Erections during sleep or upon waking up are known as nocturnal penile tumescence NPT. Such an erection is medically known as nocturnal penile tumescence informally: Anatomical terminology [ edit on Wikidata ]. Thelarche Development Lactation Breastfeeding. Some errors occurred, please try again later.
In fact, around one in ten men will experience recurring impotence problems at some point in their lives. Given the small amount of erectile tissue in a bull's penis , there is little enlargement after erection. A bird penis is different in structure from mammal penises , being an erectile expansion of the cloacal wall and being erected by lymph , not blood.
Erections are common for children and infants, and even occur before birth.
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Views Read View source View history. Erectile dysfunction can occur due to both physiological and psychological reasons, most of which are amenable to treatment. Please enter a comment. Comment cannot be longer than characters. Socially, such erections can be embarrassing if they happen in public or when undesired. Thelarche Development Lactation Breastfeeding. Hypothalamic—pituitary—gonadal axis Hypothalamic—pituitary—prolactin axis Andrology Hormone.