Each corpus cavernosum is a hollow tube, its center filled with a spongy network of open spaces, smooth muscle, and small arteries. The central spaces fill with blood during erection, which might make you think they\u2019re the most important part of the enterprise \u2014 these are, after all, the tissues that drugs like Viagra target. But you\u2019d be ignoring another, equally important element. Blood, by itself, can\u2019t raise anything\u2019s pressure: it needs to push against something. And the only thing it can push against is the corpora\u2019s thick outer wall.<\/p>\n

The wall of the corpora cavernosa, called the tunica albuginea<\/em>, isn\u2019t your average sheet of connective tissue. Like other connective tissues that surround and separate organs, it\u2019s mostly made of a protein called collagen. But in each layer of the tunica albuginea, those collagen fibres are densely packed and highly organised. Rather than pointing any which way, each strand of collagen lies stacked next to its neighbours, as orderly as the pasta inside a box of spaghetti.<\/p>\n

Primed for Action<\/strong><\/p>\n

A penis stays flaccid as long as the smooth muscles inside the vascular spaces are contracted. Contracted muscles keep the tiny arteries inside the erectile tissue squeezed shut, making blood move at a trickle instead of a flow. The lack of blood keeps blood pressure inside the cavernous space low \u2014 lower than the average blood pressure in arteries throughout the rest of the body. And as long as the volume of blood moving through the space stays small, there\u2019s not enough inside the organ to really push on the tunica wall.<\/p>\n

While the wall is relaxed, it\u2019s bunched up like a wadded up sock. The collagen fibres inside the wall are folded up, too \u2014 each fibre looking a bit like a strip of accordion- folded paper. The combination of low blood volume and loose, bunchy tissue gives the penis its \u201cflaccid\u201d character: flexible, a bit stretchy, and considerably smaller than when it\u2019s deployed for sex.<\/p>\n

Rapid Deployment<\/strong><\/p>\n

Everything changes when the brain flips on \u2018arousal.\u2019 The signal that told smooth muscle to squeeze down vanishes, arteries open up, and blood rushes into the central cavernous spaces, eager to equalise the pressure difference between penis and body. As blood enters, it fills the available space and starts to push on the wall.<\/p>\n

The wall doesn\u2019t push back. Instead, it stretches as the collagen fibres inside of it expand and unfold. As the tunica albuginea expands outward, it squeezes off the drainage veins that leave the corpora cavernosa, trapping blood inside and increasing the penis\u2019s length and girth.<\/p>\n

Brake for Erection<\/strong><\/p>\n

Obviously, this process doesn\u2019t go on forever. There\u2019s a stop point, a stable size where the penis will max out its growth. That point comes when the collagen fibres in the wall fully unfold.<\/p>\n

A collagen fibre is like a steel cable; if you pull on its ends, it will resist (and transmit) that force. And like steel, collagen is very stiff when it\u2019s fully loaded. So while the folded<\/em> collagen fibres inside the wall didn\u2019t resist the push of blood filling the penis, once all those folds are gone the extended<\/em> collagen fibres act like a brake. The wall tissue rapidly becomes very stiff, stops expanding, and pushes back if more blood tries to enter the central space. With no more space to fill, blood pressure inside the corpora rises to match the blood pressure of the rest of the body. Since all of the spaces in both corpora cavernosa are interconnected (remember the beaded curtain?), the pressure inside every part of the structure rises together, making the penis stiffen as a single unit.<\/p>\n

And now it\u2019s ready for action.<\/p>\n

(I will note that this is probably also how the clitoris gets erect \u2014 penis and clitoris are homologous tissues!<\/em>)<\/p>\n","protected":false},"excerpt":{"rendered":"

  Your spam folder is probably full of the offers. (Mine certainly is.) But none of the emails promising to let you \u201cplease your partner\u201d […]<\/p>\n","protected":false},"author":2,"featured_media":2872,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[76,83],"tags":[],"_links":{"self":[{"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/posts\/3246"}],"collection":[{"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/comments?post=3246"}],"version-history":[{"count":1,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/posts\/3246\/revisions"}],"predecessor-version":[{"id":5494,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/posts\/3246\/revisions\/5494"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/costaricasex.com\/wp-json\/"}],"wp:attachment":[{"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/media?parent=3246"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/categories?post=3246"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/costaricasex.com\/wp-json\/wp\/v2\/tags?post=3246"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}