Exam 3 Pelvis and Perineum Flashcards
The pelvis is divided into the greater and lesser pelvis by the…
What forms this structure?
pelvic brim.
Formed by:
- Sacral promontory
- Sacral ala
- Right and left pubic crest, pectin pubis, and arcuate line of ilium.
The pelvic diaphragm forms the…
floor of the pelvic cavity and the roof of the perineum.
What is the sacral hiatus and why is it clinically relevant.
Where lamina of S5 do not fuse. Administration site for caudal anesthesia.
Parts of the sacrum:
- Sacral promontory
- Ala of sacrum
- Anterior sacral foramina
- Sacral promontory: projection of S1 at anterior midline. Point of reference to make sure pelvis large enough for vaginal birth.
- Ala of sacrum: wings of S1. Articulates with os coxae
- Anterior sacral foramina: larger than posterior sacral foramina. Anterior rami exit here.
The ox coxae is formed by what three bones? Where do they meet?
- Ilium, ischium, pubis
- Meet at acetabulum
Ilium
- What is it?
- Parts
- Forms superior and lateral part of hip bone
- Parts: Body
- Ala: contains
- Iliac fossa
- Iliac crest: rim between ASIS and PSIS
- Arcuate line: Inferior to iliac fossa
- Greater sciatic notch
- Ala: contains
Ischium
- What is it?
- Parts
- Forms posterior part of coxal bone. Contributes to obturator foramen
- Parts:
- Body
- Ischial spine
- Ischial tuberosity
- Lesser sciatic notch
- Ramus: joins inferior pubic ramus to form ischiopubic ramus
- Body
What form the greater and lesser sciatic notch?
- The sacrotuberous ligament closes the notches to form foramen.
- The sacrospinous ligament divides foramen into greater and lesser sciatic foramen
What passes through the greater sciatic notch?
- Piriformis m
- Superior and inferior gluteal artery, vein, and nerve
- Sciatic nerve
- Internal pudendal artery and vein
- Pudendal nerve
What passes through the lesser sciatic foramen?
- Internal pudendal artery and vein
- Pudendal nerve
- Tendon of obturator internus
Pubis
- What is it?
- Parts?
- Forms anterior part of coxal bone.
- Parts:
- Body
- Articulates with other pubic body via pubic symphysis
- Superior ramus
- Contributes to acetabulum
- Inferior ramus
- Contributes to obturator foramen and ischiopubic ramus
- Body
What does the greater pelvis contain?
Abdominal viscera
What does the lesser pelvis contain?
Pelvic viscera
The inferior muscular pelvic aperture is closed off by what?
What is the purpose of these structures?
- Pelvic diaphragm
- Urogenital diaphragm
- Prevent prolapse of bladder, vagina, uterus, and rectum
What are the muscles of the lesser pelvis?
- Piriformis
- Obturator internus
- Pelvic diaphragm
- Levator ani
- Coccygeus
What are the parts of the levator ani?
What is their function?
- Puborectalis: Medial portion, thicker and narrow. Forms sling around anorectal junction for fetal continence.
- Pubococcygeus: Intermediate portion. Wider but thinner than puborectalis
- Iliococcygeus: Posterolateral portion. Thinnest part.
Perineum
Parts
Boundaries
- Diamond shaped region made up by urogenital triangle and anal triangle.
- Boundaries:
- Anterior: Pubic symphysis
- Anterolateral: Ischiopubic rami
- Lateral: Ischial tuberosities
- Posterolateral: Sacrotuberous ligaments
- Posterior: Inferior sacrum and coccyx
- Superior: Inferior aspect of pelvic diaphragm
Ischioanal fossa
- What is it?
- Boundaries
- Large, wedge-shaped spaces b/w sking of anal region and inferior surface of pelvic diaphragm. Contains fat, tough fibrous bands of CT, and neurovasculature of inferior rectal region.
- Boundaries:
- Lateral: Ischium and obturator internus
- Medial: anal canal, external anal sphincter, and inferior surface of levator ani
- Posterior: sacrotuberous ligament and gluteus maximus
- Anterior: body of pubic bones
- Base: perianal skin
- Apex: where levator ani muscle arises from obturator fascia
Pudendal Canal
- Where is it?
