Penis: Difference between revisions

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* '''With the penis on stretch in a standing position, the superior surface of the penis is known as the dorsum and the inferior surface, is known as the ventrum'''

* The shaft of the penis and the base of the glans are separated by the corona

* The penile shaft skin is very elastic and its '''only glandular elements are the smegma-producing glands, called glands of Tyson, located at the base of the corona'''

* '''Layers surrounding the corpora cavernosa, from superficial to deep (5):'''

* '''~~The layers~~ surrounding the corpora cavernosa ~~are~~:'''

*# '''Skin'''

*# '''Dartos (continuous with Scarpa’s and Colle’s fasciae)'''

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*# '''Buck’s fascia'''

*# '''Tunica albuginea'''

[[File:Penis_Anatomy_Cross_Section.png|frameless|644x644px]]

[[File:Penis_Anatomy_Cross_Section.png|center|frameless|644x644px]]

=== Corpus cavernosum ===

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** '''The erectile tissues of the normal corpora cavernosa are separated from the tunica by the space of Smith'''

* '''Proximal ends, the crura, originate at the undersurface of the puboischial rami as separate structures but merge under the pubis to form the body of the penis and remain attached up to the glans'''

* '''A septum separates the corpora cavernosa but is permeable distally to allow for free communication between their vascular spaces'''

* '''A septum separates the corpora cavernosa but is permeable distally to allow for free communication between their vascular spaces'''

[[File:Wiki_Penis_Base_Cross_Section.jpg|alt=Wiki Penis Base Cross Section|center|frameless|503x503px]]

* '''Each corpus cavernosum is a conglomeration of sinusoids,''' larger in the center and smaller in the periphery.

** '''In the flaccid state, the blood slowly diffuses from the central to the peripheral sinusoids, and the blood gas levels are similar to those of venous blood.'''

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* The urethra travels through the corpus spongiosum, with its proximal segment known as the bulb.

* '''The glans penis is an expansion of the corpus spongiosum'''

* '''The glans penis is an expansion of the corpus spongiosum'''

=== Tunica albuginea ===

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*Tough connective tissue layer composed primarily of type I collagen

* '''A bilayered structure (inner circular, outer longitudinal)''' with multiple sublayers.

** '''Outer longitudinal layer'''***Thinnest at the 3 and 9 o'clock positions of the corpora

** '''Outer longitudinal layer'''

***'''Completely absent on the ventral groove between the 5 and 7 o'clock positions.'''

****'''The most vulnerable area in the tunica albuginea'''

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=== Buck fascia ===

* '''External to the tunica albuginea'''

* '''External to the tunica albuginea'''

* '''Surrounds corpora cavernosae; ventrally, splits to surround the corpus spongiosum'''

* '''Distally, fuses with the glans at corona'''

* '''The paired dorsal arteries, paired dorsal nerves, and deep dorsal vein are deep to Buck’s fascia'''

* '''The paired dorsal arteries, paired dorsal nerves, and deep dorsal vein are deep to Buck’s fascia'''

* '''The superficial dorsal penile vein is external to Buck’s fascia'''

* '''The superficial dorsal penile vein is external to Buck’s fascia'''

* '''A penile fracture is a tear in the tunica albuginea; the hematoma is contained by Buck’s fascia'''

* '''A penile fracture is a tear in the tunica albuginea; the hematoma is contained by Buck’s fascia'''

=== Penile skin ===

* Very elastic

* '''Only glandular elements are the smegma-producing glands, called glands of Tyson, located at the base of the corona'''

=== External penile support ===

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* '''Deep arterial system:'''

** '''The internal pudendal artery, (derived from the anterior branch of the internal iliac) gives off the perineal branch and posterior scrotal arteries before continuing on to become the common penile artery.'''

** '''The internal pudendal artery, (derived from the anterior branch of the internal iliac) gives off the perineal branch and posterior scrotal arteries before continuing on to become the common penile artery.'''

