Flashcards in Perineum I Deck (61):
What is the anterior boundary of the perineum?
the symphysis pubis.
What is the posterior boundary of the perineum?
What is the lateral boundary of the perineum?
the ischial tuberosities
What is the posterolateral boundary of the perineum?
the sacrotuberous ligament and gluteus maximus muscle
What is the floor of the perineum?
the skin and subcutaneous fascia.
What is the roof of the perineum?
the pelvic diaphragm
What is the anterolateral boundary of the perineum?
the ischiopubic rami.
The perineum is divided into two triangles by an imaginary line drawn between what structures?
the ischial tuberosities.
The line made connecting the ischial tuberosities and dividing the perineum makes what regions?
the urogenital (UG) triangle (anterior) and the anal triangle
What muscles make up the pelvic diaphragm?
the levator ani and coccygeus muscles
What structures pass through this diaphragm to enter the perineum?
The urethra, vagina (via the urogenital hiatus) and the anal canal (via the anal hiatus)
What is the innervation to the levator ani?
Inferior Rectal Nerve (S2-S4) and Direct Branches from S4
What is the innervation to the coccygeus?
Direct Branches from S3 and S4
What three fused bones compose the os coxae?
the ilium, pubic, and ischium
The two os coxae are fused to one another anteriorly at the _____ and are fused with the sacrum posteriorly at the _____ , forming the pelvic girdle.
pubic symphysis; the right and left sacroiliac joints
What does the linea terminalis define and what is it composed of?
it defines the superior pelvic aperture, a line circumscribing the sacral promontory (S1 Vertebra), the arcuate line of the ilium, the pectineal line of the pubis and the pubic symphysis.
What are the boundaries of the pelvic outlet?
the inferior margin of the pubic symphysis, inferior pubic rami, sacrotuberous ligaments and tip of the coccyx.
What are the main contents of the anal canal?
the anal canal and its external orifice (anus) in the midline and the right and left ischioanal fossa on either side of the canal
What are the The ischioanal fossae filled with?What does this space allow for?
mostly fat. These spaces allow for movement of the pelvic diaphragm and expansion of the anal canal during defecation.also contains the External Anal Sphincter muscle
What is the lateral boundary of the sischioanal fossa?
Obturator Internus muscle (perineal portion)
What is the superomedial boundary of the sischioanal fossa?
What is the inferior boundary of the sischioanal fossa?
What is the posterior boundary of the sischioanal fossa?
sacrotuberous ligament with overlying fibers of gluteus maximus, fascia, and skin.
What are the three parts of the external anal sphincter (EAS)?
the deep, superficial, and subcutaneous portions
What is the EAS anchored to posteriorly and anteriorly?
a) anterior- the perineal body b) posterior- anococcygeal body.
What kind of muscle is the EAS composed of?
skeletal and under voluntary control
What kind of muscle is the IAS composed of?
smooth and under involuntary control
T or F. The tone of the sphincter muscles (both internal and external) keep the lateral walls of the anal canal opposed to one another except when the sphincters relax during defecation
What is the EAS controlled by?
somatic innervation via the inferior rectal nerves (S2‐4) which are branches of the pudendal nerve.
What is the IAS controlled by?
The IAS is under autonomic control via the lumbar splanchnic nerves (sympathetic) and pelvic splanchnic nerves (parasympathetic)
Where is the pudendal canal located?
It is a specialization of the fascia of the obturator internus muscle on the lateral wall of the ischioanal fossa
How does the pudendal canal (Alcock's canal( form?
The deep fascia of this muscle splits into lateral and medial lamina forming a fascial canal that transmits the pudendal nerve and internal pudendal vessels and their branches, which are destined for the urogenital triangle
Where does the pudendal nerve arise from?
as a branch of the sacral plexus (that arises in the pelvis)
Where do the internal pudendal nerve arise from?
as branches of the internal iliac artery and vein
Describe the route of the pudendal nerve(s)?
The pudendal nerve exits the pelvis via the greater sciatic foramen, wraps around the sacrospinous ligament and then enters the perineum via the lesser sciatic foramen. It travels through the ischioanal fossa within the pudendal canal where it divides into three terminal branches.
