when are genitalia undifferentiated
what partitions cloaca, and what does it partition it into?
posterior region: rectum
anterior region: bladder
what membranes form from cloacal partitioning?
anterior: urogenital membrane
posterior: anal membrane
at 6 weeks!
when and how does the urethral plate form?
development of male external genitalia
endodermal cells proliferate, fold upon itself > urethral plate
2 edges of plate meet, ectoderm fuse, closing urethra inside penis
what forms spongy urethra area?
how does penile (median) raphe form?
surface ectoderm of urethral plate meet, fuse as line down ventral side of penis
how does scrotal raphe get created?
labioscrotal swellings come together
what is urethral epithelium made of?
both spongy urethra and ectoderm; surrounded by connective tissue
which part of cloaca does spongy urethra come from?
what is meant by the urethra's dual origin?
canalizing betweeen spongy urethra (endoderm) and glandular part of spongy urethra (ectoderm) forms urethra urethral orifice at tip
what does prepuce form from and when
at tip of foreskin middle ectoderm cells die, form cleft week 12
what are the 2 penile rathes, where do they come from?
labio-scrotal fusion > scrotal rathe urethral folds fusion > penile rathe
where do labio scrotal folds first fuse?
what forms labia minora
unfused urogenital folds
what forms labia majora
unfused labioscrotal folds
what produces estrogens > female genitalia development?
mostly placenta, some from fetal ovaries also
where is clitoris nestled
between labio-scrotal swellings
what is the hymen
tissue that hasn't canalized with the outside; thin membrane of tissue remains; breaks either at first intercourse or spontaneously
what are the parts of the labia majora that first form?
posterior fusion > posterior commissure anterior fusion > anterior commissure middle remains open > labia majora
homologous structures of urogenital sinus
male: bladder, urethra (part), prostatic utricle, prostate, bulbourethral glands female: bladder, urethra, vagina, para/urethral glands, bartholins
homologous structures from genital tubercle
male: penis female: clitoris
homologous structures from urogenital folds
male: ventral penis female: labia minora
homologous structures from labioscrotal folds
male: scrotum female: labia majora
typical sexual differentiation def'n
external and internal genitalia consistent with sex chromosome content
errors in sex determination and differentiation def'n
disorders of sexual development, incongruence between external genitalia, internal genitalia, sex chromosome content
both ovarian and testicular tissue present, either in same or opposite gonads majority 46XX, others 46XX/46XY or 46XY ovotestis nonfunctional - no egg or sperm produced ambiguous genitalia- clitoral enlargement/penile underdevelopment indistinguishable at birth causes poor understood, very rare
why might 46XX individual manifest/what do you see?
internal genitalia not different, external genitalia virilization due to exposure of female fetus to excess androgens
congenital adrenal hyperplasia cause- overexposure to androgens occurs b/c steroid hormones from adrenal gland, cholesterol based hormones metabolized - 12 hydroxylase precursors shunted to produce excess testosterone even in female who's missing 12 hydroxylase
how to treat CAH in known carrier
give pt high doses of steroids that overcome block in pathway, prevent masculinization of female penis
how does 46XY individual appear
male with feminized genitalia; opp of CAH variable external/internal genitalia due to inadequate testosterone, MIS production by fetal testes can have normal or very rudimentary testes 5 alpha reductase deficiency > many diff manifestations from this
androgen insensitivity syndrome
aka testicular feminization - normal-appearing females 46XY normal hormone produce, but cell surface receptors don't receive testosterone correctly - defect in androgen receptor female external genitalia; blind-ending vagina; absent/rudimentary uterus - vaginal plate doesn't break down
hypospadias incidence, cause
incidence: 1/300 inadequate production of androgens and/or inadequate receptors > failure of canalization of ectodermal cord and/or failure of fusion of urogenital folds > incomplete spongy urethra forms most commonly, distal end of urethra, under urethral orifice- see opening in glans of penis
agenesis of external genitalia cause, presentation
very rare urethra opens into perineum near anus- no genital tubercle develops congenital absence of clitoris/penis
different causes of anomalies of uterus and vagina
1) incomplete fusion of paramesonephric ducts 2) incomplete development of a paramesnophric duct 3) incomplete canalization of vaginal plate to form vagina
incomplete fusion of distal/inferior part of paramesonephric duct
incomplete fusion of upper part of paramesonephric duct; duplication only of superior part of body of uterus
bicornate uterus with rudimentary horn
unequal incomplete fusion- more rudimentary horn on 1 side than the other, 1 short and 1 long portion, pregnancy usu forms in longer portion hematocolpos - no communication between inside and outside
no communication between inside and outside in bicornate uterus w/ rudimentary horn when woman menstruates, blood from endometrium and sloughs off starts to accumulate inside uterine cavity b/c has nowhere to go blood collects behind cervix very painful
abnormal fusion of septum - external uterus appears normal, internal septum present though one cause for recurrent miscarriages, but fixable very common!
results from failure of 1 paramesonephric duct to develop, have only 1 half of uterus
why would vaginal atresia occur? common?
absence of vagina/uterus very rare - 1/80,000 failure of endoderm and ectoderm to fuse, failure of sinovaginal bulbs to develop and form vaginal plate, so get no canalization of vaginal plate, blockage of vagina
what do inguinal canals provide
pathway for descent of testes through anterior abdominal wall, into scrotum
long connective tissue strand connecting gonad-labioscrotal swellings of scrotum pulls testes down into scrotum, through inguinal canal
what does inguinal canal form from
evagination of peritoneum ventral to gubernaculum
what forms coverings of spermatic cord/testes
layers of tissue from abdominal wall that get pulled down as testes descent into scrotum via gubernaculum pulling
what does gubernaculum become
tiny strand of tissue, anchoring down scrotum remains to scrotal sac
where do 2 inguinal canal rings form from
deep inguinal ring: external oblique m. superficial inguinal ring: transversalis fascia
what enables testes to pass through deep inguinal rings?
atrophy of paramesonephric ducts
what guides testes through inguinal canal?
what happens as testes descent?
enlarge, mesonephric kidneys atrophy, paramesonephric ducts atrophy, processus vaginalis guides thru canal
what helps testes descned through canal
increase in intra-abdominal pressure from enlarging abdominal organs
when do testes descend
where do testes move from/to
"relative movement" from posterior abdominal > inguinal canal > scrotum
do all newborns have descended testes?
no, 97% spontaneous descent no longer occurs after 1 yr
what does transversalis fascia become in testes coverings?
internal spermatic fascia
what does internal oblique m. become in testes coverings?
what does external oblique m. become in testes coverings?
external spermatic fascia
what happens to processus vaginalis after testes descent
during perinatal pd, remnant of stalk of processus vaginalis obliterates tunica vaginalis remains as isolated peritoneal sac around testes
undescended testes anywhere along pathway of descent caused by androgen deficiency in fetal testes if remain undescended, increased risk of sterility, testicular cancer
ectopic testes cause
gubernaculum passing to abnormal location
congenital inguinal hernia
failure of complete closure btwn tunica vaginalis & peritoneal cavity persistent processus vaginalis remains
what does gubernaculum become in females
ovarian ligament, connects ovary-uterus, and round ligament
where does gubernaculum pull down into in female
labium majora, to labial-scrotal swellings
abdominal end of processus vaginalis has small opening, allows peritoneal fluid to pass through