Illustration of an erect penis during intercourse. The erection is reflex of the parasympathetic nervous system that occours in case of sexual arousal. It is necessary for penetration with the penis. It is ended by ejaculation which is regulated by the sympathetic nervous system. Biologically, the goal is the fertilization of an egg cell.
The illustration shows a sagittal section during intercourse of a person with a vagina and a person with a penis. The anatomical proportions are visible.
Inside the erect penis the corpora cavernosum and spongiosum penis with the urethra and glans penis are visible. These structures are erectile tissue. The scrotim and the testicles are also pictured. The penis fills the vagina and ends with its tip at the cervix.
A few bones and parts of the intestine and other tissue and the bladder and prostate are shown.
(black and white)