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Flashcards in Session 1 - Notes Deck (24)

Define genotype

The genetic makeup of an individual as defined by the particular sets of genes they possess


Define phenotype

The observable physical characteristics of an individual as determined by their genes


Should the external genitalia be ambiguous at birth, suggest what investigations may
be undertaken to assign sex.

Information on karyotype, gonadal sex, hormonal tests, and anatomy)

(e.g., palpation of gonads, length and diameter of any phallus, position of urethral meatus,
degree of labio-scrotal fold fusion, presence of vagina/pouch/urogenital sinus) (including
ultrasound study).


What tissue forms the matrix of the gonads in which the primordial germ cells migrate?

somatic mesenchymal tissue


An individual has a genotype of XXY. Will they have ovaries or testis? Explain your



Which gene on the short arm of the Y chromosome determines formation of the

SRY gene (sex determining region of Y gene) also called TDF gene (testis determining


What will be the presenting sign of Turner's syndrome (45 XO) at puberty

Failure to menstruate
Failure of secondary sexual characteristics


Which hormones prevent the spontaneous development of the female genitalia in the
male and from which cells are they secreted?

Interstitial cells of Leydig in the testes secrete androgens, principally testosterone, from 9
weeks gestation.

Sertoli cells lie within the walls of the seminiferous tubules and secrete MIH (Müllerian
inhibitory hormone; MIS Müllerian inhibitory substance)


What structures do the Müllerian ducts develop into?

uterine tubes


Which structures do the Wolffian ducts develop into?

vas deferens
seminal vesicles


The prostate develops from the urogenital sinus in the male (under the influence of
testosterone), but what does the urogenital sinus form in the female?

(Lower part of) vagina


What would occur in a male (XY) with low levels of MIH or resistance to MIH?

The presence of testicular testosterone will promotes male external genitalia and
Wolffian ducts, but the Müllerian ducts are also retained. Hence, genetically and gonadally
male but with internal genitalia of both sexes


What are the mesoneprhic and paramesonephric ducts?

Pair of ducts which end at cloaca and develop in both males and females,


Outline the process of mesonephric duct making contact with urogenital sinus in both male and female

• Mesonephric ducts reach Urogenital sinus
• Ureteric bud sprouts from mesonephric duct
• Smooth musculature begins to appear, UGS begins to expand


What happens to mesoneprhic duct in male?

• Ureteric bud & MD make independent openings in UGS
• Prostate and prostatic urethra form


What happens to mesonephric duct in female?

• Mesonephric ducts regresses due to lack of androgens
• Ureteric bud opens into urogenital sinusW


What are the paramesonephric ducts?

Arise close to mesonephric ducts, no relation to kidney function. Actually invaginations of epithelium of urogenital ridge. Fuse to form fallopian tube and uterus.


What happens to paramesonephric ducts in males?

• Androgen secretion supports mesonephric ducts
• Testis secretes Mullerian Inhibiting Substance -> Paramesonephric duct degenerates


What happens to paramesonephric ducts in females?

• No androgen -> Mesonephric duct degenerates
• No testis derived Mullerian Inhibiting Substance -> Paramesonephric duct degenerates


What are the three basic components of genital development in both male and female

• Genital tubercle
• Genital folds
• Genital swellings


What happens to
• Genital tubercle
• Genital folds
• Genital swellings

Driven by dihydrotestosterone
Genital tubercle – Elongates to form penis
Genital folds – Fuse to form spongy urethra
Genital swellings -> Fuse to create the scrotum


What happens to
Genital tubercle
• Genital folds
• Genital swellings

Drive by absence of dihyrdotestosterone
Genital tubercle – Becomes the clitoris
Genital folds – No fusion, become labia minora
Genital swellings – Become labia majora


Outline the descent of the testes

Testis attached to gubernaculum and runs all the way to -----
Gubernaculum shortens and testes descend, behind processus vaginalis. Pushes through anterior abdominal wall, the deep inguinal ring, through abdominal wall and out into the scrotum though the superficial inguinal ring.


Outline the descent of the ovary

Gubernaculum attaches ovary inferiorlyto labioscrotal folds. Ovary descends to the pelvis, and is prevented from descending further by mechanical blockage of uterus. Gubernalculum becomes round ligament of the uterus, and runs through inguinal canal.