The Testis

Gonads

Bipotential structures for the first 7 weeks of gestation.

Y Chromosome

Essential for sex determination and gonadal differentiation.

SRY Gene

Genetic determinant of maleness; encodes for Testis Determining Factor (TDF).

Testis Determining Factor (TDF)

Promotes the production of Mullerian Inhibiting Factor (MIF; AMH).

Sertoli Cells

Support and protect spermatogonia, create nutritive fluids, and form the framework of seminiferous tubules.

Leydig Cells

Interstitial endocrinocytes responsible for testosterone production.

Blood-Testis Barrier

A barrier formed by Sertoli cells that protects developing sperm from damaging agents.

Spermatogenesis

The complex process of proliferation and differentiation transforming spermatogonia into mature spermatozoa.

Inhibin

A hormone that exerts negative feedback regulation of FSH secretion.

Meiosis

Halves the chromosome number and generates genetic diversity in sperm cells.

Apoptosis

Programmed cell death that controls the number and quality of sperm produced.

Intracytoplasmic Sperm Injection (ICSI)

A method pioneered in 1992 for direct injection of a single sperm into an oocyte.

Azoospermia

A condition characterized by the absence of sperm in ejaculate.

Hypothalamus-Pituitary-Testicular Axis (HPT)

The regulatory system involving the hypothalamus, pituitary gland, and testes for male fertility.

Feedback Mechanisms

Processes where the action of one hormone influences the effect of another hormone.

Fertilization

The process in which sperm nucleus decondenses and fuses with the oocyte during conception.

Spermiogenesis

The final stage of spermatogenesis, where spermatids develop into mature sperm cells.

Protamines

Nuclear proteins used in sperm DNA packaging, replacing histones to compact DNA.

Epigenetic inheritance

Transmission of traits or gene expression patterns that are not solely due to DNA sequence.

Free Testosterone

The unbound form of testosterone that circulates in the plasma and is biologically active.

Luteinizing Hormone (LH)

A hormone released from the pituitary gland that stimulates testosterone production.

Follicle Stimulating Hormone (FSH)

A hormone that stimulates Sertoli cells and promotes spermatogenesis.

Sex Determination

The process by which the sex of an organism is determined, strongly influenced by SRY gene activity.

Germ Cells

Cells involved in the production of gametes, specifically spermatogonia in males.