What is the primary nerve supply to the perineum?
the pudendal nerve- it is the sole motor supply to the perineum and is sensory to most of the perineal skin**It is clinically important because gynecological/obstetric procedures frequently require local anesthetic (i.e. pudendal nerve block)**
What are the three main branches of the pudendal nerve?
a) inferior rectal nerveb) perineal nervec) Dorsal Nerve of the Clitoris/Penis
Describe the route and roles of the inferior rectal nerve
course medially in the ischioanal fossa to provide motor innervation to the external anal sphincter muscle and sensory innervation to the lower part of the anal canal and the perianal skin. This nerve often occurs as multiples. This nerve has mixed motor/sensory function.
The Perineal Nerve enters the superficial perineal space by passing superficial to what?
The UG diaphragm
What is the role of the perineal nerve?
This nerve provides motor innervation to the five muscles of the superficial and deep perineal spaces and sensory innervation to the posterior scrotum/labia, the bulb of the penis and the urethra. This nerve has mixed motor/sensory function.
T or F. the dorsal nerve of the clitoris/penis enters the superficial perineal space
F. It enters the deep perineal space
What is the role of the dorsal nerve of the clitoris/penis?
It provides sensory innervation to the body and glans of the clitoris/penis. This nerve has sensory function only
The internal pudendal artery is a branch of what artery?
internal iliac artery in the pelvis
Does the internal pudendal artery enter the pudendal canal?
yes. It exits the pelvis via the greater sciatic foramen, wraps around the sacrospinous ligament and then enters the perineum via the lesser sciatic foramen.
What are the three branches of the internal pudendal artery?
a) inferior rectal arteryb) perineal arteryc) continuation of the internal pudendal artery
What does the inferior rectal artery do?
follows the inferior rectal nerve and supplies blood to the lower portion of the anal canal, the anal opening, and the skin around it. The inferior rectal artery often occurs in multiples.
What does the inferior rectal artery anastomose with?
It forms an anastomoses with superior and middle rectal arteries.
What does the perineal artery do?
enters the superficial perineal space to supply the perineal muscles and posterior scrotum/labia
Where does the internal pudendal artery continue to after it's initial branching?
continues within the deep perineal space where it gives off two branches (the artery to the urethra and the artery to the bulb of the penis) before dividing into its two terminal branches
What are the two terminal branches of the internal pudendal artery?
1) dorsal artery of the penis/clitoris2) deep artery of the penis/clitoris
Why are the ischioanal fossae are particularly vulnerable to infection?
due to their close proximity to the anal canal. Infection commonly tracks laterally from the anal mucosa through the external anal sphincter
Could infection in the ischioanal fossa spread to the urigential triangle? Why?
No, because of the presence of fascial layers that form a separation between the two spaces
The deeper membranous layer of the superficial abdominal fascia (Scarpa’s) continues into the perineum to become what in both men and women?
the superficial perineal or Colles’ fascia. It continues posteriorly to attach to the free posterior margin of the UG diaphragm.
Where does the the urogenital (or UG) diaphragm run from?
It stretches between the ischiopubic rami
What is the main role of UG diaphragm?
The UG diaphragm serves as the foundation for the attachment of the external genitalia. It also contributes to the physical support of the pelvic viscera.
The superior surface of the UG diaphragm is lined with a layer of deep fascia called what?
the superior fascia of the UG diaphragm. The inferior surface of this diaphragm is covered with a denser, more fibrous layer of deep fascia called the inferior fascia of the UG diaphragm ((often called the perineal membrane))
What does the more superficial fatty layer (Camper’s) of the abdomen do in women?
increases in size and continues inferiorly to form the mons pubis and fill the labia majora
What does the more superficial fatty layer (Camper’s) of the abdomen do in men?
The fatty layer (Camper’s) thins out and disappears
Describe the route of Colles’ fascia in men?
It changes names when it turns to follow the dorsal surface of the penis where it is called the superficial penile fascia. After returning along the ventral surface of the penis, the fascia follows the inside margin of the scrotum where it is called the tunica dartos or just the darts fascia. This fascial layer continues posteriorly from the scrotum to the posterior margin of the UG diaphragm. The name returns to Colles’ in this region. Note the fusion of the Colles fascia with the fascia of the UG diaphragm.
What are the contents of the tunica dartos?
the dartos fascia contains a layer of smooth muscle (dartos muscle) that is innervated by sympathetic nerve fibers (lumbar splanchnic nerves). This muscle can assist the cremaster muscle (of the spermatic cord) to raise or lower the scrotal sac, thus regulating scrotal temperature for optimal sperm production.