The five basic elements necessary for pregnancy are all equally important and indispensable:

  • Healthy sperm
  • Healthy egg cells
  • Unobstructed fallopian tubes (where sperm meets the egg)
  • High-quality sperm that can fertilize the egg
  • A healthy embryo that can implant in the uterus

Sperm

Sperm contributes half of the genetic material to the offspring, known as “DNA.” In simple terms, half of a child’s traits—such as appearance—are determined by the father who provides the sperm.

Sperm is produced in the seminiferous tubules within the testes. Its production is regulated by the hypothalamus-pituitary endocrine axis and further influenced by autocrine and paracrine signals within the testes. The process of sperm production begins with the most primitive germ cells, known as spermatogonia. In adult males, these cells continuously undergo mitosis and growth to become primary spermatocytes. These spermatocytes then undergo meiosis: DNA is replicated once and then divided twice, resulting in four spermatids. These spermatids go through a complex process of morphological changes, transforming from round cells into streamlined sperm with highly condensed nuclei, forming acrosomes and shedding excess cytoplasm, ultimately becoming motile sperm that resemble tiny tadpoles.

Each sperm contains a haploid set of chromosomes, meaning the chromosome count is halved. Therefore, the father contributes only half of the genetic material necessary to form a baby, with the other half coming from the mother, which will be discussed later.

The entire process from spermatogonia to mature sperm takes 2 to 3 months. Because sperm production is continuous, a man’s lifestyle and environment can easily affect the quantity and quality of sperm at any stage. A healthy male produces approximately 10^12 (one trillion) sperm throughout his life.

Sperm is sensitive to heat, which is why the testes are located outside the body in the scrotum. If the testes remain inside the abdominal cavity after birth, as is the case with cryptorchidism (undescended testicles), it can damage sperm production and increase the risk of cancer. Therefore, surgical correction of cryptorchidism should be performed as early as possible.