Perineum Anatomy PDF

17. Perineum The diamond-shaped shallow compartment bounded by the pelvic outlet Separated from the pelvic cavity by the fascia covering the inferior aspect of the pelvic diaphragm o Levator ani o Coccygeus Boundaries of the perineum: Anterior pubic symphy...

17. Perineum The diamond-shaped shallow compartment bounded by the pelvic outlet Separated from the pelvic cavity by the fascia covering the inferior aspect of the pelvic diaphragm o Levator ani o Coccygeus Boundaries of the perineum: Anterior pubic symphysis Anterolateral ischiopubic rami Lateral ischial tuberosities Posterolateral sacrotuberous ligaments Posterior Inferior-most sacrum and coccyx Divisions of the perineum: Transverse line joining the anterior ends of the ischial tuberosities o Divides the perineum into anal triangle posteriorly and urogenital triangle anteriorly § Urogenital triangle further divided by perineal membrane into superficial and deep pouches o Perineal body- central tendon at the midpoint of this line § Lies deep to the skin with little subcutaneous tissue § Posterior to the vestibule of the vagina/bulb of the penis § Anterior to the anus and anal canal § Site of attachment for: 1. Bulbospongiosus 2. External anal sphincter 3. Superficial and deep transverse muscles 4. External urethral sphincter 5. Levator ani A: Fasciae and Pouches of the Urogenital Triangle Perineal Fasciae Superficial (subcutaneous tissue) Deep only present in urogenital (Gallaudet/investing) triangle Superficial fatty layer deep membranous layer (Colles fascia) Continuous with Camper’s fascia in abdomen and ischio-anal fat pad posteriorly Superficial fatty layer: o Continuous posteriorly with ischio-anal fat pad in the anal region in both sexes o In females § Makes up substance of labia majora and mons pubis § Continuous anteriorly and superiorly with abdominal Camper fascia o In males § Diminished in the urogenital triangle § Replaced by dartos muscle in the penis and scrotum § Continuous between the penis/scrotum and thighs with Camper fascia 1 Zaid Ganie  Deep membranous layer: o Does not extend into the anal triangle o Attachments: Posterior margin of perineal membrane Posterior Perineal body Lateral Fascia lata of superomedial thigh In males- dartos fascia of scrotum and penis Anterior In females- continuous with Scarpa fascia of abdomen after passing superiorly to fatty layer of labia majora Deep perineal fascia: o AKA Gallaudet fascia/investing fascia o Invests § Ischiocavernosus § Bulbospongiosus § Superficial transverse perineal muscles o Attached laterally to ischiopubic rami o Continuous with deep fascia covering external oblique muscle o In males § Fused anteriorly to suspensory ligament of penis o In females § Fused anteriorly to suspensory ligament of the clitoris Superficial Perineal Pouch Potential space Boundaries: o Floor: perineal (Colle’s) fascia o Roof: perineal membrane o Laterally: ischiopubic rami and obturator internus Contents: In males In females 1. Root (bulb and crura) of penis 1. Clitoris and ischiocavernosus 2. Ischiocavernosus and bulbospongiosus 2. Bulbs of vestibule and bulbospongiosus 3. Proximal part of spongy urethra 3. Greater vestibular glands 4. Superficial transverse perineal muscles 4. Superficial transverse perineal muscles 5. Deep perineal br. of internal pudendal vessels 5. Deep perineal br. of internal pudendal vessels 6. Pudendal nerves 6. Pudendal nerves 2  Deep Perineal Pouch Boundaries: o Inferior- perineal membrane o Superior- inferior fascia of pelvic diaphragm o Lateral- inferior portion of obturator fascia Contents: In both sexes In males In females 1. Part of external urethral sphincter 1. Intermediate part of urethra 1. Proximal part of urethra 2. Anterior extensions of ischio-anal 2. Deep transverse perineal muscles 2. Vaginal hiatus fat pads 3. Bulbourethral glands 3. Muscles: 4. Dorsal neurovascular structures of the penis o Deep transverse perineal muscles o Sphincter urethrovaginalis o Compressor urethrae o External urethral sphincter 4. Dorsal neurovasculature to clitoris Overview: layers and contents of the perineum 3  B: Anal Triangle Ischio-anal Fossae On each side of the anal canal Large fascia-lined wedge-shaped spaces o Apex superiorly where levator ani arises from the obturator fascia o Wide base inferiorly at the skin of the anal region Boundaries: Ischium Lateral Inferior part of obturator internus External anal sphincter Medial Medial part of levator ani Sacrotuberous ligament