Anatomy Perineum –pelvis BRS - Part 1

The prostate gland may be palpated on rectal examination. The ejaculatory
duct runs within the prostate gland and cannot be felt. In the male, the pelvic part of the ureter
lies lateral to the ductus deferens and enters the posterosuperior angle of the bladder, where it is
situated anterior to the upper end of the seminal vesicle, and thus cannot be palpated during rectal
examination. However, in the female the ureter can be palpated during vaginal examination
because it runs near the uterine cervix and the lateral fornix of the vagina to enter the posterosuperior
angle of the bladder. The testis are examined during a routine annual check-up but obviously
not during a rectal examination.

The ureter runs under the uterine artery near the cervix; thus, the ureter is
sometimes mistakenly ligated during pelvic surgery. The other structures mentioned are not
closely related to the uterine artery near the uterine cervix.

The pelvic diaphragm is formed by the levator ani and coccygeus, whereas
the urogenital diaphragm consists of the sphincter urethrae and deep transverse perinei muscles.
The piriformis passes through the greater sciatic notch and inserts on the greater trochanter of
the femur. The obturator internus forms the lateral wall of the ischiorectal fossa. The sphincter
ani externus is composed of three layers, including the subcutaneous (corrugator cutis ani), superficial,
and deep portions and maintains a voluntary tonic contracture.

The normal position of the uterus is anteverted (i.e., angle of 90 degrees at
the junction of the vagina and cervical canal) and anteflexed (i.e., angle of 160 to 170 degrees at
the junction of the cervix and body).

Fertilization takes place in the infundibulum or ampulla of the uterine tube. The
glans clitoris is derived from the corpora cavernosa, whereas the glans penis is the expanded terminal
part of the corpus spongiosum. Erection of the penis is caused by parasympathetic stimulation,
whereas ejaculation is mediated via the sympathetic nerve. The ovaries are not enclosed in the broad
ligament, but their anterior surface is attached to the posterior surface of the broad ligament.

The round ligament of the uterus is found in the inguinal canal along its
course. Other ligaments are not passing through the inguinal canal.

A needle should be inserted through the posterior fornix, just below the
posterior lip of the cervix while the patient is in supine position, to aspirate abnormal fluid in the
cul-de-sac of Douglas (rectouterine pouch). Rectouterine excavation is not most efficiently aspirated
by puncture of other structures

Parasympathetic preganglionic fibers in the pelvic splanchnic nerve are responsible
for erection of the penis. Sympathetic preganglionic fibers in the sacral splanchnic
nerve are responsible for ejaculation. The pudendal nerve supplies the external anal sphincter and
perineal muscles and supplies general somatic afferent (GSA) fibers to the perineal region. The
dorsal nerve of the penis is a terminal branch of the pudendal nerve and supplies sensation of the
penis. The posterior scrotal nerves are superficial branches of the perineal nerve and supply sensory
fibers to the scrotum.

The deep perineal space contains the bulbourethral (Cowper's) glands. The
crus of the penis, bulb of the vestibule, spongy urethra, and great vestibular gland are found in
the superficial perineal space.

The middle lobe of the prostate gland is commonly involved in benign prostatic
hypertrophy, resulting in obstruction of the prostatic urethra, whereas the posterior lobe is
commonly involved in carcinomatous transformation. The anterior lobe contains little glandular
tissue, and the two lateral lobes on either side of the urethra form the major part of the gland.

The round ligament of the uterus runs laterally from the uterus through the
deep inguinal ring, inguinal canal, and superficial inguinal ring and becomes lost in the subcutaneous
tissues of the labium majus. Thus, carcinoma of the uterus can spread directly to the
labium majus by traveling in lymphatics that follow the ligament. The pubic arcuate ligament attaches
across the inferior aspect of the pubic symphysis and attaches to the medial borders of the
inferior pubic rami. The suspensory ligament of the ovary runs from the ovary to the pelvic wall
and transmits the ovarian vessels. The cardinal (transverse cervical) ligament runs from the cervix
and the vagina to the pelvic walls. The suspensory ligament of the clitoris runs from the pubic
symphysis and the arcuate pubic ligament to the deep fascia of the body of the clitoris.

