Spermatogenesis Process

Sperm Production in Testicles

• Sperm production occurs in the seminiferous tubules of the testicles.

Leydig Cells

• Leydig cells are located in the interstitial tissue of the testicles and produce testosterone in response to luteinizing hormone (LH).

Testicular Structure

• The testis is divided into 250-300 pyramidal compartments or testicular lobules.
• The tunica albuginea is a layer of fibrous tissue surrounding the testis, providing support and protection.

Embryonic Development

• The testes develop embryonically in the abdomen near the kidneys before moving to the scrotal sac.

Sperm Production Process

• The first part of sperm production involves mainly mitosis and meiosis, known as spermatocytogenesis.
• Spermatogonia act as stem cells, dividing infrequently and giving rise to more rapidly dividing cells.

Meiosis

• The first meiotic prophase is characterized by cells with partially condensed chromosomes in various stages of synapsis and recombination, known as zygotene.
• The second meiotic division involves homologous chromosomes separating and producing secondary spermatocytes.
• The result of the second meiotic division is the formation of haploid spermatids.

Spermatogenesis

• Intercellular bridges allow for free cytoplasmic communication among male germ cells during mitotic and meiotic divisions.
• The pampiniform venous plexus surrounding the testicular artery helps regulate testicular temperature.

Hormone Regulation

• Luteinizing hormone (LH) triggers testosterone synthesis in interstitial cells (Leydig cells).
• Fetal interstitial cells produce testosterone during embryonic development.
• Testosterone promotes the development of secondary male sex characteristics.

Spermiogenesis

• During spermiogenesis, the cytoplasm of spermatids is eliminated.
• Type A spermatogonia act as stem cells, dividing infrequently and giving rise to more rapidly dividing cells.
• Intercellular bridges allow for the exchange of molecules and ions between spermatogenic cells.

Sertoli Cells

• Sertoli cells physically and metabolically support developing sperm cell precursors.
• Sertoli cells secrete inhibin, which feeds back on follicle-stimulating hormone (FSH) to regulate spermatogenesis.
• Sertoli cells produce müllerian-inhibiting substance (MIS) in the fetus, which prevents the development of female reproductive structures.
• Sertoli cells secrete transferrin, which helps regulate iron levels in the testes.
• Sertoli cells produce androgen-binding protein (ABP), which helps regulate testosterone levels.
• Sertoli cells form the blood-testis barrier, which separates the testicular tissue from the bloodstream.

Sperm Development

• During spermiogenesis, excess cytoplasm is shed as residual bodies.
• The acrosome phase of sperm development involves the formation of a structure that remains embedded in the Sertoli cell.
• The middle piece of the sperm develops from the aggregation of organelles around the flagellum.
• Protamines are proteins that help compact the sperm nuclei during sperm development.

Blood-Testis Barrier

• The main function of tight occluding junctions in Sertoli cells is to form the blood-testis barrier.
• The three general functions of Sertoli cells in establishing the blood-testis barrier are to regulate the movement of molecules, to provide mechanical support, and to secrete factors that influence spermatogenesis.

Unknown Function

• One of the functions of exocrine secretion by Sertoli cells is to provide nutrients to developing sperm cells.