Campbell-Walsh Urology, 11th Edition

PART V

Reproductive and Sexual Function

22

Male Reproductive Physiology

Paul J. Turek

Questions

  1. Embryologically, the vas deferens is derived from what developmental structure?
  2. Müllerian ducts
  3. Wolffian ducts
  4. Urogenital ridge
  5. Gubernaculum testis
  6. Metanephros
  7. The bulk of testicular volume in the adult human testicle is composed of:
  8. Leydig cells.
  9. Sertoli cells.
  10. spermatogenic cells.
  11. myoid cells.
  12. vascular endothelium.
  13. Which of the following anterior pituitary hormones directly influences testicular function?
  14. Estradiol and adrenocorticotropic hormone (ACTH)
  15. Follicle-stimulating hormone (FSH) and estradiol
  16. Luteinizing hormone (LH) and FSH
  17. Testosterone and LH
  18. Thyroid-stimulating hormone (TSH) and testosterone
  19. The bulk of the ejaculate volume is derived from:
  20. the epididymides.
  21. the Cowper gland.
  22. the seminal vesicles.
  23. the testes.
  24. the prostate.
  25. Which of the following veins are responsible for varicoceles?
  26. The hypogastric veins
  27. The deferential veins
  28. The internal iliac veins
  29. The internal spermatic veins
  30. The cavernosal veins
  31. A 25-year-old body builder eschews the merits of "natural" bodybuilding and uses injectable anabolic steroids regularly to maximize muscle bulk. His fertility potential would be expected to be:
  32. normal, because exogenous testosterone does not impair production of endogenous testosterone.
  33. low, because exogenous testosterone stimulates pituitary production of FSH and LH.
  34. low, because exogenous testosterone inhibits pituitary production of FSH and LH.
  35. low, because exogenous testosterone is not as potent as endogenous testosterone at nurturing spermatogenesis.
  36. normal, because intratestis testosterone concentrations are 50 times higher than serum levels, whether or not the blood contains exogenous testosterone.
  37. Tight junctions between which testis cell types are structurally integral to the blood-testis barrier?
  38. Sertoli-Sertoli cells
  39. Myoid-Leydig cells
  40. Spermatids-Sertoli cells
  41. Leydig-Leydig cells
  42. Endothelial-endothelial cells
  43. A 26-year-old man has a 1-year history of infertility and abnormal bulk semen parameters (low sperm concentration and motility). Hormonal testing reveals normal testosterone, FSH, and LH levels, but an elevated serum prolactin level (20 ng/dL, normal level, 2-18 ng/dL). The most likely cause of his elevated prolactin level is:
  44. pituitary microadenoma.
  45. pituitary macroadenoma.
  46. drug polypharmacy.
  47. stressful blood draw.
  48. timing of blood draw relative to sleep-wake cycle.
  49. What is the normal developmental progression of spermatogenic cells?
  50. Sertoli, spermatogonia, spermatocyte
  51. Spermatocyte, spermatogonia, spermatid
  52. Spermatid, Sertoli, spermatocyte
  53. Spermatogonia, spermatid, spermatocyte
  54. Spermatogonia, spermatocyte, spermatid
  55. Which hormone is the primary feedback inhibitor of pituitary LH secretion?
  56. Inhibin
  57. Testosterone
  58. Activin
  59. Prolactin
  60. Sertolin
