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Anatomy
Urogenital Triangle
| Question | Answer |
|---|---|
| Perineum: | region of trunk inferior to pelvic diaphragm & b/w thighs |
| Boundaries of perineum: | diamond-shaped space bounded peripherally by pubic symphysis, inferior pubic rami & ischial rami (ischiopubic rami), ischial tuberosities, sacrotuberous ligaments, & coccyx; pelvic diaphragm (levator ani & coccygeus) forms its roof |
| What divides perineum into urogenital (ant) & anal (post) triangles? | imaginary line b/w anterior portion of ischial tuberosities |
| Do the urogenital & anal triangles lie in the same place? | no |
| Which plane is urogenital triangle oriented in? | horizontal plane |
| perineal body: | central tendon of perineum; is fibromuscular mass on midline, near division b/w 2 triangles; impt in supporting this region |
| What muscles insert into perineal body? | medial aspect of levator ani (puborectalis), superficial & deep transverse perineal muscles, external anal sphincter, bulbospongiosus, & sphincter urethrovaginalis |
| perineal membrane: | strong sheet of triangularly-shaped fascia that spans b/w ischiopubic rami |
| Where does perineal membrane stop? | short of pubic symphysis & is thickened anteriorly, forming transverse perineal ligament |
| What allows passage of deep dorsal vein of penis/clitoris? | gap b/w transverse perineal ligament & inferior (arcuate) pubic ligament |
| Urogenital triangle contents: | external genitalia + distal part of urethra + several small skeletal muscles associated w/ this region |
| What does perineal membrane divide urogenital triangle into? | superficial perineal space (which has most of perineal structures) & deep perineal space ( which has part of urethra w/ its sphincter, another small muscle, part of vagina (female) & bullbourethral glands (male) |
| Primary blood and nerve supply to urogenital triangle: | internal pudendal artery, vein, & pudendal nerve |
| Location of root of penis: | deep to scrotum, attached to perineal membrane |
| What is root of penis composed of? | 2 crura + the bulb -- all of which are formed of erectile tissue |
| What is each crus attached to? | internal surface of isciopubic ramus |
| Where's bulb of penis? | midline structure that's firmly attached to perineal membrane |
| Where does urethra enter bulb? | superior surface & continues forward, surrounded by erectile tissue |
| Describe body of penis: | free middle portion of penis that lies below symphysis pubis, when flaccid, & anterior to scrotum |
| In flaccid state, what lies anteriorly & what faces the scrotum? | dorsal surface faces anteriorly & ventral (urethral) surface faces scrotum |
| What is the glans? | expanded, distal end of penis |
| What is corona? | prominent margin of glans that projects backwards over body of penis |
| What is the constriction b/w body of penis & glans called? | neck of the glans |
| Describe cavernous (erectile) tissue: | sponge-like system of communicating vascular spaces; usually contain little blood & appear collapsed; during sexual excitement, spaces become engorged b/c blood enters faster than it can be drained; results in erection of penis |
| Describe corpora cavernosa: | paired erectile tissues that form crura of penis; @ inferior border of pubic symphysis, these 2 structures fuse & form dorsal portion of body of penis |
| What are corpora cavernosa surrounded by? | thick capsule, tunica albuginea, which extends inwards as septum b/w these 2 structures in body of penis; there are occasional openings in septum that allows these 2 vascular spaces to communicate |
| Corpus spongiosum penis: | single erectile mass surrounded by tunica albuginea; surrounds spongy urethra & is expanded posteriorly to form bulb of penis |
| What expands and caps distal ends of corpora cavernosa to form glans penis? | corpus spongiosum |
| Part of urethra w/in penis is called: | spongy urethra |
| Describe spongy urethra: | surrounded by corpus spongiosum during its course thru bulb, body, & glans of penis |
| What is dilated urethra w/in glans termed? | navicular fossa |
| Where does urethra terminate? | @ external urethral orifice, which is slit-like opening near tip of glans |
| What are present in lining of spongy urethra? | numerous small openings of mucus-secreting urethral glands |
| Where do the larger pair of ducts that open into the initial portion of the spongy urethra comes from? | bulbourethral glands |
| bulbourethral glands: | pea-sized, accessory sex glands embedded in fibers of urethral sphincter muscle, superior to bulb of penis |
| Where do ducts from bulbourethral glands pass through? | perineal membrane & open into lumen of initial portion of spongy urethra |
| Describe skin on body of penis: | thin, hairless, loosely connected to deeper tissues |
| The urethral surface of the penis has a median, ____ ____ that is continuous w/ the _____ _____. | penile raphe; scrotal raphe |
| What is skin over glans firmly attached to? | deeper tissue |
