Perineum Anatomy PDF

**PERINEUM** **Definition** **It is defined as:** the tissue between the thighs which close the pelvic outlet and lies below the pelvic diaphragm (levator ani muscles). **Pelvic outlet** **Pelvic Diaphragm** **Pelvic Perineum** **Shape and Boundaries:** **It is diamond in shape with 4 angles...

**PERINEUM** **Definition** **It is defined as:** the tissue between the thighs which close the pelvic outlet and lies below the pelvic diaphragm (levator ani muscles). **Pelvic outlet** **Pelvic Diaphragm** **Pelvic Perineum** **Shape and Boundaries:** **It is diamond in shape with 4 angles and 4 boundaries:** **Anteriorly**: the symphysis pubis **Laterally**: the pubic arches and sacrotuberousligaments. **Posteriorly**: the coccyx **Divisions** 1. The perineum is divided by an imaginary transverse line connecting the 2 ischial tuberosities into**:** Anterior urogenital triangle. Posterior anal triangle. **Perineum boundaries** The imaginary line passes across the perineal body which forms the central point of the perineum and lies one inch in front of the anal orifice. **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **216** **Perineum Division** **Urogenital triangle** It is the anterior division of the perineum. **Boundaries:** **Posteriorly:** imaginary transverse line passing between 2 ischial tuberosities **Anterolateral**: pubic arches **Anterior:** symphysis pubis **Contents:** The contents of the urogenital triangle are enclosed into 2 spaces, the superficial & deep perineal pouches. The two spaces are separated by the perineal membrane. **Urogenital triangle ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **217** **Perineal membrane:** Is the inferior fascia of the urogenital diaphragm that forms the inferior boundary of the deep perineal pouch and the superior boundary of the superficial pouch. Lies between the urogenital diaphragm and the external genitalia, is perforated by the urethra, and is attached to the posterior margin of the urogenital diaphragm and the ischiopubic rami. **Perineal membrane** **Deep & superficial Perineal pouches in male** **Fig.75: Deep & superficial Perineal pouches in male** 1. Deep perineal pouch **Boundaries:** ***Roof***: is pelvic fascia (superficial layer of urogenital diaphragm) ***Floor***: is the perineal membrane (Inferior layer of urogenital diaphragm). ***Laterally***: pubic arches **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **218** ***Anteriorly*** is fusion between the roof and floor. ***Posterioly*** is fusion between the roofs and floor. **Contents in male:** **1-Membranous urethra** **2-Two bulbourethral glands that are small glands secrete into bulbar part of urethra as a result of erotic stimulation.** **3- Muscles** a-External urethral sphincter surroundingthe membranous urethra. **Content of deep perineal pouch in male** b- deep transverse perinii muscles **4-Blood vessels and Nerves** a- Internal pudendal artery. b-dorsal nerve of penis. c-perineal nerve. d-Artery of the bulb. **Contents in female:** **Content of deep perineal pouch in male** 1-Urethra **2- Vagina that lies in the middle of pouch.** **3- Muscles** a. \- External urethral sphincter surrounding the urethra. b- deep transverse perinii muscles **4- Blood vessels and Nerves** a- Internal pudendal artery b- Dorsal nerve of clitoris c- Perineal nerve d- Artery of the bulb **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **219** Content of deep perineal pouch in female **Content of deep perineal pouch in female** **The superficial perineal pouch:** **Boundaries:** **Roof:** perineal membrane **Floor:** the membranous layer of superficial fascia (Coll's fascia). **On each side** it is bounded by the pubic arch. **Posteriorly**: it is closed by the fusion of the membranous layer of superficial fascia to the perineal membrane. **Anteriorly:** it is opened. It is continous with the space deep to the membranous fascia of the anterior abdominal wall. **Root of the penis** **Contents in male:** **1- Root of penis that consists of bulb and 2 crura.** The bulb of penis is the posterior enlarged of corpus spongiosum. Each crus of penis is the posterior enlarged of corpus cavernosum. **Penile urethra &ducts of bulbourethral glands ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **220** **2-Penile urethra inside the bulb of penis and ducts of bulbourethralglands.** **3- Muscles** a-Ischio-cavernous and bulbo-spongiosus muscles a. \- Superficial transverse perinii muscles **Muscles of superficial perineal pouch in male** **4- Blood vessels and Nerves.** a- Internal pudendal artery b- Dorsal nerve of penis c- Perineal nerve d- Scrotal nerves and vessels e- Perineal branches of S4 nerve f- Perineal branches of posterior cutaneous nerve of the thigh. **Nerves of superficial perineal pouch in male** **Vessels of superficial perineal pouch in male ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **221** **Contents in female:** **1-Root of clitoris:** that formed of 2 crura and 2 bulbs of vestibule of vagina. Each crus of clitoris is the posterior enlarged of corpus cavernosum. Two bulbs of vestibule of vagina that formed of erectile tissue and extends on each side of vaginal opening. **2-Vestibule of vagina and greater vestibular glands.