Perineum, Rectum, Anal Canal & BVS Anatomy PDF

THE PERINEUM Joyce El-Haddad [email protected] @orientatewithjoyce Learning outcomes Boundaries and subdivisions of the perineum Location, structure and applied anatomy of the ischioanal fossa Boundaries and contents of the perineal pouches and the muscles of the perineum Nerve supply, blood s...

THE PERINEUM Joyce El-Haddad [email protected] @orientatewithjoyce Learning outcomes Boundaries and subdivisions of the perineum Location, structure and applied anatomy of the ischioanal fossa Boundaries and contents of the perineal pouches and the muscles of the perineum Nerve supply, blood supply and lymphatic drainage What is the perineum? The perineum is a diamond-shaped region that lies below levator ani between the inner aspects of the thighs and anterior to the sacrum and coccyx Superficial and deep boundaries Pubic symphysis Mons pubis Ischiopubic rami Ischial tuberosity Coccyx Inner aspects of the thighs Natal cleft “Perineal region” Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Sacrotuberous ligament Subdivisions A line joining the two ischial tuberosities divides it into : Urogenital triangle (anteriorly) Anal triangle (posteriorly) Location of the perineal body Centre of the perineum: Perineal body Urogenital triangle Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Anal triangle ANAL TRIANGLE RECTUM Fig. 66.4 The endoscopic appearance of the caecum. The characteristic trefoil appearance of the confluence of the three taeniae is usually obvious. Fig. 66.5 The endoscopic appearance of the orifice of the appendix, seen as a slit-like depression near the centre of this view of the caecal pole. The orifice varies from a small depression to an obvious luminal structure. The ileocaecal junction is just visible in the top left corner. (Courtesy of Dr Michael Schultz.) Fig. 66.6 The endoscopic appearance of the ascending colon. Rectum starts @ S3 From a mid sagittal view, the rectum Fig. 66.7 The mimics theendoscopic concavity of the sacrum appearance of the transverse colon. Note the characteristic triangular appearance of the haustrations when viewed collectively (see also Fig. 66.11C). ION @orientatewithjoyce 8 The rectum is directed anteriorly, while the anal canal posteriorly. The angle between them – anorectal angle. Gray’s Anatomy: The Anatomical Basis of Clinical Practice 2016 Fig. 66.9 The endoscopic appearance of the sigmoid colon. Multiple large mucosal folds are characteristic. Fig. 66.8 The endoscopic appearance of the descending colon. The lumen tends to look rather more featureless than the more proximal colon. Fig. 66.10 The endoscopic appearance of the rectum. Note the large transverse folds, with little else in the way of mucosal folds, characterizing the rectum. Prominent submucosal vessels are often seen, particularly in the lower third. retroperitoneum on the right. The transverse colon may contain faeces or gas and lies in a variable position, suspended by its mesentery. The descending colon lies in the retroperitoneum on the left and often contains little faecal residue. The volume data sets produced by modern and superior rectal arteries, with a small contribution from branches of the internal iliac artery (the middle and inferior rectal arteries). The arteries of the midgut and hindgut contribute to an anastomotic vessel, the marginal artery of Drummond, which runs in the mesentery behind the lower part of the pubic symphysis and just above the plane of the inferior aperture of the lesser pelvis. The bladder neck is, essentially, the internal urethral orifice, which lies in a constant position that is independent of the varying positions of the bladder and rectum. In males, the neck rests on, and is in direct continuity with, the base of the prostate; in females, it is related to the pelvic fascia that surrounds the upper urethra. In both sexes, the apex of the bladder faces towards the upper part of the pubic symphysis. The median Rectal Relations on to the uterus at the level of the internal os (the junction of the uterine body and cervix), to form the vesicouterine pouch. The posterior part of the superior surface, devoid of peritoneum, is separated from the supravaginal cervix by fibroareolar tissue. These relationships are important in managing bladder trauma. Extraperitoneal injuries can often be managed conservatively because urine is contained, whereas intraperitoneal injuries usually require surBLADDER, PROSTATE