Pelvis Flashcards
1
Q
Anal Canal
A
Description/Features:
* The anal canal measures ~4cm long * Continuous with the rectum at the anorectal junction (which is the right angle the rectum takes at levator ani) * Anal canal is a circular muscular tube and has external and internal anal sphincters * Anal canal ends at the anus * Dentate (pectinate) line separates the anal canal into an upper and lower parts * in structure and neurovascular supply (reflecting the differing embryological origin) * dentate line is a "watershed area" * above the dentate line the epithelium is a mucous membrane * below the dentate line the epithelium is considered cutaneous (ie. stratified squamous keratinised)
Arterial Supply:
* Above dentate line * superior rectal artery (from inferior mesenteric artery) * Below dentate line * inferior rectal artery (from internal pudendal artery) * middle rectal artery (from inferior vesical artery)
Venous drainage:
* Above dentate line: superior rectal vein to inferior mesenteric vein (portal venous system) * Below dentate line: inferior and middle rectal veins to internal iliac veins
Nerve supply:
*
Above dentate line: inferior hypogastric plexus
*
Below dentate line: inferior rectal branches of the pudendal nerve
Lymphatic drainage: * Above dentate line: internal iliac nodes * Below dentate line: superficial inguinal nodes
Variant anatomy:
*
Imperforate anus
* 1 in 1500-5000 newborns * failure of the bowel to open to the external world * may vary from stenosis to blind anal canal/rectum to absent anal canal
2
Q
Anal triangle
A
Description:
* Posterior part of the perineum * Contains the anal canal
Boundaries:
* Posterior: coccyx bone * Lateral: ischial tuberosities * Anterior: perineal membrane * Posterolateral: sacrotuberous ligaments
Contents:
* Ischioanal fossa * Anococcygeal body * Sacrotuberous ligament * Sacrospinous ligament * Pudendal nerve * Internal pudendal artery and vein * Anal canal * Muscles: external anal sphincter, gluteus maximus, obturator internus, levator ani, coccygeus
3
Q
Epididymis
A
Description/Features:
* Lies upon the lateral edge of the posterior border of the testes * Parts: head, body and tail (which is continuous with the ductus deferens) * head located at superior pole and may contain a small projection called the appendix of the epididymis * tail located at the inferior pole * The head is connected with the upper end of the testis by efferent ductules * Between the body and the testis is the sinus of the epididymis * Primary function is the collection, maturation and transport of sperm via the vas deferens * seminiferous tubules carry the sperm via tubuli recti into rete testes * rete testes drains into the epididymis via efferent ductules * efferent ductules open into the head of the epididymis and unite to form a single duct in the body/tail which continues as the ductus deferens
Embryology:
* The epididymis is derived from mesonephric ducts which form the epididymis, vas deferens, seminal vesicle and ejaculatory duct * The appendix epididymis is vestigial remnant of mesonephric duct
Arterial supply:
*
Artery of vas
Venous drainage:
* Pampiniform plexus to testicular vein
Lymphatic drainage:
* Para-aortic lymph nodes (L2)
Nerve supply:
* Sympathetic: coeliac ganglion
Variants:
* Epididymal appendages
4
Q
Gonadal veins
A
Description/Origin/Course:
* Gonadal veins are paired structures that drain the testicles in males and ovaries in females * Gonadal veins ascend with the gonadal arteries in the abdomen along the psoas muscle anterior to the ureters (retroperitoneal) * Ovarian veins: * ovarian veins arises from the left and right ovarian plexus (which is continuous with the uterine plexus) and lies lateral to the ureters * ascends anterior to psoas and parallels the ureter, in the suspensory ligament of the ovary * crosses the ureter halfway through its course * right empties into the IVC and left drains into the left renal vein * Testicular veins: * veins of the testes and epididymis form the pampiniform plexus * which ascends to form four veins at the level of the superficial inguinal ring * then a single testicular vein at the level of the deep inguinal ring * ascends through the inguinal canal in the spermatic cord * testicular vein ascends in the retroperitoneum on psoas major * variable communications with retroperitoneal veins, abdominal wall veins and renal capsular veins * left drains into the left renal vein, right drains into IVC just below the renal vein * 90 degree insertion of left testicular vein into left renal vein make left varicocoele more common in left
Relations:
* Posterior: psoas major, crosses ureter * Anterior: left (sigmoid colon, descending colon), right (caecum, ascending colon) * Lateral: ureter (upper part), kidney * Medial: ureter (lower part), aorta, SVC * Testicular veins are related to structures within spermatic cord
