The Perineum and External Genitalia Flashcards
An imaginary line drawn between the ischial tuberosities divides the pelvic outlet into an anterior __1__ and a posterior __2__
1) urogenital triangle
2) anal triangle
What structures are contained in the anal triangle?
Anal canal, with the ischioanal fossa and its contents on either side
Where does the rectum become the anal canal?
At the u-shaped sling created by puborectalis
How does the arterial supply change in the anal canal?
Upper two-thirds: From inferior mesenteric artery
Lower third: from internal iliac atery
How does the venous drainage change in the anal canal?
Upper two-thirds: to portal venous system
Lower third: to caval venous system
How does the lymphatic drainage change in the anal canal?
Upper two-thirds: to internal iliac lymph nodes
Lower third: to superficial inguinal lymph nodes
How does the nerve supply change in the anal canal?
Upper two-thirds: Visceral motor (mixed sympathetic and parasympathetic) and sensory information
Lower third: Somatic motor and sensory innervation
What boundary is marked by the pectinate line?
The approximate boundary between the embryologically different region of the anal canal
What is the nerve supply to the internal anal sphincter?
Autonomic
What is the nerve supply to the external anal sphincter?
Somatic
What are the different parts of the external anal sphincter called?
Subcutaneous, superficial and deep parts
Which part of the external anal sphincter is related posteriorly to the fibres of puborectalis?
Deep part
The ischioanal fossa are largely filled with __1__ and are a common site for infection, resulting in abscesses which may rupture to produce a fistula. A fistula in this region might open between the ischioanal fossa and __2__
1) fat
2) anal canal
The pudendal nerve and internal pudendal vessels travel in the __1__, in the __2__ wall of each ischioanal fossa
1) pudendal canal
2) lateral
What branches leave the pudendal neurovascular bundle as it traverses the ischioanal fossa?
Inferior rectal artery, vein and nerve
Why would you carry out a pudendal nerve block?
To anaesthetise the perineum during episiotomy
The urogenital triangle is subdivided into deep and superficial parts by the __?__
Urogenital diaphragm - a triangular layer of muscle and dense fascia (perineal membrane) that extends between the inferior ischiopubic rami and merges with the perineal body posteriorly
The urogenital triangle is pierced by the __1__ in both sexes and by the __2__ in females. In both sexes, muscles within the urogenital diaphragm form the __3__
1) urethra
2) vagina
3) external urethral sphincter
What is the nerve supply to the external urethral sphincter?
Deep branch of perineal nerve
From which vessel does the external pudendal artery branch? What does it supply?
Femoral artery; skin of scrotum and labia
What is contained within the superficial perineal pouch? What is the name of the membranous layer of superficial fascia?
Contains testes, vas deferens and root of penis
Colle’s fascia
Which structures do the bulb of the penis and the crura of the corpora cavernosa attach to?
Perineal membrane and ischiopubic ramus
what are the actions of bulbospongiosus and ischiocavernosus? What is their nerve supply?
Contraction of these muscles prevents venous return, thereby allowing engorgement of the erectile tissues.
Deep branch of perineal nerve
Which arteries supply the penis?
Internal pudendal:
artery of bulb, deep artery of penis, dorsal artery of penis
What is the sensory nerve supply to the skin of the scrotum?
Anterior: Ilioinguinal, genital branch of genitofemoral
Posterior: Pudendal, posterior scrotal
From what is the tunica vaginalis derived?
Processus vaginalis
During descent of the testes the testis pushes through a serous pouch of the peritoneum
Wy are UTIs more common in females than males?
Shorter urethra
Deep to the skin and fat of each __1__ lies a mass of erectile tissue called the bulb of the __2__, which is firmly attached to the underlying __3__.
1) labia majora
2) vestibule
3) perineal membrane
The bulbs of the vestibule partially overlie the __1__ glands and are, themselves, covered with thin sheets of muscle: the __2__ muscles
1) greater vestibular
2) bulbospongiosus
The bulbs of the vestibule join together anteriorly to form the __?__
glans of the clitoris
Which tissues contribute to the formation of the clitoris?
Bulb of vestibule and corpora cavernosa
How is the clitoris anchored in the perineum?
Via crura which insert onto ischiopubic ramus
What is the function of of the vestibular glands (Bartholin’s glands)?
Secretion of mucus into vagina during sexual arousal
To which nodes does lymph from perineal structures drain?
Superficial inguinal lymph nodes, the deep and then internal iliac
