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69 Cards in this Set
- Front
- Back
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When and how does sex determination occur?
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sex determination is established by the sex chromosomes of the genome at fertilization
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What two sex differnetiation factors must be present in order to from a proper male
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-presence of androgens
-presence of MIS/MIF |
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What is the function of MIS/MIF
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MIS/MIF if a glycoprotein secreted by the testis until age 10. The receptors are located on the paramesonephric (mullerian) ducts and binding to the receptor causes the ducts to apoptose. The ducts are the precursors of the oviducts, uterus, and part of the vagina so presence of MIS is necessary for proper male development
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Describe the result of sex differntiation in the brain
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Determines how GnRH will be released. Males release it in a pulsitile manner while females are cyclic. In males, the differentiation of the brain is caused by a surge of testosterone at 6 months after birth
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When and where do the gonad primorida form
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Form during the 4th week in the ventromedial portion of the nephrogenic ridge as a proliferation of the overlying coelomic epithelium and ridge mesenchyme. This becomes the urogenital ridge
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What three cell types contribute to the formation of the gonad
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1. germinal cells
2. supporting cells 3. interstitial cells |
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Describe the origin and migration of the primordial germ cells which will form the stem cells for gamete production
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Originate extragonadally in the yolk sac (from epiblast?) during week 3. During weeks 4-5 they migrate to the gonad within the dorsal mesentery of the hindgut where they continue to divide.
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Describe the formation of the supproting cells (males= sertoli, females= granulosa)
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originate from cord lke proliferations of the coelomic epitheium overlying the gonad primordium. They play a major role in organizing the gonad
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Describe the formation o fthe intersitial cells (males=leydig, females= theca)
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Originate from mesonephric mesenchyme. They synthesize and secrete steriod hormones.
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What are the two attachesments of the primitive gonad
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Both are formed crom surronding mesenchymal tissues
1. cranial= suspensorly ligament (vascualr supply develops here) 2. Caudally= gubernaclum (attaches gonad to ventral body wall) |
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What is the origin of the mesonephric/ wolffian ducts
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form during week 4 within the neprhogenic ridge as part of the mesonephros
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What is the origin of the paramesonephric ducts
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Devleop during week 6 as a response to signals from the mesonephric ducts. They being as an invagination of the ceolomic epithelium covering the lateral aspect of the UG ridge
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Describe the formation of the uterovaginal primordium
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A fusion of the inferior 1/3 of the paramesonephric ducts
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Where do the paramesonephric ducts terminate
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They open into the UG sinus on either side of teh sinus tubercle
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What are the three primordia of the external genitalia
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1. Genital tubercle=midline swelling of mesenchyme adjacent to phallic part of UG sinus
2. Urethral folds=paried swellings surronding the cloacal membrane 3. Labioscrotal swellings= swellings lateral to the urethral folds |
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Describe how testicular determination occurs
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The SRY gene on the Y chromosome encodes testicular determining factor causing the supporting cells of teh genital ridge to differntiatie into sertoli cells which being to express Sox9 genes
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Describe the formation of the seminiferous tubules
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During week 7 sertioli and primordial germ cells organize into testicular cords. At or before puberty the cords develop a lumen and become the seminiferous tubles
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Explain how the leydig cells are formed
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At ~8 weeks, signals from the sertoli cells recruit adjacent mesenchyme cels to differentiate into the leydig cells
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How is the tunica albuginea formed
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The tunica albuginea is a condensation of mesenchyme cells that forms a thick connective tissue over the testis as it grows and rounds and separates from the mesonephros.
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Describe the relocation of the testis
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Occurs from the 7th week to the 9th month,
descend into the scrotum by shortening of the gubernaculum (failure= cryptorchidism) |
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Describe the formation of the primordial follicle
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Primordial germ cells enter the meiotic phase and become oocytes. The oocytes produce FIGa which stimulates the supporting cells to become follicle cells. The oocyte an dits surronding follicle cells form a primordial follicle
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What is the role of the primordial follice in oocyte cell cycle?
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The follicle secretes Meosis inhibiting factor that arrests the oocyte in prophase
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What factors ensure that the interstital cells of a female become theca rather than leydig cells
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Wnt 4
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What male structures derived from the mesonephric ducts
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duct of epididymis, ductus deferens, ejaculatory duct
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What male structures develop from the mesonepheric tubles
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efferent ductules
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How does the prostate gland develop
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Develops during week 10 as epithelial buds of endoderm form the prostatic urethra
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How do the seminal vesicles form
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Originate as outgrowth of the mesonephric duct before it enters the prostate gland.
