Male anatomy Flashcards
Mm of urogenital diaphragm
The urogenital diaphragm, also known as the triangular ligament, is a strong sheet of striated skeletal muscle that occupies the area between the pubic symphysis and ischial tuberosities.
external urethral sphincter (somatic control)
bulbospongiosus muscle (med)
ischiocavernosus muscles (lat)
superficial transverse perineal muscle
Parts of urethra
type of epithelium
length
stratified columnar epithelium with mucous secreting glands
15-20cm long
- Prostatic urethra: bladder neck, passes through prostate gland, receives the ejaculatory ducts (containing spermatozoa from the testes and seminal fluid from the seminal vesicle glands) and the prostatic ducts (containing alkaline fluid). Widest / most dilatable.
inferior vesical artery (branch of the internal iliac artery which also supplies the lower part of the bladder).
obturator and internal iliac LN - Membranous urethra: Passes through the pelvic floor and the deep perineal pouch. Surrounded by the external urethral sphincter (vol control of micturition). Narrowest/ least dilatable portion of the urethra.
bulbourethral artery (branch of the internal pudendal artery)
obturator and internal iliac LN - Penile (bulbous) urethra: Passes through the bulb and corpus spongiosum of the penis, ending at the external urethral orifice (the meatus). Receives the bulbourethral glands proximally.
directly by branches of the internal pudendal artery.
deep and superficial inguinal LN
In the glans (head) of the penis, the urethra dilates to form the navicular fossa.
The nerve supply to the male urethra is derived from the prostatic plexus, which contains a mixture of sympathetic, parasympathetic and visceral afferent fibres.
Accessory glands
Secrete fluids that enter the urethra.
Seminal vesicles
Prostate gland
Bulbourethral glands
Seminal Vesicles (60% of semen)
Posterior to bladder
Short duct that joins with the ductus deferens at the ampulla to form an ejaculatory duct, which then empties into the urethra.
Fluid is viscous and contains fructose (energy), prostaglandins (mobility, viability), and proteins (cause slight coagulation reactions in the semen after ejaculation).
Prostate (nearly 40%)
Inferior to the urinary bladder.
Numerous short ducts from the substance of the prostate gland empty into the prostatic urethra. The secretions of the prostate are thin, milky colored, and alkaline. They function to enhance the motility of the sperm.
Bulbourethral (Cowper’s) Glands (small vol)
Pea sized at base of penis. A short duct from each gland enters the proximal end of the penile urethra. In response to sexual stimulation, the bulbourethral glands secrete an alkaline mucus-like fluid. This fluid neutralizes the acidity of the urine residue in the urethra, helps to neutralize the acidity of the vagina, and provides some lubrication for the tip of the penis during intercourse.
Seminal Fluid
Seminal fluid, or semen, is a slightly alkaline mixture (7.2) of sperm cells and secretions from the accessory glands.
Epididymis
6m long
sperm complete maturation process here
Ductus Deferens/ Vas deferens
fibromuscular tube
1. continuous from epididymis
2, goes up along post margin of testes
3. goes through inguinal canal to ap cavity
4. goes along the lateral pelvic wall
crosses over ureter and post bladder goes down prostate gland. (just before it reaches the prostate gland, each ductus deferens enlarges to form an ampulla).
Sperm are stored in the proximal portion of the ductus deferens, near the epididymis, and peristaltic movements propel the sperm through the tube.
Ejaculatory Duct
Each ductus deferens, at the ampulla, joins the duct from the adjacent seminal vesicle (one of the accessory glands) to form a short ejaculatory duct. Each ejaculatory duct passes through the prostate gland and empties into the urethra.
Spermatic cord
The spermatic cord contains the ductus deferens, testicular artery and veins, lymph vessels, testicular nerve, cremaster muscle
Processus vaginalis
mbryonic developmental outpouching of the peritoneum. It is present from around the 12th week of gestation, and commences as a peritoneal outpouching. In males, it precedes the testis in their descent down within the gubernaculum, and closes. This closure (also called fusion) occurs at any point from a few weeks before birth, to a few weeks after birth.
The remaining portion around the testes becomes the tunica vaginalis.