  61. Which of the following testicular volumes would be considered low for an adult human of any ethnicity?
  62. 12 mL
  63. 18 mL
  64. 22 mL
  65. 30 mL
  66. 40 mL
  67. Major anatomic regions of the epididymis include:
  68. septa, efferent ductules, and corpus
  69. globus minor, ductus deferens, and cauda.
  70. rete testis, efferent ductules, and caput.
  71. efferent ductules, caput, and cauda.
  72. caput, corpus, and cauda
  73. Which of the following is characteristic of meiosis?
  74. It is a process that occurs in all somatic cells.
  75. The chromosome number is maintained with cell division.
  76. It is a process that occurs only in gametes.
  77. There is no chromosomal crossing over.
  78. Daughter cells are identical to parent cells.
  79. When do testosterone peaks occur during a human male's life?
  80. First trimester gestation, 2 months of age, puberty
  81. 1 year of age, puberty, 50 years of age
  82. Puberty, 30 years of age, 70 years of age
  83. Puberty, 50 years of age
  84. First trimester gestation, puberty, 70 years of age
  85. With chronic obstruction, sperm motility is highest in what region of the epididymis?
  86. Rete testis
  87. Efferent ducts
  88. Caput epididymis
  89. Corpus epididymis
  90. Cauda epididymis
  91. What occurs during spermiogenesis?
  92. Division of spermatogonia to form primary spermatocytes
  93. Division of primary spermatocytes to form secondary spermatocytes
  94. Cellular remodeling and nuclear compaction of spermatid DNA
  95. Cytokinesis
  96. Meiosis
  97. Changes to sperm during epididymal transit include:
  98. decreased motility.
  99. sulfhydryl reduction.
  100. decreased phospholipid content.
  101. reduced membrane rigidity.
  102. increased capacity for glycolysis.
  103. Which of the following germ cell types is considered a true stem cell?
  104. Elongating spermatids
  105. Primary spermatocytes
  106. Round spermatids
  107. Secondary spermatocytes
  108. Type A spermatogonia
  109. During their development within the male reproductive tract before ejaculation, sperm spend the majority of time in which organ?
  110. Epididymis
  111. Ejaculatory ducts
  112. Seminal vesicle
  113. Testis
  114. Urethra
  115. The sperm region containing mitochondria is the:
  116. tail.
  117. head.
  118. acrosome.
  119. midpiece.
  120. axoneme.
  121. Which of the following statements about testosterone is the most accurate?
  122. It is produced by the exocrine testis.
  123. It exists mainly in the unbound or "free" form in the circulation.
  124. It is regulated by follicle-stimulating hormone.
  125. Its production is increased by excess prolactin.
  126. One of its metabolites is dihydrotestosterone (DHT).
  127. Processes that must occur for a sperm to normally fertilize an egg include all of the following EXCEPT:
  128. development of motility.
  129. acrosome reaction.
  130. capacitation.
  131. zona pellucida binding.
  132. sexual intercourse.
  133. After ejaculation the contents of the vas deferens are:
  134. returned to the seminal vesicles.
  135. maintained in the ampulla.
  136. released into the ejaculatory ducts.
  137. propelled back into the epididymis.
  138. released into the bladder.

