Structure of the prostate

• The prostate, a walnut sized structure located superior to the pelvic floor and inferior to the neck of the bladder, is uniquely in the male. The glandular structure is encapsulated in a shiny capsule that is, in turn, surrounded by a thickened periprostatic fascia derived from pelvic visceral fascia. The posterior aspect of this fascia is especially thickened and is named the fascia of Denonvillier. A considerable amount of smooth muscle within the stroma adds firmness to the gland. Glandular follicles drain by way of 15 - 20 prostatic ducts into the prostatic sinuses of the prostatic urethra.
• The median lobe of the prostate is posterior to the prostatic urethra. This lobe includes the ejaculatory ducts, seminal colliculus, urethral crest, and most distal aspect of the uvula. Benign prostatic hypertrophy commonly affects the median lobe. In addition to the median lobe, there designated two lateral lobes and an anterior lobe. There are no anatomical landmarks delineating the lobes.
• The prostatic urethra occupies about 2.5 cm of the central prostate. The superior posterior wall receives a projection of the uvula that becomes the urethral crest within the prostatic urethra. Approximately one-third of the way into the prostatic urethra the urethral crest widens for 2-4 mm to form the seminal colliculus. The ejaculatory ducts empty into the prostatic urethra on either side of the seminal colliculus. Lateral to the seminal colliculus the posterior wall deepens posteriorly to the form the prostatic sinuses receiving the prostatic ducts. The utrical, thought to be a vestigial uterus in the male, might be visible on the anterior surface of the seminal colliculus.

Support of the prostate

• Puboprostatic ligament - Condensation of pelvic visceral fascia secures prostate to anterior pelvic wall
• Lateral ligaments - Condensation of pelvic visceral fascia secures prostate to lateral pelvic wall
• Median umbilical ligament - obliterated urachus secures bladder, and thus prostate, to anterior abdmoninal wall
• Levator prostatae muscle - fibers of pubococcygeus insert into the prostatic fascia and capsule

Relations of the prostate

• Inferior - superior fascia fascia of the pelvic diaphragm located at the urogental hiatus of the urogenital diaphragm
• Superior - neck of the bladder and the uvula
• Anterior - inferior aspect of the pubic symphysis
• Posterior - rectum, rectovesical space
• Posterior/superior - ampulla of ductus deferens, ureter, seminal vesical
• Lateral - pelvic diaphragm, superior aspect of conjoint rami, pelvic wall

Vasculature of prostate

• The arterial supply to the prostate is derived from the inferior vesical, middle rectal, and inferior rectal (internal pudendal) arteries. Each of these arteries is a branch of the internal iliac artery
• The prostatic venous plexus is superficial to the capsule and deep to prostatic fascia. It receives the deep dorsal vein of the penis and the vesical venus plexus. Venus drainage to internal iliac veins follow the aforementioned arterial pathways. There is free drainage by the lateral sacral veins into the internal vertebral venus plexus. This drainage is thought to account for the propensity of prostatic cancers to metastasize to the vertebral column.

Innervation of prostate

• The prostatic autonomic plexus is derived from the inferior hypogastric plexus. Preganglionic sympathetic cell bodies are located in the IMLCC of L1-2. Preganglionic fiber pathways involve the superior hypogastric plexus and the right and left hypogastric nerves. Further, preganglionic fibers can follow the common iliac plexus to the internal iliac plexus and arrive at the prostatic plexus by way of the arterial supply. Postganglionic sympathetic cell bodies are thought to be located in unnamed ganglia distributed throughout the inferior hypogastric plexus. Additionally, preganglionic fibers within the sacral sympathetic trunk contribute sacral splanchnics to the inferior hypogastric plexus.
• Parasympathetic preganglionic cell bodies are located in the IMLCC of S2-4. Pelvic splanchnic nerves convey preganglionic fibers to the inferior hypogastric plexus. Postganglionic cell bodies are located in enteric ganglia at the target location.
• The inferior hypogastric plexus form extensions that spread out over the pelvic organs. The prostatic autonmomic plexus froms a collection of nerves the run along the lateral aspect of the prostate and onto the the membranous urethra to enter the cavernous tissue of the perineum. The cavernous nerves provide the parasympathetic innervation to the helecine arteries. To avoid impotency, it is essential that the cavernous nerves are preserved during prostatic surgery.