** '''The common penile artery has 3 paired branches CBD:'''

** '''The common penile artery has 3 paired branches: CBD'''

**# '''~~Cavernosal~~ artery'''

**# '''Cavernosal artery'''

**#* Penetrates the corpus cavernosum in the penile hilum to nearly the center of the erectile tissue

**#* '''Provides straight and helicine arteries that supply the cavernous sinuses'''; the helicine arteries supply the trabecular erectile tissue and the sinusoids. These helicine arteries are contracted and tortuous in the flaccid state and become dilated and straight during erection

**#* '''Effects tumescence of the corpus cavernosum'''

**# '''~~Bulbourethral~~ artery'''

**# '''Bulbourethral artery'''

**#* '''Supplies the corpus spongiosum, urethra, and glans'''

**#* Penetrates the perineal membrane where it enters the corpus spongiosum from above at its posterolateral border

**# '''~~Dorsal~~ artery'''

**# '''Dorsal artery'''

**** '''Supplies''' the dorsal surfaces of the '''corporeal bodies''' '''and''' circumferential branches to the urethra and the '''corpus spongiosum; responsible for engorgement of the glans during erection; supplies distal shaft skin'''

**#* '''Supplies''' the dorsal surfaces of the '''corporeal bodies''' '''and''' circumferential branches to the urethra and the '''corpus spongiosum; responsible for engorgement of the glans during erection; supplies distal shaft skin'''

**** '''Travels between the crus and the pubis then between the dorsal vein and the dorsal penile nerve, all of which attach to the underside of Buck fascia,''' then travels distally toward the glans

**#* '''Travels between the crus and the pubis then between the dorsal vein and the dorsal penile nerve, all of which attach to the underside of Buck fascia,''' then travels distally toward the glans

*** Distally, these arteries join to form a vascular ring near the glans.

*** ~~There can~~ be a great deal of variability in penile arteries. '''In many instances, accessory arteries exist; they may constitute the dominant or only arterial supply to the corpus cavernosum in some men.''' '''Accessory pudendal arteries arise most commonly from the obturator artery.'''

*** Can be a great deal of variability in penile arteries.

*** '''The bulbourethral''' ''[“and urethral”?]'' '''arteries are situated outside the tunica albuginea of the corpus spongiosum''' on the lateral and dorsal sides

***'''The bulbourethral''' ''[“and urethral”?]'' '''arteries are situated outside the tunica albuginea of the corpus spongiosum''' on the lateral and dorsal sides

*** '''The cavernous artery and branches of the dorsal artery''' that supply the corpus ~~covernosae~~ '''are surrounded by a periarterial soft-tissue sheath, which protects the arteries from occlusion by the tunica albuginea during erection'''

***'''The cavernous artery and branches of the dorsal artery''' that supply the corpus cavernosae '''are surrounded by a periarterial soft-tissue sheath, which protects the arteries from occlusion by the tunica albuginea during erection'''

***'''Accessory penile arteries'''

****'''Exist in many instances'''

****'''May constitute the dominant or only arterial supply to the corpus cavernosum in some males.'''

****'''Accessory pudendal arteries arise most commonly from the obturator artery.'''

* '''Superficial arterial system:'''

** '''Branches from the external pudendal (originates from femoral artery) artery supply the penile skin; these vessels run in the dartos fascia layer'''.

** '''Branches from the external pudendal (originates from femoral artery) artery supply the penile skin; these vessels run in the dartos fascia layer'''.

** '''The blood supply of the skin is independent of the erectile bodies. The rich anastomotic network makes penile skin ideal for mobilization on a vascular pedicle'''

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== Innervation ==

* '''Somatic~~'''~~

=== Somatic ===

** '''Paired dorsal nerves of the penis (paired, S2-S4)'''

* '''Paired dorsal nerves of the penis (paired, S2-S4)'''

*** '''Arises in the Alcock canal as the first branch of the pudendal nerve (S2-4)'''

** '''Arises in the Alcock canal as the first branch of the pudendal nerve (S2-4)'''

*** Runs over the surface of the obturator internus under the levator, runs deep to the urogenital diaphragm, and passes through the deep transverse perineal muscle '''to run along the dorsum of the penis accompanied by the dorsal vein and dorsal artery.'''

** Runs over the surface of the obturator internus under the levator, runs deep to the urogenital diaphragm, and passes through the deep transverse perineal muscle '''to run along the dorsum of the penis accompanied by the dorsal vein and dorsal artery.'''

