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4/ RED > Sexual Differentiation and Puberty > Flashcards

Sexual Differentiation and Puberty Flashcards

1
Q

Define puberty

A

Puberty describes the physiological, morphological, and behavioural changes as the gonads switch from infantile to adult forms

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2
Q

What are the definitive signs of puberty in boy and girls

A 
Girls = menarche - first menstrual bleeding 
Boys = first ejaculation - often nocturnal
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3
Q

Describe the adolescent growth spurt

A
  • Time of minimum growth velocity = the age of take off
  • Peak height velocity (PHV)
  • Time of decreased growth velocity and cessation of growth at the epiphyseal fusion
  • Boys commence growth spurt two years later than girls
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4
Q

What is the height gain for girls and boys form the adolescent growth spurt?

A 
Boys = 28cm
Girls = 25cm
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5
Q

What are the secondary sexual characteristics of boys?

What are they caused by?

A

Testicular androgens

  • -> eternal genitalia and pubic hair growth
  • -> enlargement of larynx and laryngeal muscles –> voice deepening
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6
Q

What are the secondary sexual characteristics of girls?

What are they caused by?

A

Ovarian oestrogen
–> regulate the growth of breast and female genitalia
Ovarian and adrenal androgens
–> control public and axillary hair

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7
Q

Sequence of events is related to specific staging criteria: for example…

A
  • breast developement
  • pubic hair development
  • external genetalia development in boys
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8
Q

Describe the tanner stages in boys

A

Stage 1 = prepubertal, no pubic hair, testicular length <2.5cm, tesituclar volume <3.0ml
Stage 2 = sparse growth of slightly curly pubic hair, mainly base of penis, testies >3.0ml (>2.5cm length), scrotum thinning and reddening
Stage 3 = Thicker, curler hair spread to mons pubis, growth of penis in width and length, further growth of testis
Stage 4 = adult-type hair, not yet spread to medial surface of thighs, penis father enlarged, testes larger, darker scrotal skin colour
Stage 5 = adult-type hair spread to medial surface of thighs, genitalia adult size and shape

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9
Q

Describe the tanner stages in girls

A

Stage 1 = prepubertal, no pubic hair, elevation of papilla only
Stage 2 = sparse growth of long, straight or slightly curly, minimally pigmented hair, mainly on labia. breast bud noted, enlargement of areola, with no separation of contours
Stage 3 = Darker, coarser hair spreading over mons pubis, further enlargement of breast and areola, with no separation of contours
Stage 4 = thick adult type hair, not yet spread to medial surface of thighs, projection of areola and papilla to form secondary mound above level of breast
Stage 5 = hair adult-type and distributed in classic inverse triangle, adult contour breast with projection of papilla only

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10
Q

When does puberty start in boys and girls?

A

Boys
- testivular volume of 4 between 10 and 14
Girls
- breast stage 2 between 9.2 and 13.2

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11
Q

What 5 things do you need for normal puberty?

A
  • normal chromosomes, XX or XY
  • normal hypothalamus
  • normal pituitary
  • normal end-organ function, ovaries or testes
  • normal responsiveness of tissues to hormones
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12
Q

Describe the hormonal changes at puberty

A
  • Physical changes controlled by gonadal and adrenal sex steroids regulated by the gonadotrophons, LH and FSH
  • Marked by circadian rhythm of FSH and LH secretion
  • Sleep-augmented LH secretion - pulse like
  • Later puberty LH daytime pulses also
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13
Q

Describe the relationship between Kisspeptin, GPR54 and puberty

A
  • Kisspeptin, the product of the gene Kiss1, os a ligand for the GPCR GPR54 which is expressed in hypothalamic GnRH neurones
  • Loss of function mutations GPR53 cause failure to progress through puberty in man, due to hypogonadotrophic hypogonadism
  • Kisspeptin-GPR54 is essential for the inititation of gonadotrophon secretion at puberty
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14
Q

Describe the hypothalamic maturation hypothesis

A
  • GnRH pulse generator
  • puberty only requires increase in hypothalamic GnRH
  • emphasis the direct link CNS and pituitary and hypothalamic GnRH neurones
  • supporting evidence from the rhesus macaque
    New factors: Kisspeptin, GPR54, TAC3, TACR3
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15
Q

Define precocious puberty

A
  • onset of secondary sexual characteristics before 8yrs in girls and 9yrs in boys
  • menarche before 9yrs may lead to short stature
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16
Q

Define delayed puberty

A
  • absence of secondary sexual characteristics by 13yrs in girls and 14yrs in boys
  • delayed puberty leads to reduced peak bone mass and osteoporosis
17
Q

What are the differences between precocious and precocious pseudopuberty?

A

Precocious
- GnRH dependent
- a central problem with the HPG axis
- all stages in right order but earlier than normal
Precocious pseudopuberty
- GnRh independent
- secreting tumours in gonads, brain, lover, retroperitoneum, mediastinum

18
Q

What diagnostic tests are used to differentiate between precocious and precocious pseudopuberty?

A 
GnRH (LHRH) stimulation test
True precocious puberty 
- LH:FSH ratio >1
- stimulation in pubertal range 
Precocious pseudopuberty 
- LH:FSH ratio <1
- stimulation in prepubertal range or suppression 
- exogenous androgens decrease LH and FSH due to negative feedback
19
Q

What are the possible causes of true precocious puberty?

A 
Idiopathic
CNS tumours
- optic glioma associate with FD1 
- hypothalamic astrocytoma
CNS disorders
- developmental abnormalities, hypothalamus,ic harmartoma 
- encepahalities, brain abscess 
- hydrocephalus, myelomeningocoele, arachnoid cyst
- vascular lesion 
- cranial irradiation 
Secondary central precocious puberty 
Psychosocial i.e. adoption from abroad
20
Q

What are the possible causes of precocious pseudopuberty?

