Perineum Flashcards
What is the most inferior portion of the trunk?
Perineum
The perineum lies inferior to what?
Pelvic diaphragm
Name some structures in the male perineum
External genitalia (urethra, scrotum and penis)
Perineal muscles
Anal canal
Name some structures in the female perineum
Female external genitalia
Perineal muscles
Anal canal
We can divide the perineum into two triangular areas, with the base of each triangle being a line joining the two ischial tuberosities transversely. Name the two triangles
Urogenital triangle Anal triangle
A thin sheet of deep fascia stretches between right and left sides of the pubic arch, below the pubis symphysis. What is the name given to this fascia?
Perineal membrane (lies directly inferior to the deep perineal space)
Name 4 muscles of the perineum
External anal sphincter
Superficial transverse perineal muscle
Bulbospongiosus
Ischiocavernosus
What is the innervation of the external anal sphincter?
Branch of pudendal nerve
What are the main actions of the external anal sphincter?
Constricts anal canal during peristalsis resisting defication
Supports and fixes perineal body/ pelvic floor
What is the innervation and action of the bulbospongiosus muscle?
Branch of pudendal nerve
Supports and fixes perineal body/pelvic floor
Males:
compresses bulb of penis to expell last drops of semen/urine
Assists erection by compressing outflow of blood from penis
Female:
assists in erection of clitoris and bulb of vestibule
compresses greater vestibular gland
What is the innervation and action of the ischiocavernosus muscle?
Branch of pudendal nerve
Maintains erection of penis or clitoris
Compressing outflow veins and pushing blood from rest of penis or clitorus into body
What is the innervation and action of the superficial transverse perineal muscle and the deep transverse perineal muscle?
Pudendal nerve
Support and fix perineal body to support abdominopelvic viscera and resist increased intra abdominal pressure
What is the innervation and action of the external urethral sphincter?
Pudendal nerve
Compress urethra to maintain urinary continence
What is the perineal body?
Irregular fibromuscular mass located in the median plane between the anal canal and the perineal membrane
What muscles converge towards the perineal body?
Bulbospongiosus
External anal sphincter
Superficial and deep transverse perineal muscles
External urethral sphincter
levator ani
What is an episiotomy?
Surgical incision of the perineum and vaginal wall done during labour or vaginal surgery to avoid excessive tearing of the perineum and perineal muscles
What are the superficial and deep perineal pouches? What are their clinical significance?
Fascia- limited, potential spaces traversed by the urethra.
They can become infiltrated by urine following traumatic or surgical injury of the urethra
The external urethral sphincter is found in which perineal space?
Deep perineal space
The internal/ vesical urethral sphincter is found in which perineal space?
Subperitoneal space
Where does the superficial perineal pouch lie?
Antero-inferior to the urogenital membrane and surrounds the external genitalia
The deep perineal pouch surrounds what?
The deep transverse perineal muscle
WHat are the 3 parts of the male urethra?
Prostatic Membranous Spongy
What are the widest and narrowest parts of the male urethra and why?
Widest -> Prostatic part,
Narrowest -> Membranous,
(Surrounded by circular fibres of external urethral sphincter (very fixed))
The ischio-anal (ischio-rectal) fosse lies where?
Inferior to the pelvic floor and lateral to the anal canal
What is the function of the ischio-anal fossae?
Allows the anal canal to expand during defaecation
What is the major content of the ischia-anal fosse, and why is this often a site of abscess formation?
FAT
A neurovascular bundle enters the ischio-anal (rectal) fosse through the lesser sciatic foramen. What structures are present in this bundle?
Pudendal canal
Internal Pudendal artery
Internal Pudendal Vein
Pudendal nerve
What does the pudendal canal supply?
Supply and drain blood from perineum
Innervates most of perineum
Which perineal triangle lies inferior to the pubis symphysis?
Urogenital
Which perineal triangle lies anteroinferior to the coccyx?
Anal triangle
What are the lateral boudnries of the urogenital and anal triangles
Ischial tuberosities
