I don't think the penis has any muscle tissue in it at least not muscle that we can exert influence over. Areas surrounding the base of the penis do contain muscles that can be contracted.
erectile tissue
n.
Tissue with numerous vascular spaces that may become engorged with blood.
http://medical-dictionary.thefreedictionary.com/erectile+tissue
Erectile tissue is a special kind of tissue that swells and grows bigger, simply because blood flows into it, and can't get out. Erectile tissue has arteries that can carry blood into it, large spaces that can be filled with the trapped blood, and veins that can be blocked to trap the blood inside. In the human, you mainly find erectile tissue in the penis, in the clitoris.
http://www.abc.net.au/science/k2/homework/s95609.htm
The Structure of the Penis. The penis is composed of the following structures:
* Two parallel columns of spongy tissue called the corpus cavernosa, or erectile bodies.
* A central spongy chamber called the corpus spongiosum, which contains the urethra, the tube that carries urine from the bladder through the penis.
These structures are made up of erectile tissue . Erectile tissue is rich in tiny pools of blood vessels called cavernous sinuses . Each of these vessels are surrounded by smooth muscles and supported by elastic fibrous tissue composed of a protein called collagen .
Erectile Function and Nitric Oxide. The penis is either flaccid or erect depending on the state of arousal. In the flaccid, or unerect, penis, the following normally occurs:
* Small arteries leading to the cavernous sinuses contract, reducing the inflow of blood.
* The smooth muscles regulating the many tiny blood vessels also stay contracted, limiting the amount of blood that can collect in the penis.
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Erectile tissue is also found in the nose and in the ear.
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