Lymphatic drainage of prostate

• The internal tissues of the prostate have relatively litte lymphatic drainage. For this reason, it is thought that metastatic desease reaches the vertral column through venous channels (see above).
• The prostatic capsule and fascia drain into internal iliac nodes to common iliac, to lumbar, to cysterna chyli.

General comments

• Scarpa's fascia is membranous tela subcutanea. This fascia is capable of holding sutures and defines a potential space between it and deep fascia. This space can be invaded by infection or the extravasation of urine. The tear in the inferior fascia of the urogenital diaphragm transmits urine from the deep pouch to the superficial perineal pouch. The intact superior fascia of the urogenital diaphragm together with the intact superficial perineal fascia will prevent urine from entering the ischiorectal fossa. The accumulation of urine is restricted by the boundaries of Scarpa's (membranous) fascia.

Anterior abdominal wall - between Scarpa's fascia and deep fascia of external oblique

• Superior: Scarpa's fascia attaches to deep fascia in finger like projections at level of umbilicus
• Inferior medial: open passage to scrotum
• Inferior lateral: passage to thigh
• Lateral: near mid-axillary line at the thoracolumbar fascia
• Medial: along the linea alba, fundiform ligament
• Anterior: Scarpa's fascia
• Posterior: deep fascia of external oblique

Thigh - between Scarpa's fascia and fascia lata

• Inferior: 2 cm below inguinal ligament
• Superior: open
• Lateral: iliotibial tract
• Ledial: pubic ramus
• Anterior: Scarpa's fascia
• Posterior: fascia lata

Scrotum - between Darto's tunic (Scarpa's derivative) and external spermatic fascia (deep fascia)

• Superficial: Darto's tunic
• Deep: external spermatic fascia

Penis - between Colle's fascia (Scarpa's derivative) and Bucks fascia (deep fascia)

• Extends distally toward base of, but not including, the glans
• Superficial: Colle's fascia
• Deep: Buck's fascia

Urogenital triangle - within superficial pouch between superficial perineal fascia (derivative of Scarpa's fascia) and perineal membrane (deep fascia)

• Superior: perineal membrane (inferior fascia of the urogenital diaphragm
• Inferior: superficial perineal fascia
• Anterior: open into scrotum
• Posterior: posterior free edge of urogenital diaphragm, superficial perineal fascia
• Lateral: conjoint rami
• Medial: not restricted

Extravasation into the ischiorectal fossa? - NO

• Limited by superior fascia of UG diaphragm
• Limited by superficial perineal fascia (attached to posterior free edge of UG diaphragm and conjoint rami)

General comments

• The transverse colin is an intraperitoneal segment of the large bowel. It spans from the right colic flexure to the left colic flexure. Surgical access to the lesser sac is provided by the gastrocolic ligament. The transverse colon divides the greater sac into supracolic and infracolic compartments.

Structure

• Layers - from inner to outer
  • mucosa (columnar epitheleum) - no villi in large intestine
  • submucosa (vascular and submucosal nerve plexuses) - padding between mucosa and muscular layer
  • tunica muscularis - inner circular and outer longitudinal smooth muscle, myenteric plexus, peristalsis
  • mesothelium and connective tissue
  • serosa - visceral peritoneum covers the transverse colon except at the attachment of transverse mesocolon
• Teniae coli - 3 longitudinal bands of smooth muscle
• Haustra coli - sacculations caused by the teniae coli being shorter than the gut tube
• Appendices epiploicae - fat appendages hanging from the teniae
• Caliber is generally larger than the small intestine

Support

• Right
  • superior aspect of retroperitoneal ascending colon, cradled by right lobe of liver
  • right hepatocolic ligament
• Middle
  • transverse mesocolon attaches to posterior abdominal wall crossing right kidney, duodenum, IVC, aorta, pancreas, left kidney
  • gastrocolic ligament provides anchoring to the stomach
• Left
  • phrenicocolic ligament