The pelvic splanchnic nerves carry preganglionic parasympathetic general
visceral efferent (GVE) fibers that synapse in the ganglia of the inferior hypogastric plexus and in
terminal ganglia in the muscular walls of the pelvic organs. The sympathetic preganglionic fibers
synapse in the sympathetic chain (paravertebral) ganglia or in the collateral (prevertebral) ganglia.
The dorsal root ganglia contains cell bodies of general somatic afferent (GSA) and general visceral
afferent (GVA) fibers and have no synapsis. The two sympathetic trunks unite and terminate
in the ganglion impar (coccygeal ganglion), which is the most inferior, unpaired ganglion located
in front of the coccyx.

The superficial inguinal nodes receive lymph from the penis, scrotum, buttocks,
labium majus, and the lower parts of the vagina and anal canal. These nodes have efferent
vessels that drain primarily into the external iliac and common iliac nodes and ultimately to the
lumbar (aortic) nodes. The internal iliac nodes receive lymph from the upper part of the rectum,
vagina, uterus, and other pelvic organs, and they drain into the common iliac and then to the
lumbar (aortic) nodes.

A tender swollen left testis may be produced by thrombosis in the left renal
vein, because the left testicular vein drains into the left renal vein. The right testicular vein drains
into the inferior vena cava. The left internal pudendal vein empties into the left internal iliac
vein. The left inferior epigastric drains into the left external iliac vein and the left external pudendal
vein empties into the femoral vein.

The superior gluteal nerve leaves the pelvis through the greater sciatic foramen,
above the piriformis. The sciatic nerve, internal pudendal vessels, inferior gluteal vessels and
nerve, and posterior femoral cutaneous nerve leave the pelvis below the piriformis.

In addition to the uterine cervix, the uterus, uterine tubes, ovaries, and
ureters can be palpated. The apex of the urinary bladder is the anterior end of the bladder; thus,
it cannot be palpated. The fundus of the uterus is anterosuperior part of the uterus. The terminal
part of the round ligament of the uterus emerges from the superficial inguinal ring and becomes
lost in the subcutaneous tissue of the labium majus.

The lymphatic vessels from the ovary ascend with the ovarian vessels in
the suspensory ligament and terminate in the lumbar (aortic) nodes. Lymphatic vessels from the
perineum, external genitalia, and lower part of the anterior abdominal wall drain into the superficial
inguinal nodes.

The perineal branch of the pudendal nerve supplies the external urethral
sphincter and bulbospongiosus muscles in the male. All other nervous structures do not supply
skeletal muscles but supply smooth muscles in the perineal and pelvic organs. The pelvic and prostatic
plexuses contain both sympathetic and parasympathetic nerve fibers. The pelvic splanchnic
nerve carries preganglionic parasympathetic fibers, whereas the sacral splanchnic nerve transmits
preganglionic sympathetic fibers.

The pelvic inlet (pelvic brim) is bounded by the promontory and the anterior
border of the ala of the sacrum, the arcuate line of the ilium, the pectineal line, the pubic
crest, and the superior margin of the pubic symphysis.

Extravasated urine from the penile urethra below the perineal membrane
spreads into the superficial perineal space, scrotum, penis, and anterior abdominal wall. However,
it does not spread into the testis, ischiorectal fossa, pelvic cavity, and thigh because Scarpa's fascia
ends by firm attachment to the fascia lata of the thigh.

The superior (deep) boundary of the superficial perineal space is the perineal
membrane (inferior fascia of the urogenital diaphragm). Colles' fascia is the deep membranous
layer of the superficial perineal fascia. The deep perineal fascia essentially divides the superficial
perineal space into a superficial and deep compartment. The pelvic diaphragm consists
of the levator ani and coccygeus muscles

Ducts from the prostate gland open into the prostatic sinus, which is a
groove on either side of the urethral crest. The prostate gland receives the ejaculatory duct, which
opens into the prostatic urethra on the seminal colliculus (a prominent elevation of the urethral
crest) just lateral to the prostatic utricle, which is a small blind pouch. The bulbourethral gland
lies on the lateral side of the membranous urethra within the deep perineal space, but its duct
opens into the bulbous portion of the spongy (penile) urethra.