*** '''Supplies sensory innervation to the glans'''

** '''Supplies sensory innervation to the glans'''

** Small branches of the perineal nerve supply the ventrum of the penis as distally as the glans

* Small branches of the perineal nerve supply the ventrum of the penis as distally as the glans

** '''The skin of the penis is innervated by branches of the genitofemoral nerve'''

* '''The skin of the penis is innervated by branches of the genitofemoral nerve'''

* '''Autonomic~~'''~~

** '''Paired cavernous nerves (S2-4)'''

=== Autonomic ===

*** '''Arise from the pelvic plexus''' '''from the lateral surface of the rectum'''

* '''Paired cavernous nerves (S2-4)'''

*** Run posterolateral to the apex, mid-portion and base of the prostate '''anterior to Denonvilliers’ fascia''' between the posterolateral surface of the prostate and the rectum to '''lie between the lateral pelvic fascia and the prostatic fascia. The branches from the cavernous nerve accompany the branches of the prostatovesicular artery''' '''and provide a macroscopic landmark for nerve-sparing radical prostatectomy i.e. neurovascular bundle.'''

** '''Arise from the pelvic plexus''' '''from the lateral surface of the rectum'''

*** '''Innervates the corpus cavernosum and penile urethra'''

** Run posterolateral to the apex, mid-portion and base of the prostate '''anterior to Denonvilliers’ fascia''' between the posterolateral surface of the prostate and the rectum to '''lie between the lateral pelvic fascia and the prostatic fascia. The branches from the cavernous nerve accompany the branches of the prostatovesicular artery''' '''and provide a macroscopic landmark for nerve-sparing radical prostatectomy i.e. neurovascular bundle.'''

