penis/clitoris is a branch of the pudendal nerve that provides sensory innervation to the
skin of the shaft of the penis/clitoris. The genitofemoral nerve provides motor innervation to
the cremaster muscle and sensory innervation to the skin of the anterior scrotum/labium majus
and the upper medial thigh. Finally, the pudendal nerve is the major nerve of the perineal
region. Its branches include the inferior rectal nerve, perineal nerve, and the dorsal nerve of the
penis/clitoris.
If the venous drainage of the anal canal above the pectinate line is impaired in a patient with
portal hypertension, there may be an increase in blood flow downward to the systemic venous
system via anastomoses with the inferior rectal vein, which is a tributary of the:
A) External iliac
B) Inferior gluteal
C) Inferior mesenteric
D) Internal iliac
E) Internal pudendal✔✔E) Internal pudendal
The rectal venous plexus is one of the four portal/systemic anastomoses. Blood from the portal
system can flow into the venous system at this junction. This means that portal blood, from the
superior rectal vein, could flow through the rectal venous plexus, into the inferior rectal vein
and into the systemic venous drainage. Now, you just need to figure out what the inferior rectal
vein drains into. And it drains into the internal pudendal vein, so that's the answer. See Netter
plate 370 for a picture illustrating this concept
The boundaries of the perineum include all the following except:
A) Ischiopubic rami
B) Ischial tuberosity
C) Tip of the coccyx
D) Sacrotuberal ligament