The perineal body (central tendon of the perineum) is a fibromuscular node
at the center of the perineum. It provides attachment for the bulbospongiosus, the superficial and
deep transverse perineal muscles, and the sphincter ani externus muscles. Other muscles (ischiocavernosus,
sphincter urethrae, and obturator internus) are not attached to the perineal body.

The pelvic splanchnic nerve contains preganglionic parasympathetic fibers,
whereas the sacral splanchnic nerve contains preganglionic sympathetic fibers. Parasympathetic
fibers are responsible for erection, whereas sympathetic fibers are involved with ejaculation. The
right and left hypogastric nerves contain primarily sympathetic fibers and visceral sensory fibers.
The dorsal nerve of the penis and the perineal nerve provide sensory nerve fibers.

The ischiorectal fossa contains the inferior rectal nerves and vessels arid
adipose tissue. The bulb of the vestibule and the great vestibular gland are located in the superficial
perineal space, whereas the bulbourethral gland is found in the deep perineal space. The internal
pudendal artery runs in the pudendal canal, but its branches pass through the superficial
and deep perineal spaces.

The dorsal artery of the penis supplies the glans penis. The seminal vesicles
store no spermatozoa. The duct of the bulbourethral gland opens into the bulbous portion of the
spongy urethra, whereas the greater vestibular gland opens into the vestibule between the labium
minora and the hymen. The anterior lobe of the prostate is devoid of glandular substance, the
middle lobe is prone to benign hypertrophy, and the posterior lobe is prone to carcinomatous
transformation.

The pelvic diaphragm, particularly the levator ani, provides the most important
support for the uterus, although the urogenital diaphragm and the uterosacral and ovarian
ligaments support the uterus. The arcuate pubic ligament arches across the inferior aspect of
the pubic symphysis.

The deep dorsal vein, dorsal artery, and dorsal nerve of the penis pass
through a gap between the arcuate pubic ligament and the transverse perineal ligament. The perineal
nerve divides into a deep branch, which supplies all of the perineal muscles, and superficial
branches as posterior scrotal nerves that supply the scrotum. The superficial dorsal vein of the penis
empties into the greater saphenous vein. The deep artery of the penis runs in the corpus cavernosum
penis.

The uterine tubes lie in the broad ligament. The anterior surface of the
ovary is attached to the posterior surface of the broad ligament of the uterus. The ureter
descends retroperitoneally on the lateral pelvic wall but is crossed by the uterine artery in the
base (in the inferomedial part) of the broad ligament. The terminal part of the round ligament
of the uterus becomes lost in the subcutaneous tissue of the labium majus. The suspensory ligament
of the ovary is a band of peritoneum that extends superiorly from the ovary to the
pelvic wall

The urogenital diaphragm consists of the sphincter urethrae and deep
transverse perineal muscles. Weakness of the muscles, ligaments, and fasciae of the pelvic floor
such as the pelvic diaphragm, urogenital diaphragm, and cardinal (transverse cervical) ligaments
occurs as result of multiple child delivery, advancing age, and menopause. The pelvic diaphragm
is composed of the levator ani and coccygeus muscles. The superficial transverses perinei is one
of the superficial perineal muscles and the obturator internus forms the lateral wall of the ischiorectal
fossa.

The sacral splanchnic nerves consist primarily of preganglionic sympathetic
neurons and also contain general visceral afferent (GVA) fibers. None of the other fibers listed are
contained in these nerves.

The deep dorsal vein of the penis lies medial to the dorsal artery of the penis
on the dorsum of the penis and superficial to Buck's fascia, drains into the prostatic plexus of
veins, and is compressed against the underlying deep fascia of the penis during erection.

The greater vestibular gland is located in the superficial perineal space between
the inferior fascia of the urogenital diaphragm and the membranous layer of the superficial
perineal fascia (Colles' fascia). All of the other structures are found in the deep perineal pouch.

The iliohypogastric nerve innervates the skin above the pubis. The skin of
the urogenital triangle is innervated by the pudendal nerve, perineal branches of the posterior
femoral cutaneous nerve, anterior scrotal or labial branches of the ilioinguinal nerve, and the genital
branch of the genitofemoral nerve.