Revision as of 16:54, 21 September 2009

Genital Development

Introduction

This section of notes covers genital development. Differences in development are dependent on a protein product of the Y chromosome SRY gene. Mesonephric duct (Wolffian Duct) and paramesonephric (Mullerian Duct) contribute the majority of male and female internal genital tract respectively.

Stage 22 mesonephros

Objectives

Understand the role of the Y chromosome in sex determination.
Understand the differences in male/female duct develpoment (mesonephric/paramesonephric).
Compare the development of the cloaca in the male and female.
Understand the developmental abnormalities in male and female development.

Textbooks

Human Embryology (2nd ed.) Larson Ch10 p261-306
The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 13 p303-346

Three Stages

The mesonephric/paramesonephric duct changes are one of the first male/female differences that occur in development, while external genitaila remain indeterminate in appearance for quite a while.

Differentiation of gonad (Sex determination)
Differentiation of internal genital organs
Differentiation of external genital organs

The 2nd and 3rd stages dependent on endocrine gonad. Reproductive development has a long maturation timecourse, begining in the embryo and finishing in puberty. (More? Puberty)

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

References

Before We Are Born (5th ed.) Moore and Persaud Chapter 14 p289-326
Essentials of Human Embryology, Larson Ch10 p173-205
Human Embryology, Fitzgerald and Fitzgerald Ch21-22 p134-152
Developmental Biology (6th ed.) Gilbert Ch14 Intermediate Mesoderm

Online Links

UNSW Embryology Abnormalities | Y chromosome | X chromosome | Ovary | Stage 13/14 Embryo | Stage 22 Embryo | Stage 22 Highpower

UNSW Embryology Movies: Urogenital Movies

Embryo Images Unit: Embryo Images Online | Urongenital Development | Internal Genitalia | Definitive Kidney | External Genitalia

Histology: Male Reproductive System | Female Reproductive System

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Course Content 2009

Cite this page: Hill, M.A. (2024, May 2) Embryology 2009 Lecture 16. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2009_Lecture_16

What Links Here?

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 == Introduction ==
 [[File:Historic-testis.jpg|240px]] [[File:Historic-ovary.jpg|240px]]
 This section of notes covers genital development. Differences in development are dependent on a protein product of the Y chromosome SRY gene. Mesonephric duct (Wolffian Duct) and paramesonephric (Mullerian Duct) contribute the majority of male and female internal genital tract respectively.
 [[File:Stage22 mesonephros.jpg|thumb|Stage 22 mesonephros]]

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