| Helicine arteries of penis | |
|---|---|
 Diagram of the arteries of the penis. | |
| Details | |
| Identifiers | |
| Latin | arteriae helicinae penis |
| TA98 | A09.4.01.024 |
| TA2 | 4351 |
| FMA | 75410 |
| Anatomical terminology | |
The helicine arteries of penis are arteries in the penis. They are found in the corpora cavernosa penis. [1]
On entering the cavernous structure from the deep artery of the penis 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 Rosenmüller "helicine arteries".
These arteries have two unique features: an intimal cushion and valves. Sympathetic stimulation maintains a tonic contractile state of the intimal cushion, a 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 corpora 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 nitric oxide (NO). NO binds to the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP). cGMP in turn triggers relaxation of the smooth muscle and results in dilation of blood vessels. This signal is terminated when cGMP is broken down by the enzyme cGMP specific phosphodiesterase type 5 (PDE5), the enzyme that is targeted by sildenafil and other drugs that treat erectile dysfunction. By preventing PDE5 from breaking down cGMP, the effects of NO are amplified and vasodilation occurs, thus resulting in increased penile erection.
Priapism is a condition in which a penis remains erect for hours in the absence of stimulation or after stimulation has ended. There are three types: ischemic (low-flow), nonischemic (high-flow), and recurrent ischemic (intermittent). Most cases are ischemic. Ischemic priapism is generally painful while nonischemic priapism is not. In ischemic priapism, most of the penis is hard; however, the glans penis is not. In nonischemic priapism, the entire penis is only somewhat hard. Very rarely, clitoral priapism occurs in women.
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
Erectile tissue is tissue in the body with numerous vascular spaces, or cavernous tissue, that may become engorged with blood. However, tissue that is devoid of or otherwise lacking erectile tissue may also be described as engorging with blood, often with regard to sexual arousal.
Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). cGMP acts as a second messenger much like cyclic AMP. Its most likely mechanism of action is activation of intracellular protein kinases in response to the binding of membrane-impermeable peptide hormones to the external cell surface. Through protein kinases activation, cGMP can relax smooth muscle. cGMP concentration in urine can be measured for kidney function and diabetes detection.
The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.
Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, which is the narrowing of blood vessels.
In haemodynamics, the body must respond to physical activities, external temperature, and other factors by homeostatically adjusting its blood flow to deliver nutrients such as oxygen and glucose to stressed tissues and allow them to function. Haemodynamic response (HR) allows the rapid delivery of blood to active neuronal tissues. The brain consumes large amounts of energy but does not have a reservoir of stored energy substrates. Since higher processes in the brain occur almost constantly, cerebral blood flow is essential for the maintenance of neurons, astrocytes, and other cells of the brain. This coupling between neuronal activity and blood flow is also referred to as neurovascular coupling.
Vasospasm refers to a condition in which an arterial spasm leads to vasoconstriction. This can lead to tissue ischemia and tissue death (necrosis). Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to post-operative stroke and death especially after aneurysmal subarachnoid hemorrhage. Vasospasm typically appears 4 to 10 days after subarachnoid hemorrhage.
A phosphodiesterase type 5 inhibitor is a vasodilating drug that works by blocking the degradative action of cGMP-specific phosphodiesterase type 5 (PDE5) on cyclic GMP in the smooth muscle cells lining the blood vessels supplying various tissues. These drugs dilate the corpora cavernosa of the penis, facilitating erection with sexual stimulation, and are used in the treatment of erectile dysfunction (ED). Sildenafil was the first effective oral treatment available for ED. Because PDE5 is also present in the smooth muscle of the walls of the arterioles within the lungs, two PDE5 inhibitors, sildenafil and tadalafil, are FDA-approved for the treatment of pulmonary hypertension. As of 2019, the wider cardiovascular benefits of PDE5 inhibitors are being appreciated.
Cyclic guanosine monophosphate-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. It has also been recently discovered to play a vital role in the cardiovascular system.
A corpus cavernosum penis (singular) is one of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis during an erection.
The corpus cavernosum of clitoris is one of a pair of sponge-like regions of erectile tissue of the clitoris. It is made of a sponge-like tissue that fills with blood during erection. This is homologous to the corpus cavernosum penis. The term corpora cavernosa literally means "cave-like bodies".
The Prostatic Plexus is continued from the lower part of the pelvic plexus. It lies within the fascial shell of the prostate.
An atrial natriuretic peptide receptor is a receptor for atrial natriuretic peptide.
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.
An erection is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, and endocrine factors, and is often associated with sexual arousal, sexual attraction or libido, although erections can also be spontaneous. The shape, angle, and direction of an erection vary considerably between humans.
A nitrovasodilator is a pharmaceutical agent that causes vasodilation by donation of nitric oxide (NO), and is mostly used for the treatment and prevention of angina pectoris.
Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm.
Phosphodiesterases (PDEs) are a superfamily of enzymes. This superfamily is further classified into 11 families, PDE1 - PDE11, on the basis of regulatory properties, amino acid sequences, substrate specificities, pharmacological properties and tissue distribution. Their function is to degrade intracellular second messengers such as cyclic adenine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) which leads to several biological processes like effect on intracellular calcium level by the Ca2+ pathway.
Penile ulltrasonography is medical ultrasonography of the penis. Ultrasound is an excellent method for the study of the penis, such as indicated in trauma, priapism, erectile dysfunction or suspected Peyronie's disease.
This article incorporates text in the public domain from page 1251 of the 20th edition of Gray's Anatomy (1918)