AND URETHRA gical repair. A Ureter External iliac artery and vein Sigmoid colon Fig. 75.1 The relations Internal urethral meatusof the female bladder, sagittal section of the pelvis. (With permission from Waschke J, Paulsen F (eds), Sigmoid colon Sobotta Atlas of Human Small15th intestine Anatomy, ed, Elsevier, Urban & Fischer. Copyright 2013.) Ureteric orifice Median umbilical ligament Ovarian follicles Retropubic space (of Retzius) Uterine fundus Inferior epigastric artery and vein Rectal ampulla Parietal peritoneum Linea alba Rectovesical pouch Linea alba Pubic symphysis Recto-uterine pouch Rectal ampulla Suspensory ligament of penis Denonvilliers’s fascia Prostate Deep dorsal vein of penis Median umbilical ligament Visceral pelvic fascia Cervix Dorsal vein of penis Anococcygeal ligament Internal urethral orifice External anal sphincter Rectovaginal fascia Internal anal sphincter Ureteric orifice Deep transverse perineal muscle Corpus cavernosum clitoris Frenulum of clitoris Labium minor Perineal membrane External urethral orifice Membranous urethra Labium majus Bulb of penis 1255 Parietal peritoneum Full bladder Parietal Table from Prof Ken Ashwell, 2019 Anal canal TESTINE Endoscopic view of the anorectal junction. The transition from rectum to anal canal is near the serrated pectinate line (arrows), which shows a color change on the surface. It marks the squamocolumnar junction. A Rectal mucosa Rectal circular muscle Longitudinal muscle Levator ani Puborectalis External anal sphincter Conjoint longitudinal coat Anal gland Internal anal sphincter Rectum Terminal branches (superior rectal veins) 13.23 STRUCTURE AND FUNCTION OF THE ANORECTAL JUNCTION The rectum, the distal part of the colon, is about 12 cm long; it extends from the S3 vertebral level to the pelvic diaphragm and Submucosal venous plexus continues to the anal canal. It lacks a mesentery, so an adventitia replaces a serosa. The rectal mucosa resembles that of the colon: it is lined by simple columnar epithelium, lacks villi, and has a smooth surface with periodic invaginations equivalent to intestiIschio-anal fat nal crypts. These are longer—at 0.5-0.7 mm—than those elsewhere in the colon. They consist almost solely of goblet cells. Three Anal column transverse semilunar mucosal folds project into the rectal lumen and aid support of feces before defecation. Solitary lymphoid Anal valve Dentate line Pectinate line Inferior rectal vein Ch013-NB86.indd 308 Perineal skin Fibromuscular septum Anal verge Intersphincteric groove Lower anal mucosa Tip of coccyx Gray’s Anatomy: The Anatomical Basis of Clinical Practice 2016 into the a junction features (IH) hem veins fille pectinate Terminal branches (superior rectal veins) /White line nodules are in the lamina pro ends at the anus, where its ep with epidermis of skin. The m has 5-10 permanent longitudi gagni. They are joined at their valves. This area of the muco pectinate line because it rese the base of each anal column a hemorrhoidal artery and vein. rhoidal venous plexus, which to internal hemorrhoids. Anal triangle: contains the anal canal and the ischioanal fossa on each side The ischioanal fossa is a horse-shoe shaped fat-filled space on each side and behind the anal canal Pe lv i cd ia ph ra gm Ischioanal Fossa Ischioanal Fossa Anal canal Ischioanal fossa (fat removed) Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Boundaries of Ischioanal fossa: Ischioanal fossa: Fascial compartments Fat in the perianal space is more tightly loculated than the ischioanal space Therefore abscesses here are more painful. Inferior fascia of the pelvic diaphragm Obturator fascia Ischioanal space PUDENDAL CANAL Perianal fascia Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Membranous layer of superficial fascia- Colle’s fascia Perianal space Perianal abscesses Rupture of these abscesses may lead to formation of fistulae between the skin and the anal canal which discharge pus Fascial disposition in the perineum Note : 1. Colle’s fascia is continuous with membranous layer (Scarpa’s fascia) of fascia of the abdomen 2. Position of the perineal body 3. Superior and inferior fascia of urogenital diaphragm 4. Superficial and deep perineal pouches Red dotted line indicates the position of the perineum Richard Snell. 