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Unformatted text preview: During erection, parasympathetic neurons stimulate dilation of the arteries that deliver blood to the corpus cavernosa and spongiosum. As a result, blood collects in these blood vessels and causes the penis to begin to become erect. The developing erection also constricts the exiting veins of the penis. This causes even more erection. Ejaculation occurs when sympathetic neurons stimulate the discharge of sperm and supporting fluids from their various sources. During ejaculation, the sphincter muscle at the base of the urinary bladder constricts, preventing the passage of urine. Spermatogenesis The cells that line the walls of the seminiferous tubules are collectively called spermatogenic cells. Those cells nearest the basement membrane are called spermatogonia. These cells are stem cells —that is, they are capable of continuous division and remain undifferentiated, never maturing into...
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This note was uploaded on 11/10/2011 for the course PT 101 taught by Professor Staff during the Spring '10 term at Texas State.
- Spring '10