Answers

  1. b. Wolffian ducts.Müllerian ducts regress in the male. The indifferent gonad migrates to the urogenital ridge to become the testis. The gubernaculum testis is associated with the testis.
  2. c. Spermatogenic cells.In humans, interstitial tissue takes up 20% to 30% of the total testicular volume, whereas germ line cells constitute the remainder (70%-80%).
  3. c. Luteinizing hormone (LH) and FSH.Estradiol and testosterone are not anterior pituitary hormones, although they influence pituitary function. TSH and ACTH are derived from the anterior pituitary but do not act directly on the testicle.
  4. c. The seminal vesicles. At least 65% to 70% of ejaculate volume is derived from the seminal vesicles, with the remainder from the vas deferens (sperm) and prostatic secretions.Periurethral Cowper glands also contribute a small amount of fluid to the ejaculate.
  5. d. The internal spermatic veins.The pampiniform plexus of veins forms from the internal spermatic or gonadal veins. Deferential veins follow the vas deferens and empty into the hypogastric veins. These veins are spared during varicocele ligation surgery.
  6. c. Low, because exogenous testosterone inhibits pituitary production of FSH and LH.Negative feedback inhibition maintains homeostatic balance in the pituitary-gonadal axis. Excess testosterone from any source acts on the anterior pituitary to reduce the production of LH and FSH. Without appropriate FSH production, azoospermia results in most men taking anabolic steroids, but the effect varies based on the dose, frequency, and duration of the drugs.
  7. a. Sertoli-Sertoli cells.Sertoli-Sertoli tight junctions are the strongest cell-cell interactions in the body and give the blood-testis barrier its name. They form a high-resistance barrier that prevents the deep penetration of most drugs, molecules, and electron-opaque tracers into the seminiferous epithelium from the testicular interstitium. Sertoli cell tight junctions also segregate premeiotic germ cells (spermatogonia) from meiotic and postmeiotic germ cells.
  8. d. Stressful blood draw.All of the choices can cause elevated serum prolactin levels. However, pathologically high prolactin levels are associated with low LH, FSH, and testosterone levels and reduced semen quality. Because anterior pituitary function is preserved, the elevated prolactin is likely spurious and due to a stressful blood draw. The measurement should be repeated with a blood draw at least 2 hours after awakening from sleep.
  9. e. Spermatogonia, spermatocyte, spermatid.Proceeding from the least to the most differentiated, they are named dark type A spermatogonia (Ad); pale type A spermatogonia (Ap); type B spermatogonia (B); preleptotene primary spermatocytes (R); leptotene primary spermatocytes (L); zygotene primary spermatocytes (z); pachytene primary spermatocytes (p); secondary spermatocytes (II); and Sa, Sb1, Sb2, Sc, Sd1, and Sd2 spermatids.
  10. b. Testosterone. Inhibin and activin regulate FSH secretion. Prolactin, in excess, can downregulate LH but is not the primary regulator of LH secretion.
  11. a. 12 mL. Although ethnic and racial differences do exist, a normal testis volume is generally above 16 mL and averages 20 mL.
  12. e. Caput, corpus, and cauda.Anatomically, the epididymis is divided into three regions: the caput, the corpus, and the cauda epididymis. On the basis of histologic criteria, each of these regions can be subdivided into distinct zones separated by transition segments.
  13. c. It is a process that occurs only in gametes. Crossing over of sister chromatids, exchange of genetic material, creation of unique daughter cells, and halving of chromosomal number are the hallmarks of meiosis.Meiosis occurs only in gametes whereas mitosis occurs in somatic cells.
  14. a. First trimester gestation, 2 months of age, puberty. Testosterone peaks occur during early gestation and at approximately 2 months of age; a third spike occurs at puberty.Testosterone levels fall about 1%/year after age 30 and may fall more dramatically in the seventh and eighth decades of life.
  15. c. Caput epididymis.Studies in men with congenital absence of the vas deferens or epididymal obstruction from vasectomy generally report better sperm motility in caput versus cauda epididymal sperm.
  16. c. Cellular remodeling and nuclear compaction of spermatid DNA.In spermiogenesis, massive remodeling of postmeiotic germ cells (spermatids) occurs that involves nuclear compaction, tail and acrosome development, and cytoplasmic stripping of the mature germ cell. This is a postmeiotic process, and cell division, or cytokinesis, does not occur.
  17. e. Increased capacity for glycolysis.Sperm undergo many metabolic changes during epididymal transit. Animal studies describe an increased capacity for glycolysis, changes in intracellular pH and calcium content, modification of adenylate cyclase activity, and alterations in cellular phospholipid and phospholipid-like fatty acid content. Sperm motility increases with epididymal transit.
  18. e. Type A spermatogonia. Type A spermatogonia are the only true stem cell in the testis because they can either self-renew or differentiate to become sperm.All of the other cell types listed do not share this dual potential.
  19. d. Testis. Sperm spend 45 to 60 days developing in the testis and 2 to 12 days in the epididymis.They are not routinely found in the seminal vesicle, and spend only seconds in the ejaculatory ducts and urethra during ejaculation.
  20. d. Midpiece.The middle segment of sperm is highly organized, consisting of helically arranged mitochondria that surround a set of outer dense fibers and the 9 + 2 microtubular structure of the axoneme. The sperm head contains an acrosome and the nucleus, and the tail contains the axoneme.
  21. e. One of its metabolites is dihydrotestosterone (DHT).Testosterone is produced by the endocrine testes, exists mainly in bound forms in plasma, and is regulated by LH, not FSH. Testosterone is converted to DHT in target tissue by 5-α reductase. It is also converted to estrogen by aromatase enzymes. Excess prolactin decreases testosterone production.
  22. e. Sexual intercourse.For physiologic egg fertilization, all of the processes listed must occur. Intrauterine insemination (IUI) can replace sexual intercourse and improve the odds of natural conception. The process of in vitro fertilization (IVF)–intracytoplasmic sperm injection (ICSI) avoids many of these physiologic processes by simply injecting a sperm from any reproductive-tract source into a mature oocyte or egg.
  23. d. Propelled back into the epididymis.Studies have shown that after sexual stimulation or ejaculation, the contents of the vas deferens are propelled back toward the cauda epididymis, because of differences in the amplitude, frequency, and duration of vas deferens contractility along its length.

