Anatomy of Penis & Physiology of Erection

Anatomy of Penis & Physiology of Erection By: Dr. Kenny Robert.J PG, II year M.S ( G.S) Govt.Royapettah HospitalIntroduction: Male copulatory organ Radix and CorpusSKIN:Thin , dark, loose corona- prepuce/ foreskin confluence frenulum prepucial sac

Root: 2 crura and 1 bulb crura corpus cavernosum bulb corpus spongiosum glans penis Body: 3 erectile tissuesCorpus cavernosa: common fibrous envelope , median fibrous septum median groove

dorsal groove deep dorsal vein distally ending hollow of glans tunica albuginea covering

two layers inner circular and outer longitudinal fibres deep fibres median septum- complete proximally and distally pectiniform septum

Corpus spongiosum: bulb traversed by urethra cylindrical , tapering distally concal enlargement glans penis corona glandis preputial glands corona and neckSuperficial Penile fascia: dartos fasciaDeepest layer condensed to form tough fascia Bucks Fascia Blends at neck with all others

Suspensory ligaments:

Vascular and Lymphatic drainage: Perineal Artery: internal pudendal artery between bulbospongiosus and ischiocavernosis Anastamosis with contralateral branch, posterior scrotal and inferior rectal arteries Artery of the Bulb of Penis:

Cavernosal artery: deep artery of penis internal pudendal corpus cavernosa trabeculae / cavernous spaces/ convuluted and dilated ( helicine arteries)Dorsal Artery of penis:Deep to Bucks fascia artery/ vein / nervePenile skin circumflex branches tunica albuginea of corpus cavernosum anastamosing with themDorsal Veins of Penis:Small veins circumflex veins circumferential tributaries Deep dorsal Vein Dorsal veins: superficial and deep

superficial veins external pudendal vein

Deep dorsal vein blood from glans penis and corpora cavernosa penis course anterior margin of perineal membrane divide internal pudendal vein prostatic plexus

LYMPHATIC DRAINAGE: penile skin external pudendal vessels superficial inguinal nodes glans penis deep inguinal and external iliac nodes erectile tissue and penile urethra internal iliac nodes.Innervation: corpora cavernosa- lesser and greater cavernous nerves ( pelvic plexus) lesser cavernous nerves penile fibrous sheath erectile tissue and penile urethra Greater cavernous nerves dorsum of penis spongiosum and erectile tissue T 11 to L 2 sympatheic S2,S3,S4 ParasympatheticPhysiology of Erection: Emission ? Ejaculation? Modern investigations of penile hemodynamics ? current physiology is based on F MRI and PET- CTAnatomical orientation: Tunica albuginea outer layer absent in corpus spongiosum low pressure stucture Emissary veins cavernous artery- soft tissue sheath contains fibrillar collagen and elastin

Corpora cavernosa, spongiosum and Glans penis: within tunica smooth muscle trabeculae separating sinuisoids elastic fibres, collagen, loose areolar tissue normal state? , erection? Spongiosum- tunical thinner glans penis- absent tunicaArteries:Internal pudendal atery penile artery Dorsal, bulbourethral and cavernous vascular ring near glans.

cavernous artery- cavernosa helicine arteries erectile tissue dilated during erectionVeins:Subtunical plexus of veins emissary vein

Hemodynamics Stimulation

Neurotransmitters

Smooth muscle relaxation

Dilation of arterioles and arteries

Expanding sinuisoids

Compression of subtunical venous plexus

Expanding tunica

Emissary venous compression

P o2 , intercavernous pressure 100mm HgFull erection rigid erection Corpus spongiosum- difference Glanular tumescence- dorsal and circumflex veins Rigid erection phase ischiocavernosis and bulbo spongiosis compress penile veins

Neuro Anatomy and Neuro Physiology of erection: Sympathetic and Parasympathetic supply

erection and detumuscence

Visually evoked stimulus1) Perceptual- cognitive: recognises stimuli inferior temporal cortex 2) Emotional / Motivational: processes information right insula, inferior frontal and left cingulate cortex 3) Physiologic process Psychogenic erection:REM sleep : activation of pontine area, amygdala and anterior cingulate gyrus cholinergic activation

Adrenergic , serotonergic silent

Neurotransmitters: NO non adrenergic/ non cholinergic endings& endothelium penile erection NO c GMP relaxes cavernous smooth muscles Acetylcholine presynaptic inhibition of adrenergic neurons and stimulate NO release Flaccid state- myogenics, adrenergics and endothelin Detumescence cessation of NO Factors affecting NO? Dopamine: D1, D2 Erection 5HT inhibit it GABA Opoids Cannabinoids Oxytocin: via dopaminergic stimulation Prolactin

Smooth Muscle Physiology:

Endothelin, Prostaglandin, Thromboxane mediated IP 3/ DAG pathway RELAXATION:MLC phosphatase mediatedDecreasing intracellular calcium c GMP and c AMP mediated protein kinase ion channels / proteins opening of pottasium channels hyperpolarizationSequestration of intracellular calcium by Endoplasmic reticulum Inhibit voltage dependant calcium channels drop in cystolic free calcium C amp Adenosine, calcitocin gene related peptides, PG, VIP G amp NO, CO, natriuretic peptides, Protein kinase G PDE 11 families ( PDE 5 and PDE 3)

Ion channels : smooth muscle difference Calcium channels voltage dependent L typePottasium Channels: 1) calcium sensitive 2) metabolically regulated 3) Delayed rectifier 4) Fast transient current Molecular Oxygen:Flaccid state 35 mm hg Erection- 90 mm hg NO synthase activity Synchronous relaxation: intercellular communication gap junctions exchange of ions and messengersIntracavernous architecture: intra cavernous architecture sonic hedgehog (SHH) expression of VEGF and NOS