The Penile Shaft is Composed of Erectile Tissues That Engorge With Blood During Arousal
In order to achieve and maintain an erection, there must be sufficient blood flow into the penile shaft. The penile shaft is composed of three main chambers filled with spongy erectile tissue called corpora cavernosa. These chambers are surrounded by a sheath known as the tunica albuginea. When a man becomes aroused, his brain sends signals to the smooth muscle cells within the walls of these chambers, causing them to relax and allow for increased blood flow. As blood flows in, it fills up the spaces between the cells, creating pressure that pushes against the walls of the chambers. This results in an increase in size and firmness of the penis.
During sexual stimulation, the arteries carrying oxygenated blood to the penis become engorged with blood, while veins carrying deoxygenated blood away from the penis contract. This causes a reduction in venous outflow, which creates a vacuum effect that draws more blood into the penis. Additionally, nerve endings in the corpus cavernosum release nitric oxide, which relaxes the smooth muscle cells and allows even more blood to enter the penis.
As the amount of blood increases, the pressure builds until the penis reaches its maximum size and hardness. At this point, the glans (or head) of the penis may swell slightly and become more sensitive due to increased blood flow. The length and girth of the penis can vary depending on a number of factors such as age, genetics, and overall health. However, when fully erect, most men will experience a significant increase in both dimensions.
It's important to note that not all men achieve full erections every time they are sexually aroused. Various physical and psychological conditions can impact the ability to get or maintain an erection, including cardiovascular disease, diabetes, high blood pressure, stress, anxiety, and depression. Additionally, certain medications like antidepressants, antihistamines, and blood pressure medications can also interfere with normal erectile function. In these cases, it is recommended to seek medical advice for treatment options.