Posterior Gluteus maximus Anterior Bodies of the pubic bones o Anterior recesses of ischio-anal fossae: § Extensions into the urogenital triangle superior to the perineal membrane Contents: o Fatty tissue o Internal pudendal vessels In the pudendal canal o Pudendal nerve o Inferior rectal nerves and vessels o Posterior scrotal nerve and vessels Crossing the fossae transversely o Perineal branch of S4 o Perforating cutaneous (cluneal) nerves o Lymphatics 4  Pudendal Canal Horizontal passageway within the obturator fascia which lines o The medial aspect of obturator internus o The lateral wall of the ischio-anal fossae Contents: o Internal pudendal artery and vein o Pudendal nerve o Nerve to obturator internus Contents enter the canal at the lesser sciatic notch inferior to the ischial spine Anal Canal Terminal part of the large intestine Extent: o Superior aspect of pelvic diaphragm to anus Course: o Begins as the rectal ampulla narrows proximal to the puborectalis of levator ani o Descends posteroinferiorly between the anococcygeal ligament and perineal body Internal anal sphincter: Involuntary sphincter Surrounds the superior 2/3 of the anal canal Contraction: o Stimulated by sympathetic fibres from the superior rectal and hypogastric plexuses o Inhibited by parasympathetic fibres from the pelvic splanchnic nerves External anal sphincter: Voluntary sphincter Broad band on each side of the inferior 2/3 of the anal canal Attachments: o Anterior- perineal body o Posterior- coccyx o Superior- blends with puborectalis Internal structure: Anal columns o Longitudinal ridges in the superior half of the mucosa of the anal canal o Contain terminal branches of the superior rectal artery and vein Anorectal junction o Indicated by the superior ends of the anal columns Anal valves and sinuses o Anal columns unite inferiorly to form valves with depressions above called anal sinuses Pectinate (dentate) line o Indicates the junction of the superior and inferior parts of the anal canal o Superior part- visceral and derived from embryonic hindgut o Inferior part- somatic and derived from embryonic proctodeum 5 Arterial supply Superior rectal a. Anal canal superior to pectinate line Inferior rectal aa. Anal canal inferior to pectinate line, surrounding muscles and peri-anal skin Middle rectal aa. Forms anastomoses with the superior and inferior rectal aa. Venous drainage Superior rectal v. Inferior mesenteric v. Internal rectal venous plexus Middle rectal vv. Internal iliac vv. Inferior rectal vv. caval system Superior to pectinate line- to superior rectal v. Inferior to pectinate line- to inferior rectal vv. Middle rectal vv. o Drain muscularis externa of the ampulla o Anastomose with superior and inferior rectal vv. Lymph drainage Superior to pectinate line o Internal iliac nodes § common iliac and lumbar nodes Inferior to pectinate line o Superficial inguinal nodes Innervation Superior to pectinate line o Inferior hypogastric plexus Inferior to pectinate line o Inferior anal nerves from pudendal nerve 6  C: Male Urogenital Triangle Male External Genitalia 1. Distal male urethra Urethra subdivided into 4 parts (Intramural and prostatic described in pelvis) o Intramural (preprostatic) o Prostatic o Intermediate § Begins at the apex of the prostate § Traverses the deep perineal pouch where it is surrounded by the external urethral sphincter § Penetrates the perineal membrane § Ends as the urethra enters the bulb of the penis o Spongy § Begins at the distal end of the intermediate part and ends at the external urethral orifice § Dilated in the bulb of the penis (intrabulbar fossa) & in the glans of the penis (navicular fossa) § On each side, the ducts of the bulbourethral glands open into the proximal spongy urethra Arterial supply Venous drainage Lymph drainage Innervation Dorsal artery of the penis Dorsal vein of the penis Intermediate part- internal iliac nodes Intermediate part: Spongy urethra- deep inguinal nodes - prostatic nerve plexus from inferior hypogastric plexus (autonomic) Spongy urethra: - dorsal nerve of the penis from pudendal nerve (somatic) 2. Scrotum Cutaneous fibromuscular sac 2 layers: o Heavily pigmented skin o Dartos fascia § Fat-free layer containing smooth muscle fibres (dartos muscle) § Continuous anteriorly with abdominal Scarpa fascia and posteriorly with perineal Colles fascia § Dartos muscle attaches to the skin and causes wrinkling of the scrotum Divided internally by a continuation of the dartos fascia o Septum of the