Drains:
* Testicles * Ovaries
Variants:
* Gonadal vein is often duplicated, more commonly on the left (~13%) than on the right (~2%) * Right gonadal vein drains into right renal vein
5
Q
Sciatic Foraminae
A
Description/Origin/Course:
* Gonadal veins are paired structures that drain the testicles in males and ovaries in females * Gonadal veins ascend with the gonadal arteries in the abdomen along the psoas muscle anterior to the ureters (retroperitoneal) * Ovarian veins: * ovarian veins arises from the left and right ovarian plexus (which is continuous with the uterine plexus) and lies lateral to the ureters * ascends anterior to psoas and parallels the ureter, in the suspensory ligament of the ovary * crosses the ureter halfway through its course * right empties into the IVC and left drains into the left renal vein * Testicular veins: * veins of the testes and epididymis form the pampiniform plexus * which ascends to form four veins at the level of the superficial inguinal ring * then a single testicular vein at the level of the deep inguinal ring * ascends through the inguinal canal in the spermatic cord * testicular vein ascends in the retroperitoneum on psoas major * variable communications with retroperitoneal veins, abdominal wall veins and renal capsular veins * left drains into the left renal vein, right drains into IVC just below the renal vein * 90 degree insertion of left testicular vein into left renal vein make left varicocoele more common in left
Relations:
* Posterior: psoas major, crosses ureter * Anterior: left (sigmoid colon, descending colon), right (caecum, ascending colon) * Lateral: ureter (upper part), kidney * Medial: ureter (lower part), aorta, SVC * Testicular veins are related to structures within spermatic cord
Drains:
* Testicles * Ovaries
Variants:
* Gonadal vein is often duplicated, more commonly on the left (~13%) than on the right (~2%) * Right gonadal vein drains into right renal vein
6
Q
Inguinal canal
A
Description/Features:
* Inguinal canal is a passage in the anterior abdominal wall that transmits structures from the pelvis to the perineum * It has an oblique course which is 4cm in length * There are two openings: * deep inguinal ring * round opening in the transversalis fascia * 1cm superior to the inguinal ligament, 1cm lateral to the inferior epigastric arteries * superficial inguinal ring * V-shaped opening in the external oblique aponeurosis * superior and medial to the pubic tubercle
Walls:
* Roof: internal oblique muscle, transversus abdominis muscle * Floor: inguinal ligament, lacunar ligament (medial third) * Anterior wall: external oblique aponeurosis, internal oblique aponeurosis * Posterior wall: tranversalis fascia, conjoint tendon (internal oblique and transversus abdominis aponeurosis inserts into the pubic crest and pectineal line)
Contents:
* Females * round ligament + ilioinguinal nerve * Males * spermatic cord + ilioinguinal nerve * 3 arteries: artery to ductus deferens, testicular artery, cremasteric artery * 3 fascial layers: external spermatic (continuation of external oblique aponeurosis), cremasteric fascia (continuation of internal oblique aponeurosis), internal spermatic fascia (continuation of transversalis fascia) * tunica vaginalis is continuation of the peritoneum (processus vaginalis) * 3 other structures: pampiniform plexus, ductus deferens, testicular lymphatics * 3 nerves: genital branch of the genitofemoral nerve (L1/2), sympathetic and visceral afferent fibres, ilioinguinal nerve * ilioinguinal nerve lies outside spermatic cord but travels next to it
7
Q
Inguinal canal
A
Description/Features:
* Fibrous band extending from the ASIS to the pubic tubercule * Denotes the transition of the pelvis to the lower limb * Formed by the lower border of the external oblique aponeurosis which is thickened and folded in on itself * Lateral half runs obliquely while the medial half is almost horizontal * Forms floor of the inguinal canal * Forms base of Hesselbach triangle * Continuous with the fascia lata of the thigh * Also known as Poupart's ligament
Attachments: * ASIS * Pubic tubercle * Some fibres attach elsewhere
* superior pubic ramus forming the lacunar ligament (of Gimbernat) * fibres that run with the lacunar ligament continue to pass more laterally to attach to the pecten pubis forming pectineal ligament (of Cooper) * superior fibres run past the pubic tubercle to fuse with those of the contralateral external oblique aponeurosis forming the reflected inguinal ligament * Upper surface gives origin to the cremaster muscle from its medial part * Internal oblique muscle from the lateral two-thirds * Transversus abdominis muscle from its lateral one-third
Relations:
