Development of Genitalia Flashcards
Describe the composition and function of the Coelomic Epithelium (mesothelium).
- Outer Somatic Mesoderm lining the Urogenital (gondal) Ridge
- Gives rise to PRIMARY SEX cords
- Sex cords will becomes the Cortex and Medulla of the Gonads
Where are the Primordial Germ Cells (giving rise to oocyte and sperm) located?
Allantois and Yolk Sac
Which structures in the developing embryo are going to form the internal genitalia of males and females?
Males: Mesonephric Duct
Females: Paramesonephric Duct
Which germ layer are the Sertoli Cells and Leydig Cells coming from?
Sertoli Cells: Coelomic Epithelium
Leydig Cells: Intermediate Mesoderm
Which germ layer are the Follicle cells and Thecal cells coming from?
Follicle Cell: Coelomic Epithelium
Thecal Cell: Intermediate Mesoderm
Where do the Primordial Germ Cells come from?
Epiblast during 2nd week
Why are the Primordial Germ Cells located in the Yolk Sac and Allantois during the 4th week of embryogenesis?
They need to be as far away from the differentiation signals as possible so they can remain as a stem cell!
Where is the oocyte in meiosis during Ovulation and Fertilization?
Ovulation: Meiosis I
Fertilization: Meiosis II
Describe the Central and Secondary events involved in sex determination.
Central: Differentiation of the Testes
Secondary: Production of humoral factors by gonads
Which DNA binding protein is going to turn on production of the male genitalia?
Sex Determining Region Y (SRY) Gene
Describe what happens to sex development when SRY is present vs. when it is absent.
PRESENT: Intermediate mesoderm develops into Leydig Cells, produces Testosterone and allows Mesonephric Ducts to persist.
- Coelomic Epithelium develops into Sertoli Cells, they produce Anti-Mullerian Hormone, and cause the degeneration of the Paramesonephric Ducts.
ABSENT: Intermediate Mesoderm develops into Thecal Cells, does not produce Testosterone, and Mesonephric Ducts will degenerate.
- Coelomic Epithelium develps into Follical cells, does not produce Anto-Mullerian Hormone, Paramesonephric Ducts will persist!
Describe the Phenotype of an individual who is XY but does not have enough Anti-Mullerian Hormone.
- Development of both Female and Male Internal Genitalia
- Development of External Male Genitalia
Describe the Phenotype of an individual who is XY but has a deficiency in 5a-reductase.
- Ambiguous External Male Genitalia (Until Puberty)
- Internal Male Genitalia
Describe the Ovotesticular Disorder of Sexual Development.
- Have both Testicular and Ovarian Tissue and an ovotestis
- Phenotype can be male or female, but External Genitalia is ambiguous
Describe the 46, XX Disorder of Sexual Development.
- Caused by exposure of female fetus to excessive androgens (Congenital Adrenal Hyperplasia)
- Ovaries are present, but EXTERNAL genitalia is masculinized
- Clitoral hypertrophy, partial fusion of labia majora, and persistent urogenital sinus
Describe the 46, XY Disorder of Sexual Development.
- Caused by inadequate production of Testosterone and/or AMH or due to androgen insenitivity syndrome
- Testicular development is normal or messed up and may have persistent paramesonephric ducts
- External Genitalia are Female or Ambiguous