| Skin of glans is continuous w/: | skin of prepuce (foreskin), which is a free fold of skin that overlaps the glans |
| Frenulum of prepuce: | fold of skin connecting deep surface of prepuce w/ glans, immediately ventral to external urethral orifice |
| What is superficial penile fascia (dartos fascia) composed of? | loose areolar fascia devoid of fat, but contains some smooth muscle fibers & is continuous w/ dartos fascia of scrotum |
| Deep penile fascia (Buck's fascia): | continuous w/ deep perineal fascia; encloses erectile tissue & major vessel s& nerve of penis; extends from groove b/w corona & body of penis, backwards to root of penis |
| Suspensory ligament of penis: | triangular-shaped ligament that passes from pubic symphysis to deep penile fascia @ proximal portion of body of penis |
| Fundiform ligament of penis: | more superficial structure that arises from superficial fascia in area of linea alba; splits to encircle body of penis near pubic symphysis, blending w/ superficial penile fascia & extending to septum of scrotum |
| What are the superficial perineal muscles? | bublospongiosus, ischiocavernosus, & superficial transverse perineal muscles |
| Bulbospongiosus: | thin skeletal muscle w/ 2 symmetrical halves which covers superficial surface of bulb of penis; attaches to perineal body, perineal membrane, & has midline fibrous raphe |
| Bulbospongiosus muscle fibers encircle what? | not only bulb of penis, but also initial part of body of penis, where all 3 erectile masses converge |
| What does contraction of bulbospongiosus aid in? | expelling urine or semen from urethra + erection by compressing the bulb & slowing venous drainage from corpus spongiosum |
| Ischiocavernosus: | thin skeletal muscles that superficially cover crura of penis; arise from medial aspect of ischial tuberosity & ischiopubic rami |
| Where do ischiocavernosus fibers insert? | into sides of corpora cavernosa of crura |
| Contraction of ischiocavernosus muscles aids in: | erection by impeding venous drainage from corpora cavernosa & by pushing blood from root to body of penis |
| Superficial transverse perineal muscles: | small skeletal muscles that attach to ischial tuberosity & insert into perineal body, @ posterior border of urogenital triangle |
| What does contraction of superficial transverse perineal muscles help do? | stabilize perineal body |
| What are the deep perineal muscles? | deep transverse perineal muscles, sphincter urethrae muscle (external urethral sphincter) |
| deep transverse perineal muscles: | small & sometimes minimal muscles that lie superior to superficial transverse perineal muscles w/ perineal membrane intervening; attaches to ischial tuberosity & inserts into perineal body, just like its superficial counterpart |
| sphincter urethrae muscle (external urethral sphincter): | compresses urethra to help maintain urinary continence |
| where does sphincter urethrae muscle extend? | from base of bladder, along prostatic & membranous urethra, & ends @ perineal membrane |
| Describe scrotum: | sac enclosing testicles that's formed by continuation of skin & superficial fascia of abdominal wall into perineum |
| Location of scrotum: | posterior to body of flaccid penis |
| layers of scrotum: | skin & dartos fascia which contains smooth muscle |
| scrotum is divided into 2 chambers by: | scrotal septum |
| Scrotal septum indicated externally by: | scrotal raphe which continues forward to urethral surface of penis as penile raphe |
| Female external genitalia remain _____ instead of fusing on midline as in male. | bilateral |
| "Vulva" or "pudendum" refers to: | all the external female genitalia |
| mons pubis is: | rounded eminence located anterior to pubic symphysis & superior to pubic ramus |
| What is mons pubis formed by? | mass of fatty subQ tissue |
| What happens to mons pubis @ puberty? | skin becomes covered w/ coarse hair |
| Labiar majora are: | homologues of male scrotum; bilateral, longitudinal ridges of skin filled w/ encapsulated fatty tissue that are continuous w/ tissue in mons pubis |
| Outer surfaces of labia majora are: | covered w/ hair, while their inner surfaces are hairless, pink, & contain numerous sebaceous glands |
| What do these folds form? | lateral boundary of pudendal cleft |
| The 2 labia converge anteriorly @ midline as: | anterior labial commissure |
| Posteriorly, are labia majora joined? | not usually; however, area b/w them on posterior midline is termed posterior labial commissure & overlies perineal body |
| Where does round ligament of uterus end? | after passing thru superficial inguinal ring, ends in labium majus |
| Labia minora are: | thin, hairless folds of skin devoid of significant fat, found internal to labia majora; bound the vestibule of the vagina |
| Labia minora are united posteriorly by what fold? | frenulum of labia minora or the fourchette |
| Anteriorly, each of the folds bifurcates, w/ lateral portion from each side meeting @ midline anterior to clitoris to form the ___ ___ __ _____. | prepuce of the clitoris |
