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NGD > Sexual differentiation > Flashcards

Sexual differentiation Flashcards

1
Q

Disorder of sexual development

A

congenital condition in which development of chromosomal, gonadal, or phenotypic sex is atypical

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2
Q

Embryo sexual potential

A

bipotential
whether they’re XX/XY, each capable of producing either a male or female repro system
all three germ cells, gonadal ridge and external structures are the same

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3
Q

Requirements for the development of repro system

A

germ cells
gonadal ridge
external genitalia

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4
Q

Indifferent gonad

A

4.5-6 wks
Indistinguishable as male or female gonad
from gonadal ridge: interactive gene functions
primordial germ cells migrate from area of yolk sac
have been undergoing mitotic increases in number

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5
Q

Testis formation

A

6 wks
require presence of Y chromosome (SRY region at Yp)
testis organization under active and local control of SRY gene product
Other genes crucial (SOX9, DAX1, WT1, etc)

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6
Q

Mullerian duct inhibiting substance

A

acts locally to suppress Mullerian ducts

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7
Q

Mullerian duct derivatives

A 
= paramesonephric duct
internal structures:
uterus
tubes
upper vagina
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8
Q

Sertoli cell function during development

A

Sertoli cells: produce Mullerian duct inhibiting substance (MIS or AMH)
Derived from surface epithelium, active from 6 weeks

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9
Q

Leydig cell function during development

A

Leydig cells: begin to produce testosterone at 7 weeks (likely in response to placental hCG)

  • derived from mesenchyme
  • active influence on Wolffian duct structures
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10
Q

Wolffian duct structures

A

epididymis, vas deferens, seminal vesicles, Ejaculatory duct

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11
Q

Remnants of mullerian ducts in males

A 
utriculus prostaticulus (near seminal vesicle/prostate)
Appendix testis
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12
Q

Ovarian determination

A

10-11 wks
maybe sooner? but definitely lags behind testicular development
initially thought to be passive but there seems to be genes involved with active induction of ovary
Mesonephric duct degenerates, paramesonephric duct develops

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13
Q

Turner syndrome repro system

A

have ovaries unless Y present

however, need both X’s for maintenance

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14
Q

Paramesonephric/Mullerian duct abnormalities

A

anatomical defects

e.g. primary amenorrhea with fully developed 2ndary sexual characteristics (functional ovaries)

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15
Q

Development of external genitalia

A

initially indifferent
Male: tubercle –> penis
- genital swellings –> fuse –> scrotum
- under influence of DHT (need 5alpha reductase to convert testosterone –> DHT)

Female: looks similar to male until 9-10 wks

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16
Q

Genital tubercle derivatives

A

Glans penis/clitoris

Corpus cavernosum + spongiosum/vestibular bulbs

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17
Q

Urogenital sinus derivatives

A

Bulbourethralglands (Cowper)/Greater vestibular glands
Prostate gland/Urethral and parauretrhal glands
Ventral shaft of penis (penile urethral)/Labia minora

18
Q

Labioscrotal swelling derivatives

A

Scrotum/labia majora

19
Q

Mixed gonadal dysgenesis

A

variant of Turner with mosaicism involving Y
most commonly: 45, X/46, XY
Testis determination will depend on proportions of cells containing Y
Sex chromosome DSD

20
Q

Pure gonadal dysgenesis

A

variety of conditions
One subtype: XY with deletion of SRY (15-20%); perhaps SF1 mutations
- unambiguous female presentation
- uterus present

21
Q

Androgen insensitivity syndrome

A

X-linked

variability of expression depending on mutation

22
Q

Complete AIS

A

normal testes
abnormal Wolffian and Mullerian strctures
external phenotype umambiguous female

23
Q

Incomplete AIS

A

less common

gential ambiguity/hypospadia

24
Q

Dx of Androgen insensitivity syndrome

A

receptor studies

mutation analysis

25
Q

Androgen receptor

A

encoded by X-linked androgen receptor gene (Xq13)
similar to other steroid receptors
necessary for androgen-sensitive cells (Wolffian duct, external genitalia, brain, areas of sex-specific body hair, etc)

26
Q

Congenital adrenal hyperplasia

A

commonest cause of genital ambiguity
several types involving steroid hormone biosynthesis
21-hydroxylase deficiency - involves structural gene for adrenal cytochrome P450 specific for steroid 21-hydroxylation
Buildup of 17-hydroxyprogesterone

