Pelvis And Perineum Flashcards
The pelvis as a cavity is divided into
- greater pelvis/false pelvis (in abdominal cavity)
- lesser pelvis/true pelvis
- separated by pelvic inlet (pelvic brim/superior pelvic aperture)
What are the boundaries of the pelvic brim (pelvic inlet)
- promontory (of the sacrum)
- margin of ala (ala of sacrum)
- arcuate line (of the ilium)
- pectin pubis
- pubic crest
- symphysis pubis
What are the boundaries of the pelvic outlet (diamond shape)
- subpubic angle/symphysis pubis (anteriorly)
- ischiopubic rami/pubic arch (anterolateral)
- ischial tuberosities (anterolateral)
- sacrotuberous ligaments (posterolateral)
- tip of the coccyx (posteriorly)
Know the locations of the pelvic wall muscles
***piriformis, obturator internus, coccygeus, obturator canal
What are the muscles of the pelvic floor
- levator ani
1) puborectalis (most medial loop)
2) pubococygeus (immediate second loop)
3) illiococcygeus (most lateral of the 3). - coccygenus
What structures make up the urogenital hiatus
- urethra (males)
- urethra and vagina (female)
What are the functions of the levator ani muscles
1) “continance enforcers”
- medial fibers are lateral compressors to visceral canals
- puborectalis helps create rectoanal angle and enforce anal sphincter
2) support pelvic visceral
3) contractions increase intra-abdominal pressure during expulsive activities (urination, defecation, delivery)
Perineum
The perineum is the area inferior to levator ani (roof) and between the two thinghs
Boundaries of the perineum
1) inferior border of the pubic symphysis/subpubic angle (anterior)
2) right and left ischial rami/tuberosities (anterolateral)
3) right and left sacrotuberous ligaments (posterolateral)
4) tip of coccyx (posterior)
What are the divisions of the perineum
- divided by imaginary line between ischial tuberosities into two triangles
- urogenital triangle (anterior)
- anal triangle (posterior)
Urogenital/anterior triangle contains:
1) urethra
2) root of penis in male/root of clitoris in female
3) bulb of the vestibule and vaginal orifice in female
Posterior/anal triangle contains:
1) anal canal surrounded by 2 ischioanal fossae in males and females
Urogenital triangle/anterior triangle of perineum
- located between the pubic arch and imaginary line connecting two ischial tuberosities
- roof: levator ani muscle
- pierced by: urethra, vagina, & contains roots of external genitalia
- divided into deep & superficial spaces(pouches)
Know diagram of boundaries of superficial perineal pouch and deep perineal space (slide 22)
-Roof: perineal membrane
–>(separates superficial perineal pouch from deep perineal space)
Floor: colles fascia, superficial fat, skin
–> (going from innermost to outermost)
What are the contents of the superficial perineal pouch
1) urethra
2) vaginal orifice
3) root of the external genitalia (root of penis and clitoris) and related muscles
- bulb of penis or vestibule (bulbospongiosus)
- crus of the penis or clitoris (ischocavernosus)
- superficial transverse perineal muscle
4) greater vestibular glands (in female)
Boundaries of the deep perineal pouch
- superior fascia of the urogenital diaphragm (above)
- perineal membrane (below)
What are the contents of the deep perineal pouch
- males (urethra, external urethral sphincter)
- females (urethra, external urethral sphincter, vagina)
Blood supply of the perineum
- internal pudendal artery (major supply)
- it is a branch of anterior part of internal iliac artery
- Branches: inferior rectal artery, artery of eh bulb of penis/vestibule, urethral artery (male only), deep artery of penis/clitoris, dorsal artery of penis/clitoris
Anal triangle
The anal triangle is the posterior triangular area of the perineum between the two sacrotuberous ligaments posteriorly & imaginary line between the ischial tuberosities
What are the contents of the anal triangle
- anal canal and its sphincter
- right and left ischioanal fossae
What are the walls of the ischioanal fossa
1) levator ani (medial wall)
2) oboturator internus, ischium, sacrotuberous ligament (lateral wall)
3) sacrotuberous ligament and gluteus maximus (posterior wall)
4) posterior border of urogenital diaphragm (anterior wall)
What are the contents of the ischioanal fossa
1) fats
2) inferior rectal nerve and vessels
Anal canal
- major structure of the anal triangle
- begins where the rectal ampulla suddenly narrows
- length is on average 4cm in adults with anterior wall slightly shorter than posterior wall
What are the boundaries of the anal canal
1) posteriorly: anococcyheal raphe, separates canal form tip of coccyx
2) anteriorly: perineal body, separates canal from membranous urethra & penile bulb in male, and vagina in female
3) laterally: ischioanal or rectal fossae
Internal anal sphincter
-smooth muscle, derived from the circular muscle layer of anal canal
External anal sphincter
-skeletal muscle, supplied by inferior rectal nerve
