Pelvis 3: Perineum

Front 1

Perineum

Back 1

Diamond shaped space, same boundaries as pelvic outlet.
Floor is skin/fascia, roof is pelvic diaphragm.

Can divide into two triangles, urogenital and anal.

Front 2

Urogenital triangle (women)

Back 2

Superficial perineal space (between perineal membrane and membranous layer of superficial perineal fascia, Colle's fascia)

Deep perineal space: lies between the fascial layers surrounding the sphincter urethrae, sphincter urethrovaginalis and deep transverse perineal muscles.

Front 3

Superficial perineal space

Back 3

Ischiocavernosus is one side of triangle. Compresses crus, innverated by perineal branch of pudendal nerve. Inserts in clitoris, from ischial tuberosities.

Bulbospongiosus: (second side of triangle) from perineal body to pubic arch. Also innervated by perineal branch of pudendal nerve. Compresses erectile tissue, constricts vagina.

Third side is superficial transverse perineal muscle: from ischial rami to tuberosities. Stabilizes body, innervated by perineal branch of pudendal nerve.

Front 4

Other features of superficial perineal space

Back 4

- Perineal body (central) tendon: fibromuscular mass in center of perineum
- Site of attachment for perineal muscles, levator ani, and external anal sphincter

Bulb of vestibule:elongated erectile tissue

Greater vestibular glands:
- deep to vesticular bulbs
- when compressed, secrete vaginal lubricant

Front 5

Deep perineal space

Back 5

- Deep transverse perineal muscle
(from ischial rami to perineal body)
Innervated by perineal branches of pudendal nerve
Supports vagina, stabilizes perineal body

Sphincter urethrae: from pubic ramus to perineal body. Encircles and constricts urethrae. Innervated by perineal branches of pudendal nerve .

Front 6

Extravasated urine

Back 6

Rupture of spongy urethra can lead to urine in superficial perineal space

Urine can spread into scrotum, and around penis. Also superiorly into abdominal wall.

Can't spread laterally (to thigh) or to anal region (Colle's fascia and perineal membrane prevent this).

Front 7

Urogenital triangle, men

Back 7

Superficial perineal space is between perineal membrane and membranous layer of superficial perineal fascia (Colle's fascia)

Deep perineal space: between fascial layers surrounding sphincter urethrae and deep transverse perineal muscle

Front 8

Superficial perineal space (men)

Back 8

Ischiocavernosus, bulbospongiosus and superficial transverse border.

Ischiocavernosus insert onto crus of penis. Compresses crus and deep dorsal vein, maintaining erection.

Bulbospongiosus: inserts onto perineal body/corpus cavernosus. Maintains erection and squeezes corpus spongiosum, expelling last drops of urine or semen.

Superficial transverse perineal muscle: between ischial rami and perineal body. Stabilizes perineal body.

Perineal body: site of attachment for all the floor components.

Front 9

Deep perineal space (men)

Back 9

Deep transverse perineal muscle (from ischial rami to perineal body). Stabilize perineal body and support prostate.

Sphincter urethrae: encircle and constrict membranous urethrae.

Bulbourethral (Cowperl's) glands: ducts pass through perineal membrane and into penile urethra.

Front 10

Ligaments/Fascia of Penis

Back 10

Fundiform ligament of penis: from linea alba and Scarpa's fascia
Splits into two parts, encircles penis and blends into superficial penile fascia. Enters septum of scrotum.

Suspensory ligament of penis: arises from pubic symphysis. Inserts into deep fascia of penis.

Front 11

Scrotum (blood supply, innervation)

Back 11

Blood:
- external pudendal arteries (from femoral)
- Posterior scrotal branches of internal pudendal arteries

Innervation:
- anterior scrotal branch of ilioinguinal nerve
- genital branch of genitofemoral
- posterior scrotal branch of perineal branch of pudendal nerve
- perineal branch of posterior femoral cutaneous nerve

Front 12

Penis structure

Back 12

Three masses of vascular erectile tissue:
- corpora cavernosa (2)
- corpus spongiosum
Root is made of two crura and the bulb.
Glans penis is head of penis, including fold (prepuce).

Corpora cavernosa surrounded by tunica albuginea, impeding venous return, maintaining erection.

Corpus spongiosum is surrounded by elastic tunica albuginea, allowing passage of ejaculate.

Front 13

Anal Triangle

Back 13

Contains ischiorectal fossae, a space lateral to the anal canal made mostly of fat. Separated from pelvis by the levator ani muscles. Notable because the pudendal canal runs through it (pudendal nerves/vessels).

Also contains external anal sphincter: from tip of coccyx and anococcygeal ligament to perineal body. Innervated by inferior rectal nerve. Closes the anus.

Other muscles of anal triangle include obturator internus, levator ani and coccygeus.

Front 14

Pudendal Nerve

Back 14

Pass through greater sciatic foramen between piriformis and coccygeus. Cross ischial spine and enter perineum through lesser sciatic foramen. Enter pudendal canal.
S2-S4
Gives rise to:
- inferior rectal nerve (external anal sphincter and cutaneous anus)
- dorsal nerve (penis/clit)
- perineal nerve (scrotum/urethra/labio min/maj AND ischiocavernosus, bulbospongiosus, deep and superficial transverse perineal muscles and sphincter urethrae)

Front 15

Pudendal block

Back 15

Performed by injecting a local anesthetic near the pudendal nerve.

Accomplished by inserting needle just below diaphragm, angled towards ischial tuberosity.

Front 16

Internal Pudendal Artery

Back 16

Follows pudendal nerve (out greater, over spine, through lesser sciatic foramen)

Branches into:
- inferior rectal
- deep artery to penis
- urethral artery
- dorsal artery to penis
- artery to bulb
- perineal

Front 17

Lymphatic drainage of perineum

Back 17

Occurs via superficial inguinal lymph nodes.

These get lymph from:
- lower abd
- buttocks
- penis
- scrotum
- labium majus
- lower part of vag and anal canal

Nodes drain into external iliac nodes, then to lumbar nodes.

Internal iliac nodes drain upper rectum, rest of vagina and pelvic organs.

Superior rectum drains into IM nodes (inferior mesenteric)

Lymph from testis/ovary drains DIRECTLY into aortic nodes via gonadal vessels.

Front 18

Homologous Structures

Back 18

Penis=clitoris
Bulbourethral glands = greater vestibular glands
Scrotum = labium majus
Ventral aspect of penis: labium minus
Gubernaculum testic = round ligament of uterus, ovarian ligament