- Contents
- Posterior border of ischioanal fossa through lesser sciatic notch to posterior edge of perineal membrane.
- Contents: Internal pudendal vessels
- Pudendal nerve: S2,3,4 (supplies external anal sphincter and perianal skin)
Penis
- What is its anatomical position?
- What are its parts?
- Anatomical position is in the erect state.
- Parts:
- Body: Pendulous portion suspended from pubic symphysis by suspensory ligament.
- No muscles covering it.
- Root: Attached portion in superficial perineal pouch
- Contains bulb and crura of penis
- Covered by muscles
- Body: Pendulous portion suspended from pubic symphysis by suspensory ligament.
Corpus spongiosum
- Function
- Location
- Parts
- Covering
- Erectile tissue
- Located along ventral midline of body of penis
- Parts:
- Glans - distal expanded end that extends over corpora cavernosa.
- Contains external urethral orifice
- Surrounds spongy urethra
- Glans - distal expanded end that extends over corpora cavernosa.
- Completely surrounded by tunica abluginea penis
Corpora cavernosa
- Function
- Location
- Covering
- Paired erectile tissue
- Located laterally and dorsally in body of penis
- Surrounded by tunica albuginea
- Incompeltely separated by fenestrated septum to allow for bilateral erection event
Layers of the penis from superficial to deep
- Skin
- Prepuce (foreskin): covers corona and neck of glans
- Frenulum of prepuce: median fold that connects prepuce to body of penis
- Dartos fascia: not at glans of penis
- Buck’s fascia: binds corpora cavernosa and corpus spongiosum together
- Tunica albuginea
- Erectile tissue
Scrotum
- Layers of the scrotum from superficial to deep.
- Arterial supply
- Innervation
- Lymphatics
- Layers:
- Skin
- Dartos fascia and muscle: allows for retraction of scrotum for thermoregulation
- Arterial supply: Anterior scrotal a (off external pudendal a)
- Posterior scrotal a (off internal pudendal a)
- Innervation: Anterior scrotal n (off ilioinguinal n)
- Posterior scrotal n (off pudendal n)
- Lymphatics drain into superficial inguinal lymph nodes
Testes
- Function
- What is it composed of?
- Layers from superficial to deep.
- Produce sperm and male hormones (primarily testosterone)
- Composed of seminiferous tubules
- Layers:
- Parietal layer of tunica vaginalis
- Visceral layer of tunica vaginalis
- Tunica albuginea
Spermatic cord
- Layers from superficial to deep
- Contents and their function
- Layers:
- External spermatic fascia
- Cremasteric muscle and fascia
- Internal spermatic fascia
- Contents:
- Ductus deferens: conveys sperm from epididymis to ejaculatory duct
- Testicular artery: arises from abdominal aorta to supply testis and epididymis
- Testicular vein: starts out as pampiniform plexus
- Pampiniform plexus: surrounds testicular artery to cool blood before it reaches testis
- Internal spermatic plexus (sympathetic nerves)
- Genital branch of genitofemoral nerve
- Lymph nodes drain into R/L lumbar nodes
The vulva includes:
- Mons pubis
- Labia majorum
- Labia minorum
- Clitoris
- Bulb of vestibule
- Greater vestibular gland
- Lesser vestibular gland
Labia majorum
- Function
- Parts
- Contents
- Function: protect urethral and vaginal orifices
- External folds are pigmented, have pubic hair and sebaceous glands.
- Internal folds are pink, smooth, and hairless
- Filled with loose CT, smooth muscle, and termination of round ligament of uterus
- Where do the labia majora join anteriorly?
- Where do the labia majora join posteriorly? What is so special about this junction?
