ANATOMY
Pelvis
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Perineum
The external anal sphincter, innervated by the pudendal
nerve, provides the brief voluntary contraction necessary to counter the
passage of a -?-Peristaltic wave.
The rectal submucosal venous plexus forms anastomotic
connections between the middle rectal veins that drain directly into the
internal iliac veins and the superior rectal veins which drain int the
-?-Hepatic portal system. This is a site for varices (hemorrhoids).
The internal pudendal arteries are the -?-Sole supply of
both male and female erectile tissue.
The deep dorsal vein provides venous return from the penis or
clitoris by passing through the -?-Urogenital diaphragm and draining into the
prostatic or vesicle venous plexus, respectively.
The cremaster muscle of the spermatic cord is innervated by
the genital branch of the genitofemoral nerve. This provides the efferent limb
for the cremaster reflex (L1-L2), the elevation of the testes within the
scrotum when the inner thigh is -?-Scratched.
The cavity of tunica vaginalis is a potential space that
represents the detached portion of the peritoneal cavity that surrounds the
testis except that the -?-Mesorchium.
Because the superficial perineal space is limited by fascial
attachment to the deep transverse perineal muscle, extravasations of blood or
urine will not pass into the -?-Anal triangle.
| Gender | Superficial Perineal Space | Deep Perineal Space |
|---|---|---|
| -?-Male | Testes, crura of penis, bulb of penis, penile urethra, superficial transverse perineal muscles | Deep transverse perineal muscles, external urethral sphincter, bulbourethral glands, membranous urethra |
| -?-Female | Crura of the clitoris, vestiular bulbs, superficial transverse perineal muscles, greater vestibular glands | Deep transverse perineal muscle, external urethral sphincter, urethra |
The male external urethral sphincter is formed by the deep
transverse perineal muscle completely surrounding the membranous -?-Urethra. The
female external urethral sphincter is formed by muscle fascicles of the deep
transverse perineal muscle that arch anterior to the urethra but do not pass
posterior because the urethra is embedded in the adventitia of the -?-Anterior
vaginal wall. The arrangement in the female -?-Perineum predisposes to urinary stress
incontinence.
A pudendal block can be effected by injecting an anesthetic
into the vicinity of the pudendal nerve in the pudendal canal close to the
-?-Ischial spine.
| Function | Sympathetic | Parasympathetic |
|---|---|---|
| -?-Erection -?-Emmission |
L1-L2: Lumbar splanchnic nerves, hypogastric plexus, pelvic plexus, cavernous plexus |
|
| Ejaculation | S3-S5 |
Pelvic viscera
The female pelvis is less massive, the subpubic angle is
greater (almost -?-90°), and the pelvic inlet more ovoid than the male pelvis.
The obstetric conjugate is the least anateroposterior
diameter of the pelvic inlet from the sacral promontory to a point a few
millimeters below the -?-Superior margin of the pubic symphysis.
The transverse midplane diameter, measured between the
ischial spines, is the -?-Smallest dimension of the pelvic outlet.
The levator ani muscle forms most of the pelvic floor and its
puborectalis portion (rectal sling) is the principal mechanism for maintenance
of -?-Fecal continence when the rectum is full.
| Characterization | Organ |
|---|---|
| -?-Peritoneal (-?-supported by mesentery) |
Sigmoid colon, uterus, uterine tubes, ovaries, testes |
| -?-Extraperitoneal | Rectum, anal canal, urinary bladder, cervix, prostate gland, seminal vesicles |
The rectum is usually empty because feces are stored in the
sigmoid colon. Movement of feces into the rectal -?-ampulla generates the urge to
defecate.
Metastatic carcinoma of the rectum may be widely disseminated
within the abdomen, pelvis, and inguinal region. The upper rectum drains along
the superior rectal lymphatics. The mid-rectum drains along the middle rectal
-?-lymphatics.
The lower rectum drains along the inferior rectal lymphatics,
then along both internal and external -?-Pudendal lymphatic channels.
Urinary bladder -?-innervation is by both sympathetic and
parasympathetic routes.
| Function | Pathway |
|---|---|
| -?-Sensory awareness of bladder fullness | Hypogastric nerve (sympathetic pathways) to spinal segments T12-L2 |
| -?-Afferent limb of the detrusor (bladder-emptying) reflex | Pelvic plexus and pelvic splanchnic nerves (parasympathetic pathways) to spinal segments S2-S4 |
| -?-Efferent limb of the detrusor reflex | Pelvic splanchnic nerves (parasympathetic pathways) from S3-S5 |
Urinary continence of the partially full to full urinary
bladder is a function of the external urethral -?-Sphincter.
A patent urachus (rare) allows -?-Reflux of urine through the umbilicus.
The testes develop as retroperitoneal structures, but become
peritoneal (supported by mesorchium) in the scrotum. A -?-Mesorchium may
predispose to testicular torsion with high potential for testicular ischemia
and necrosis.
The testicular pampiniform plexus functions as a
counter-current heat exchanger tht maintains testicular temperature a few
degrees below -?-Core body temperature.
Compression of the left testicular vein by a full sigmoid
colon produces varices of the pampiniform plexus on the -?-left side;
fertility may -?-diminish.
In the -?-Male, palpable per rectum are posterior and
lateral lobes of the prostate gland, seminal vesicles if enlarged, and bladder
when filling.
Each uterine artery crosses immediately superior to ta rreter
in the transverse cervical ligament-an important -?-surgical consideration.
Normal uterine position is anteflexed (uterus bent forward on
itself at the level of the internal os) and anteverted (angled approximately
90° anterior to the -?-Vagina), lying on the urinary bladder.
In the -?-Female, palpable per vagina are the cervix and ostium of
the uterus, the vagina, the body of the uterus if retroverted, the rectouterine
fossa, and variably the ovary and uterine tubes.
The lymphatic drainage from the vagina is by three routes:
the external and internal -?-Iliac nodes from the upper third of the vagina; the
internal iliac nodes from the middle third of the vagina; and the internal
iliac nodes as ell as the superficial inguinal nodes from the lowest third.
| Organ | Referral Area | Pathway |
|---|---|---|
| Testes and ovaries | -?-T10-T12: Umbilical and pubic regions | Gonadal nerves to aortic plexus then to lesser and least splanchnic nerves |
| Middle urters, urinary bladder, uterine body, uterine tubes | -?-L1-L2: Pubic and inguinal regions, anterior scrotum or labia, anterior thigh | Hypogastric plexus to aortic plexus then to lumbar splanchnic nerves |
| Rectum, superior anal canal, pelvic ureters, cervix, epididymis, vas deferens, seminal vesicles, prostate gland | -?-S3-S5: Perineum and posterior thigh | Pelvic plexus to pelvic splanchnic nerves |