1. Male urethra. Penis and erection
Anna L.Kiss
Department of Human Morphology and Developmental Biology
Semmelweis University Budapest
2014

2. The male urethra has three parts
Long (about 20cm) muscular tube)
Prostatic part: pierces the prostate
Membranous part: the shortest part, passes through the pelvic diaphragm
Spongy part: the longest part, running in the axis of the penis

3. 1.) Prostatic part: median longitudinal ridge: urethral crest in the middle of this crest: rounded eminence: seminal colliculus with a slitlike orifice, leading into a small vestigeal cul-de-sac: prostatic utricule, on each side of this utricle: openings of the ejaculatory ducts
2.) Membranous part: voluntary sphincter that compress the urethra (from the pelvic diaphragm)
3.) Spongy part: ends: glans penis
fossa navicularis
proximal: bulbourethral glands
mucus secreting urethral glands

4. Three parts of the male urethra1 3 2

5. Endoscopy of the urethra
When inserting catheters and sounds the curves in the urethra must be considered:
The membranous part runs inferiorly and anteriorly,
The prostatic part takes a slight curve that is concave anteriorly
The spongy part: well covered inferiorly and posteriorly erectile tissue
Short segment of the membranous urethra is unprotected!!
In the navicular fossa: transverse mucosa fold (about 2cm from the external opening of the urethra)

6. Histological structure of the male urethra
Prostatic part: urothelium (vesical sphincter m.: smooth muscle!)
Membranous part: pseudostratified or stratified columnar epithelium
the urogenital diaphargm: striated muscle makes a sphincter: sphincter urethrae m.
Penil (or spongy) part: pseudostratified columnar epithelium
distal end: stratified non-keratinized squamous epithelium
at the orifice: stratified keratinized squamous epithelium
Bulbourethral glands and mucus secreting Littre glands empty into it

7. Penis

8. Penis Three cylindrical bodies:
Corpora cavernosa – two erectile bodies enclosed by a dense white fibrous capsule: tunica albuginea.
Corpus spongiosum – ventrally (corpus cavernosum urethrae) containing the spongy urethra, ending in the glans penis
Crura – attached to the conjoint rami of pubis ans ischium.
body
Root: bulb+crura+bulbospongiosus m.)

9. Erectile bodies of the penis and urethra
skin
spf fascia: thin smooth m.+ spf. dorsal v.
fascia penis: deep dorsal v dorsal art.
tunica albuginea

10. Blood supply of the penis
Two dorsalis penile aa. –terminal branch of the pudendal artery
Deep arteries (cavernous artery) – paired, principal artery supplying the caveosnous spaces. They are involved in erection. (helicine arteries-in flaccid penis)
Bulbourethral artery– spongy urtethra (internal pudendal)

13. Venous drainage Superficial – spf. dorsal vein
Deep – deep dorsal vein sinuses – emissary veins - circumflex veins

14. Innervation of the penis
Autonom (vegetative)
sympathetic (T11-L2) fibers parasymphathetic (S2-S4) fibers: nervus cavernosus (in the pelvis)
Somatic innervation sensory and motor innervation
of the extracorporal striated muscles: nervus pudendus

15. Innervation of the penis
Cavernous nerves
posterolaterally to the
prostate enters the CC
and CS, regulates the
blood flow of the
penis.
Dorsal n. of the penis
(from pudendal nerve)
somatic nerve, primary
innervates the skin of the penis

16. AZ ERECTION

17. Erection is: sexual reponse
Erection (haemodinamic event regulated by neural mechanism) is resulted in by various sexual stimuli:
Touch and mechanical stimulation of the penis (reflexogen)
Erotic view, sound, and smell (central or psychogenic)
The erection can be caused but also inhibited by any emotional or higher mental activity
The third type of the erection is the so called nocturnal erection associated to sleeping period.

18. ERECTIO view smell touch imagination (occipital) (rhiencephalon)
(thalamus)
imagination
(limbic systems)

19. ERECTION Occlusion of the venous dranaige.
Relaxation of the smooth muscle in cavernous spaces and arterioles.
Sexual stimulus
Occlusion of the venous dranaige.
Blood inflow to the caveornous spaces.
Intracavernous blood pressure > systemic blood pressure
ERECTION

20. In erectile stage: relaxation of the trabecular and arteriolar smooth muscles, vasodilation of aa. helicinae increased blood flow cavernous spaces (sinusoids) are filling in with blood. Expansion of sinusoids press the emyssary and circumflex veins. The streches of the tunica albuginea increases this effect significant decrease in venous blodd flow. In flaccid stage: helicine arteries are coiled, arterious blood flow is minimal, venous drainaige is not blocked.

21. Anatomy of the erection

22. Erection of the penis (and the clitoris)

23. Erection of the penis (and the clitoris)

24. Physiology of the erection
Szexual stimulus
EAA, OXYTOCIN,
DOPAMINE, NO
ERECTION
Smooth muscle
relaxation!
SACRAL
PARASYMPATHETIC
FIBERS
cGMP NO

25. NO NO NO NA Ca Ca 2+ 2+ nNOS a1 CONTRACTION cGMP RELAXATION
SYMPATHETIC
NEURON
PARASYMPATHETIC NEURON
nNOS Ca 2+ NA NO
Smooth muscle
soluble
Guanylyl
Cyclase a1 NO
CONTRACTION NO
cGMP
RELAXATION

26. Intracellular calciumNA ET
PGF2a
TXA2
AngII
PGE1
VIP NO NA a1
SMOOTH MUSCLE
ETA
EP-R
VIP-R R
sGC b2 AC
cGMP
cAMP
Intracellular calcium
RELAXATIO
CONTRACTIO

27. EJACULATION

28. MEDIATORS OF THE EJACULATION
DOPAMINE
5-HT
EJACULATION
Smooth muscle
contraction!
SYMPATHETIC
NEURONS NA

29. Ejaculation Ejaculation = emission + propulsion (expulsio)
Ejaculation ≠ orgasmus
Ejaculatum (~2ml)=10% from the prostate + 10% from vas deferens + 75% a from seminal vesicule + 5% from Cowper’s glands + <0.1% spermatozoa

30. Seminalis emission and ejaculation.
Contraction of the reproductiv ducts and accessory organs and release their contant.

31. Seminalis emissio és ejaculation
Sphincter of the bladder sontracts, preventing expulsion of the urine.
Bulbospongiosus muscles contract fast and serially;
The semen is released (ejaculated) form the urethra (propulsion).

32. “My brain is my second favorite organ.”
Woody Allen