scrotum o Demarcated externally by the scrotal raphe Scrotal raphe- indication of bilateral embryonic formation of the scrotum o Continuous on the ventral surface of the penis with penile raphe o Continuous posteriorly along the median line of the perineum with the perineal raphe Arterial supply Venous drainage Lymph drainage Innervation Posterior scrotal branches Accompany aa. Superficial inguinal nodes Genital br. of genitofemoral n. - From perineal a. of internal pudendal a. - To external - To anterolateral surface Anterior scrotal branches pudendal vv. Anterior scrotal nn. of ilioinguinal n. - From deep external pudendal a. of - To anterior surface femoral a. Posterior scrotal nn. of pudendal n. Cremasteric a. - To posterior surface - From inferior epigastric a. Perineal br. of post. cutaneous n. of thigh - To posteroinferior surface 7 3. Testes Suspended in the scrotum by the spermatic cords Internal structure: o Mediastinum of the testis § Thickened ridge on the internal posterior aspect of tunica albuginea § From this ridge, septa extend inward between lobules of seminiferous tubules o Rete testis § Network of canals in the mediastinum of the testis § Seminiferous tubules are joined by straight tubules to the rete testis Tunica albuginea- tough fibrous outer surface of testes Tunica vaginalis- closed peritoneal sac o Surface of testis is covered by visceral layer of tunica vaginalis § Except where the testis attaches to the epididymis and spermatic cord o Parietal layer is adjacent to internal spermatic fascia Arterial supply Venous drainage Lymph drainage Innervation Testicular aa. from abdominal aorta Pampiniform venous plexus Right and left lumbar nodes Testicular nerve plexus Artery of the ductus deferens - to right and left testicular vv. Preaortic nodes - on the testicular a. Right testicular v. to IVC - T10 and or T11 Left testicular v. to left renal v. 8 Epididymis Formed from convolutions of the epididymal ducts Located on posterior aspect testis Consists of head, body and tail o Tail is continuous with ductus deferens Functions: sperm storage and maturation Blood supply: Testicular artery & artery of the vas deference Venous drainage: Pampiniform plexus from the testicular vein Ductus deferens 25cm long Ascends posterior to testis, medial to epididymis Primary content of spermatic cord Connects tail of epididymis to ejaculatory duct Traverses the inguinal canal Crosses the ureter medially to enter ejaculatory duct Blood supply: Deferential artery (artery of the vas) from superior (occasionally inferior) vesical artery Venous Drainage: testicular artery and distal pampiniform plexus Pathway of sperm: Seminiferous tubules ® straight tubules ® rete testis ® efferent ductules ® head of epididymis Body of epididymis ® tail of epididymis ® ductus deferens ® ejaculatory duct ® prostatic urethra Duct of seminal vesicle Membranous urethra ® bulbous urethra (in bulb of penis) ® spongy urethra 9 4. Penis Consists of a root, body and glans Layers: Composed of 3 cylindrical cavernous bodies of erectile tissue o Paired corpora cavernosa dorsally o Single corpus spongiosum ventrally Each cavernous body has its own outer covering o tunica albuginea Buck fascia o Deep fascia of the penis o Superficial to the tunica albuginea o Continuation of the deep perineal (Gallaudet) fascia Superficial Dartos fascia and skin Corpora cavernosa o Fused in the median plane except posteriorly o Crura of the penis- posterior separation of the corpora cavernosa Corpus spongiosum o Contains the spongy urethra o Separated from the corpora cavernosa by the intercavernous septum of deep (Buck) fascia Root of the penis o Consists of the crura, bulb, ischiocavernosus muscles and bulbospongiosus muscle o Located in the superficial perineal pouch o Crura and bulb consist of erectile tissue o Each crus is attached to the inferior part of the internal surface of the ipsilateral ischial ramus o Posterior bulb is penetrated superiorly by urethra Body of the penis o Suspended from the pubic symphysis o Has no muscles Glans penis o Distal conical expansion of the corpus spongiosum Suspensory ligament of the penis o Deep fascia from anterior pubic symphysis o Passes inferiorly and splits to form a sling o Attached to the deep (Buck) fascia of the penis at the junction of the root and body Fundiform ligament of the penis o Fibres of the subcutaneous tissue descending from the linea alba o Splits to surround the penis and blends inferior with dartos fascia forming