2012. Clinical Anatomy by Region, 9th ed, Lippincott Williams and Wilkins penile The inferior rectal nerves and vessels (branches of pudendal nerve and internal pudendal vessels) traverse the ischioanal fossa to supply the anal canal Contents of the pudendal canal: Inferior rectal nerve and vessels Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins UROGENITAL TRIANGLE The urogenital region Location of the perineal body Centre of the perineum: Perineal body The urogenital part of the perineum Urogenital triangle Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Anal triangle Bladder Fascia over levator ani White line of pelvic fascia Thick fascia over obturator internus Tendinous arch of levator ani Ilium Obturator internus Urethra Obturator membrane Levator ani Prostate Corpus spongiosum Corpus cavernosum Ischiocavernosus Bulbospongiosus Superficial perineal fascia Thin fascia over obturator internus Thin endopelvic fascia Ischiopubic ramus Deep perineal fascia Deep transverse perineal muscle Perineal membrane Skin of perineum and thigh Fig. 73.14 Muscles and fasciae of the male perineum: coronal view. The section passes through the bulb of the penis at the level of the urethra. The Gray’s Anatomy – The anatomical basis of clinical practice deep perineal space is continuous with the ischio-anal fossa posteriorly. The visceral and parietal fasciae have been omitted for clarity. The pelvic fascia over the ‘pelvic’ aspect of the deep transverse perinei is very thin and does not form a distinct layer: in places it blends with the parietal pelvic fascia Urogenital diaphragm = deep perineal pouch Covered by fascia superiorly and inferiorly (perineal membrane) Is the main component of the deep perineal pouch Related superiorly to the : o apex of the prostate in males o neck of bladder in females Traversed by the: o Membranous part of the urethra in males & external urethral sphincter o Urethra and vagina in females Female Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Male Where is the urogenital diaphragm? Urogenital hiatus in the pelvic diaphragm Perineal membrane Below the pelvic diaphragm Bridging the urogenital hiatus Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Drake R, Vogl W, Mitchell AWM 2004 Gray's Anatomy for Students. Edinburgh: Churchill Livingstone. Superficial and deep perineal pouches Deep pouch: Between the superior and inferior fascia of the urogenital diaphragm Contents: Urogenital diaphragm (+bulbourethral glands in males) Superficial pouch: Between the perineal membrane and Colle’s fascia Colle’s Fascia Richard Snell. 2012. Clinical Anatomy by Region, 9th ed, Lippincott Williams and Wilkins Muscles of the urogenital diaphragm (Deep perineal pouch) 1. External urethral sphincter mechanism 2. Deep transverse perinei muscle Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Urethral Sphincter Mechanism B Body of clitoris Urethra Urinary bladder Crus of clitoris Vagina Compressor urethrae Bulb of vestibule Deep transverse perineal muscle Sphincter urethrae Compressor urethrae Perineal body Sacrotuberous ligament Anus Vaginal wall Urethra Lesser Vestibular glands External anal sphincter Vagina Sphincter urethrovaginalis Perineal body (central perineal tendon) Fibromuscular node Located at the junction of the urogenital and anal triangles Receives the insertion of: Paired muscles 1. Superficial transverse perinei 2. Deep transverse perinei 3. Bulbospongiosus 4. Pubococcygeus (levator ani) Unpaired muscles: 1. External anal sphincter 2. Longitudinal muscle coat of rectum Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Perineal tears Neurovasculature of the pelvis and perineum Joyce El-Haddad [email protected] @orientatewithjoyce ARTERIAL SUPPLY Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Common iliac artery Posterior division Internal iliac artery An Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems te r io rd iv i s io n Note the divisions of the internal iliac artery Common iliac artery - Divided into external and internal iliac artery at the pelvic brim - The internal iliac artery is the main parent artery responsible for supply the pelvis and perineum - The internal iliac artery at the superior margin of the great sciatic foramen divides into anterior and posterior trunks. - The veins have the exact same tributaries. Posterior division of the internal iliac artery Branches of the posterior division Iliolumbar artery Posterior division o Passes upwards across the ala of the sacrum Lateral sacral arteries An te r io rd Iliolumbar artery: 2-3 Lateral sacral arteries (lumbosacral) o Enter the pelvic sacral foramina iv i s io n Superior gluteal artery o Continuation of the superior gluteal o Exits through the greater sciatic foramen (above the piriformis, between roots of the sacral plexus) Superior gluteal artery Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Anterior division of the internal iliac artery Superior vesical artery (continues as umbilical artery) Inferior vesical artery (supplies lower parts of bladder and male reproductive organs) 1. Branches to pelvic viscera (cut ends seen here) 2. Obturator artery o 3. 