** **Content of Superficial perineal pouch in female** **NB: Greater vestibular glands (Bartholin, sglands):** are 2 mucous glands, each gland has a small ducts open in the groove between the hymen and the posterior part of labiaminora. **3- Muscles:** a-Ischio-cavernous and bulbo-spongiosus muscles b- Superficial transverseperinii muscles **Content of Superficial perineal pouch in female** **4-Blood vessels and Nerves:** a- Internal pudendal artery b- Dorsal nerve of clitoris c- Perineal nerve d- Labial nerves and vessels e- Perineal branches of S4 nerve f-Perineal branches of posterior cutaneous nerve of the thigh. **Content of Superficial perineal pouch in female ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **222** **Perineal body** Perineal body( centrum tendinum) is the central point of the perineum and is a fibro-muscular structure located in the midline of the perineum at the junction of the anus and urogenital triangle in both females and male. It provides attachment to all muscles and membranes of perineum. **Perineal body** **Applied anatomy** Rupture of the penile urethra which is a content of the superficial pouch by a trauma, the urine extravasates into the superficial perineal pouch. The urine flows into the walls of the scrotum and penis and then ascends into the lower part of the anterior abdominal wall till the level of umbilicus. - Deep perineal pouch is completely closed pouch from all directions. - Episiotomy (periniotomy): Is an incision through the area between the vagina and anus to enlarge the vaginal opening for obstetrical purposes during the child birth. **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **223** Blood supply of pelvis **Internal Iliac Artery:** **It is the smaller of the two terminal branches of the common iliac artery. It passes down in the pelvis to the upper margin of the greater sciatic foramen, where it divides into anterior and posterior divisions.** **Branches of the Anterior Division** **1. Superior vesical artery**: It is the persistent proximal part of the umbilical artery in fetus. It runs forward and medially to supply the upper part of the urinary bladder. **2. Obturator artery**: It leaves the pelvis through the obturator canal. It gives an important pubic branch which anastomoses with the corresponding branch of the inferior epigastric artery on the pelvic surface of the body of pubis. This anastomosis may replace the obturator artery (accessory obturator artery). **3. Inferior vesical artery (vaginal artery in the female):** It supplies the base of the bladder, prostate, and seminal vesicles in males. It also gives rise to the artery of the vas deferens. **4. Middle rectal artery**: It is a small branch which passes medially to the rectum. **5. Internal pudendal artery:** It is the principal artery of the perineum. It enters the perineum through the lesser sciatic foramen. **6. Inferior gluteal artery:** It is the largest branch of the anterior division. It enters the gluteal region through the greater sciatic foramen. **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **224** **7. Uterine artery:** It runs medially on the floor of pelvis along the root of broad ligament, crosses the ureter superiorly (***water under the bridge***) to reach the lateral fornix of the vagina. Here it first ascends upward along the lateral margin of the uterus, then runs along the uterine tube to terminate by anastomosing with the ovarian artery. **8. Vaginal artery:** It corresponds to the inferior vesical artery of the male. It supplies the vagina and the base of the bladder. **Branches of the Posterior Division:** **1. Iliolumbar artery:** It divides into lumbar and iliac branches. **2. Lateral sacral arteries:** There are usually two (upper and lower) on each side. Their branches enter the sacral canal through anterior sacral foramina to supply its contents. **3. Superior gluteal artery:** It leaves the pelvis through the greater sciatic foramen. **The internal iliac vein:** ▪ It runs upward lateral to the internal iliac artery and joins the external iliac vein to form the common iliac vein. ▪ Its tributaries correspond to the branches of the internal iliac artery except umbilical and lumbar veins which drain, respectively, into the portal and common iliac veins. **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **225** **Internal Pudendal Artery:** **Origin:** It is one of the two terminal branches of the anterior division of the internal iliac artery**.** **Course:** It leaves the pelvis through greater sciatic foramen below the piriformis. It crosses the dorsal surface of the ischial spine (lateral to the pudendal nerve) and enters the perineum through the lesser sciatic foramen, where it passes through the pudendal canal in the lateral wall of the ischiorectal fossa. **Branches:** 1. **Inferior rectal artery** arises in the pudendal canal, accompanies the inferior rectal nerve and traverses across the ischiorectal fossa to supply the structures in the perianal region. 2. **Perineal branch** arises in the anterior part of the canal, pierces the perineal membrane to enter the superficial perineal pouch, where it divides into a transverse perineal artery and two posterior scrotal or labial arteries. 3. **Artery to the bulb and urethra** arises in the deep perineal pouch, pierces the perineal membrane and supplies the erectile tissue of the bulb of penis in male or bulbs of vestibule of the vagina in female. It also supplies the urethra in both sexes. 4. **Deep artery of penis or clitoris** pierces the perineal membrane and supplies the erectile tissue, corpora cavernosa. 5. **Dorsal artery of penis or clitoris** pierces the perineal membrane, It supplies prepuce and glans of penis. **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **226** **Internal pudendal artery** **Nerve supply of pelvis** **Pudendal Nerve** It is the chief nerve of the perineum. **Origin:** From ventral rami of S2, S3, S4 nerves in the pelvis. **Course:** It leaves the pelvis through the greater sciatic foramen below the piriformis muscle, It crosses the dorsum of ischial spine and immediately disappears through the lesser sciatic foramen to enter the pudendal canal (***Alcock's canal***) present in the lateral wall of ischiorectal fossa. **Branches:** 1.Inferior rectal nerve, which crosses the fossa to innervate the external anal sphincter, perianal skin. Two terminal branches: 2\. Large perineal nerve 3\. Small dorsal nerve of the penis (or clitoris). **ENDOCRINE & REPRODUCTIVE SYSTEM MODULE 2024-2025** **227** **Pudendal nerve block:** The pudendal nerve is infiltrated with a local anaesthetic where it crosses the ischial spine (palpated through the vagina). A long needle is inserted through the vaginal wall and guided by a finger to the ischial spine. The needle can also be inserted through the skin of perineum. When the pudendal block is carried out bilaterally, there is a loss of anal reflex (which is a useful test to know that a successful block is achieved), relaxation of the pelvic floor muscles, and loss of sensation to the vulva and lower one-