the scrotal septum o Superficial to suspensory ligament Arterial supply of penis: Artery Supply Tissue around corpora cavernosa Dorsal aa. of penis Corpus spongiosum and spongy urethra Penile skin Pierce the crura proximally and run in the corpora Deep aa. of penis cavernosa to supply the erectile tissue Posterior part of corpus spongiosum Arteries of bulb of penis Bulbourethral gland Br. of external pudendal aa. Penile skin Venous drainage: o From cavernous spaces- deep dorsal v. of penis to prostatic venous plexus o From skin and subcutaneous tissue- superficial dorsal vv. to superficial external pudendal v. Innervation: o S2-S4 from pelvic splanchnic nerves and pudendal nerves o Dorsal nerve of the penis from pudendal nerve (sensory & sympathetic) o Ilioinguinal nerve to skin of the root of the penis o Cavernous nerves from prostatic nerve plexus- responsible for erection (parasympathetic) Lymph drainage- superficial inguinal nodes 10  D: Female Urogenital Triangle Female External Genitalia: Vulva (Pudendum) Composed of the o Mons pubis o Labia majora o Labia minora o Clitoris o Bulbs of the vestibule o Greater and lesser vestibular glands Functions of the vulva: o Sensory and erectile tissue for sexual arousal and intercourse o Directs the flow of urine o Prevents entry of foreign material into the urogenital tract Mons pubis Rounded fatty eminence Anterior to pubic symphysis, pubic tubercles and superior pubic rami Covered with coarse pubic hairs after puberty Labia majora Prominent folds of skin Largely filled with a finger-like process of loose subcutaneous tissue o Contains smooth muscles and the termination of the round ligament of the uterus Passes inferoposteriorly from the from the mons pubis toward the anus Thicker anteriorly where they join to form the anterior commissure Posterior commissure: o Merging of the labia majora posteriorly o Ridge overlying the perineal body in nulliparous women o Disappears after the first vaginal birth Pudendal cleft: o Between the labia majora when the thighs are adducted o Contains the labia minora and vestibule Labia minora Rounded folds of fat-free, hairless skin Have a core of spongy connective tissue with erectile tissue at their base Form 2 laminae anteriorly o Medial laminae unite as the frenulum of the clitoris o Lateral laminae unite anterior to the glans clitoris § Forms the prepuce (foreskin) of the clitoris Clitoris Erectile organ located where the labia minora meet anteriorly Consist of a root and a small cylindrical body composed of o 2 crura o 2 corpora cavernosa o Glans clitoris Crura attach to o Inferior pubic rami o Perineal membrane deep to the labia Body is covered by prepuce 11  Vestibule of the vagina External urethral orifice o Posteroinferior to glans clitoris and anterior to vaginal orifice Paraurethral glands o Ducts open on each side of the external urethral orifice Greater vestibular glands o Ducts open at the upper medial aspects of labia minora Vaginal orifice o Size depends on condition of the hymen § Thin anular fold of mucus membrane Bulbs of the vestibule Paired masses of elongated erectile tissue Lie along the sides of the vaginal orifice immediately inferior to the perineal membrane Covered inferiorly and laterally by the bulbospongiosus muscles Greater vestibular glands (Bartholin glands) Located in the superficial perineal pouch Lie on each side of the vestibule of the vagina o Posterolateral to vaginal orifice o Inferior to perineal membrane o Partly overlapped posteriorly by bulbs of the vestibule Partly surrounded by bulbospongiosus muscles Secrete mucus into the vestibule during sexual arousal Lesser vestibular glands Ducts open into the vestibule between the urethral and vaginal orifices Secrete mucus into the vestibule to moisten the labia and vestibule Arterial supply Venous drainage Lymph drainage Innervation External pudendal aa. Labial vv. to internal pudendal v. Superficial inguinal nodes Anterior labial nerves from ilioinguinal nerve Labial and clitoral br. of Perineal branch from posterior femoral internal pudendal a. cutaneous nerve Posterior labial nerves from pudendal nerve Cavernous nn. from uterovaginal plexus - Parasympathetic to erectile bodies 12  Homologous structures: Male Female Glans penis Glans clitoris Shaft of penis Body of clitoris Raphe of penis Labia minora Scrotum Labia majora E: Neurovascular Structures of the Perineum Arteries of Perineum Artery Distribution Course Anterior division of internal iliac - Leaves