A 
Increased androgen androgen secretion 
- congenital adrenal hyperplasia 
- virilising neoplasm 
- leydig cell adenoma 
- familial male precocious puberty - testotoxicosis
Gonadotrophin secreting tumours 
- chorioepithliomas, germinoma, teratoma
- hepatoma, choriocarcinoma 
McCune-Albright Syndrome 
Ovarian cyst
Oestrogen secreting neoplasm 
Iatrogenic or exogenous sex hormones
21
Q

Describe sex determination in utero

A
  • Migration of primordial germs cells from dorsal endoderm to urogenital ridge by 6-8 weeks gestation (biopotential gonad)
  • Development of indifferent gonad of urogenital ridge
  • Presence of SRY gene –> testes differentiated by week 9
  • Absence of SRY gene –> ovaries present by 11-12 weeks
22
Q

What is the difference between sex determination and sex differentiation?

A

Chromosomal sex =presence or absence of testis-determining genes
—> sex determination
Gonadal sex = gonadal steroids and peptides (T, DHT, AMH)
–> sex differentiation
Phenotypic Sex

23
Q

What are the major events in sex determination and sex differentiation in males?

A
  • urogenital ridge
  • bipotential gonad
  • 46XY +SRY
  • testis
  • Sertoli cells –> AMH –> Mullerian regression
  • Leydig cells –> T and DHT –> male sex differentiation
24
Q

What genes on the Y chromosome are responsible for male sex development?

A

SOX9
WT1
SF1

25
Q

What enzyme converts testosterone to DHT?

A

5alpha reductase 2

26
Q

What cells and their associated hormones are responsible for Mullerian regression and Wolffian development

A

Mullerian regression
- Sertoli cells –> AMH
Wolffian development
- Leydig cells –> T –> DHT –> virilisation

27
Q

Describe the development of the external genitalia

A
  • common genital tubercle at 8 weeks, with lateral urethral folds, labioscrotal swellings
  • tubercle becomes gland penis in male, clitoris in female
  • urethral folds become corpus spongiosum enclosing urethra in males and labia minora in female
  • labioscrotal folds duse to form scrotum and ventral penis or labio majora
28
Q

Describe the sex steroid synthesis pathway

A

see lecture

29
Q

What are the new nomenclature for the following disorders of sex development?

  • Intersex
  • Male pseudohermaphrodite
  • Female pseudohermaphrodite
  • True hermaphrodite
  • XX male or XX sex reversal
  • complete sex reversal
A
  • Intersex = disorder of sex development (DSD)
  • Male pseudohermaphrodite = 46, XY DSD
  • Female pseudohermaphrodite = 46, XX DSD
  • True hermaphrodite = ovotesticular DSD
  • XX male or XX sex reversal = 46, XX testicular DSD
  • complete sex reversal = 46, XY complete gonadal dysgenesis
30
Q

What are the Prader stages?

A

Stages I –> V
I = normal female
V = normal male
Describes stages of virilisation

31
Q

Describe the layers of the adrenal cortex and what they produce

A

Zona glomerulosa = salt, aldosterone
Zona fasciculata = sugar, cortisol
Zona reticularis = sex, DHEA

32
Q

Describe the HPA axis in congenital adrenal hyperplasia

A
  • Mutation in CYP21A2
  • No negative feedback, XS CRH, XS ACTH
  • Cortisol cannot be produced as defective CYP21A2
  • Therefore XS androgen produced
33
Q

Which enzyme is deficient in CAH?

What 3 hormonal stages does it result in?

A

21-hydroxylase deficiency
Mineralcorticoid deficiency
Glucocorticoid deficiency
Sex hormone excess

34
Q

What hormonal/physical states results from 17alpha hydroxylase deficiency?

A 
Mineralocorticod excess 
(glucocorticoid deficiency)
Sex hormone deficicieny --> undervirilised male
35
Q

Describe the disorder resulting from 5alpha reductase type 2 deficiency

A 
Karyotype = 46, XY
Inheritance = autosomal recessive 
Genitalia = usually ambiguous with small, hypospadic phallus, blind vaginal pouch 
Wolffian duct derivatives = normal 
Mullerian duct derivates = absent 
Gonads = normal testes
Habitus = decreased facial and body hair, no temporal hair recession, prostate no palpable 
--> virilise at puberty
36
Q

What is the cause of androgen insensitivity syndrome?

What is the clinical and biochemical phenotype?

A

Mutations = in androgen receptors Xq11-12 –> AR does not respond to androgens
Clinical and biochemical phenotype
- very high testosterone and DHT
- internal genitalia male (due to AMH production)
- external genitalia and external appearance female
- gender identity female –> diagnosis usually because of primary amenorrhoea

37
Q

What factors are taken into account when determining the sex of a child?

A
  • underlying diagnosis
  • likely gender identity
  • appearance of genitalia
  • options for urological and sexual function
  • probable need for hormone replacement
  • potential for fertility
  • tumour risk
  • consideration within the context of the views of the family and social and cultural circumstances
38
Q

Which conditions lead to assumed female assignment/

Which conditions are not straightforward?

A 
Female assumed 
- 46XX DSD due to CAH early diagnosis 
- 46XY due to CAIS
Not stragithforward
- mixed gonadal dysgenesis 
- ovotesticular DSD
- partial gonadal dysgenesis 
- severe PAIS
- androgen biosynthetic defects

4/ RED (19 decks)

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