- Anterior labial commissure
- Posterior labial commissure
- Dissappears after 1st vaginal birth
Labia minora
- Function
- Features
- Surrounds vestibule of vagina
- Rounded folds of skin that are fat-free and hairless
- Frenulum (fourchette) of labia minora: where labia minora meet posteriorly
- Forms frenulum of clitoris
- Forms prepuce of clitoris
Clitoris
- Parts and their features
- Body: covered by prepuce
- Root:
- composed of 2 crura attached to ischiopubic rami
- Composed of corpora cavernosa
- Covered by ischiocavernous muscle
- composed of 2 crura attached to ischiopubic rami
What two structures are contained within the vestibule of the vagina?
- External urethra orifice
- Vaginal orifice
- Contains greater vestibular glands (Bartholin glands)
- Contains lesser vestibular glands (Skene’s glands)
Arterial supply and innervation of labia
- Anterior labial nerve: branch of ilioinguinal n
- Posterior labial nerve: branch of pudendal n
- Anterior labial artery: branch of external pudendal a
- Posterior labial artery: branch of internal pudendal a
Superficial dorsal vein of penis
- Where is it located?
- Where does it drain?
- Located on dorsum of penis between dartos and Buck’s fascia.
- Drains into external pudendal veins
Deep dorsal vein of penis/clitoris
- Where is it located?
- What does it drain?
- Where does it drain?
- Located between Buck’s fascia and tunica albuginea
- Drains erectile tissue
- Drains into prostatic venous plexus in males/vesicle venous plexus in females
Dorsal artery of penis/clitoris
- Where does it arise from?
- Where is it located?
- Arises from internal pudendal artery in deep perineal pouch
- Runs on either side of deep dorsal vein on dorsum of penis/clitoris
- Deep to Buck’s fascia
Dorsal nerve of penis/glans
- Where is it located?
- What does it supply?
- On dorsum of penis/clitoris lateral to dorsal artery of penis/clitoris
- Deep to Buck’s fascia
- Supplies skin and glans
Urogenital triangle
- Boundaries
- Function
- Parts
- Layers
- Stretches between pubic arch and terminates at ischial tuberosities
- Anterior portion of inferior pelvic aperture
- Provides support for erectile tissue and urogenital hiatus of pelvic diaphragm via perineal membrane
- Divided into superficial and deep perineal pouches
- Layers:
- Skin: contains external genitalia
- Superficial fatty layer: continuous with Camper’s fascia and ischioanal fossa fat
- Colles’ fascia: continuous with Scarpa’s fascia
- Superficial perineal pouch
- Perineal membrane
- Deep perineal pouch
- Inferior surface of pelvic diaphragm
Where does Colles’ fascia attach?
Why is this clinically relevant?
- Continuous with dartos fascia over penis and scrotum in males
- Continous with Scarpa’s fascia
- Attaches to perineal membrane at posterior border of urogenital triangle
- Attaches laterally to ischiopubic rami
- Can allow infection to spread to anterior abdominal wall from UG triangle
Superficial male perineal pouch
- Contents
- Root of penis
- Crura of penis
- Bulb of penis
- Spongy urethra
Crura of penis
- What is it?
- Where does it run and attach?
- Coverings
- Erectile tissue in root of penis continous with corpora cavernosa
- Run laterally to attach to ischiopubic rami anterior to ischial tuberosities
- Covered by ischiocavernous muscles
Bulb of penis
- What is it?
- Where does it run?
- Covering and function
- Erectile tissue in root of penis that is continuation of corpus spongiosum
- Enlarged posterior portion at the midline pierced by spongy urethra.
- Covered by bulbospongiosus muscle
Vestibular bulbs
- What are they?
- Where are they located?
- Covering
- Paired erectile tissue
- Homologous with bulb of penis
- On either side of vaginal orifice
- Covered by bulbospongiosus muscle
Superficial female perineal pouch
- Contents
- Vestibular bulb
- Crura of clitoris
- Greater vestibular gland
- Lesser vestibular gland
Superficial perineal pouch in both sexes
- Contents
- Ischiocavernous muscle
- Force blood from crura into distal parts of corpora cavernosa to maintain an erection.
