3.1 - Perineum Flashcards
Where does the perineum lie?
Inferior to the pelvic diaphragm and is the most inferior part of the trunk
What are the structures found in the male perineum?
- External genitalia (urethra, scrotum and penis)
- Perineal muscles
- Anal canal
What are the structures found in the female perineum?
- Female external genitalia
- Perineal muscles
- Anal canal
The perineum is split into 2 triangles, what are they?
Urogenital
Rectal/anal
Which triangle lies inferior to the pubic symphysis?
Urogenital triangle
Which triangle lies inferior to the coccyx?
Anal triangle
A thin sheet of deep fascia stretches between the right and left sides of the pubic arch, below the pubic symphysis, what is this called?
Perineal membrane
(‘closes’ the urogenital triangle; covers the anterior part of the pelvic outlet and is perforated by the urethra in both sexes and by the vagina of the female)
Name the 6 muscles of the perineum
External anal sphincter Bulbospongiosus Ischiocavernosus Superficial transverse perineal Deep transverse perineal External urethral sphincter
What is the innervation and main action of the external anal sphincter?
- Branch of pudendal nerve
- Constricts anal canal during peristalsis, resisting defaecation; supports and fixes perineal body/pelvic floor
What is the innervation and main action of bulbospongiosus?
- Branch of pudendal nerve
- Supports and fixes perineal body/pelvic floor
Male = compresses bulb of penis to expel last of semen; assists erection
Female = ‘sphincter’ of vagina; assists erection of clitoris; compresses greater vestibular gland
What is the innervation and main action of ischiocavernosus?
- Branch of pudendal nerve
- Maintains erection of penis/clitoris
What is the innervation and main action of the superficial transverse perineal muscle?
- Branches of pudendal nerve
- Support and fix perineal body (pelvic floor) to support abdomino-pelvic viscera and resist increased intra-abdominal pressure
What is the innervation and main action of the deep transverse perineal muscle?
- Branches of pudendal nerve
- Support and fix perineal body (pelvic floor) to support abdomino-pelvic viscera and resist increased intra-abdominal pressure
What is the innervation and main action of the external urethral sphincter?
- Somatic fibres S2-S4 through pudendal nerve
- Compress urethra to maintain urinary continence
What is the perineal body?
Irregular fibromuscular mass located at the junction of the urogenital and anal triangles (central point of perineum)
What is the clinical significance of the perineal body?
Childbirth can lead to damage thus possible prolapse of pelvic viscera - may be avoided by episiotomy
Which 4 muscles converge at the perineal body?
External anal sphincter
Superficial transverse perineal (and deep (?))
Levator ani
Bulbospongiosus
What are the names of the 2 fascia-limited, potential spaces traversed by the urethra? What is their clinical significance?
The superficial and deep perineal pouches
They can become infiltrated with urine following traumatic or surgical injury of the urethra
In which perineal pouch is the external urethral sphincter found?
Deep
Is the external urethral sphincter voluntary or involuntary? What is its innervation?
Voluntary
Somatic fibres from S2-S4 through pudendal nerve
Where is the internal/vesical urethral sphincter found?
Junction of the urethra with the urinary bladder
Is the internal urethral sphincter voluntary or involuntary? What is its innervation?
Involuntary
Sympathetic fibres from T10-L2 through inferior hypogastric plexus then vesical nerve plexus
Where does the superficial perineal pouch lie? And what does it surround?
Antero-inferior to the urogenital membrane
Surrounds the external genitalia
What muscle does the deep perineal pouch surround?
Deep transverse perineal