Chapter review

  1. The steroid hormones testosterone, dihydrotestosterone, and estradiol are translocated to nuclear DNA recognition sites and regulate the transcription of target genes.
  2. The hypothalamus is anatomically linked to the pituitary gland by both a portal vascular system and neuronal pathway. The hypothalamic hormone GnRH (sometimes called LHRH) stimulates the secretion of luteinizing hormone and follicle-stimulating hormone.
  3. GnRH output exhibits three types of rhythmicity: (1) seasonal, peaking in the spring; (2) circadian, peaking in the early morning; and (3) pulsatile, periodic peaks per 24 hours. The importance of pulsatile GnRH secretory pattern is demonstrated when a GnRH agonist is given; this eliminates the pulsatile activity and therefore suppresses GnRH output.
  4. Both androgens and estrogens regulate LH secretion through negative feedback.
  5. Increased levels of prolactin abolish gonadotropin pulsatility by interfering with the episodic GnRH release, thus causing a reduction in LH and FSH.
  6. Testosterone is metabolized to dihydrotestosterone (5-α reductase) and estradiol (aromatase).
  7. Sertoli cells produce inhibin, which inhibits FSH, and activin, which stimulates FSH. The presence of these hormones accounts for the relatively secondary independence of FSH from GnRH secretion. Sertoli cells produce androgen-binding protein, which maintains high levels of androgen in the seminiferous tubules and epididymis.
  8. Negative feedback for testosterone occurs at the hypothalamus; for estrogens, it occurs at the pituitary.
  9. The SRY (sex-determining region Y gene) on the short arm of the Y chromosome is a critical gene for sex determination.
  10. Dihydrotestosterone masculinizes the external genitalia; müllerian-inhibiting substance prevents müllerian duct development, that is, the uterus, fallopian tubes, and proximal third of the vagina.
  11. A slow but progressive decline in testosterone production occurs with age > 30 years.
  12. Androgen production during the early male neonate's life is thought to hormonally imprint the hypothalamus, liver, and prostate.
  13. The blood-testis barrier is more appropriately termed blood-seminiferous tubule barrier; it allows sperm development to occur in an immunologically privileged way.
  14. An insult to the testes, such as biopsy, torsion, or trauma, will not induce anti-sperm antibodies if the event occurs before puberty.
  15. The X chromosome appears to be important for spermatogenesis.
  16. The azoospermic factor region (AZF) is located on the long arm of the Y chromosome. Deletions in this region are found in some patients with abnormal spermatogenesis. Microdeletions in the AZF region are subdivided into a, b, and c. Sperm may be found in AZFc microdeletions but not in AZFa and AZFb.
  17. With paternal age, there are increases in structural chromosomal abnormalities in sperm and autosomal-dominant mutations leading to specific (sentinel) phenotypes in offspring.
  18. Lymph from the caput and corpus epididymis travels the same route as that for the testes. Lymph from the cauda epididymis joins the vas deferens and terminates in the external iliac nodes. There is a blood-epididymis barrier that extends from caput to cauda epididymis.
  19. The epididymis serves to transport sperm, store it, increase fertility, and promote motility maturation. Epididymal function is temperature and androgen (DHT) dependent. Sperm fertility maturation is achieved at the level of the late corpus or early cauda epididymis.
  20. Semenogelin, a component of semen that results in semen coagulation, is produced in the seminal vesicle. Seminal vesicle secretions have an alkaline pH and contain antioxidant enzymes, fructose, vitamin C, flavins, and prostaglandins.
  21. At least 65% to 70% of ejaculate volume is derived from the seminal vesicles,
  22. Testosterone peaks occur during early gestation and at approximately 2 months of age, and a third spike occurs at puberty.
  23. Sperm spend 45 to 60 days developing in the testis and 2 to 12 days in the epididymis.