Reproduction I

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Questions and Answers

What genetic combination typically signifies a female in mammals?

XX (correct)

Testosterone is produced by Sertoli cells.

False

What initiates the differentiation of the testes during embryonic development?

Transient expression of testis differentiation factor from the SRY gene.

The absence of _____ leads to the development of the paramesonephric duct.

Müllerian inhibiting substance (MIS) Signup and view all the answers

Match the following cells with their functions:

Leydig Cells = Produce testosterone Sertoli Cells = Produce Müllerian inhibiting substance Primordial Germ Cells (P.G.C.) = Form spermatogonia Coelomic Epithelium = Form cortex of ovary Signup and view all the answers

Which of the following structures regresses in the absence of testosterone?

Wolffian duct Signup and view all the answers

Where do primordial germ cells originate?

They have an extra-embryonic origin. Signup and view all the answers

The mesonephric duct remains in females after development.

False Signup and view all the answers

What are the sex chromosomes that typically signify a male in mammals?

XY Signup and view all the answers

Leydig cells are responsible for the production of testosterone.

True Signup and view all the answers

What is the primary function of Sertoli cells in the testes?

Produce MIS Signup and view all the answers

The differentiation of the cortex into an ovary occurs in the absence of _____ and testosterone.

MIS Signup and view all the answers

Match the following cell types with their functions:

Leydig cells = Produce testosterone Sertoli cells = Produce MIS Primordial germ cells = Form spermatogonia Coelomic epithelium = Form Sertoli cells Signup and view all the answers

What triggers the differentiation of the testes during early development?

Testes Differentiation Factor (TDF) Signup and view all the answers

What structure regresses in females during development?

Mesonephric duct Signup and view all the answers

The ovarian development includes the formation of testicular chords.

False Signup and view all the answers

Study Notes

Sexual Differentiation

Sex is determined by genes, specifically sex chromosomes. These chromosomes are responsible for the sexual dimorphism observed between individuals. In mammals, females have XX chromosomes while males have XY chromosomes. This is different in birds, where females have ZW and males have ZZ chromosomes.
The gonads, which are the reproductive organs, are undifferentiated in early fetal life.

Embryonic Sex Differentiation

During this stage, primordial germ cells (PGCs) develop. These cells have an extra-embryonic origin and circulate in the vasculature before migrating through different tissues until they reach the genital ridge.
The genital ridge is where the indifferent gonads form.
Differentiation of the cortex into an ovary or the medulla into a testis depends on the expression of specific genes.
The key gene is the sex-determining region Y (SRY). It is located on the Y chromosome and is responsible for the development of the testis. The SRY gene codes for a protein called the testes differentiation factor (TDF), which triggers the differentiation of the medulla into a testis.

Gonadal Development

The testes develop from the deep part of the sex cords, and the rete tubules connect to them.
The testes also comprise testicular chords containing PGCs, which eventually become spermatogonia.
The coelomic epithelium develops into Sertoli cells, which produce the Müllerian Inhibiting Substance (MIS), which plays a vital role in male sexual development.
The mesonephric mesenchyme forms the connective tissue (tunica albuginae), blood vessels, and Leydig cells.
Leydig cells are responsible for producing testosterone, which is essential for male development. Testosterone stimulates the development and maintenance of the mesonephric duct, which will become the male reproductive tract.
The ovary develops differently. The medulla forms a rudimentary rete.
The coelomic epithelium will form the cortex.
The second generation of cord epithelium forms the primordial follicle, which contains the oocyte precursor.
The mesonephric tubules regress to form a rudimentary rete in females.

Sex Differentiation of the Brain

The presence or absence of different hormones during development influences the differentiation of the brain, leading to the development of sex-specific behavioral patterns.
In males, the presence of testosterone and MIS promotes the development of the Wolffian duct, which becomes the male reproductive tract. It also leads to the regression of the Müllerian duct.
In females, the absence of testosterone and the absence of MIS allow the Mullerian duct to develop into the female reproductive tract, while the Wolffian duct regresses.

Sexual Differentiation

Sex: determined by sex chromosomes (XX=female, XY=male in mammals)
Gonadal Differentiation: early fetal gonads are undifferentiated
Primordial Germ Cells (PGCs):
- Originate outside the embryo
- Migrate through tissues
- Colonize the genital ridge
- Form indifferent gonads
TDF Gene:
- Testes determining factor
- Located on the SRY (Sex-determining region Y) gene
- Triggers differentiation of the medulla into testes
Development of the Testes:
- Deep layer of sex cords form testes
- Sertoli cells: produced by coelomic epithelium, secrete MIS (Mullerian Inhibiting Substance)
- Leydig cells: formed from mesonephric mesenchyme, produce testosterone
- Testosterone stimulates the development of the mesonephric duct (Wolffian duct)
Development of the Ovaries:
- Cortex forms from the coelomic epithelium
- Primordial follicles form from second generation of cord epithelium
- Mesonephric tubules regress, forming a rudimentary rete
Female Tract Development:
- Occurs in the absence of MIS
- Paramesonephric duct develops
- Mesonephric duct regresses in the absence of testosterone

Sex Differentiation of the Brain

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Description

This quiz explores the mechanisms of sexual differentiation at both genetic and embryonic levels. Key concepts include the role of sex chromosomes and the differentiation of gonads during fetal development. Test your understanding of important genes and processes involved in sexual dimorphism.