Rectum arterial supply
Arterial supply via 3 main arteries:
Superior rectal artery (IMA)
Middle rectal artery (branch internal iliac artery)
Inferior rectal artery (branch of the internal pudendal artery)
Rectum venous drainage
Venous drainage via the 3 main veins:
Superior rectal vein - portal venous system
Middle rectal vein - systemic venous system
Inferior rectal vein - systemic venous system
Rectum innervation
Innervation:
Sympathetic supply
Lumbar splanchnic nerves
Superior hypogastric plexus
Inferior hypogastric plexus
Parasympathetic supply (from S2-4)
Pelvic splanchnic nerves
Inferior hypogastric plexuses
Sensory fibres follow parasympathetic supply only
External anal sphincter innervation
INFERIOR ANAL NERVES FROM PUDENDAL
The external anal sphincter is under voluntary control and is innervated bilaterally by the inferior anal nerves, branches of the pudendal nerve (S2 - S4)
Rectum lymph drainage
Lymphatic drainage:
Via the pararectal lymph nodes - inferior mesenteric nodes
Lymph from the lower aspect drains directly into the internal iliac lymph nodes
Oropharyngeal innervation
Sensory innervation by branches of the trigeminal nerve (CN V)
Tongue is innervated by sensory fibres for taste from chorda tympani; a branch of the facial nerve CN VII
Male urethra epithelium
Prostatic
Transitional epithelium (as per the bladder; urothelium)
Membranous
Transitional epithelium (some sources say pseudostratified)
Spongy (sometimes called ‘bulbar’ urethra)
Pseudostratified columnar epithelium for majority
Stratified squamous epithelium within the urethral meatus (opening – the most hardy)
The root of the penis
The most proximal and fixed part of the penis
Located in the superficial perineal pouch of the pelvic floor and not visible externally
Contains 3 erectile tissues - 2 crura and the bulb of the penis
The bulb is equivalent to the clitoris in female anatomy
Contains two pairs of muscles – ischiocavernosus and bulbospongiosus
Contains two ligaments – suspensory and fundiform ligaments
The body of the penis
Free part of the penis, suspended off of the pubic symphysis
Composed of 3 cylinders of erectile tissue – 2 corpora cavernosa (from Crura) and corpus spongiosum (from the Bulb)
Glans: Formed by the distal expansion of the corpus spongiosum tissue
Penis: skin
Prepuce (foreskin) = double layer of skin and fascia located at the neck of the glans
The prepuce (foreskin) is connected to the surface of the glans by the frenulum
The space between the glans and the prepuce (foreskin) is the preputial sac
Male erectile tissues
3 masses of erectile tissue – left and right crura and the penile bulb
Bulb = in the midline of the penile root; traversed by the urethra
The bulb continues anteriorly into the penile body - corpus spongiosum
Lies ventrally
Urethra runs through it
The corpus spongiosum expands distally to form the glans penis
The left and right crura are located laterally
Attached to the ipsilateral ischial rami
Covered by paired ischio-cavernosus muscles
Crura continue anteriorly into the body of the penis - 2 x corpora cavernosa
These are incompletely separated by the septum of the penis (formed of the tunica albuginea)
The ligaments within the root of the penis:
Suspensory ligament – deep fascial layer connecting the erectile bodies of the penis to pubic symphysis
Fundiform ligament – dense abdominal subcutaneous tissue which continues down from the linea alba, surrounds the penile base like a sling and attaches it to the pubic symphysis
Vasc supply of the penis
Arterial supply:
The penis receives arterial supply from 3 sources which are all branches of the internal pudendal artery (originating from the internal iliac artery):
Dorsal artery of the penis
Deep arteries of the penis
Bulbourethral artery
Both ischiocavernosus and bulbospongiosus have their vascular supply from the perineal artery (branch of the internal pudendal artery)
Venous drainage of the cavernous spaces is via the deep dorsal vein of the penis -> prostatic venous plexus
The superficial dorsal veins drain the superficial structures of the penis, such as the skin and cutaneous tissues
Penis: innervation
(including erection and ejactulation)
Both ischiocavernosus and bulbospongiosus receive motor innervation via the deep branch of the perineal nerve (originating from the pudendal nerve, S2 – S4)
Erection = Point (PNS) double P
PNS dilates the blood vessels within the spongiform tissue of the penis and causes erection. PNS fibres are carried by the cavernous nerves - these originate from the pelvic splanchnic nerves primarily/ element of involvement of prostatic nerve plexus.
Injury to the periprostatic nerves i.e. during prostate procedures likely à erectile dysfunction
Ejaculation = Shoot (SNS)
Sympathetic nervous system directs the smooth muscle to contract and push the semen through at ejaculation
Also causes contraction of the internal urethral sphincter to prevent retrograde ejaculation and to maintain continence
(NB parasympathetic supply relaxes the internal urethral sphincter during micturition)
SNS and sensory nerve fibres are carried by the dorsal nerve of the penis (branch of the pudendal nerve
Lymphatic drainage of testes vs scrotum
Lymphatic drainage of testes = lumbar and para-aortic nodes (originally retroperitoneal organs!)
Lymphatic drainage of scrotum distinct from testes = superficial inguinal lymph nodes
