Normal pH of human semen
**Core Concept**
The pH of human semen is a critical factor in fertility, as it affects the function and survival of spermatozoa. Semen pH is slightly alkaline due to the presence of various buffering substances.
**Why the Correct Answer is Right**
The normal pH of human semen ranges from 7.2 to 7.8, with an average pH of approximately 7.4. This alkaline environment is maintained by the secretions of the seminal vesicles, which contribute about 60% of the semen volume. The seminal vesicles secrete a thick, alkaline fluid rich in fructose, which helps to neutralize the acidity of the prostate secretions and maintain an optimal pH for sperm function. The buffering capacity of semen is also enhanced by the presence of bicarbonate ions (HCO3-).
**Why Each Wrong Option is Incorrect**
**Option A:** A pH of 6.0 is too acidic for optimal sperm function and would likely result in reduced fertility.
**Option B:** A pH of 8.0 is too alkaline and may lead to sperm damage and decreased motility.
**Option C:** A pH of 5.5 is extremely acidic and would be incompatible with sperm survival.
**Clinical Pearl / High-Yield Fact**
The pH of semen is a crucial factor in fertility, and any significant deviation from the normal range may be associated with impaired sperm function and reduced fertility.
**Correct Answer: D. 7.4**