** '''Innervates the corpus cavernosum and penile urethra'''

== Questions ==

@@ Line 3: / Line 3: @@
 * '''<span style="color:#ff0000">With the penis on stretch in a standing position, the superior surface of the penis is known as the dorsum and the inferior surface, is known as the ventrum</span>'''
 * The shaft of the penis and the base of the glans are separated by the corona
-* The penile shaft skin is very elastic and its '''only glandular elements are the smegma-producing glands, called glands of Tyson, located at the base of the corona'''
+* '''<span style="color:#ff0000">Layers surrounding the corpora cavernosa, from superficial to deep (5):</span>'''
-* '''<span style="color:#ff0000">The layers surrounding the corpora cavernosa are:</span>'''
 *# '''<span style="color:#ff0000">Skin</span>'''
 *# '''<span style="color:#ff0000">Dartos (continuous with Scarpa’s and Colle’s fasciae)</span>'''
@@ Line 10: / Line 9: @@
 *# '''<span style="color:#ff0000">Buck’s fascia</span>'''
 *# '''<span style="color:#ff0000">Tunica albuginea</span>'''
-[[File:Penis_Anatomy_Cross_Section.png|frameless|644x644px]]
+[[File:Penis_Anatomy_Cross_Section.png|center|frameless|644x644px]]
 === Corpus cavernosum ===
@@ Line 18: / Line 17: @@
 ** '''The erectile tissues of the normal corpora cavernosa are separated from the tunica by the space of Smith'''
 * '''Proximal ends, the crura, originate at the undersurface of the puboischial rami as separate structures but merge under the pubis to form the body of the penis and remain attached up to the glans'''
-* '''A septum separates the corpora cavernosa but is permeable distally to allow for free communication between their vascular spaces'''
+* '''<span style="color:#ff0000">A septum separates the corpora cavernosa but is permeable distally to allow for free communication between their vascular spaces</span>'''
+[[File:Wiki_Penis_Base_Cross_Section.jpg|alt=Wiki Penis Base Cross Section|center|frameless|503x503px]]
 * '''Each corpus cavernosum is a conglomeration of sinusoids,''' larger in the center and smaller in the periphery.
 ** '''In the flaccid state, the blood slowly diffuses from the central to the peripheral sinusoids, and the blood gas levels are similar to those of venous blood.'''
@@ Line 27: / Line 26: @@
 * The urethra travels through the corpus spongiosum, with its proximal segment known as the bulb.
-* '''The glans penis is an expansion of the corpus spongiosum'''
+* '''<span style="color:#ff0000">The glans penis is an expansion of the corpus spongiosum</span>'''
 === Tunica albuginea ===
@@ Line 33: / Line 32: @@
 *Tough connective tissue layer composed primarily of type I collagen
 * '''A bilayered structure (inner circular, outer longitudinal)''' with multiple sublayers.
-** '''<span style="color:#ff0000">Outer longitudinal layer</span>'''***Thinnest at the 3 and 9 o'clock positions of the corpora
+** '''<span style="color:#ff0000">Outer longitudinal layer</span>'''
 ***'''<span style="color:#ff0000">Completely absent on the ventral groove between the 5 and 7 o'clock positions.</span>'''
 ****'''The most vulnerable area in the tunica albuginea'''
@@ Line 44: / Line 43: @@
 === Buck fascia ===
-* '''External to the tunica albuginea'''
+* '''<span style="color:#ff0000">External to the tunica albuginea</span>'''
 * '''Surrounds corpora cavernosae; ventrally, splits to surround the corpus spongiosum'''
 * '''Distally, fuses with the glans at corona'''
-* '''The paired dorsal arteries, paired dorsal nerves, and deep dorsal vein are deep to Buck’s fascia'''
+* '''<span style="color:#ff0000">The paired dorsal arteries, paired dorsal nerves, and deep dorsal vein are deep to Buck’s fascia</span>'''
-* '''The superficial dorsal penile vein is external to Buck’s fascia'''
+* '''<span style="color:#ff0000">The superficial dorsal penile vein is external to Buck’s fascia</span>'''
-* '''A penile fracture is a tear in the tunica albuginea; the hematoma is contained by Buck’s fascia'''
+* '''<span style="color:#ff0000">A penile fracture is a tear in the tunica albuginea; the hematoma is contained by Buck’s fascia</span>'''
+=== Penile skin ===
+* Very elastic
+* '''Only glandular elements are the smegma-producing glands, called glands of Tyson, located at the base of the corona'''
 === External penile support ===
@@ Line 62: / Line 66: @@
 * '''Deep arterial system:'''
-** '''The internal pudendal artery, (derived from the anterior branch of the internal iliac) gives off the perineal branch and posterior scrotal arteries before continuing on to become the common penile artery.'''
+** '''<span style="color:#ff0000">The internal pudendal artery, (derived from the anterior branch of the internal iliac) gives off the perineal branch and posterior scrotal arteries before continuing on to become the common penile artery.</span>'''
-** '''The common penile artery has 3 paired branches CBD:'''
+** '''<span style="color:#ff0000">The common penile artery has 3 paired branches: </span><span style="color:#0000ff">CBD</span>'''
-**# '''Cavernosal artery'''
+**# '''<span style="color:#0000ff">C</span><span style="color:#ff0000">avernosal artery</span>'''
 **#* Penetrates the corpus cavernosum in the penile hilum to nearly the center of the erectile tissue
 **#* '''Provides straight and helicine arteries that supply the cavernous sinuses'''; the helicine arteries supply the trabecular erectile tissue and the sinusoids. These helicine arteries are contracted and tortuous in the flaccid state and become dilated and straight during erection
 **#* '''Effects tumescence of the corpus cavernosum'''
-**# '''Bulbourethral artery'''
+**# '''<span style="color:#0000ff">B</span><span style="color:#ff0000">ulbourethral artery</span>'''
 **#* '''Supplies the corpus spongiosum, urethra, and glans'''
 **#* Penetrates the perineal membrane where it enters the corpus spongiosum from above at its posterolateral border
-**# '''Dorsal artery'''