| On undersurface of glans of clitoris, the 2 sides of the labia minora merge as: | frenulum of clitoris |
| Clitoris is homologous to: | penis, but it's not traversed by urethra |
| clitoris formed by: | paired masses of erectile tissue termed corpora cavernosa clitoridis |
| Each of cavernous bodies forms a: | crus of the clitoris |
| What's crus of the clitois attached to? | ischiopubic ramus & perineal membrane |
| corpora cavernosa clitoridis meet anteriorly on midline to form the: | body of the clitoris (attached by suspensory ligament of clitoris to pubic symphysis) |
| Distally, what does clitoris end as? | glans of clitoris |
| glans of clitoris: | portion seen beneath prepuce of clitoris |
| clitoris, particularly glans of clitoris, is richly supplied by: | nerve endings & plays an impt role in female sexual response |
| What's vestibule of vagina? | space b/w labia minora |
| What's external urethral orifice? | opens into anterior part of vestibule, ~2-3cm posterior to glans clitoris |
| orifice of vagina (introitus) is: | median slit located posterior to urethral orifice |
| Until ruptured, what is the thin fold of mucous membrane that partially closes vaginal orifice posteriorly? | hymen |
| Hymenal caruncles are: | rounded elevations around margins of vaginal orifice that represent remnants of hymen |
| bulb of vestibule homologous to: | bulb of penis & corpus spongiosum in male |
| Vestibular bulbs are: | paired, 3 cm elongated masses of erectile tissue lying along lateral sides of vaginal orifice; their deep surfaces contact perineal membrane |
| Anteriorly, what do vestibular bulbs taper into? | pars intermedia |
| What are these then joined to? | to each other & the glans clitoris by commissure of the bulb |
| What are greater vestibular glands (Bartholin's glands) homologous to in male? | bulbourethral glands |
| greater vestibular glands (Bartholin's): | paired structures ~0.5cm in diameter; located posterior to, & partially overlapped by, the vestibular bulbs, on the lateral aspect of the vaginal orifice; their ducts open into the vestibule, in groove b/w hymen & labia minora |
| What are these glands stimulated by? | sexual arousal to secrete mucous; can get infected or can have cysts form (Bartholin's cysts) |
| What are paraurethral glands? | (Skene's glands); appear to be homologous to male prostate gland, open via minute channels on either side of urethral orifice |
| Female bulbospongiosus: | paired, thin, skeletal muscles, cover vestibular bulb & greater vestibular glands, lying lateral to orifice of vagina |
| Where do bulbospongiosus insert in females? | posteriorly into perineal body, anteriorly into clitoris |
| Contraction of these muscles does what? | tends to constrict vaginal orifice & help express secretions from greater vestibular glands |
| What do anterior fibers do? | aid in erection of clitoris by compressing deep dorsal vein of clitoris |
| Female ischiocavernosus muscles: | paired, thin, skeletal muscles that attach to ischiopubic rami & cover crura of clitoris |
| Contraction of these muscles does what? | retards return of blood from crus of clitoris & thus helps maintain erection of clitoris |
| Are superficial transverse perineal muscles the same for males and females? | yes |
| How is deep transverse perineal muscle different in female versus male? | similar except that female muscle frequently even less substantial & may be composed of smooth muscle |
| In female, what are analogous structures to male sphincter urethrae (external urethral sphincter)? | complex of skeletal muscles that includes sphincter urethrae, compressor urethrae, & urethrovaginal sphincter muscles |
| Where does sphincter urethrae begin? | @ base of bladder & surrounds proximal part of urethra |
| What does compressor urethrae do? | forms arch over next portion of urethra; inserts bilaterally into ischiopubic rami |
| What does urethrovaginal sphincter surround? | distal urethra & vagina & inserts into perineal body; can compress both distal urethra & vagina when it contracts |
| What does urethrovaginal sphincter do? | compresses both distal urethra & vagina when it contracts |
| In the female, the superficial perineal fascia is like what? | like the superficial fascia in the lower anterior abd region in that there's fatty superficial layer (which gives mons pubis & labia majora their shape) & more membranous layer that's deep (deep membranous layer or Colles' fascia) & continuous w/ Scarpa's |
| In the male, the fatty superficial layer is what? | hardly evident; instead, a more membranous layer is found throughout = Colles' fascia except where it invests penis & scrotum, in which case it's termed dartos fascia; this continuous w/ Scarpa's fascia |
| Dartos fascia: | continuous w/ Scarpa's fascia; attached laterally where it meets fascia lata of thigh & posteriorly to margin of perineal membrane |
| investing fascia: | deep perineal fascia AKA Gallaudet's fascia; attached laterally to ischiopubic rami, posteriorly to margin of perineal membrane, & anteriorly to symphysis pubis; covers superficial perineal muscles & continuous w/ deep penile fascia (BUCK'S FASCIA) |
