Perineum and External Genitalia - Anatomy Flashcards
What divides the perineum into the urogenital and anal triangle?
Imaginary line between ischial tuberosities
What does the anal triangle contain?
- Anal opening
- Anal aperture
- Ischioanal fossa x2
What is ischioanal fossa?
Fat filled space between ischium and anus
What does ischioanal fossa allow for?
Expansion during defecation
What forms the lateral boundary of the ischioanal fossa?
Obturator internus
What forms the medial boundary of the ischioanal fossa?
Levator ani
What forms the inferior boundary of the ischioanal fossa?
Subcutaneous fat and tissue
Describe the course of the internal pudendal artery / nerve / vein
Leaves pelvis via greater sciatic foramen, loops around sacrospinous ligament and enters into perineum via lesser sciatic foramen
What branches does the internal pudendal artery give off?
Branches to levator ani, inferior rectal branches
Where does the pudendal neurovascular bundle course?
In ischioanal fossa
Describe the course of the piriformis muscle
Leaves pelvis via greater sciatic foramen to attach to the femur
What can the urogenital triangle be divided into?
Superficial and deep perineal pouches
What separates the superficial and deep perineal pouches?
Perineal membrane
Where does the perineal membrane project from/to?
Membrane projects from ischiopubic ramus to ischial tuberosities
What are the only openings that the perineal membrane contains?
Opening for urethra and vagina in female
What does the perineal membrane act as?
Perineal membrane acts as an attachment point for the external genitalia, so external genitalia hang and are located in the superficial perineal pouch
What is found deep to the perineal membrane?
The external urethral sphincter and deep transverse perineal muscles
What is found superficial to the perineal membrane?
Erectile tissues and associated muscles
Where does the bulb of the penis hang from?
Perineal membrane in the midline
What muscle surrounds the bulb of the penis?
Bulbospongiosus
What does the bulb of the penis project forward as?
The corpus spongiosum
What is the corpus spongiosum?
An erectile chamber that attaches to perineal membrane at the bulb of the penis where it is covered by bulbospongiosus muscle
What does the corpus spongiosum contain?
Penile urethra
What surface does the corpus spongiosum form?
Ventral surface
How does the corpus spongiosum terminate?
Dilates to form glans penis
What is found laterally to bulb of penis?
The corpora cavernosa (one corpus cavernosum either side)
What are the corpora cavernosa?
Erectile chambers with overlying muscle
What muscle overlies corpora cavernosa?
Ischiocavernosus muscles
Where do the isciocavernosus muscles attach to?
Ischiopubic ramus
What happens as the 2 corpora cavernosa approach the midline in males?
Converge at level of pubic arch and project forwards on the dorsal aspect of the penis
What hangs from the perineal membrane in males?
- Bulb of penis formed by the corpus spongiosum
2. 2 chambers: the corpora cavernosa, covered by the ischiocavernosus muscles
What differs in the male and female bulb?
Bulb in male is fused but unfused in female
What is found either side of vaginal opening?
Vestibular bulbs (one bulb of vestibule either side as unfused)
Where do vestibular bulbs hang from?
Perineal membrane
What is the bulb of vestibule covered by?
Thin filament of muscle - bulbospongiosus
What do the bulbs of vestibule continue forward to form?
Glans of clitoris
What are vestibular bulbs formed from?
Corpus spongiosum tissue
What is found lateral to vestibular bulbs?
Corpora cavernosa, hanging from perineal membrane, covered by ischiocavernosus muscle
What do corpora cavernosa project forward to form in females?
Body of clitoris
Where are labia majora found?
Either side of vaginal opening with bulb of vestibule either side
What is found within the spermatic cord?
Vas deferens, testiculary artery, pampiniform plexus
What is the pampiniform plexus?
Venous network that drains the testis and epipdidymis
The network surrounds the testicular artery in the spermatic cord and lies anterior to the vas deferens
What surrounds the testes?
Tunica vaginalis –> remnant of processus vaginalis (layer of peritoneum that invaginates during descent of testes)
What scrotal layer comes from the transversalis fascia?
Internal spermatic fascia
What scrotal layer comes from the internal oblique?
Cremasteric fascia
What scrotal layer comes from the external oblique?
External spermatic fascia
What scrotal layer comes from the parietal peritoneum?
Tunica vaginalis
What scrotal layer comes from the transversus abdominis?
None
What is the crus of the clitoris formed by?
The part of the corpus cavernosus attaching to the ischiopubic rami.
What is the body of the clitoris formed by?
2 corpora cavernosa (right and left) projecting anteriorly.
What part of the penis is formed from the attachment of the corpora cavernosa to the ischiopubic rami?
Crura
