Testis Development

Introduction

The male gonad is the testis. The initial difference in male and female gonad development are dependent on testis-determining factor (TDF) the protein product of the Y chromosome SRY gene. Recent studies have indicated that additional factors may also be required for full differentiation.

The seminiferous tubules are considered the parenchyma of the testis.

Links: Y Chromosome | Week 1 - Spermatogenesis | Ovary | Puberty | original page

Development Overview

Sex Determination

• Humans (week 5-6)
• Germ cells migrate into gonadal ridge
• Gonads (male/female) identical at this stage, Indifferent

Gonad Development

• dependent on sex chromosome
• Y testes
• No Y ovary

SRY

SRY protein (Testes determining factor, TDF) binds DNA Transcription factor, Bends DNA 70-80 degrees

Internal Genital Organs

• All embryos form paired
• Mesonephric duct, see kidney development
• Paramesonephric duct, Humans 7th week Invagination of coelomic epithelium Cord grows and terminates on urogenital sinus
• Male Gonad (testes) secretes Mullerian duct inhibitory factor (MDIF) which causes regression of paramesonephric duct
• Male Gonad (testes) secretes Testosterone which retains mesonephric duct

External Genital Organs

• All embryos initially same (indifferent)
• Testosterone differentiates male

Additional Images

• 

  molecular model of SRY and DNA interaction

• 

  Historic image of early testis development

• 

  Historic image of later testis development

• 

  labelled start image of animation of testis descent

• 

  labelled end image of animation of testis descent

• 

  adult testis histology overview

• 

  adult testis histology overview

• 

  adult testis histology Seminiferous tubules and Tunica albuginea

• 

  adult testis histology Seminiferous tubule and Interstitial cells