2. OBJECTIVES
PRE-PUBERTAL SEXUAL GROWTH AND
DEVELOPMENT
Sex determination
Sex differentiation
Disorders of sexual development
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3. SEX DETERMINATION
Human chromosomes
Human gametes
Genetic sex determination
Formation of Barr body
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4. Sex determination
(Genetic differentiation)
Genotype of the fetus,
whether male or
female.
Determined by the
presence of sex
chromosomes,
So also known as
chromosomal sex
differentiation
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5. Human chromosomes
Each cell in a normal adult male and female
possesses 46 chromosomes (44 autosomes +
2 sex chromosomes)
Except ovum and sperm
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7. Genetic sex determination
Occurs during
fertilization, i.e.
penetration of the
ovum by the sperm.
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8. Formation of Barr body
One of X chromosomes of
somatic cells in the female
embryo becomes inactive
while the other remains
active.
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9. Formation of Barr body
The inactive X
chromosome of each
somatic cell forms a
condensed mass called sex
chromatin or Barr body
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10. Significance of Barr body
• By cytological tests.Identification
of sex
genotype
• In abnormal cells with 3
or more x chromosomes,
there are 2 or more barr
bodies.
Identification
of abnormal
genotype.
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12. Gonadal Differentiation
Gonadogenesis
Formation of gonads, i.e. testes in males and
ovaries in females.
Dependent on the genotype of the embryo.
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13. Genital Ridge
Condensation of
mesenchymal tissue
present on each side near
the adrenal glands.
Proliferation of both
germinal and non-germinal
cells migrated to genital
ridge leads to formation of
bipotential gonads.
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14. Bipotential Gonads
Primordial or primitive or
indifferent or ambisexual
gonads.
Up to 6 weeks of gestation
the bipotential gonads are
identical in both sexes
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15. Structure.
Consists of a medulla, a
cortex and primordial
germ cells.
The germ cells are
embedded in the layer
of cortical epithelium
surrounding a core of
medullary
mesenchymal tissue
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16. Testicular Differentiation
At about 6th week
At about eighth week
At about ninth week
At about the 35th week
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17. At about 6th week
Begins with the
appearance of primitive
seminiferous cords (sex
cords) from the
germinal epithelium
covering the medulla of
bipotential gonad
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18. At about eighth week
Leydig (interstitial) cells
appear in the interstitial
spaces of seminiferous
tubules and continue to
proliferate.
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19. At about eighth week
The membrane of Leydig cells has receptors
for human chorionic gonadotropins (HCG)
and for luteinizing hormone (LH).
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20. At about ninth week
The Leydig cells synthesize and secrete
testosterone in response to HCG secreted by
placenta.
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21. At about the 35th week
Occurs descent of testes through inguinal
canal into scrotum.
Final stage of testicular differentiation.
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22. Role of Y chromosome in
testicular differentiation
Y chromosome contains
2 transcription genes,
For Testicular
differentiation
For the formation of
Mullerian duct inhibitory
substance (MIS)
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23. Gene for testicular
differentiation
Called SRY gene (Sex-determining region of
the Y chromosome)
Encodes the testis-determining factor (TDF) -
triggers the testicular differentiation.
The TDF gene product causes Sertoli cell
differentiation.
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26. Differentiation Of Internal
Genitalia
During 6th week - neutral sex anlagen develops
along with the development of bipotential gonad.
The primordia consists of 2 ducts
Paired set of Wolffian (male) ducts
Paired set of Mullerian (female) ducts.
By seventh week of gestation, the embryo has both
male and female primordial ducts
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28. Differentiation Of Male
Internal Genitalia
Leydig cells secrete
testosterone –stimulate
wolffian duct & forms
epididymis, vas
deferens & seminal
vesicles.
The MIS causes
regression of the
Mullerian ducts by
apoptosis.
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29. Differentiation Of Female
Internal Genitalia
In the absence of MIS,
the female ducts
(Mullerian ducts)
proliferate and form
oviduct (uterine tubes),
uterus and upper two
thirds of vagina.
In the absence of
testosterone, Wolffian
ducts degenerate.
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30. Differentiation Of External
Genitalia
Develop from common
anlagen, which are the
urogenital sinus, the
genital sinus, the genital
tubercle, the genital
swelling and the genital
(urethral) folds
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31. Differentiation Of External
Genitalia
The external genitalia are bipotential till
eighth week of gestation,
i.e. it can develop along either male or female
lines.
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33. Psychological Differentiation
It is determined by the effect of androgens
on the development of brain in the
embryonic stage.
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36. Trisomy
During gametogenesis
due to non-disjunction
of sex chromosomes.
The presence of extra
X or Y chromosome
(Trisomy)
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37. XXY pattern of chromosomes
Klinefelter syndrome
Characteristic features
Poor development of testis
with hyalization of
seminiferous tubules, leading
to sterility. (seminiferous
dysgenesis.)
Patient has normal male
internal and external
genitalia.
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38. XXY Pattern Of Chromosomes
Patients are usually tall
(due to growth of lower
body segment) and
obese.
Gynaecomastia
(development of breast
in male).
The secondary sex
characters are poorly
developed.
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39. XXX (Genotype) Pattern Of
Chromosomes
poor sexual development
(infantile), scanty
menstruation and mental
retardation.
Low or normal plasma
testosterone level,
High plasma level of
gonadotropins (LH and FSH),
High plasma level of
oestradiol
Positive sex chromatin test
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40. Monosomy
Turner’s syndrome.
(karyotype) is 44 + XO
ovarian dysgenesis because of XO karyotype.
Puberty is delayed, scanty menstruation,
amenorrhoea (no menstruation), primary
infertility and amastia.
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41. Turner Syndrome
mental retardation
Dwarfism.
Webbed neck (folds of skin
on the side of the neck
face is peculiar with low
hair line, ptosis (drooping
of eyelids),
epicanthus (low set ears),
micrognathia (small jaw)
and co-arctation of aorta
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42. Diagnosis Of Chromosomal
Abnormalities
Amniocentesis - by inserting a needle into
the amniotic cavity through anterior
abdominal wall.
Chorionic villus sampling - by a needle
biopsy of chorionic villi.
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43. Hormonal Abnormalities
Pseudohermaphroditism - individual
having genotype (gonads) of one sex (either
testes or ovaries) and genitalia of other sex.
True hermaphroditism - gonads of both
sexes are present; its rare.
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44. Pseudohermaphroditism
Female – Genotypically
–female.
Gonads and internal
genitalia are feminine
like (ovaries, oviduct
and uterus are present),
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45. Pseudohermaphroditism
But at pre-pubertal
age masculinization
occurs in the form of
diamond-shaped
pubic hair growth and
development of penis.
Increased plasma
levels of testosterone
and androgens
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