Semen

6 ASCP MLS practice questions on Semen, part of Urinalysis and Body Fluids. The first 6 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   A 31-year-old man is evaluated for infertility. Semen: volume 0.7 mL, pH 6.6, no sperm even after centrifugation, fructose absent. His testes are of normal size. What is the most likely cause?

   1. ALoss of the first part of the ejaculate
   2. BPrimary testicular failure
   3. CCongenital bilateral absence of the vas deferens
   4. DRetrograde ejaculation

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   Answer: C · Congenital bilateral absence of the vas deferens

   Low volume, acid pH and absent fructose show that seminal vesicle fluid, which is alkaline and rich in fructose, is missing; what remains is mainly acidic prostatic fluid. With no sperm, this points to absent or blocked ducts, most often congenital bilateral absence of the vas deferens, in which the seminal vesicles are usually missing or underdeveloped. The condition is linked to CFTR gene variants, so genetic testing and counseling are offered. In testicular failure, volume, pH and fructose are normal, because the glands still work.

   • A: The first portion carries most of the sperm, but the later fructose-rich vesicle fluid would still be present.
   • B: Testicular failure causes azoospermia with normal volume, pH and fructose.
   • D: Retrograde ejaculation is shown by sperm in urine passed after ejaculation; it does not explain an acidic, fructose-free fluid.

2. Question 2 · Easy

   Which gland supplies most of the fructose in semen?

   1. ASeminal vesicles
   2. BEpididymis
   3. CProstate
   4. DBulbourethral glands

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   Answer: A · Seminal vesicles

   The seminal vesicles produce about 60 to 70% of semen volume, including fructose, the main energy source for sperm motility. The prostate adds acidic fluid with citric acid, zinc, acid phosphatase and the enzymes that liquefy the clot. Low or absent fructose points to absent seminal vesicles or a blocked ejaculatory duct. The epididymis is where sperm mature and gain motility.

   • B: The epididymis stores and matures sperm.
   • C: The prostate supplies acid phosphatase, citric acid and the liquefying enzymes.
   • D: Bulbourethral glands add a small amount of alkaline mucus.

3. Question 3 · Easy

   In an eosin-nigrosin vitality stain of semen, live sperm:

   1. AStain pink to red with eosin
   2. BStain only at the acrosome cap
   3. CStay unstained against the dark background
   4. DStain dark purple with nigrosin

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   Answer: C · Stay unstained against the dark background

   Eosin enters sperm whose membranes are damaged, so dead sperm stain pink to red. Live sperm keep the dye out and appear white or bluish-white against the purple nigrosin background. Vitality is checked when motility is low, to tell dead sperm from live sperm that cannot move. Many live but immotile sperm suggest a structural defect of the tail.

   • A: Pink to red sperm have taken up eosin, so they are dead.
   • B: The stain separates dead from live sperm; it does not pick out the acrosome.
   • D: Nigrosin stains the background, not the sperm.

4. Question 4 · Medium

   Many round cells are seen in a semen wet preparation. To tell leukocytes from immature germ cells, the laboratory should use:

   1. AA peroxidase stain
   2. BAn eosin-nigrosin stain
   3. CA seminal fructose test
   4. DA hypo-osmotic swelling test

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   Answer: A · A peroxidase stain

   Round cells in semen may be white cells or immature germ cells (spermatids and spermatocytes), which look alike in a wet preparation. Neutrophils, the main leukocytes in semen, contain peroxidase and stain positive, while germ cells do not. More than 1 x 10^6 leukocytes/mL (1 x 10^9/L) suggests infection or inflammation of the reproductive tract. Many immature germ cells instead suggest a problem with spermatogenesis.

   • B: Eosin-nigrosin separates live from dead sperm.
   • C: Fructose reflects seminal vesicle function.
   • D: The hypo-osmotic swelling test checks the integrity of sperm tail membranes.

5. Question 5 · Medium

   A semen sample has a volume of 2.5 mL and a sperm concentration of 36 x 10^6/mL. The total sperm count per ejaculate is:

   1. A36 x 10^6 sperm
   2. B900 x 10^6 sperm
   3. C90 x 10^6 sperm
   4. D14.4 x 10^6 sperm

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   Answer: C · 90 x 10^6 sperm

   Total sperm count = concentration x volume = 36 x 10^6/mL x 2.5 mL = 90 x 10^6 sperm per ejaculate. The total count reflects sperm output by the testes better than concentration alone, because concentration also depends on how much fluid the glands add. A short abstinence period or a lost first portion lowers the total count. The first portion of the ejaculate carries most of the sperm, so complete collection matters.

   • A: 36 x 10^6 is the concentration per mL, not the total.
   • B: 900 x 10^6 is a tenfold decimal error.
   • D: 14.4 x 10^6 divides the concentration by the volume instead of multiplying.

6. Question 6 · Medium

   Semen results: volume 3.2 mL, pH 7.6, concentration 11 x 10^6/mL (11 x 10^9/L), motility 62% at 1 hour, normal forms 40%. Using ASCP reference ranges, the abnormality is:

   1. AAbnormal morphology (teratozoospermia)
   2. BLow semen volume (hypospermia)
   3. CPoor motility (asthenozoospermia)
   4. DLow sperm concentration (oligozoospermia)

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