Perineum Flashcards
What are the boundaries of the perineum?
- Anterior: Pubic symphysis
- Lateral: Ischial tuberosities
- Posterior: Coccyx
What are the components of levator ani?
- Puborectalis
- Pubococcygeus (poboanalis, puboprostaticus/vaginalis)
- Iliococcygeus
What are the origins and insertions of puborectalis?
Origins: Posterior surface of pubis
Insertions: Posterior surface of pubis (forms sling around anal canal)
What are the origins and insertions of pubococcygeus?
Origins: Posterior surface of pubis
Insertions: Anococcygeal raphé
What are the origins and insertions of iliococcygeus?
- Origins: Whitle line on obturator internus
- Insertions: Anococcygeal raphé
What is the innervation and function of the levator ani?
Innervation:
- Anterior rami of S4
- Pudendal nerve
Function:
- Forms pelvic floor
- Supports pelvic viscera
- Reinforces external anal sphincter
What are the structures associated with the perineum?
- Perineal membrane
- Perineal body
- Perineal pouches (superficial/deep)
What is the transverse perineal line?
Imaginary line between ischial tuberosites dividing perineum into urogenital and anal triangles.
What are the attachments of the perineal membrane?
- Anterior: Missing
- Lateral: Ischiopubic rami
- Posterior: Perineal body and Colles’ fascia
What are the structures piercing the perineal membrane?
- Urethra
- Vagina (females)
- Nerves and vessels
What attaches to the perineal body?
- Superficial/deep transverse perineal muscles
- External anal sphincter
- Bulbospongiosus
What are the contents of the deep perineal pouch?
- Membranous urethra
- External urethral sphincter
- Bulbourethral glands
- Deep transverse perineal muscles
- Anterior aspects of ischioanal fossa
- Nerves and vessels of the penis/cloitoris
What are the contents of the superficial perineal pouch?
- Male external genitalia (testes, spermatic cord, penis)
- Clitoris
- Ischiocavernosus
- Bulbospongiosus
- Superficial transverse perineal muscle
- Greater vestibular (Bartholin’s) glands (females)
What are the boundaries of the anal triangle?
- Base: Transverse perineal line
- Lateral: Sacrotuberous ligaments
- Apex: Coccyx
What are the contents of the anal triangle?
- Anal canal
- Ischio-anal fossa
What is the structure of the anal canal?
- Upper 2/3 is mucosa
- Lower 1/3 is skin
- Boundary between mucosa and skin is the pectinate line
What are the differences between the mucosal and skin parts of the anal canal?
- Blood supply: Mucosal part supplied by the superior rectal artery while skin part supplied by the inferior rectal artery
- Innervation: Mucosal part is autonomic while skin part is somatic
- Lymphatic drainage: Mucosal part into the internal iliac nodes while skin part into superficial inguinal nodes
- Embryological origin: Mucosal part from the endoderm while skin part from the ectoderm
What are the parts of the external anal sphincter?
- Deep: Fused posteriorly to puborectalis
- Superifical: Attached anteriorly to the perineal body
- Subcutaneus: Directly beneath the skin in the perineum
What is the structure of the penis?
- Root
- Body
- Glans
What are the structures supporting the roots of the penis?
- Crura: Attachments root to the ischiopubic rami.
- Suspensory ligament: Attachment of the root to the pubic symphysis.
- Fundiform ligament: Attachment of the root to the linea alba.
What attaches the foreskin to the glans?
Frenulum
What is the structure of the male urethra?
- Prostatic urethra: Part running through the prostate.
- Membranous urethra: Part running through the deep perineal pouch and the perineal membrane. It is the most rigid part and is surrounded by the external urethral sphincter.
- Penile urethra: Part running in the corpus spongiosum to the external urethral meatus.
What is the sensory supply to the scrotum?
Anterior 1/3: Ilioinguinal nerve
Posterior 2/3: Pudendal nerve
What are the origins of the pudendal nerve?
Anterior rami of S2-4
What is the path of the pudendal nerve?
- It exits the pelvic cavity through the greater sciatic foraman.
- Curves around the sacrospinous ligament.
- Re-enters the pelvic cavity through the lesser sciatic foraman.
What are the branches of the pudendal nerve?
- Inferior rectal nerve
- Perineal nerve
- Dorsal nerve of the penis
What are the structures supplied by the inferior rectal nerve?
- External anal sphincter
- Perianal skin
- Levator ani
What are the structures supplied by the doral nerve of the penis?
- Skin of penis
- Glans
What are the parts of the perineal nerve?
- Scrotal/labial branches
- Muscular branches
- Nerve to bulb
What structures are supplid by the scrotal/labial branch of perineal nerve?
- Scrotum
- Anus
What structures are supplid by the muscular branch of perineal nerve?
- Transverse perineal muscle
- Ischiocavernosus
- Bulbospongiosus
- External urethral sphincter
- External anal sphincter
- Levator ani
What structures are supplid by the nerve to bulb (perineal nerve)?
Bulb of corpus spongiosum
