Others e.g. glomerulonephritis, erectile problems etc Flashcards
What is involved in the process of an erection (neurovascular phenomenon under hormonal control)
Arterial dilation
Smooth Muscle relaxation
Activation of the corporeal veno occlusive mechanism
What are the 3 shafts of the penis
2 corpora cavernosa
Corpus spongiosum
What covers the corpora cavernosa
Tunica albuginea
corpus spongiosum has a similar thinner tunica
What is contained in the 2 Corpora Cavernosa
Spongy vascular erectile tissue - trabeculated smooth muscle lined by endothelial cells
What structure is found in the Corpus spongiosum
Urethra
Describe arterial supply of the penis in order
Internal Iliac
-Internal pudendal artery:
Dorsal penile artery, Cavernosal artery (deep penile arteries), Bulbar artery
Describe venous drainage of the penis sinusoids
Subtunical plexus:
to circumflex veins to deep dorsal vein
Describe venous drainage of the corpora cavernosa
Cavernous veins:
to crural veins to internal pudendal veins
Autonomic supply of penis
Parasympathetic - erectile S2-4
Sympathetic - T11 to L2
What nerve carries both types of fibres that supply penis
Cavernous nerve (passes posterolateral to prostate thus risk damage in prostatectomy)
Describe physiology of flaccid state of penis
sympathetic tone
arterioles constricted
Sympathetic nerve terminal releases neuropeptide Y and noradrenaline
Vascular endothelium releases endothelin and prostanoids
all act on smooth muscle cells
Describe physiology of erect state
Parasympathetic stimulation – arteriolar dilatation, trabecular smooth muscle relaxation
Parasympathetic nerve terminal releases Vasoactive intestinal polypeptide, Nitric oxide that act one smooth muscle cells
Parasympathetic nerve terminal also releases Acetylcholine and Calcitonin gene related peptide. ACh inhibits sympathetic nerve terminal and (like calcitonin gene related peptide) increases production of nitric oxide from vascular endothelium.
Prostanoids also secreted by vascular endothelium and act on smooth muscle cell
Where is the central control of erections
Higher stimuli:
Hypothalamus, oxytocin pro-erectile pathways
Spinal reflex
Give example of a hormone required for normal erectile function
Testosterone
Examples of testosterone deficiency
Acquired: Primary or Secondary
Congenital e.g. Kleinfelters
Where is problem in primary testosterone deficiency
Pituitary gland or Hypothalamus
Where is problem in secondary testosterone deficiency
Testes - tumour, injury, drugs
Describe the peripheral control of erections
Smooth muscle mediated - arteriolar dilation and trabecular relaxation
Nitrous oxide release
Why is the release of nitrous oxide important
Acetylcholine effect on endothelium
In smooth muscle cell stimulates Guanylate Cyclase enzyme which converts GTP to cGMP. This then stimulates the enzyme protein kinase G (PKG) to close L-type calcium channels and open Potassium channels.
Results in decreased cytoplasmic calcium concentration and smooth muscle relaxation.
How does phosphodiesterase work?
Returns penis to flaccid state
Example if Phosphodiesterase inhibitor
Sildenafil (Viagra)
Define erectile dysfunction
The persistent inability to attain and maintain an erection sufficient to permit satisfactory sexual performance.
Risk factors of ED
Lack of exercise Obesity Smoking Hypercholestrolaemia Metabolic syndrome (diabetes at x3 risk)
Surgical cause of ED
Post-radical prostatectomy
Indicators of psychological aetiology
Sudden onset of ED
Good nocturnal and early morning erections
Situational ED
Younger patient
Assessment of ED
Bloods and Examination often normal Sexual Hx (International Index for Erectile Function) Physical examination - BP, HR, Hepatosplenomegaly, Genitalia (Peyronies disease), Prostatic enlargement or cancer, Hypogonadism (small testes or other)
Lab testing of ED
Fasting glucose
Lipid profile
Morning testosterone (if low then perform prolactin, FSH, LH)
Treatment of ED (non-pharmacological)
Identify and treat reversible causes of ED
Lifestyle and risk factor modification
Patient and partner involvement in education and counselling
When is ED curable
Hormonal causes such as testosterone deficiency, thus testosterone replacement Psychosexual counselling (variable results)
Treatment of ED (pharmacological)
Lifestyle and risk factor modification should accompany ED treatment. If a cause of ED is detected it should be treated first.
1st line = Phosphodiesterase (PDE5) inhibitors
2nd line = Apomorphine SL; Intracavernous injections; Intraurethral alprostadil; vacuum devices
Describe physiology of first line therapy of ED
PDE5 inhibitors result in increased arterial blood flow, vasodilatation, and erection
Action on Nitric oxide
3 PDE5 inhibitors have been approved. Not initiators of erections – require sexual stimulation
