Prostate

Found only in men, the prostate is a walnut-sized gland that grows throughout a man’s life and may eventually interfere with or prevent urination by blocking the urethra. The prostate makes a significant contribution to the production and ejaculation of semen during sexual intercourse. Prostate cancer is a common disorder of the prostate that often necessitates the surgical removal of the prostate....

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    Full Prostate Description

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    Anatomy of the Prostate

    Gross Anatomy
    The prostate is a small muscular gland located inferior to the urinary bladder in the pelvic body cavity. It is shaped like a rounded cone or a funnel with its base pointed superiorly toward the urinary bladder. The prostate surrounds the urethra as it exits the bladder and merges with the ductus deferens at the ejaculatory duct.

    Several distinct lobes make up the structure of the prostate:

    • On the anterior end of the prostate are the two lateral lobes, which are rounded and shaped like orange slices when viewed in a transverse section. The lateral lobes are the largest lobes and meet at the midline of the prostate.
    • Posterior and medial to the lateral lobes is the much smaller anterior lobe, a triangle of fibromuscular tissue just anterior to the urethra. The fibromuscular tissue of the anterior lobe contracts to expel semen during ejaculation.
    • The median lobe is found just posterior to the urethra along the midline of the prostate. The median lobe contains the ejaculatory ducts of the prostate.
    • The posterior lobe forms a thin layer of tissue posterior to the median lobe and the lateral lobes.

    Microanatomy
    The prostate contains two main types of tissue: exocrine glandular tissue and fibromuscular tissue.

    • Exocrine glandular tissue in the prostate is epithelial tissue specialized for the secretion of the components of semen. Most of the prostate is made of exocrine glandular tissue, as the prostate’s primary function is the production of semen.
    • Fibromuscular tissue is a mixture of smooth muscle tissue and dense irregular connective tissue containing many collagen fibers. The collagen fibers of the tissue provide strength to the tissue while the smooth muscle permits the tissue to contract to expel fluids. Fibromuscular tissue forms the outermost layer of the prostate and the tissue surrounding the urethra.

    Physiology of the Prostate

    Secretion
    The prostate produces a secretion that makes up a large portion of semen volume. The prostatic secretions are a milky white mixture of simple sugars (such as fructose and glucose), enzymes, and alkaline chemicals. The sugars secreted by the prostate function as nutrition for sperm as they pass into the female body to fertilize ova. Enzymes work to break down proteins in semen after ejaculation to free sperm cells from the viscous semen. The alkaline chemicals in prostatic secretions neutralize acidic vaginal secretions to promote the survival of sperm in the female body.

    Ejaculation


    The prostate contains the ejaculatory duct that releases sperm during ejaculation. The ejaculatory duct opens to allow semen to pass from the ductus deferens into the urethra and eventually out of the body. During orgasm, smooth muscle tissue in the prostate contracts in order to push semen through the urethra.

    Urination
    Urine released from the urinary bladder is carried by the urethra to the body’s exterior. Under normal conditions, urine in the urethra passes through the prostate with no complications whatsoever. The prostate enlarges slowly throughout a man’s lifetime, potentially leading to the restriction or blockage of the urethra by the time a man reaches his fifties or sixties. An enlarged prostate can lead to difficulty urinating or eventually even an inability to urinate. There are many treatments for an enlarged prostate including medications, lifestyle changes, and prostatectomy, the surgical removal of the prostate.

    Prepared by Tim Taylor, Anatomy and Physiology Instructor