• narrow diamond-shaped region between the proximal thighs
• extends from the pubis symphysis around the ischial tuberosities to the back of the coccyx
• Urogenital triangle – anterior portion of the perineum; contains external genitalia and urethra
• Superficial Perineal Space – made up of three muscles: ischiocavernosa, bulbospongiosa, and transverse perninei superficalis–also contains proximal erectile tissue (see root of penis, below)
• Urogenital diaphragm (Deep Perineal Space) – formed by three structures: the sphincter urethrae muscles, the deep transverse perineal muscle, and the superior and inferior fascia
• contains the bulbourethral glands (contibute to the semen), vessels, and nerves
• everything above the UG diaphragm gets pelvic splanchnic innervation, everything below gets pudendal innervation
• memory key for dermatomes: "S2, 3, 4 keeps the penis off the floor"
• If the male urethra ruptures into the superficial perineal space, urine will flow into the scrotum, penis, and anterior abdomen because of the attachments of the perineal fascia to the Dartos muscle and Scarpa’s fascia.

• anatomical position is erect, so dorsal is facing forward when flaccid
• Structure – 3 bodies of erectile tissue each enclosed in a tough layer that holds it together (tunica albuginea)
• superficial to tunica albuginea, deep fascia (Buck's fascia) covers two corpora cavernosa and the corpus spongiosum
• corpus spongiosum contains the urethra and expands distally to form the glans penis
• skin and fascia are extended in a double layer forming the prepuce (foreskin), which covers the glans
• Root of the penis – consists of crura (right and left extensions of the corpora cavernosa at the base), the bulb, and three muscles covering the erectile tissue (these are important for keeping blood in the penis to maintain an erection):
• (1) ischiocavernosa (one on each side) – from the ischium covering the crura
• (2) bulbospongiosus – from the median raphe covering the bulb
• suspensory ligament of the penis–superficial fasica extending inferiorly from the symphysis pubis
• forms a sling attached to the deep fascia
• Arteries – the penis is supplied by the internal pudendal artery
• the paired dorsal arteries run between and superior to the two corpus cavernosa
• the deep arteries run within the corpus cavernosa and are the main supply of blood for an erection
• when the penis is flaccid, the terminal branches of the deep arteries are called the helicine (coiled) arteries
• Veins – blood from the cavernous sinuses is drained into the deep dorsal vein of the penis in the deep fascia
• the superficial dorsal vein drains the more superficial tissues
• Innervation –dorsal nerve of the penis (a terminal branch of the pudendal nerve) supplies sensory fibers to skin and glans

Urethra – three parts:

• Bladder – stores urine, lies posteriorly and superiorly to the pubic bones
• retropubic space (prevesicular space) – the space between the pubic bones and the bladder
• rectovesicular space – the space posterior to the bladder anterior to the rectum
• Blood Supply for the Bladder – superior and inferior vesicular arteries, from the internal iliac
• Ureters – convey urine from the kidneys to the urinary bladder passing anterior to the internal iliac arteries
• the ureters enter the bladder just superior to the seminal vesicles at the trigone

• Testes – located in the scrotum and produce sperm
• sperm are collected via the epididymus and enter the ductus (vas) deferens to start their journey to the outside world
• Seminal vesicles – behind the bladder, produce semen which gets mixed with the sperm from the ductus deferens
• sperm and semen are emptied into the prostatic urethra through ejaculatory ducts
• Prostate gland – produces fluid for semen; size of a walnut and surrounds the prostatic urethra
• Blood Supply - the testes migrate from the abdomen and retain their original blood and lymph supply (testicular artery)
• the testicular artery comes from aorta (or renal artery); the rest of the pelvis is supplied by the external and internal iliac
• therefore testicular tumors metastasize to abdominal nodes, whereas scrotal and penile tumors metastasize to iliac nodes
• external iliac artery supplies anterior scrotum, internal pudendal artery supplies posterior scrotum
• Peritoneal folds – an elevation of peritoneum with a free edge, some are old fetal circulation structures.
• lateral = inferior epigastric vessels; medial = remnants of umbilical arteries; median = remnant of the fetal urachus