Anatomy & Physiology

Anatomy & Physiology Study Guide contains a thick layer of smooth muscle. Peristaltic contractions in this layer propel spermatozoa and fluid along the duct, which is lined by a pseudostratified ciliated columnar epithelium. The ductus deferens can store spermatozoa for several months, in addition to transporting spermatozoa. The junction of the ampulla with the duct of the seminal gland marks the start of the ejaculatory duct . The Urethra In males, the urethra extends 18–20 cm (7–8 in.) from the urinary bladder to the tip of the penis. It is divided into spongy, prostatic, and membranous regions. The male urethra is a passageway used by both the reproductive and urinary systems. The Accessory Glands The seminiferous tubules and the epididymis contribute fluids that account for only about five percent of the volume of semen. The fluid component of semen comes from many glands. Important glands include the seminal glands, the prostate gland, and the bulbo-urethral glands, all of which occur only inmales. Among the major functions of these glands are activating spermatozoa; providing the nutrients spermatozoa need for motility; propelling spermatozoa and fluids along the reproductive tract, mainly by peristaltic contractions; and producing buffers that counteract the acidity of the urethral and vaginal environments. The seminal glands, also called the seminal vesicles , are extremely active secretory glands with an epithelial lining that contains extensive folds. Sixty percent of the volume of semen comes from the seminal vesicles. The secretions of the seminal glands are slightly alkaline in order to aid in neutralizing acids in the secretions of the prostate gland and within the vagina. When mixed with the secretions of the seminal glands, previously inactive but functional spermatozoa undergo the first step in capacitation and begin beating their flagella, becoming highly motile. The prostate gland is a small, muscular, rounded organ that produces prostatic fluid, a slightly acidic solution that contributes 20–30 percent of the volume of semen. Prostatic secretions are ejected into the prostatic urethra by peristaltic contractions of the muscular prostate wall. The paired bulbourethral glands , or Cowper glands, are situated at the base of the penis. The duct of each gland travels alongside the penile urethra for 3–4 cm (1.2–1.6 in.) before emptying into the urethral lumen. The bulbo-urethral glands are compound tubular mucous glands that secrete a thick, alkaline mucus. The secretion helps neutralize any urinary acids that may remain in the urethra, and it lubricates the glans, or tip of the penis. Semen A typical ejaculation releases 2–5 mL of semen. If problems with the prostate gland or seminal glands exist, an abnormally low volume of semen may result. The volume of fluid produced by an ejaculation, called the ejaculate, typically contains spermatozoa, seminal fluid, and enzymes. The External Genitalia The male external genitalia consist of the scrotum and penis. The penis is a tubular organ through which the distal portion of the urethra passes. It functions in both the reproductive system and urinary system by introducing semen into the female's vagina during sexual intercourse and by conducting urine to the exterior, respectively. The penis is divided into three regions: the root, the Achieve Page 342 of 368 ©2018