| Boundaries of superficial perineal space: | limited inferiorly (superficially) by membranous layer of superficial fascia (Colles' fascia) & superiorly (deeply) by perineal membrane |
| Contents of superficial perineal space in the male: | bulb of penis, crura of penis, bulbospongiosus muscle, ischiocavernosus muscle, superficial transverse perineal muscle, spongy urethra, branches of internal pudendal vessel & pudendal nerve |
| Contents of superficial perineal space in female: | bulbospongiosus muscles, ischiocavernosus muscle, superficial transverse perineal muscle, bulb of vestibule, crura of clitoris, greater vestibular glands, & branches of internal pudendal vessels & pudendal nerve |
| Inferior limit of deep perineal space: | perineal membrane |
| superior limit of deep perineal space: | inferior fascia of pelvic diaphragm |
| lateral limit of deep perineal space: | inferior part of obturator fascia |
| Contents of deep perineal space: | anterior recess of ischioanal fossa |
| Contents of deep perineal space in males: | deep transverse perineal muscle, sphincter urethrae (external urethral sphincter), membranous urethra, bulbourethral glands, the internal pudendal vessels, & branches of pudendal nerve |
| Contents of deep perineal space in females: | deep transverse perineal muscle, sphincter urethrae (external urethral sphincter), compressor urethrae, urethrovaginal sphincter, proximal portion of urethra, a portion of vagina, internal pudendal vessels, & branches of pudendal nerve |
| origin & initial course of internal pudendal artery: | arises in pelvis from ant div of internal iliac artery, leaves pelvis thru greater sciatic foramen, passing b/w piriformis & coccygeus; in gluteal region, curves around ischial spine & passes thru lesser sciatic foramen, then thru pudendal canal |
| Where does internal pudendal artery pass through the pudendal canal? | on lateral wall of ischioanal fossa |
| inferior rectal artery: | 1st branch of internal pudendal artery in pudendal canal |
| perineal artery: | arises from internal pudendal artery near anterior limit of pudendal canal; courses in superficial perineal space in interval b/w bulbospongiosus & ischiocavernosus muscles which it supplies |
| transverse perineal artery: | arises from perineal artery in superficial perineal space & courses along superifical transverse perineal muscle medialward to anastomose w/ vessel on opposite side |
| posterior scrotal/labial artery: | arises from perineal artery or transverse perineal artery & supplies skin & fascia of posterior aspect of scrotum or labia majora |
| artery of the bulb: | arises from internal pudendal artery w/in deep perineal space; courses medially & pierces perineal membrane to enter superficial perineal space before entering bulb of penis or vestibular bulb; also supplies bulbourethral & greater vestibular glands |
| urethral artery (only discernible in male): | arises from internal pudendal artery w/in deep perineal space close to or in common w/ artery of bulb; pierces perineal membrane to enter superficial perineal space, then enters corpus spongiosum to run alongside urethra to glans penis |
| deep artery (cavernosal artery) of penis/clitoris: | 1 of 2 terminal branches of internal pudendal artery; pierces perineal membrane & enters crus of penis/clitoris & runs thru center of erectile tissue in this structure (e.g. corpus cavernosum) |
| What do the terminal, normally coiled branches of these arteries form? | helicine arteries of the penis, which send much of their blood thru an arteriovenous shunt, when the penis is flaccid |
| What closes the shunt? | parasympathetic innervation |
| What does closing of the shunt result in? | more of the blood from helicine arteries entering cavernous space; as these spaces fill w/ blood, the penis become erect & helicine arteries straighten |
| dorsal artery of the penis/clitoris: | other terminal branch of internal pudendal artery; passes b/w crus of penis & pubic symphysis & pierces suspensory ligament of penis; lies deep to deep penile fascia where it lies b/w deep dorsal vein & dorsal nerve, w/ dorsal nerve lying most laterally |
| As dorsal artery courses forward on the penis, what happens? | it give off branches that run around the body of the penis; a similar but smaller artery, the dorsal artery of the clitoris is present in females |
| superficial external pudendal artery: | branch of femoral artery w/in femoral triangle (inferior to inguinal ligament); courses medially across spermatic cord/round ligament of uterus to supply skin of penis/vulva & anterior aspect of scrotum/labia majora |
| deep external pudendal artery | branch of femoral artery that arises w/in femoral triangle, but passes medially over medial thigh muscles, staying deep to fascia lata; eventually pierces fascia lata & enters perineum where assists in supplying skin of scrotum/labia majora |
| superficial dorsal vein of penis/clitoris: | drains prepuce & skin of penis/clitoris |
Created by:
aostromecki