Erection Emission and Ejaculation

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Erection, accompanied by increases in the length and width of the penis, is achieved as a result of blood flow into the "erectile tissues" of the penis. These erectile tissues include two paired structures—the corpora cavernosa—located on the dorsal side of the penis, and one unpaired corpus spongiosum on the ventral

Urinary bladder

V v T * Symphysis pubis-

Ductus (vas) deferens



Bulbourethral Gland Inflammation


Glans penis-^


Ampulla of ductus deferens

Seminal vesicle Ejaculatory duct Prostate

Bulbourethral gland Anus

Ductus (vas) deferens

Epididymis Testis


■ Figure 20.21 The organs of the male reproductive system. The male organs are seen here in a sagittal view.

side (fig. 20.22). The urethra runs through the center of the corpus spongiosum. The erectile tissue forms columns that extend the length of the penis, although the corpora cavernosa do not extend all the way to the tip.

Erection is achieved by parasympathetic nerve-induced vasodilation of arterioles that allows blood to flow into the corpora cavernosa of the penis. The neurotransmitter that mediates this increased blood flow is now believed to be nitric oxide (fig. 20.23). Nitric oxide released by parasympathetic axons and produced by the endothelial cells of penile blood vessels activates guanylate cyclase in the vascular smooth muscle cells. Guanylate cyclase catalyzes the production of cyclic GMP (cGMP), which closes Ca2+ channels in the plasma membrane (fig. 20.23). This decreases the cytoplasmic Ca2+ concentration, causing smooth muscle relaxation (chapter 12). The penile blood vessels thereby dilate to increase the blood flow into the erectile tissue, producing an erection.

As the erectile tissues become engorged with blood and the penis becomes turgid, venous outflow of blood is partially occluded, thus aiding erection. The term emission refers to the movement of semen into the urethra, and ejaculation refers to the forcible expulsion of semen from the urethra out of the penis. Emission and ejaculation are stimulated by sympathetic nerves, which cause peristaltic contractions of the tubular system, contractions of the seminal vesicles and prostate, and contractions of muscles at the base of the penis. Sexual function in the male thus requires the synergistic action (rather than antagonistic action) of the parasympathetic and sympathetic systems.

Erection is controlled by two portions of the central nervous system—the hypothalamus in the brain and the sacral portion of the spinal cord. Conscious sexual thoughts originating in the cerebral cortex act via the hypothalamus to control the sacral region, which in turn increases parasympathetic nerve activity to promote vasodilation and erection of the penis. Conscious thought is not required for erection, however, because sensory stimulation of the penis can more directly activate the sacral region of the spinal cord and cause an erection.

Nitric oxide, released in the penis in response to parasympathetic nerve stimulation, diffuses into the smooth muscle cells of blood vessels and stimulates the production of cyclic guanosine monophosphate (cGMP). The cGMP, in turn, causes the vascular smooth muscle to relax, so that blood can flow into the corpora cavernosa (fig. 20.23). This physiology is exploited by sildenafil (trade named Viagra), which can be taken as a pill to treat erectile dysfunction. Sildenafil blocks cGMP phosphodiesterase, an enzyme that functions to break down cGMP. This increases the concentration of cGMP and thus promotes vasodilation, leading to increased engorgement of the erectile spongy tissue with blood and consequently promoting erection (fig. 20.23).


Ductus-(vas) deferens

Urinary bladder


Seminal vesicle


Spermatic cord

Physiology Ejaculation

Spermatic cord

Cremasteric fascia Epididymis Scrotum

Symphysis pubis

Suspensory ligament of penis

Body of penis

Dorsal vein of penis Dorsal artery of penis

Corona glandis Glans penis Prepuce

Deep fascia


Corona Glandis


Skin Areolar tissue

Deep fascia


Dorsal vein of penis Deep dorsal vein of penis Dorsal nerve of penis Dorsal artery of penis Deep artery of penis Corpora cavernosa penis


Corpus spongiosum penis

Internal Structure The Penis


■ Figure 20.22 The structure of the penis. The attachment, blood and nerve supply, and arrangement of the erectile tissue are shown in both longitudinal and cross section.

