L4 - Sexual Differentiation COPY Flashcards
INTRO
i) when is sex determined?
ii) when do the gonads differentiate?
iii) after which week do the internal and external genitalia differentiate?
i) at fertilisation
ii) at week 5
iii) post week 5
PRIMORDIAL GERM CELLS
i) which week do primordial germ cells arise from the epiblast?
ii) what do PGCs ultimately become?
iii) what potency do they have? (eg uni, multi, pluripotent)
iv) where do PGCs migrate to to avoid becoming imprinted
v) which ridge do they travel to 2 weeks later? what do they become once there?
i) week 2
ii) PGCs become the gonads
iii) they are pluripotent
iv) PGCs migrate to the yolk sac to avoid being imprinted
v) travel to the genital ridge and become the indifferent gonad
PGCs AND GONADS
i) what happens to the genital ridge around 6 weeks?
ii) do the sex cords degenerate in males or female?
iii) where do the PGCs replicate if the embryo is XX or if it is XY?
iv) at what week is testis or ovarian development underway?
i) increases in size
ii) sex cords degenerate in females and are retained in males
iii) PGCs replicate at the cortex if XX but in the medulla if XY
iv) week 8
SEX DECISION IN THE GONADS
i) which two things does the decision rely on?
ii) name two general transcription factors that need to be expressed for the gonads to develop
iii) name two specific promoters of testis development
iv) name two specific promoters of ovarian development
v) name three things a bipotential gonad contains (before deciding testis or ovary)
i) hormones and genetic switches
ii) general TFs = WT1 and Sf1
iii) testis promoters = SRY and SOX9
iv) ovarian promoters = Wnt and FOXL2
v) bipotential gonad = PGCs, supporting precursor cells, steroidgenic precursor hormones
FATE OF GONAD CELL LINES
i) what do female PGCs become?
ii) what do sex cord cells become in females? what is their role? what happens eventually?
iii) what cells make up the cortex in females? what do these cells secrete
iv) what do PGCs become in males?
v) what factor influences definition and identification of sertoli cells? what hormone do sertoli cells secrete? what does that do?
vi) what cell type does the above hormone induce the intermediate mesoderm to become? what do these cells secrete?
i) female PGCs become oogonia (primary oocytes)
ii) sex cords become granulosa in females which nourish and support the ovum (these eventually degenerate)
iii) theca cells make up the cortex and these secrete androgens
iv) male PGCs become spermatogonia
v) SRY influences identity of sertoli cells
- sertoli cells secrete anti mullerian hormone which supresses the female development pathyway
vi) AMH induces intermediate mesoderm to become leydig cells which secrete testosterone
KIDNEY DEVELOPMENT
i) which specific tissue/germ layer does the kidney originate from? what organs also orig from this tissue
ii) where is this tissue found? (between which two areas)
iii) what are the three stages of kidney development?
iv) which stage dissapears quickly? which stage leaves remnants? what do these remnants become?
v) which stage becomes the final kidney?
i) intermediate mesoderm (reproductive organs also orig from this tissue)
ii) found between the lateral plate mesoderm and somites
iii) pronephros, mesonephros and metanephros
iv) pronephros dissapears quickly
- mesonephros leaves remnants that become ducts that become part of the reproductive system
v) metnephros becomes final kidney
INTERNAL GENITAL ORGANS
i) when do they begin differentiation into female and male specific organs?
ii) before specification which two paired ducts do each sexes posses? which one does the male retain and which does the female retain?
iii) the absence of which hormone allows female duct development? name four things this duct becomes
iv) which duct does testosterone promote the development of? name three things this differentiates to
i) 8 weeks
ii) two ducts = mullerian (paramesonephric) and
Wolffian (mesonephric)
- male maintains wolffian and female maintains mullerian duct
iii) absence of anti mullerian hormone allows females to dev mullerian duct
- dev into uterus, cervix, top of vagina and oviduct
iv) testosterone promotes the development of the wolffian duct
- becomes epididymis, vas deferens and the seminal vesicles
EXTERNAL GENITAL ORGANS
i) what is the elevated midline swelling seen in embryos of both sexes? name three things this consists of and what each become in male and females
ii) which hormone stimulates development of urethra/prostate/ext genitals in males?