* Structures passing through inguinal canal (spermatic cord in males, round ligament of the uterus in females) * Inferior epigastric vessels * Deep (retroinguinal passage / subinguinal space)
* iliopsoas muscle * femoral artery and vein and nerve * lymphatic channels draining inguinal lymph nodes * Lateral: deep circumflex iliac artery
8
Q
Iliac artery
A
Description/Features:
* Internal Iliac Artery is the artery that supplies the pelvic walls, pelvic viscera, external genitalia, the perineum, buttock and medial part of the thigh
Origin:
* Common iliac artery bifurcates into the internal iliac artery and external iliac artery at the level of the pelvic brim anterior to the sacroiliac joint
Course/Relations:
* Courses posteromedially towards the greater sciatic foramen * Approximately 4 cm in length * At the superior margin of the greater sciatic foramen it divides into an anterior and posterior division * Anterior division continues down to the ischial spine anterior to piriformis giving off visceral and parietal branches * Posterior division only gives rise to parietal branches
Branches:
* Mnemonic - I Love Going Places In My Very Own Ugly Underwear * I: iliolumbar artery - psoas and iliacus * L: lateral sacral artery - sacral canal and muscle of the back * G: gluteal (superior and inferior) arteries * P: (internal) pudendal artery - external genitalia, one of two terminal branches of internal iliac artery * I: inferior vesical artery - fundus of the bladder, the prostate, and the seminal vesicles; artery to the ductus deferens is a branch * M: middle rectal artery - rectum, usually arises from the inferior vesical artery * V: vaginal artery (females) - usually arises from uterine artery * O: obturator artery - divides into an anterior and posterior branch, supplied pelvic walls * U: umbilical artery - gives rise to superior vesical artery * U: uterine artery - runs lateral to the cervix, crosses in front of the ureter, ascends between the two layers of the broad ligament to the junction of the uterine tube and uterus * * first three are letters are from the posterior trunk, rest are branches from the anterior trunk
Relations:
* Anteriorly: ureter, ovary, uterine tube * Posteriorly: internal iliac vein, lumbosacral trunk, sacroiliac joint * Medially: peritoneum * Laterally: external iliac vein, obturator nerve
Variants:
* Common iliac artery is absent and internal and external iliac arteries arise from the aorta (<1%) * All arteries branch from one main stem of the internal iliac artery (10%) * The internal iliac divides into two main stems which give off the other branches (60%) * The internal iliac divides into three main stems which give off the other branches (20%) * The internal iliac divides into four or more main stems which give off the other branches (10%) * High division of internal iliac (higher than pelvic brim)
9
Q
Internal pudendal artery branches
A
- Inferior rectal artery
- Artery of the bulb of the penis / vestibule
- Perineal artery
- Posterior scrotal / labial branches
- Deep artery of the penis / clitoris
- Dorsal artery of the penis / clitoris
10
Q
Ischioanal canal
A
Description/Features:
* The ischioanal fossa is a paired triangular-shaped space lateral to the anal canal * Fat filled space in the perineum * The apex is directed anteromedially towards the pubic symphysis * Each ischioanal fossa is separated from the other by the anococcygeal body * fibrous median raphe in the floor of the pelvis which extends between the coccyx and the anus * They communicate superior to anococcygeal body and posterior to the anal canal
Boundaries:
* Roof - levator ani muscle * Floor - deep transverse perineal fascia, skin * Medial wall - external anal sphincter, levator ani muscle * Lateral wall - ischial tuberosity, obturator internus muscle, obturator fascia * Apex - intersection of levator ani and obturator internus muscle * Base - sacrotuberous ligament, gluteus maximus muscle
Contents:
* Inside Alcock's canal (on the lateral wall)
* internal pudendal artery * internal pudendal vein * pudendal nerve * Outside Alcock's canal (crossing the space transversely)
* inferior rectal artery * inferior rectal veins * inferior anal nerves * fatty tissue across which numerous fibrous bands extend from side to side
11
Q
Levator ani
A
- Inferior rectal nerve from pudendal nerve (S3, S4)
- Levator ani nerve (S4)
Blood supply:
*
Inferior gluteal artery
Variation:
* Thinning / aplasia of one or both sides is common (~50%)
12
Q
lumbar plexus
A
Formed by the lower thoracic and lumbar ventral nerve roots (T12 to L5) which supplies motor and sensory innervation to the lower limb and pelvic girdle
Additionally, the ventral rami of L4-5 pass communicating branches, the lumbosacral trunk, to the sacral plexus
