Sexual Differentiatio n By Vamsi Krishna Murthy Ginjupalli UNIVERSITY OF SIENA
Jun 02, 2015
Sexual Differentiation
By
Vamsi Krishna Murthy Ginjupalli
UNIVERSITY OF SIENA
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
each human cell contains 46 chromosomes, occurring in pairs 23 pairs of chromosomes
22 autosomes (determines e.g., hair color) 23rd pair are the sex chromosomes
male: XYfemale: XX
Chromosomal sex
Germ cells: male: sperm - contains “X” or
“Y” female: ovum - contains an “X” “Y” chromosome contains less
genetic material than “X” chromosome
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Gonadal Differentiation
Undifferentiated gonad develops as a ‘germinal ridge’ off of the protokidneyThe gonad at this stage (pre 7-weeks) has a medullary and cortical region (inner and outer)(testes develop during the 7th week of gestation, ovaries develop during the 13th to 16th week)Without TDF input, the cortical region will develop into an ovary, and the medullary region will regressSRY causes development of the medullary region into a testis, and development proceeds from there, resulting from the hormones secreted by the gonads
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Ovaries: fairly quiescent during embryogenesis. They secrete very low levels of estrogens, but don’t produce significant quantities of hormones until pubertyto repeat: in the absence of hormones from a testis (differentiated because of SRY), morphological, neural, and behavioral development is female
Testes: produce testosterone (from the leydig cells) and proteins (mullerian inhibiting hormone MIH from the sertoli cells)
hormonal sex
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Ductal system
External genitalia
Differentiation of the brain
Mullerian and Wolffian Duct Systems
cervix
The progenitors for the duct systems are present for both male and females embryologically
In contrast to gonadal development, where one gonad becomes either male or female.
mullerian vs wolffian1) With no hormones, the mullerian duct develops, and the wolffian duct undergoes
programmed cell death (regresses and degenerates)1) This causes formation of female internal morphology2) Mullerian system becomes fallopian tubes, uterus, and cervix
2) With testes present:1) Leydig cells produce testosterone, cause development of wolffian ducts (turn
off programmed cell death)1) Wolffian ducts become vas deferens, seminal vessicles, and prostate gland
2) Sertoli cells produce Mullerian inhibitory hormone(MIH), cause regression of mullerian ducts
1) If the sertoli cells fail to produce MIH, a male can have both male and female internal structures
Mullerian and Wolffian Duct Systems
External Genitalia
Development of male external genitalia is dependent on dihydrotestosterone (DHT), an androgen -The skin of the genitalia contains the enzyme necessary to convert testosterone to DHT (5-alpha reductase) -The testis produces androgens, and in the genital area, that is converted to DHT, causing masculinization of the external genitalia (fusion of the genital swelling)
Both males and females have this enzyme (5-alpha reductase) in the developing genitalia, but females have no T to convert at this time, so no DHT produced -If female is accidentally producing T, she can have masculinized genitalia at birth - If male does not produce the enzyme, external genitalia will be female.
Male: Testosterone secreted into the blood reaches the brain testosterone converted to estradiol and dihydrotestosterone
in the brain estradiol masculinizes the brain
Female: alpha-fetoprotein binds to estradiol prevents estradiol from entering the brain protects female brains from being masculinized by estradiol
Brain Differentiation
Brain Differentiation
testis
testosterone
TE
BRAIN
Tonic secretion of GnRH in puberty
IN FEMALES?Alpha-fetoprotein
Blocks estrogen in blood from entering brain
Brain Sexual Chemistry
Summary
Undifferentiated gonad
Y-chromosome:SRYTDF
Embryonic Testis
Sertoli cells
Leydig cells
MIH Mullerian ductregression
testosterone Wollfian duct
DHT
Masculinization ofexternal genitalia
estrogen
Masculinization of the brain
Sexual Differentiation
chromosomal sex
gonadal sex
hormonal sex
morphological sex
differences in physiology
Pathophysiology• Male Anomalies
• Androgen insensitivity syndrome
• No functional androgen receptors
• 5-alpha reductase deficiency
• Cannot produce DHT
• Female Anomalies
• Masculinization
• Exogenous treatment with androgenic steroids
• Endogenous production of androgenic steroids (CAH)
• Chromosomal Abnormalities
• Turner Syndrome
• Lack of (or damage to) second X chromosome
• Kleinfelter Syndrome (XXY)
• XYY
thank you for your attention
vamsi