- Compress venous outflow
- Bulbospongiosus muscle
- Compress venous outflow
- Assist in erection similar to ischioacavernous m
- Constricts to asist in emptying of urine or ejactulate from bulb of penis
- Superficial transverse perineal muscle
- Act as crossbeams to stabilize superficial perineal pouch and provide a firmer base for penis during erection
- Perineal artery
- Superficial perineal nerve
- Deep perineal nerve
- Gallaudet’s fascia (deep investing perineal fascia)
Perineal membrane
- What does it separate?
- Features
- Separates superfical and deep perineal pouch (roof of superficial, floor of deep)
- Pierced by urethra in males; urethra and vagina in females
- Anterior defect allows deep dorsal vein of penis/clitoris to drain into pelvis
- Also allows passage of cavernous nerves
Perineal body
- What is it?
- What muscles converge here?
- Mass of CT and muscle that acts as central point of perineum
- Converging muscles:
- Bulbospongiosus
- Superficial transverse perineal
- Deep transverse perineal
- External urethral sphincter
- Levator ani
- External anal sphincter
- Muscular portion of rectum
Deep perineal pouch
- Boundaries
- Contents
- Boundaries:
- Floor: Perineal membrane
- Roof: Inferior surface of pelvic diaphragm
- Lateral: Obturator internus
- Contents:
- External urethral sphincter
- Deep transverse perineal muscles
- Bulbourethral glands (males only)
- Dorsal artery and nerve of penis
- Anterior recess of ischioanal fossa
Deep transverse perineal muscle
- Where is it located?
- What usually happens to this muscle in females?
- Superior to perineal membrane
- Runs transversely from ischial tuberosity and ramus to median raphe and perineal body
- Usually replaced by smooth muscle in females
Bulbourethral (Cowper’s) Glands
- Where are they located?
- What are their function?
- Embedded in muscles of deep perineal pouch in males only
- Ducts pierce through perineal membrane into spongy urethra
- Secrete non-viscous material into urethra before and during ejaculation (pre-cum)
Urogenital diaphragm
- What makes it up?
- What is its purpose?
- Made up by:
- Perineal membrane
- External urethral sphincter
- Deep transverse perineal muscle
- Superior fascia of UG diaphragm
- Provides addition support to UG hiatus of pelvic diaphragm and strucutres passing through this hiatus
Differences between male and female urethra.
Parts of the male urethra.
- The female urethra is shorter in length than the male urethra. The male urethra is also more mobile than the female urethra.
- Parts of the male urethra:
- Intramural: short part from neck of bladder to prostate. Surrounded by internal urethral sphincter.
- Prostatic: within prostate gland. Site of entrance of secretions from prostate and seminal vesicles and sperm (via ejaculatory ducts)
- Membranous (intermediate): narrowest part of urethra (most easily ruptured). Surrounded by external urethral sphincter.
- Spongy: Longest and most mobile portion. Receives substances from bulbourethral glands.
- Enlarges as navicular fossa in glans of penis
Rupture of Intermediate Urethra
- How can it happen?
- Where can fluid escape to?
- Occurs from fracture of pelvic girdle above perineal membrane.
- Urine and blood flow into deep perineal pouch and can pool subperitoneally
Rupture of Spongy Urethra
- Where does it usually occur?
- Where can fluid accumulate?
- Occurs in bulb of penis
- Urine and blood can escape into superficial perineal pouch and pool in:
- Scrotum: deep to dartos fascia
- Around penis: deep to dartos fascia
- Inferior anterior abdominal wall: deep to scarpa’s
What are the branches of the internal pudendal artery?
What do they supply?
Branches:
- Inferior rectal a: Supplies inferior portion of anal canal, anal sphincters, perianal skin
- Perineal a: Supplies muscles of superficial pouch and scrotum/vestibule
- Dorsal a of the penis/clitoris: run on eitehr side of deep dorsal vein. Travels in deep perineal pouch
- Deep (central) a of the penis/clitoris: Supplies corpora cavernosa of penis. Primary artery for erection. Branches in deep perineal pouch
- Artery of the bulb: Supplie corpus spongiosum. Branches within deep perineal pouch
Lymphatics of the perineum.
- Where do skin and subcutaneous tissue drain?
- Where do deep structures drain?
- Superficial inguinal nodes
- Deep inguinal nodes