+**# '''<span style="color:#0000ff">D</span><span style="color:#ff0000">orsal artery</span>'''
-**** '''Supplies''' the dorsal surfaces of the '''corporeal bodies''' '''and''' circumferential branches to the urethra and the '''corpus spongiosum; responsible for engorgement of the glans during erection; supplies distal shaft skin'''
+**#* '''Supplies''' the dorsal surfaces of the '''corporeal bodies''' '''and''' circumferential branches to the urethra and the '''corpus spongiosum; responsible for engorgement of the glans during erection; supplies distal shaft skin'''
-**** '''Travels between the crus and the pubis then between the dorsal vein and the dorsal penile nerve, all of which attach to the underside of Buck fascia,''' then travels distally toward the glans
+**#* '''Travels between the crus and the pubis then between the dorsal vein and the dorsal penile nerve, all of which attach to the underside of Buck fascia,''' then travels distally toward the glans
 *** Distally, these arteries join to form a vascular ring near the glans.
-*** There can be a great deal of variability in penile arteries. '''In many instances, accessory arteries exist; they may constitute the dominant or only arterial supply to the corpus cavernosum in some men.''' '''Accessory pudendal arteries arise most commonly from the obturator artery.'''
+*** Can be a great deal of variability in penile arteries.
-*** '''The bulbourethral''' ''[“and urethral”?]'' '''arteries are situated outside the tunica albuginea of the corpus spongiosum''' on the lateral and dorsal sides
+***'''The bulbourethral''' ''[“and urethral”?]'' '''arteries are situated outside the tunica albuginea of the corpus spongiosum''' on the lateral and dorsal sides
-*** '''The cavernous artery and branches of the dorsal artery''' that supply the corpus covernosae '''are surrounded by a periarterial soft-tissue sheath, which protects the arteries from occlusion by the tunica albuginea during erection'''
+***'''The cavernous artery and branches of the dorsal artery''' that supply the corpus cavernosae '''are surrounded by a periarterial soft-tissue sheath, which protects the arteries from occlusion by the tunica albuginea during erection'''
+***'''Accessory penile arteries'''
+****'''Exist in many instances'''
+****'''May constitute the dominant or only arterial supply to the corpus cavernosum in some males.'''
+****'''Accessory pudendal arteries arise most commonly from the obturator artery.'''
 * '''Superficial arterial system:'''
-** '''Branches from the external pudendal (originates from femoral artery) artery supply the penile skin; these vessels run in the dartos fascia layer'''.
+** '''<span style="color:#ff0000">Branches from the external pudendal (originates from femoral artery) artery supply the penile skin;</span> these vessels run in the dartos fascia layer'''.
 ** '''The blood supply of the skin is independent of the erectile bodies. The rich anastomotic network makes penile skin ideal for mobilization on a vascular pedicle'''
@@ Line 113: / Line 121: @@
 == Innervation ==
-* '''Somatic'''
+=== Somatic ===
-** '''Paired dorsal nerves of the penis (paired, S2-S4)'''
+* '''<span style="color:#ff0000">Paired dorsal nerves of the penis (paired, S2-S4)</span>'''
-*** '''Arises in the Alcock canal as the first branch of the pudendal nerve (S2-4)'''
+** '''Arises in the Alcock canal as the first branch of the pudendal nerve (S2-4)'''
-*** Runs over the surface of the obturator internus under the levator, runs deep to the urogenital diaphragm, and passes through the deep transverse perineal muscle '''to run along the dorsum of the penis accompanied by the dorsal vein and dorsal artery.'''
+** Runs over the surface of the obturator internus under the levator, runs deep to the urogenital diaphragm, and passes through the deep transverse perineal muscle '''to run along the dorsum of the penis accompanied by the dorsal vein and dorsal artery.'''
-*** '''Supplies sensory innervation to the glans'''
+** '''Supplies sensory innervation to the glans'''
-** Small branches of the perineal nerve supply the ventrum of the penis as distally as the glans
+* Small branches of the perineal nerve supply the ventrum of the penis as distally as the glans
-** '''The skin of the penis is innervated by branches of the genitofemoral nerve'''
+* '''<span style="color:#ff0000">The skin of the penis is innervated by branches of the genitofemoral nerve</span>'''
-* '''Autonomic'''
-** '''Paired cavernous nerves (S2-4)'''
+=== Autonomic ===
-*** '''Arise from the pelvic plexus''' '''from the lateral surface of the rectum'''
+* '''<span style="color:#ff0000">Paired cavernous nerves (S2-4)</span>'''
-*** Run posterolateral to the apex, mid-portion and base of the prostate '''anterior to Denonvilliers’ fascia''' between the posterolateral surface of the prostate and the rectum to '''lie between the lateral pelvic fascia and the prostatic fascia. The branches from the cavernous nerve accompany the branches of the prostatovesicular artery''' '''and provide a macroscopic landmark for nerve-sparing radical prostatectomy i.e. neurovascular bundle.'''
+** '''Arise from the pelvic plexus''' '''from the lateral surface of the rectum'''
-*** '''Innervates the corpus cavernosum and penile urethra'''
+** Run posterolateral to the apex, mid-portion and base of the prostate '''anterior to Denonvilliers’ fascia''' between the posterolateral surface of the prostate and the rectum to '''lie between the lateral pelvic fascia and the prostatic fascia. The branches from the cavernous nerve accompany the branches of the prostatovesicular artery''' '''and provide a macroscopic landmark for nerve-sparing radical prostatectomy i.e. neurovascular bundle.'''
+** '''Innervates the corpus cavernosum and penile urethra'''
 == Questions ==