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What do the paramesonephric ducts become in males
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mostly nothing, MIS causes them to atrophy
note that the cranial part of the prostatic utricle is derived from them |
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What do the mesonephric ducts become in females
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nothing, absence of testosterone causes them to atrophy
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What is the origin of the uterus
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Lack of MIF allows development of the paramesonephric ducts. The inferior 1/3's fuse together forming the uterovaginal primordium which becomes the uterus
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how is the vagina formed
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Dual origin
1. Fused inferior 1/3 of paramesonephric ducts becomes uterovaginal primordium which forms the eipthelial lining of the upper vagina 2. The UV primordium contacts the pelvic part of the UG sinus forming the sinus tubercle. Sinovaginal bulbs extend dorsally form the tubercule and fuse forming the vaginal plate which becomes the epithelial lining of the lower vagina. The surronding mesenchyme forms the rest of the tissue. |
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The fused paramesonephric ducts (uterovaginal primordium) become which part of the vagina
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epithelial lining of the upper part
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The sinovaginal bulbs derived from the sinus tubercle form which part of the vagina
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epithelial lining of the lower part
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What separates the lumen of the vagina from the UG sinus
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hymen (note formation of a complete septum= imperforate hymen)
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Vaginal atresia is most likely the result of problems with which structure
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Failure of the paired paramesonehric ducts to form the unpaired uterovaginal primordium
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In males, the pelvic part of the UG sinus becomes
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1. distal part of prostatic urethra
2. membranous urethra |
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In females, the pelvic part of the urethra becomes
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1. epithelial ling of the inferior part of the vagina
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In males, the phallic part of the UG sinus becomes...
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the epithelial lining of the penile urethra
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In females, the phallic part of the UG sinus becomes
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the vestibule of the vagina
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What structures give rise to the phallus
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Derived from the genital tubercle which is a midline swelling derived from the mesenchyme adjacent to the phallic part of the UG sinus
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What two structures contribute to the formation of the penis
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urethral plate and urethral folds
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What is the precursor of the scrotum
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labioscrotal swellings
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What is hypospadias? What causes it?
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The urethral opening is located on the ventral surface of the penis proximal to the tip. It occurs becaomes of incomplete fusion of the urethral folds.
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What is epispadias?
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In epispadias the urethra and penis are open dorsally.
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What is the precursor of the clitoris
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the phallus
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What is the precursor of the epithelial linging of the vestibule of the vagina
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the phallic portion of teh UG sinus
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What do the urethral folds form in females
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labia minora
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What do the labioscrotal folds become in females
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labia majora
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What is the difference between a hermophrodite and a pseudohermaphrodite
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herm=induvidual with charateristics of both sexes
pseudo= gonads and sex chromosomes don't match secondary characteristics |
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What are the characteristics of a true hermaphrodite
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-both ovarian and testicular tissue (ofen as ovotestis)
-may have uterus on one side and vas deferens on the other -external genitalia may be ambigous, but penis is often present |
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What might be a genetic explanation for a true hermaphordite
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mosaicism where two distinct cell lines develop
or XX induvidal with remnant Y from abnormal crossover during clevage |
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What are the characteristics of a female pseudohermaphrodite
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genetic female who has ovaries but masculine external genitalia
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What might be a cause of female pseudohermaphrodites
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-exposure to increased androgen
intrinsic= congenital adrenal hyperplasia |
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What are the charateristics of a male pseudohermaphrodite
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genetic male who has testis but feminized or ambigous external genitalia
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List some causes of male pseudohermaphrodites
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1. insufficent androgen production due to enzyme defect
2. decrease in MIS 3. Androgen insensitivity syndrome |
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What are the characteristics of an induvidual with Kinefelter XXY
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-seminiferous tubule dysgensis and gynecomastia due to androgen deficiency
tall, long limbs, mental "dullness" |
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What are the characteristics of pure gondal dysgenesis
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Streak gonads and female genitalia
-in XY induviduals it is because of a mutation that inhibits SRY expression -XO geneotype= Turner's syndrome |
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Describe mixed gondal dysgenesis
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-ranges from turner like to male
-can have testis on one side and undifferentiated gonad on the other as well as a uterus -may be varient of true hermaphrodism |
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What is the cause of XX,XY sex reversed
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xx=> male, xy=> female
may be due to Z gene, an inhbitor for male pathway mutation of lack of Z gene in an XX induvidual would result in male development |
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1. The hormone responsible for the external genitalia is:
a. Progesterone b. Dehydroepiandosterone c. Androstenedione d. Testosterone e. Dihydrotestosterone |
e. Dihydrotesterone
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2. Which one of the following is NOT a characteristic of complete androgen insensitivity in a 28 year old phenotypic female?
a. Increased LH b. Normal adult female testosterone level c. Complete breast development d. Absent or sparse pubic hair e. Undecended testes |
b. Normal adult female testosterone level (testerone level will be like that of male)
This person is a genetic male but their cells are insensitive to androgne. |
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3. Deficiency of 17α-hydroxylase is:
a. autosomal dominant b. X-linked dominant c. X-linked recessive d. autosomal recessive e. a multifactorial disorder |
d. autosomal recessive (Dr. Robb says all enzyme deficiencies are autosomal
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4. Mullerian-inhibiting substance is secreted by:
a. Leydig cells b. spermatogonia c. sertoli cells d. granulosa cells e. endothelial cells |
c. sertoli cells (of the testes)
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What does aromatase do?
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converts testoderone to estradiol
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What is the "peritoneal" relatinoship of the gonads
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retroperitoneal
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what is the origin of the tunica albuginea
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-forms under the coelomic epitheium as fibrous connective tissue by week 7
-derived from intermediate mesoderm |
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what is the genotype of an induvidual with mixed gonadal dysgenesis
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45X/46XY
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What might be the ause of a bicornuate uterus (partially unfused uterus)
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A partial duplication of the uterus but the distal 1/3 of the paramesonephric ducts still fused.
The superior part of the body is duplicated while the inferior part is fused. |
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What happens if the wall between the two fused paramesopheric ducts fails to atrophy
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the cavity of the uterus may be complelety or partially divided by a midline septum
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