BGDB Practical - Sexual Differentiation

From Embryology

Introduction

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Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Quiz | Audio | 2013 Notes PDF

This practical will introduce the topic of sexual differentiation during development through a series of online resource pages.


Aim: This practical is an introduction to the earliest events in Sexual Differentiation.


Key Concepts: Primordial germ cells, gonad, internal genitalia, external genitalia, ovary, testes, puberty, hormonal changes, gametogenesis, abnormalities.

Background

Historic-testis.jpg

Historic-ovary.jpg

Historic Gonad Images

Two key systems, neural and reproductive, develop over an extended period from the early embryo to puberty and the emerging adult. The genital system is closely linked developmentally to the urinary system, often called the urogenital system. This practical will therefore cover early development of both system.

In understanding embryonic sexual development, think of a cascade of sequence dependent events that transform indifferent gonads, internal and external genitalia into distinct male and female structures.

The process begins with gonad differentiation, which itself is tied developmentally back at the initial event of fertilization and the presence of either a Y or X chromosome in the sperm.

The endpoint of development could be considered the post-puberty active reproductive system. Interestingly, recent research is pointing to a link between neural and reproductive systems in how male and female brains may differentially develop under the influence of sex hormones and perhaps even the sex chromosomes.


  • There are 6 pages to work through in today's practical class, listed beside the small BGD icon at the top and bottom of each page.
  • Additional information sections are not part of the practical class content.

Genital Timeline

These are approximate timings and stages only.

  • 24 days - intermediate mesoderm, pronephros primordium
  • 28 days - mesonephros and mesonephric duct
  • 35 days - uteric bud, metanephros, urogenital ridge
  • 42 days - cloacal divison, gonadal primordium (indifferent)
  • 49 days - paramesonephric duct, gonadal differentiation
  • 56 days - paramesonephric duct fusion (female)
  • 100 days - primary follicles (ovary)
  • postnatal 2 months of age - male primordial germ cells (gonocytes) are replaced by adult dark (Ad) and pale (Ap) spermatogonia forming the spermatogonial stem cell (SSC) population.

Textbooks

Textbooks
Embryo logo Hill, M.A. (2017). UNSW Embryology (17th ed.) Retrieved November 18, 2017, from https://embryology.med.unsw.edu.au
Genital Links: Introduction | Lecture - Medicine | Lecture - Science | Lecture Movie | Medicine - Practical | Primordial Germ Cell | Meiosis | Female | Ovary | Oocyte | Uterus | Vagina | Reproductive Cycles | Menstrual Cycle | Male | Testis | Spermatozoa | Penis | Prostate | Genital Movies | Abnormalities | Assisted Reproductive Technology | Puberty | Category:Genital
Historic Embryology - Genital 
1902 The Uro-Genital System | 1904 Ovary and Testis | 1904 Leydig Cells | 1904 Hymen | 1905 Testis vascular | 1909 Prostate | 1912 Prostate | 1912 Urinogenital Organ Development | 1914 Female | 1915 Cowper’s and Bartholin’s Glands | 1920 Wolffian tubules | 1921 Urogenital Development | 1921 External Genital | 1927 Female Foetus 15 cm | 1932 Postnatal Ovary | 1935 Prepuce | 1935 Wolffian Duct | 1942 Sex Cords | 1943 Testes Descent | 1953 Germ Cells | Historic Embryology Papers | Historic Disclaimer
The Developing Human, 10th edn.jpg Moore, K.L., Persaud, T.V.N. & Torchia, M.G. (2015). The developing human: clinically oriented embryology (10th ed.). Philadelphia: Saunders. (links only function with UNSW connection)

Chapter 12 Urogenital System

Larsen's human embryology 5th ed.jpg Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., Francis-West, P.H. & Philippa H. (2015). Larsen's human embryology (5th ed.). New York; Edinburgh: Churchill Livingstone.(links only function with UNSW connection)


Chapter 15 Development of the Urinary System

Chapter 16 Development of the Reproductive System

Endocrinology - An Integrated Approach.png Nussey, S and Saffron Whitehead, S. Endocrinology: An Integrated Approach. Oxford: BIOS Scientific Publishers; 2001.

Chapter 6 The gonad


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Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Quiz | Audio | 2013 Notes PDF



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BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial


Glossary Links

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Cite this page: Hill, M.A. 2017 Embryology BGDB Practical - Sexual Differentiation. Retrieved November 18, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Practical_-_Sexual_Differentiation

What Links Here?
© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G