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EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
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2. The Male Reproductive System

Review of MEDICAL EMBRYOLOGY Book by BEN PANSKY, Ph.D, M.D.
  1. The testes are the male gonads, normally found outside the body proper in a sac called the scrotum.
    1. THE TESTES ARE EGG-SHAPED ORGANS about 3.7-5.0 cm (1.5-2.0 inch) in length and about 2.5 cm (1 inch) in each of its other dimensions.
    2. THE MASS OFTHE SPECIALIZED TESTICULAR TISSUE is arranged in tubules, in the walls of which the spermatozoa are produced.
    3. THE INTERSTITIAL CELLS between the tubules are small groups of cells that secrete the hormone testosterone.
  2. The male tubes are tubes for carrying the spermatozoa. They begin with the seminiferous tubules inside the testes themselves. From these tubules, the spermatozoa are collected and transported via the following tubes (in order):
    1. THE STRAIGHT TUBULES to the rete testis to the efferent ductules of the epididymis
    2. THE EPIDIDYMIS is a coiled, C-shaped, long tube (600 cm or 20 feet) found inside the scrotal sac. It has a head, at the upper pole of the testis; a body, found on the back of the testis; and a tail, attached to the lower pole of the testis
      1. While temporarily stored here, the spermatozoa mature and become mobile
      2. The coiled epididymal ducts all empty into a single duct, the ductus epididymis which itself becomes more and more convoluted as it forms the body and tail of the epididymis. The ductus is 0.4 mm in diameter and about 5 m (21 feet) long
    3. THE DUCTUS (VAS) DEFERENS OF THE SPERMATIC CORD is a continuation of the ductus epididymis and is 2-3 mm in diameter and only 45 cm (18 inches) long. It runs in the spermatic cord, through the inguinal canal, accompanied by fascias, the cremaster muscle of the cord, the testicular artery, the pampiniform plexus of veins, and the lymph and nerve supply of the testis and epididymis
      1. The ductus curves behind the urinary bladder, over the ureter, and just medial to the seminal vesicl Each ductus dilates into an ampulla and joins with the seminal vesicle (one on each side) to form the ejaculatory duct
    4. THE EJACULATORY DUCTS (2.0 cm or 0.8 inch) pierce the glandular tissue of the prostate to open into the prostatic urethra at the urethral crest
  3. Auxiliary male genital glands
    1. THE SEMINAL VESICLES are tortuous muscular tubes with small outpouchings and are about 7.5 cm (3 inch) long and are in back of the bladder. They produce a thick, yellow secretion that forms most of the semen volume and helps nourish the spermatozoa
    2. THE PROSTATE GLAND is a pyramid-shaped fibromuscular gland about 3.7 cm (1.5 inches) in diameter and is wrapped around the urethra at the base of the urinary bladder
      1. Tubules from the gland enter the prostatic urethra and add prostatic secretion to the sex cells as they pass through. This helps maintain motility
    3. THE BULBOURETHRAL OR COWPER'S GLANDS are the largest of the mucus-secreting glands in the male reproductive system and are a pair of pea-shaped organs in the pelvic floor tissue just below the prostate gland. Their ducts empty into the urethra.
      1. Other small urethral glands also secrete mucus into the penile urethra
  4. The urethra and penis
    1. THE URETHRA serves a dual role: conveying urine from the bladder and carrying reproductive cells and their accompanying secretions to the outside
    2. THE EJECTION OF SEMEN is made possible by the erection of the penis. The latter consists of a spongelike tissue containing many blood spaces that are relatively empty during organ flaccidity, but fill with blood and distend on erection
    3. THE PENIS AND SCROTUM are the male external genitalia
    4. THE SEMEN passes from the urethra to the membranous urethra to the penile urethra before it reaches the outside
the male reproductive system: image #1