Sex Determination Flashcards
When is the sex determined?
When gonads are made
Where are the gonads developed?
Trunk of body, between shoulder and pelvis
Where are the germ line stem cells in the embryo?
Epiblast cells not included in gastrulation therefore in yolk sac
How do the germ cells travel to the gonad?
Primordial germ cells use gut and mesentery (sheet-like connection between gut and body) to invade body and move to the gonadal ridge vis the gonad rudiment
How is sex determined?
Different chromosome constitution; if SRY (sex-determining region of Y chromosome) is expressed= male
How does SRY act?
Primitive gonads consist of somatic and germ line cells; somatic cells express SRY if present so forces testis development
How is development changed due to SRY expression?
If testis developed, communicates with rest of body by excreting androgenic hormones
How is the rest of the body forced to be male?
Female= default/ natural state, testosterone and AMH production forces soma cells to develop male
What are the main somatic differences between the reproductive systems?
Mullerian ducts- oviducts and Wolffian ducts disappear in female/ Mullerian ducts disappear (AMH) and Wolffian ducts into vas deferens in male
What are external differences in sexual dimorphism?
Height, mass, shape, genitalia, mammary glands, body hair
What is CAIS?
Complete Androgen Insensitivity syndrome- XY chromosomes but mutant receptors= no oviducts/ uterus but lower vagina and internal testes
How does testosterone work?
Testes secrete testosterone, stimulates androgen receptors weakly, 5a-reductase converts it to 5a- dihydrotestosterone in tissues to stimulate androgen receptors more strongly
Why do guevadoces occur?
XY children with deficient 5a-reductase make female bodies, testosterone rises enough at puberty to act as androgen even in the absence of 5a-reductase so develop male genitalia
What layer is the testis formed from?
Mesoderm