pelvis through greater sciatic foramen - Hooks around ischial spine to enter perineum Internal pudendal via lesser sciatic foramen - Enters pudendal canal - Anal canal inferior to pectinate line - Arises at entrance to pudendal canal Inferior rectal - Anal sphincters and peri-anal skin - traverses ischio-anal fossa to anal canal - Superficial perineal muscles - Arises within pudendal canal Perineal - Scrotum of male/vestibule of female - Passes to superficial pouch (space) on exit Posterior scrotal/labial - Skin of scrotum or labia majora and minora - Bulb of penis/bulb of vestibule Artery of bulb of penis/vestibule - Bulbourethral gland/greater vestibular gland - Erectile tissue of corpora cavernosa of penis Deep artery of penis/clitoris or clitoris via helicine arteries - Deep perineal pouch - Skin of penis - Fascia of penis or clitoris Dorsal artery of penis/clitoris - Distal corpus spongiosum of penis, - Spongy urethra - Glans penis or clitoris Femoral External pudendal - Anterior aspect of scrotum and skin at root of (superficial and deep br.) penis ♂ - Mons pubis and anterior aspect of labia ♀ 13  Nerves of Perineum Nerve Course Ilioinguinal - Arise as ilio-inguinal exits superficial inguinal ring Anterior labial/scrotal nn. L1 - Pass anteriorly and inferiorly Genitofemoral Genital br. L1-L2 - Emerges through or near superficial inguinal ring Posterior cutaneous n. of thigh - Arises deep to inferior border of gluteus maximus Perineal br. S1-S3 - Passes medially over sacrotuberous ligament to parallel ischiopubic ramus - Arise deep to and emerge from inferior border of gluteus maximus Inferior cluneal nn. S1-S3 - Ascending in subcutaneous tissue - Exits pelvis via infrapiriform part of greater sciatic foramen - Passes posterior to sacrospinous ligament Pudendal n. S2-S4 - Enters perineum via lesser sciatic foramen - Immediately divides into branches as it enters pudendal canal - Passes medially from area of ischial spine Inferior anal (rectal) S3-S4 - Traverses ischio-anal fat body - Arises near entrance to pudendal canal Perineal n. S2-S4 - Parallels parent nerve to end of canal - Passes medially - Arise in anterior (terminal) end of pudendal canal Posterior labial/scrotal S2-S4 - Pass medially and superficially - Arise in anterior (terminal) end of pudendal canal Deep perineal n. S2-S4 - Pass medially then deeply in superficial perineal pouch 14 Lymphatic Drainage of External Genitalia F: Muscles of the Perineum 15 16  Muscle Origin Course Innervation Main action - Skin and fascia surrounding External anal anus - Passes around lateral aspects of anal canal, - Constricts anal canal during peristalsis sphincter - coccyx via anococcygeal - Insertion into perineal body Inferior anal (rectal) n. - Supports and fixes perineal body and pelvic floor ligament - Surrounds lateral aspects of bulb of penis Inserts into - Supports and fixes perineal body/pelvic floor - Median raphe on ventral - Perineal membrane - Compresses bulb of penis to expel last drops of surface of bulb of penis - Dorsal aspect of corpus spongiosum urine/semen Bulbospongiosus - Perineal body - Corpora cavernosa - Assists erection by compressing outflow - Fascia of bulb of penis - Perineal body - Passes on each side of lower vagina, enclosing - Supports and fixes perineal body/pelvic floor bulb and greater vestibular gland - “Sphincter” of vagina - inserts into pubic arch and fascia of corpora Muscular (deep) - assists in erection of clitoris cavernosa of clitoris branch of perineal n. - compresses greater vestibular gland - Embraces crus of penis or clitoris Inserts onto - Maintains erection of penis or clitoris by compressing Ischiocavernosus - Inferior and medial aspects of crus outflow - Perineal membrane medial to crus - Internal surface of Superficial transverse - Passes along inferior aspect of posterior border of ischiopubic ramus perineal muscles perineal membrane to perineal body - Supports and fixes perineal body/pelvic floor to support - ischial tuberosity - Passes along superior aspect of posterior border of abdominopelvic viscera Deep transverse perineal membrane to perineal body and external - Resists increased intra-abdominal pressure perineal muscle anal sphincter - Surrounds urethra superior to perineal membrane External urethral - Ascends anterior aspect of prostate Dorsal nerve of - Compresses urethra sphincter penis/clitoris - Urethrovaginal sphincter portion also compresses vagina - Fibres enclose vagina (urethrovaginal sphincter) 17 Zaid Ganie