🧬 How Sperm is Made — And Why Motility & Shape Matter

🏗️ Where It Starts: The Testes (Testicles)

Sperm production begins in the seminiferous tubules — tiny coiled structures located inside each testicle. These tubules house spermatogonia, the immature sperm stem cells.

Under the influence of two key hormones:

• FSH (Follicle Stimulating Hormone)

• LH (Luteinizing Hormone) — which stimulates Leydig cells to produce testosterone

…spermatogonia begin the process of spermatogenesis.

🔄 Step-by-Step: How Sperm is Created

1. Spermatogonia (stem cells) divide and mature into:

2. Primary spermatocytes, which undergo meiosis (chromosome reduction).

3. These become secondary spermatocytes, then...

4. Spermatids — immature sperm cells with half the genetic material.

5. Finally, spermatids transform into spermatozoa — complete with a head, midpiece, and tail (flagellum).

🕒 This process takes about 72–76 days.

🧪 The Journey Continues: Epididymis & Vas Deferens

Once formed, sperm move into the epididymis, a long coiled tube on the back of the testicle, where they:

• Mature

• Gain motility

• Are stored for ejaculation

When ejaculation occurs, sperm travel through the vas deferens, mix with seminal fluid from the seminal vesicles and prostate gland, and exit via the urethra.

📊 How Sperm Is Evaluated: Motility, Morphology, and More

In fertility clinics, sperm is examined through a semen analysis, which looks at:

1. Sperm Count

• Normal: >15 million/mL

• Low: <15 million/mL (oligospermia)

2. Motility (How they swim)

• Progressive motility: sperm swim in a straight or large circular path — these are the most desirable

• Non-progressive motility: sperm wiggle but don’t move forward

• Immotile: sperm don’t move at all

A normal semen sample should have 40–50% motile sperm, with at least 32% progressive.

3. Morphology (Shape and structure)

Evaluated using Kruger strict criteria:

• Ideal shape: oval head, intact acrosome, midpiece, and tail

• Abnormal morphology can include double heads, short tails, or large vacuoles

A “normal” result may have as little as 4% normal forms — that’s considered good enough for fertilization in most cases.

4. Volume and pH

• Normal volume: 1.5–5 mL per ejaculation

• Normal pH: 7.2–8.0

• Low volume or acidic pH may suggest blockages or gland dysfunction

🧠 Why This Matters in IVF

Even men with low count or abnormal shape can still father children with help from modern technology. Procedures like ICSI (Intracytoplasmic Sperm Injection) allow embryologists to select a single sperm — ideally one that swims well and looks normal — and inject it directly into an egg.

But knowing the quality ahead of time can help tailor treatments and improve success rates.

💡 Did You Know?

• Sperm are one of the few cells that don’t regenerate quickly after damage.

• Antioxidants like zinc, CoQ10, and vitamin C have been shown to improve sperm parameters in some men.