Helicine arteries of penis
Encyclopedia
The helicine arteries of penis are arteries in the penis
. They are found in the corpora cavernosa penis.
They are involved in the process of erection
.
the arteries divide into branches, which are supported and enclosed by the trabeculae. Some of these arteries end in a capillary net-work, the branches of which open directly into the cavernous spaces; others assume a tendril-like appearance, and form convoluted and somewhat dilated vessels, which were named by Müller "helicine arteries".
contractile state of the intimal cushion
, smooth muscle lying in the center of the artery. This keeps the artery coiled and little blood flow occurs, instead routing to arteriovenous shunts to the deep dorsal vein. Parasympathetic stimulation removes the tonic state and allows vasodilation of the intimal cushion. Blood now pools in the corpus cavernosa, resulting in erection. The valves prevent backflow in the now-tortuous route through the cavernosa.
This parasympathetic relaxation response is mediated by a release of NO
and is the primary target of Viagra. Viagra inhibits a key phosphodiesterase
that reduces the effect of NO. NO binds to the receptors of the enzyme guanylate cyclase, which results in increased levels of cGMP
. cGMP has a very short half-life, and blocking PDE5
results in vasodilation even with small amounts or no stimulation.
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
. They are found in the corpora cavernosa penis.
They are involved in the process of erection
Erection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
.
Anatomy
On entering the cavernous structure from the deep artery of the penisDeep artery of the penis
The deep artery of the penis , one of the terminal branches of the internal pudendal, arises from that vessel while it is situated between the two fasciæ of the urogenital diaphragm ....
the arteries divide into branches, which are supported and enclosed by the trabeculae. Some of these arteries end in a capillary net-work, the branches of which open directly into the cavernous spaces; others assume a tendril-like appearance, and form convoluted and somewhat dilated vessels, which were named by Müller "helicine arteries".
Clinical significance
These arteries have two unique features: an intimal cushion and valves. Sympathetic stimulation maintains a tonicTonic (physiology)
Tonic in physiology refers to a physiological response which is slow, and may be graded. This term is typically used in opposition to a fast response...
contractile state of the intimal cushion
Intimal cushion
The intimal cushion is smooth muscle in the center of arteries that paradoxically keep the artery patent by serving as valves. It is present in Helicine arteries of penis and in the patent ductus arteriosus....
, smooth muscle lying in the center of the artery. This keeps the artery coiled and little blood flow occurs, instead routing to arteriovenous shunts to the deep dorsal vein. Parasympathetic stimulation removes the tonic state and allows vasodilation of the intimal cushion. Blood now pools in the corpus cavernosa, resulting in erection. The valves prevent backflow in the now-tortuous route through the cavernosa.
This parasympathetic relaxation response is mediated by a release of NO
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
and is the primary target of Viagra. Viagra inhibits a key phosphodiesterase
Phosphodiesterase
A phosphodiesterase is any enzyme that breaks a phosphodiester bond. Usually, people speaking of phosphodiesterase are referring to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below...
that reduces the effect of NO. NO binds to the receptors of the enzyme guanylate cyclase, which results in increased levels of cGMP
Cyclic guanosine monophosphate
Cyclic guanosine monophosphate is a cyclic nucleotide derived from guanosine triphosphate . cGMP acts as a second messenger much like cyclic AMP...
. cGMP has a very short half-life, and blocking PDE5
CGMP specific phosphodiesterase type 5
cGMP-specific phosphodiesterase type 5 is an enzyme from the phosphodiesterase class. It is found in various tissues, most prominently the corpus cavernosum and the retina....
results in vasodilation even with small amounts or no stimulation.