Block 7 Anatomy Perineum Pelvis BRS W Exp Prt 2

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 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).

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 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 pudendal nerve, which arises from the sacral plexus, provides sensory
innervation to the labium majus (or scrotum in a male). It leaves the pelvis through the greater
sciatic foramen and enters the perineum through the lesser sciatic foramen near the inferior margin
of the ischial spine. Therefore, it can be blocked by injection of an anesthetic near the inferior
margin of the ischial spine.

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 ischiorectal fossa is bounded posteriorly by the gluteus maximus and
the sacrotuberous ligament. It contains fat, the inferior rectal nerve and vessels, and perineal
branches of the posterior femoral cutaneous nerve. The pudendal canal runs along its lateral wall.
Urine leaking from a ruptured bulb of the penis does not spread into the ischiorectal fossa because
Scarpa's fascia ends by firm attachment to the fascia lata of the thigh.

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 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 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 bulbourethral glands lie on either side of the membranous urethra, embedded
in the sphincter urethrae. Their ducts open into the bulbous part of the penile urethra.
Semen—a thick, yellowish white, viscous, spermatozoa-containing fluid—is a mixture of the secretions
of the testes, seminal vesicles, prostate, and bulbourethral glands. Sperm, or spermatozoa,
are produced in the seminiferous tubules of the testis and matured in the head of the epididymis.
The seminal vesicles are lobulated glandular structures, produce the alkaline constituent
of the seminal fluid that contains fructose and choline, and lie inferior and lateral to the ampullae
of the ductus deferens against the fundus (base) of the bladder.

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 pectinate line is a point of demarcation between visceral and somatic
portions of the anal canal. Characteristics above the pectinate line include columnar epithelium,
venous drainage into the portal system, lymphatic drainage into the internal iliac nodes, visceral
sensory innervation, and internal hemorrhoids.

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 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 sphincter urethrae is striated muscle that lies in the deep perineal space
and forms a part of the urogenital diaphragm but not the pelvic diaphragm. It is not enclosed in
the pelvic fascia. It is innervated by a deep (muscular) branch of the perineal nerve.

The ejaculatory ducts, which open onto the seminal colliculus, may be
injured. The prostate ducts open into the urethral sinus, the bulbourethral ducts open into the
bulbous part of the penile urethra, and the ducts of the seminal vesicle join the ampulla of the
ductus deferens to form the ejaculatory duct. The prostatic utricle is a minute pouch on the summit
of the seminal colliculus.

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.