Relationships

• Right - level of L2
  • Superior - liver, gallbladder, descending duodenum
  • Inferior - coils of jejunum and ileum
  • Anterior - costal margin, diaphragm, liver
  • Posterior - diaphragm, right kidney, inferior vena cava, pancreas, quadratus lumborum
  • Medial - itself
  • Lateral - liver, right paracolic gutter, hepatorenal recess
• Middle - level of L1-2
  • Superior - stomach, gastrocolic ligament, liver, lesser sac
  • Inferior - coils of jejunum and ileum
  • Anterior - greater omentum, costal margin, diaphragm, falciform ligament
  • Posterior - pancreas (head, body, and tail), horizontal duodenum, aorta, superior mesenteric artery, intestinal mesentery
  • Lateral left - left colic flexure (see below)
  • Lateral right -right colic flexure (see above)
• Left - level of T12-L1
  • Superior - spleen, diaphragm
  • Inferior - jejunum, descending colon, left paracolic gutter
  • Anterior - diaphragm
  • Posterior - diaphragm, left kidney, quadratus lumborum
  • Lateral - phrenicocolic ligament, superior aspect of left paracolic gutter
  • Medial - itself

Innervation

• Right Side
  • Parasympathetic
    • Preganglionic
      • vagus nerves * preganglionic pathway - vagus nerves, superior mesenteric ganglion (no synapse), superior mesenteric plexus, right and middle colic arteries
    • Postganglionic
      • enteric ganglia at the target
      • cell bodies in submucosal layer - postganglionic fibers contribute to submucous plexus, enteric plexus
  • Sympathetic
    • Preganglionic
      • cell bodies within intermediolateral cell column (IMLCC) of T10-11
      • preganglion fiber path - ventral root to spinal nerve, to ventral ramus, white ramus communican, thoracic sympathetic trunk, thoracic splanchnic nerves, lesser splanchnic nerve
    • Postganglionic
      • cell bodies in the superior mesenteric ganglion
      • postganglionic fiber pathway - superior mesenteric plexus, right colic artery, middle colic artery, enteric plexus
  • Visceral Afferent
    • High threshold (pain)
      • follow sympathetic preganglionic and sympathetic postganglionic pathways
    • Low threshold (homeostatic)
      • follow the vagus nerves
• Left Side
  • Parasympathetic
    • Preganglionic
      • pelvic splanchnics
      • preganglionic pathway - IMLCC S2-4, pelvic splanchnics, inferior hypogastric plexus, left hypogastric nerve, sigmoid mesocolon, retroperitoneal along medial margin of descending colon, left transverse mesocolon
    • Postganglionic
      • enteric ganglia at the target
      • cell bodies in submucosal layer - postganglionic fibers contribute to submucous plexus, enteric plexus
  • Sympathetic
    • Preganglionic
      • cell bodies within intermediolateral cell column (IMLCC) of L1-3
      • preganglion fiber path - ventral root to spinal nerve, to ventral ramus, white ramus communican, lumbar sympathetic trunk, lumbar splanchnic nerves, aoric plexus, inferior mesenteric ganglia (synapse here)
    • Postganglionic
      • cell bodies in the inferior mesenteric ganglia
      • postganglionic fiber pathway - inferior mesenteric plexus, left colic artery, enteric plexus
  • Visceral Afferent
    • High threshold (pain)
      • follow sympathetic preganglionic and sympathetic postganglionic pathways
    • Low threshold (homeostatic)
      • follow parasympathetic preganglionic pathway (see parasympathetic preganglionic pathway)

Vasculature - provided by the arteriovenous supply of midgut and hindgut, venous drainage is into portal system

• Right
  • Right colic artery/vein from superior mesenteric artery/vein
    • retroperitoneal up to right colic flexure
    • contributes to marginal artery/vein
• Middle
  • Middle colic artery/vein from superior mesenteric artery/vein
    • travels through to transverse mesocolon
    • contributes to marginal artery/vein
• Left
  • Left colic artery/vein from inferior mesenteric artery/vein
    • retroperitoneal up to left colic flexure
    • contributes to marginal artery/vein

Lymphatic drainage

• General
  • intestinal nodes to central nodes (superior and inferior mesenteric nodes) to intestinal lymph trunks to cysterna chyli
• Right
  • paracolic nodes to superior mesenteric nodes
• Middle
  • paracolic nodes to superior mesenteric nodes
• Left
  • paracolic nodes to inferior mesenteric nodes