iii) which structure gets bigger and becomes the penis? which structure becomes the spongy urethra? which becomes the scrotum?
iv) the absence of which hormone dictates female genital development?
v) what structure does the clitoris develip from? labia majora? vestibule?
vi) label A-D
i) genital tubercle
- consists of urethral groove, paired urethral folds, paird labioscrotal swellings
iii) DHT (from testosterone) stimulates dev of ureth/pros/ext gen in males
iii) genital tubercle becomes the penis, fusion of urethral folds becomes spongy urethra and labioscrotal swell becomes scrotum
iv) absence of DHT > female
v) clitoris develops from the genital tubercle, labia majora from the labioscrotal swellings and vestibule from urethral groove
vi) A = genital tubercle, B = labioscrotal swelling, C = urethral groove, D = urethral fold
TURNER’S SYNDROME
i) how is the X chromosome implicated?
ii) does it affect males or females?
iii) what % of embryos are non viable? if they survive what happens at puberty? name 3
iv) how is diagnosis confirmed?
v) name four phenotypic features
i) partly or fully missing X chromo (monosomy)
ii) only affects females
iii) 99% are non viable
- dont sexually mature at puberty if they survive
- undeveloped gonads, lack of breast dev and lack of menstruation
iv) dx confirmed by amniocentesis
v) short stature, constric of aorta, elbow deform, shortened metacarpals
KLINEFELTERS SYNDROME
i) how are the chromosomes altered? what is the karyotype
ii) does it affect males or females?
iii) how does the patient appear at birth?
iv) can they reproduce?
v) how is dx confirmed?
vi) name four features they may exhibit
i) 3 sex chromosomes - XXY
ii) only affects males
iii) at birth the patient appears normal
iv) they are infertile
v) dx by amniocentesis
vi) female features eg gynaecomastia, shrunken testes, depos of fat on hips, reduced body hair
which syndrome is characterised by syndrome A and B?
A = klinefelter (XXY)
B = turner (XO)
TRUE HEMAPHRODITES
i) which gonadal tissue are they born with?
ii) name two karyotypes a patient may have
iii) what is a possible cause?
iv) how many external genitals appear?
i) both ovarian and testes
ii) 46XX(+sry), 45X(=sry), 45X
iii) two eggs fertilised by two sperm that fuse to form a teragametic chimera
iv) may be ambiguous, male or female
FEMALE PSEUDOHERMAPHRODITE
i) what sex are they genetically?
ii) what characteristics may they have? why?
iii) what internal sex organs do they have? are they normal?
iv) what may ext appearance and genitals look like?
v) name two features of genitalia
vi) what is a possible cause?
i) female
ii) may have male characteristics due to androgens
iii) female internal sex organs eg ovaries that are normal
iv) ext genitals may look male
v) fusion of labia and enlarged clitoris
vi) possible caused by exposure to male hormone prior to birth eg congenital virilising adrenal hyperplasia
MALE PSEUDOHERMAPHRODITE
i) what is the cause that is also known as testicular feminisation? are male hormones normal? what is abnormal
ii) what happens in leydig cell hyperplasia? what may cause this? how will ext genitalia look? what is the person genetically?
iii) what is XY gonadal dysgenesis also known as? what causes it? what is the external appearance?
iv) does the above have functional gonads? what can be a complication
i) testic feminisation = androgen insensitivity syndrome
- male hormones are normal
- receptor to the hormones is abnormal
ii) leydig cell hyperplas = no testosterone is secreted
- may be caused by insensitivity to LH
- ext genitalia look female or ambiguous
- genetically person is male
iii) XY gonadal dysgen = Swyers syndrome
- caused by an alteration to the Sry gene
- ext appearance is female
iv) Swyers syndrome doesnt have functional gonads (you have them but they dont dev to testes)
- gonads can becomes malignant
TRACT ABNORMALITIES
i) give an example in the uterus
ii) give an example in the vagina
iii) give two examples in the vas deferens
i) unicornuate uterus
ii) vaginal agenesis
iii) uni or bilateral absence
failure of mesonephric duct to differentiate
