Perineum Anatomy PDF

Perineum DPM PROGRAM 1. Describe the differences between the pelvic cavity and perineum. 2. Describe what makes up the perineum: anal triangle urogenital triangle. 3. Describe what the urogenital triangle and perineal membrane. 4. Describe the perineal pouches and contents of each. 5. Describe the...

Perineum DPM PROGRAM 1. Describe the differences between the pelvic cavity and perineum. 2. Describe what makes up the perineum: anal triangle urogenital triangle. 3. Describe what the urogenital triangle and perineal membrane. 4. Describe the perineal pouches and contents of each. 5. Describe the female external genitalia. 6. Describe the superficial perineal pouch-female. 7. Describe the superficial perineal pouch-male. 8. Describe the fascia of the perineum. 9. Perineal fascia clinical correlate: Extravasation of Urine. 10.Describe the neurovasculature of the perineum. 1 SMU - Internal Data Describe the differences between the pelvic cavity and perineum. Pelvic Diaphragm The space defined by the bones of the lesser pelvis is further subdivided by the pelvic diaphragm. The pelvic cavity is the inferoposterior portion of the abdominopelvic cavity. It is bounded superiorly by the pelvic inlet (brim) and inferiorly by the pelvic diaphragm. The pelvic cavity contains pelvic viscera and inferiorly projecting portions of abdominal viscera, it is completely protected by the bones of the lesser pelvis. The perineum is the region between the thighs inferior to the pelvic diaphragm (between the pelvic diaphragm and the skin). It is partially protected by the bones of the lesser pelvis (the pelvic outlet forms part of its outer boundary). It includes all of the structures in the anal and urogenital triangles including external genitalia and anus. 2 SMU - Internal Data Describe what makes up the perineum: anal triangle urogenital triangle. UG A -diamond shaped region inferior to the pelvic diaphragm -Divided into two subregions by a line connecting the ischial tuberosities -Posteriorly:Anal triangle -Anteriorly: Urogenital triangle SMU - Internal Data NOTE: In this region, superficial = inferior Anal Triangle Urogenital Triangle 3 Describe what the urogenital triangle and perineal membrane. The perineal membrane - thin sheet of deep fascia, stretching between the ischiopubic rami forming the ‘skeleton’ of the urogenital triangle. -It contains passageways for the urethra and, in females, the vagina. -It divides the UG triangle into superficial and deep perineal pouches -Its posterior edge is thickened centrally to form the perineal body. The perineal body serves as an attachment site for many of the muscles of both the superficial and deep perineal pouches, the anal triangle and also the levator ani. Perineal membrane 4 SMU - Internal Data Describe the perineal pouches and contents of each. Structures in the perineum receive their neurovasculature primarily from perineal branches of the internal pudendal vessels and pudendal nerves Superficial Perineal Pouch - Between the membranous layer of the subcutaneous tissue and the perineal membrane (i.e.,superficial to perineal membrane). Lateral boundaries are formed by the ischiopubic rami Main Contents in Males: Bulb of the penis and bulbospongiosus m. Crura of the penis and ischiocavernosus m. Proximal part of the spongy urethra Main Contents in Females: Bulbs of the vestibule and bulbospongiosus m. Crura of the clitoris and ischiocavernosus m. Greater vestibular glands Both perineal branches of the internal pudendal vessels and pudendal nerves Deep Perineal Pouch -Between inferior fascia of pelvic diaphragm (levator ani + coccygeus) and the perineal membrane (i.e., deep to perineal membrane). Lateral boundaries are formed by the lower portion of the obturator internus mm. (and the obturator fascia). - Contains part of the urethra (in males the intermediate urethra) and several skeletal muscles including the external urethral sphincter. 5 SMU - Internal Data Describe the female external genitalia. The external genital organs include the mons pubis, labia majora, labia minora, and clitoris. The area containing these organs is called the vulva. The external genital organs have three main functions: •Enabling sperm to enter the body •Protecting the internal genital organs from infectious organisms •Providing sexual pleasure The mons pubis is a rounded mound of fatty tissue that covers the pubic bone. During puberty it becomes covered with hair. Mons pubis The labia majora (literally, large lips) are relatively large, fleshy folds of tissue that enclose and protect the other external genital organs. They are comparable to the scrotum in males. During puberty, hair appears on the labia majora. The labia minora (literally, small lips) can be very small or up to 2 inches wide. The labia minora lie just inside the labia majora, the