The Perineum

Question 1

Answer 1

Question 2

which triangle is shown by the shaded orange area above?
which triangle is shown by the shaded green area?

Answer 2

orange = urogenital triangle
green = anal triangle

Question 3

which bony prominences separate the urogenital and anal triangle?

Answer 3

ischial tuberosity

Question 4

A thin sheet of deep fascia stretches between right and left sides of the pubic arch, below the pubic symphysis.

What is the name given to this fascia?

Answer 4

perineal fascia

Question 5

what is the main action of the highlighted muscle?
what is its innervation?

Answer 5

• external anal sphincter
• constricts anal canal during peristalsis, resists defecation
• innervation: branches of pudendal nerve S2-S4

Question 6

what is the main action and innervation of the highlighted muscle?

Answer 6

• superficial transverse perineal muscle
• support and fix perineal body to support abdominopelvic viscera
• innervation: branches to pudendal nerve S2-S4

Question 7

what is the main action and innervation of the highlighted muscle?

Answer 7

• deep transverse perineal muscle
• support and fix perineal body to support abdominopelvic viscera
• branches to pudendal nerve S2-S4

Question 8

what is the main action and innervation of the highlighted muscle?

Answer 8

• bulbospongiosus (female diagram)
• sphincter of vagina and assists in erection of clitoris
• branches to pudendal nerve S2-S4

Question 9

what is the main action and innervation of the highlighted muscle?

Answer 9

• ischiocavernosus (female diagram)
• maintains erection of clitoris by compressing outflow veins and pushing blood from the root to the body
• branches of pudendal nerve S2-4

Question 10

what is the highlighted muscle called?

Answer 10

superficial transverse perineal muscle (male)

Question 11

what is the main action and innervation of the highlighted muscle?

Answer 11

• bublospongiosus (male)
• compresses bulb of penis to expel drops of urine/semen
• assists erection by compressing outlflow via deep perineal vein and pushing blood from bulb into body of penis

Question 12

what is the main action and innervation of the highlighted muscle?

Answer 12

• ischiocavernosus (male)
• maintaining erection by impeding venous return from corpora cavernosa of penis.
• The muscle also undergoes rhythmic contraction in conjunction with bulbospongiosus during ejaculation which serve to help maintain the erection and possibly to aid in moving the ejaculate through the urethra.
• innervation: pudendal branch S2-S4

Question 13

what are the potential consequences if the perineal body is damaged/ruptured during childbirth?

Answer 13

Childbirth can lead to damage (stretching/tearing) of the perineal body, thus leading to possible prolapse of pelvic viscera. This may be avoided by an episiotomy (a surgical cut in the perineum). This inevitably causes damage to the vaginal mucosa, but prevents uncontrolled tearing of the perineal body.

Question 14

There are 2 layers of fascia important as additional support for the pelvic organs within the perineum.

These are the superior and inferior fascia, making up the pelvic diaphragm.

Which structures pierce through the pelvic diaphragm?

Answer 14

urethra
vagina