2 1 3 4 Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Inferior gluteal artery o 4. Leaves the obturator foramen Leaves greater sciatic foramen below piriformis Internal pudendal artery o Winds around ischial spine o Greater sciatic to lesser sciatic o supplies the perineum Branches to the pelvic viscera Ovarian artery Uterine artery (additional branch in the female pelvis) Superior vesical artery Vaginal artery corresponds to the territory of the inferior vesical Middle rectal artery Male pelvis Inferior vesical artery (supplies lower parts of bladder and male reproductive organs) Internal Pudendal Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems INTERNAL PUDENDAL ARTERY Internal pudendal artery Similar course as pudendal nerve, a few extra named branches Anterior/ Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins NERVES OF THE PELVIS AND PERINEUM Nerves in the pelvis Somatic nerves: Obturator nerve Lumbosacral trunk Sacrococcygeal plexus Autonomic nerves: Pelvic parts of the sympathetic chains and ganglion impar aka the Sacral splanchnic branches Pelvic splanchnic nerves (S2-4) supply the parasympathetics Nerve plexuses: Superior hypogastric plexus Inferior hypogastric plexus SOMATIC NERVES Nerves in the pelvis Lumbosacral trunk Obturator nerve Sympathetic chain Sacro-coccygeal plexus Anterior to the piriformis Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems The highlighted nerves are the nerves relevant to ANAT3121 The sacral plexus (L4,5,S1,2,3) Lumboscaral trunk (L4,5) 1. Branches that enter the gluteal region (greater sciatic foramen) 3. Nerves that supply the musculature of the pelvis Sciatic nerve Superior and inferior gluteal nerves Nerve to quadratus femoris Posterior cutaneous nerve of thigh Perforating cutaneous nerve of thigh S1 S2 S3 2. Branches that wind around the ischial spine (greater sciatic foramen to lesser) and pass from pelvis to perineum Pudendal nerve (accompanying artery?) Nerve to obturator internus Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Direct branches from the roots supply piriformis and the pelvic diaphragm Nerve to obturator internus (mentioned earlier) The muscles of the perineum are supplied by branches of the pudendal nerve Posterior view (Gluteal region and perineum) P ir The highlighted nerves are the nerves relevant to ANAT3121 Superior and inferior gluteal nerves if o rm is Sciatic nerve Nerve to obturator internus Branches of the pudendal nerve Nerve to quadratus femoris Posterior cutaneous nerve of thigh Netter, F. H. (2003), Interactive Atlas of Anatomy Version 3.0, Icon Learning Systems Pudendal nerve SOMATIC Branch of sacral plexus (S2,3,4) Course from pelvis to perineum through the gluteal region Accompanying structures Course and branches in the pudendal canal Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Pudendal nerve block Autonomic nerves in the pelvis Autonomic nerve plexuses in the pelvis: Superior and inferior hypogastric Pelvic parts of the sympathetic chains and ganglion impar aka the Sacral splanchnic branches Pelvic splanchnic nerves (S24) supply the parasympathetics Clinically Oriented Anatomy, 7th edition © 2014 Wolters Kluwer Health/ Lippincott Williams & Wilkins Pelvic pain lines Visceral afferent pain fibers from the intraperitoneal uterine fundus and body (superior to the pelvic pain line) follow the sympathetic innervation retrograde to thoracolumbar spinal ganglia (T10-L1). Visceral afferent pain fibers from the subperitoneal uterine cervix and vagina (inferior to the pelvic pain line) follow the parasympathetic fibers retrograde through the uterovaginal and inferior hypogastric plexuses and pelvic splanchnic nerves to reach the spinal sensory ganglia of S2–S4. Lymphatic drainage Most of the perineum drains into superficial inguinal nodes The glans penis/clitoris drains into deep inguinal nodes Most the pelvis and pelvic viscera drain into internal and external iliac nodes