“I Twice Get Laid On Fridays”
I: iliohypogastric nerve I: ilioinguinal nerve G: genitofemoral nerve L: lateral cutaneous nerve of the thigh O: obturator nerve F: femoral nerve
2 from 1, 2 from 2, 2 from 3
I: L1 I: L1 G: L1, L2 L: L2, L3 O: L2, L3, L4 F: L2, L3, L4
*Iliohypogastric also receives contribution from T12
Forms in psoas major. Nerves exit:
* anterior: genitofemoral * medial: obturator, lumbosacral trunk * lateral: iliohypogastric, ilioinguinal, lateral femoral cutaneous, femoral
13
Q
Male Urethra
A
Male urethra:
* Commences at the internal urethral orifice in the trigone of the bladder * Opens at the glans penis at the external urethral meatus
Pre-prostatic urethra:
* Intramural part of the urethra * 0.5-1.5 cm in length * Transitional cell epithelium
Prostatic urethra:
* Crosses through the prostate gland * Several openings * ejaculatory duct receives sperm from the vas deferens and ejaculate fluid from the seminal vesicle * several prostatic ducts where fluid from the prostate enters and contributes to the ejaculate * prostatic utricle is merely an indentation * openings are collectively called the seminal colliculis / verumontanum * Transitional cell epithelium
Membranous urethra:
* 1-2 cm portion passing through the external urethral sphincter * Narrowest part of the urethra * Located in the deep perineal pouch * Bulbourethral glands (Cowper's gland) are found posterior to this region but open in the spongy urethra * Pseudostratified columnar epithelium
Spongy urethra:
* Runs along the length of the penis on its undersurface * Bulbar urethra is part of the spongy urethra: traverses the root of the penis * Is about 15-16 cm in length * Travels through the corpus spongiosum * Receives the ducts from the bulbourethral glands and the urethral glands (of Littré) * Epithelium
* proximal: pseudostratified columnar * distal: stratified squamous
14
Q
Mullerian tract abnormalities
A
Description:
* Müllerian duct anomalies (MDAs) are congenital abnormalities that occur when the Müllerian ducts (paramesonephric ducts) do not develop correctly * May be as a result of complete agenesis, abnormal fusion or resorption failure * Renal anomalies are frequently associated
Anomalies:
* Uterine agenesis (~10%)
* complete absence of uterine tissue above the vagina * Arcuate uterus (~7%) * least commonly associated with reproductive failure * mild indentation of the endometrium at the uterine fundus * occurs due to a failure of complete resorption of the uterovaginal septum * Septate uterus (~34-55%) * partial or complete failure of resorption of the uterovaginal septum after fusion of the para-mesonephric ducts * septum is usually fibrous but can also have varying muscular components * septum may be partial, complete and may extend into the vagina * Unicornuate uterus (~5-25%) * one müllerian duct develops normally while the other develops abnormally * Uterine duplicational anomalies
* Uterus didelphys (~5-11%)
* complete duplication of uterine horns as well as duplication of the cervix, with no communication between them * Bicornuate uterus (~10-39%)
* partial failure of fusion of the ducts, resulting in a uterus divided into two horns * bicornuate bicollis: two cervical canals * bicornuate unicollis: one cervical canal
15
Q
Ovary
A
Description/Features:
* Paired organs of the female reproductive and endocrine systems * Lie within the ovarian fossa on the posterior wall of the true pelvis * Suspensory ligament of the ovary is a peritoneal fold and runs from the side wall of the pelvis to the ovary * the ovarian vessels run in this ligament, crossing over the external iliac vessels. * Portion of broad ligament that attaches ovary to uterus is mesovarium * Portion of broad ligament that attaches ovary to uterine tube is mesosalpinx * Ovarian ligament is a continuation of the round ligament and attaches the ovary to the side of the uterus
Relations:
* Medial: uterus, ovarian ligament * Lateral: obturator vessels and nerves * Anterior: broad ligament, mesovarium, ovarian vessels, obliterated umbilical vein * Posterior: internal iliac vessels, ureter * Superior: external iliac vessels * Inferior: levator ani
Arterial supply:
* Ovarian artery
Venous drainage:
* Pampiniform plexus to the ovarian veins * right ovarian vein drains into the inferior vena cava * left ovarian ven drains into the left renal vein
Lymphatic drainage:
* Para-aortic nodes
Nerve supply:
* Ovarian plexus (formed by the aortic, renal, and superior and inferior hypogastric plexuses)
Variants:
* Position: It may fail to descend and lie in the suprapelvic region; or follow the round ligament through the inguinal canal to the labia majora. * Irregular Shape: triangular, crescenteric * Ovaries may contain displaced adrenal tissue * Supernumerary ovaries * Absence is rare