space between them, where the openings of the vagina and urethra are located, is called the vestibule of the vagina. The opening to the urethra, which carries urine from the bladder to the outside, is located superior and anterior to the vaginal opening (the introitus). A rich supply of blood vessels gives the labia minora a pink color. They do NOT develop hair. The clitoris, located between the labia minora at their superior end, is a small protrusion that corresponds to the penis in the male. The clitoris, like the penis, is very sensitive to sexual stimulation and can become erect. Lithotomy Position SMU - Internal Data 6 Describe the superficial perineal pouch-female. Tissues: -2 Corpora cavernosa (form the crura, body & glans of the clitoris). The crura are covered by ischiocavernosus mm. - 2 bulbs of the vestibule (composed of corpus spongiosum) are located on either side of the vaginal orifice along with the greater vestibular glands. The bulbs and glands are covered by bulbospongiosus m. SMU - Internal Data Surface anatomy 7 Describe the superficial perineal pouch-male. Spongy tissues: - Corpus spongiosum: forms bulb of penis and continues through the shaft/body of the penis taking the urethra to the end. Distally it forms the glans penis, where the urethra terminates (external urethral orifice). The bulb is covered with bulbospongiosus muscle. - Paired Corpora Cavernosa form the crura of the penis and continue into the shaft/body. The crura are covered with ischiocavernosus muscle. 3 parts: - The root of the penis is fixed to the inferior surface of the perineal membrane. It is composed of the crura and bulb and their overlying striated muscles - The body of the penis is suspended from the pubic symphysis by the suspensory ligament of the penis - The glans of the penis is the distal expansion of the corpus spongiosum 8 SMU - Internal Data Describe the fascia of the perineum. Abdomen! Penis! Scrotum! Perineum! Skin! Skin! Skin! Skin! Camper’s!fascia! 0!blends!with!Scarpa’s! 0!blends!with!Scarpa’s! to!form!dartos!muscle/! to!form!dartos! fascia! muscle/!fascia! Fatty!layer!of!superficial!fascia!(in! mons!pubis!&!labia!majora)! 0!continuous!with!fat!in!anal! triangle!(ischioanal!fat!pad)! Scarpa’s!fascia! 0!forms!fundiform! ligament!of! penis/clitoris! 0!blends!with!campers! to!form!dartos! muscles/!fascia! 0!blends!with!campers! to!form!dartos! muscles/!fascia! Colle’s!Fascia!(superficial!perineal! fascia)! - fuses!to!posterior!edge!of! perineal!membrane!and!to! ischiopubic!rami! - Does!not!extend!into!anal! triangle! Deep!Fascia!of! External!Oblique! Buck’s!Fascia! 0!forms!suspensory! ligament!of! penis/clitoris! External!Spermatic! Fascia!(with!the! aponeurosis)! Deep!Perineal!fascia!(deep!fascia! of!the!Muscles!of!the!Superficial! Perineal!Pouch*)! ! * Ischiocavernosus, Bulbospongiosus and Superficial Transverse Perineal Muscles SMU - Internal Data 9 Perineal fascia clinical correlate: Extravasation of Urine. Deep fascia Scarpa’s Fascia Fundiform ligament Suspensory ligament The most proximal portion of the spongy urethra is the most commonly ruptured portion of the male urethra. The extravasated urine will lie in the space between the fascial layers that are continuous with the superficial (scarpa’s) and deep fasciae of the anterior abdominal wall. Perineal membrane Superficial Fascia of Penis Buck’s fascia Deep perineal fascia Colle’s Fascia External spermatic fascia Dartos fascia 10 SMU - Internal Data Describe the neurovasculature of the perineum. -The pudendal nerve and internal pudendal vessels exit the pelvis through the greater sciatic foramen. -They travel between sacrotuberous and sacrospinous ligaments, then enter the perineum through the lesser sciatic foramen. Common Iliac Internal Iliac INTERNAL PUDENDAL a. External Iliac -They give off the inferior rectal nerve and vessels which can be identified as they travel across the ischioanal fossa (in the anal triangle) toward the anal canal and external anal sphincter -The pudendal nerve and internal pudendal vessels can be seen entering the pudendal canal (in the fascia of the obturator internus muscle) as they travel anteriorly to reach the urogenital triangle where they give off perineal branches to all of the structures in the superficial and deep perineal pouches. Inferior Rectal a. Perineal aa. -The pudendal nerve and its branches supply motor (GSE) to all skeletal muscles of the perineum, and sensory (GSA) from the skin of the perineum, the distal vagina and the inferior one-third of the anal canal. Gluteal Region Internal pudendal artery (with vein & Pudendal nerve in pudendal canal) Sacrospinous ligament Piriformis muscle Sacrotuberous ligament Pudendal nerve Internal pudendal artery and vein SMU - Internal Data Sciati c nerve Inferior rectal a.(with vein & nerve) Inferior view of Perineum 11