27
Q

Salt-losing CAH

A

no mineralocorticoids
can die of adrenal crisis
may present with hypovolemia, shock

28
Q

Simple virilizing CAH

A

excess androgens due to shunting

some females severely virilized enough to appear umambiguously male

29
Q

Late onset CAH

A

most common

mixes with population of PCOS females

30
Q

Evaluation of infants with ambiguous genitalia

A 
some may have life-threatening conditions that need to be assessed immediately - e.g. heart, renal
Look carefully at genitalia
Look for other anomalies
Document adequacy of urinary tract
metabolic status - glucose, electrolytes
chromosomes, 17-OH progesterone
review pregnancy/family history
reassure parents; have team approach
31
Q

Dx CAH

A

very high serum concentration of 17-hydroxyprogesterone

dx 21-hydroxylase deficiency, classic

32
Q

Females of salt-losing/simple virilizing CAH

A

neonate presentation: ambiguous genitalia (clitoral enlargement, common urethral-vaginal orifice)
Partial/complete fusion of labial folds and rostral migration of urogenital orifice may also occur
internal female reproductive organs normal
rare instances: ambiguous genitalia may not be identified - may present with adrenal crisis at 1-2 wks

33
Q

males of salt-losing/simple virilizing CAH

A

neonate: salt-losing adrenal crisis
Toddler: signs of puberty (non-salt losing form)
newborn males: no overt signs of CAH, although phallic enlargement/scrotal hyperpigmentation sometimes present
Typically diagnosed before they develop clinical symptom

34
Q

Neonatal screening for CAH

A

17-OHP on spot card

most affected neonates have concentrations > 3500 ng/dl (105 nmol/L)

35
Q

Adrenal ultrasound for CAH

A

potential adjunctive test for CAH in neonates wiht ambiguous genitalia and/or life threatening salt loss, when diagnosis is equivocal based upon ohter testing
adrenal limb width >4 mm, lobulated surface, or abnormal echogenicity

36
Q

Prenatal diagnosis of CAH

A

considered when fetus is known to be at risk due to affeted sibling/partners are carriers
Measurements of amniotic fluid 17-OHP, HLA typing of fetal cells, molecular analysis of fetal CYp21A2 in AC or CVS
method of choice: molecular analysis of CYP21A2 gene

37
Q

Tx CAH

A

providing GC in sufficient doses to reduce excess CRH/ACTH and hyperandrogenemia
Salt-losing form: MC given to restore serum electrolyte concentrations and extracellular fluid volume to normal

38
Q

Prenatal CAH therapy

A

Maternal administration of dexamethasone

  • not degraded by placenta, crosses into fetal circulation
  • suppression of fetal pituitary ACTH
  • initiated as soon as pregnancy recognized - if not begun at 9 wks, don’t give it at all
  • d/c if genetic testing reveals male /unaffected female fetus

85% of pretreated females born with N/slightly virilized genitalia

39
Q

Prenatal CAH therapy adverse effects

A

may have adverse effects, long-term risks unknown
Mother: increased appetite, early and excessive wt gain, edema, striae, SSx of Cushing’s
Fetus: postnatal failure to thrive, psychomotor developmental delay

40
Q

Investigations for ambiguous genitalia

A

Hx/P
Pelvic US and possibly adrenals
karyotype/FISH for sex chromosome (SRY)
17-OHP
nonpalpable gonads - presumed to have CAH, empirically treated until dx is confirmed/excluded
- after 17OHP sample drawn, tx with GC + MC + NaCl in all infants to prevent adrenal crisis

41
Q

CAH surgery

A

girls with classical CAH typically undergo reconstructive surgery, usually clitoroplasty/vaginoplasty
Clitoral reduction should preserve neurovascular bundle, glans, and preputial skin related to glans

42
Q

Outcomes of CAH therapy (long term)

A

Growth: fewer pts reach adult height due to hyperandrogenism/hypercortisolism

Bone: dependent upon age, but tend to have lower bone mineral density

May have irregular menstrual cycles

Testis: ectopic adrenal tissue located in testes commonly found in males with CAH, can interfere with testicular fxn resulting in infertility

Obesity: complication in GC-txed patients with 21-hydroxylase deficiency

Mortality: 3x in 1-4 y, due to adrenal crisis after an infection
education of parents/caregivers important

NGD (16 decks)

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