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  • Toini
    Is there a ligament at the base of the penis?
    9 years ago
  • berylla
    Does the vas deferens pubis?
    9 years ago
  • Kaiju
    What is penile emission and ejaculation?
    8 years ago
  • Eila Olamo
    Where is the The ductus (vas)?
    8 years ago
  • leonardo
    How to activate penish erection?
    8 years ago
  • luwam
    Does figs increase blood flow to penis?
    8 years ago
  • cameron
    What is a side view of a human male of its dick?
    8 years ago
  • Cassidy Ferguson
    What activates the blood vessels in penis?
    8 years ago
  • yohannes
    Where is the gland located on the penis?
    8 years ago
  • celendine
    What controls the blood flow into penile erectile tissue?
    8 years ago
  • patty
    Which tissues are paired dorsal erectile tissues?
    8 years ago
  • Magnus
    Is emission increased blood flow to the penis?
    8 years ago
  • Lavinia
    What mediates erection and ejaculation?
    8 years ago
  • Jacopo
    Where on the skinareolar connective tissue found?
    8 years ago
  • alannah
    What is erection, emission, ejaculation?
    8 years ago
  • miikka
    Where is deep fascia located?
    7 years ago
  • edda esposito
    What controls blood flow into penile erectile tissues?
    7 years ago
  • Gualtiero Beneventi
    Where is the ampulla of vas deferens?
    7 years ago
  • Frank
    What is emission physiology?
    6 years ago
  • millie
    How veins dialate in ejaculation?
    5 years ago
  • sofia
    How to increase vasolidation of penile tissues?
    4 years ago
  • mackenzie
    What is the male emission other than ejaculation?
    4 years ago
    What neurotransmitter causes emission of the penis?
    4 years ago
  • grossman
    What are the physoilogy of erection emision and ejaculation?
    3 years ago
  • sabrina
    Is ejaculation sympathetic?
    3 years ago
  • selam
    Is ejaculation sympathetic or parasympathetic?
    3 years ago
  • colby
    What causes semenal emmission in the penes?
    3 years ago
  • brigitte fisher
    Which sex organ is responsible for penis turgidity?
    2 years ago
  • patrizio
    Is erection sympathetic or parasympathetic?
    2 years ago
  • Sky
    What is the physiology of an erection?
    2 years ago
  • evelyn
    What is emission in anatomy and physiology?
    2 years ago
  • giovanna
    Which nerve responsible for ejaculation of sperm?
    2 years ago
    How to have erection after sperm emission?
    2 years ago
  • willie
    What is emmitted during erection?
    2 years ago
  • nina
    Which blood vessel in the penis allows blood flow to the erectile tissue?
    2 years ago
  • Priamus
    Do all erectile tissues get engorged during erection?
    1 year ago
    What causes male emissions?
    1 year ago
  • Robert
    Is the increase of blood flow to the penis under sympathetic control?
    1 year ago
  • eyob filmon
    How to improve blood flow to penile tissue?
    1 year ago
  • hamza
    What nervous system causes emission in men?
    1 year ago
  • j
    What muscle causes emission?
    1 year ago
    Is the male erection stimulated by the sympathetic nervous system?
    1 year ago
  • Gigliola Nucci
    What muscles that control boners and surting of seman?
    1 year ago
  • Efrem
    How a female causes male penis to get erect and ejaculate videls?
    11 months ago
  • adelia
    Which gases is released by erectile tissues when the penis is stimulated.?
    11 months ago
  • henri
    Which nerves system control erectile of penis and ejaculation?
    10 months ago
    How is the sympathetic nervous system involved in penile erection?
    9 months ago
  • Manuel
    What starts emission stage in ejaculation?
    9 months ago
  • eleleta
    What controlls sperm emission?
    8 months ago
  • jussi
    What is emission in male reproductive system?
    1 month ago

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