Urinary and Reproductive systems development

what does the urinary system develop from?

the intermediate mesoderm (nephrotome)

what does the nephrotome give rise to?

urinary system, suprarenal glands, gonads, genital duct system

what are the 3 sets of nephrite systems, cardiocaudally?

pronephros, mesonephros, metanephros

where are pronephroi (pronesphros) formed?

cervical region, and are non-functional

are the mesonephroi (mesonephros) temporary or permanent?

temporary

what do the metanephros form?

excretory part of the kidney (from bowman’s capsule to DCT)

mesonephric/Wolffian/nephric duct

small tube that develops in the intermediate mesoderm adjacent to the 3 sets of nephric systems

induces formation of mesonephros and continue to grow caudally to fuse with the cloaca

gives rise to several male genital ducts and glands

cloaca

expanded portion of the primitive handgun tube deep to the cloacal membrane

ureteric bud

from the caudal end of the mesonephric duct and evagination forms this

it forms the collecting part of the kidney (from ureter to collecting ducts)

what are the 2 embryological sources that form the kidney?

metanephric blastema and ureteric bud

formation of kidney

ureteric bud grows towards the metanephroi

cranial part then undergoes repetitive branching to give rise to major calyces, minor calyces, and the collecting tubules

metanephric blastema under the influence of these collecting tubules differentiates into the nephrons- the glomerulus, proximal convoluted tubules, loops of henle, and distal convoluted tubules

metanephric blastema

the mesenchyme of the metanephros

renal agenesis

faulty interactions between ureteric bud and metanephroi

associated with oligohydramnios

if bilateral infants are stillborn or live only a few days

if unilateral- usually live due to compensatory hypertrophy of the remaining kidney

relocation of the kidneys

developing kidneys ascend up to their adult location in the lumbar region

one factor for this is differential growth of the lumbar and sacral regions

right kidney not able to ascend as high as the left due to presence of liver

as it ascends, kidney receives new more cranial arteries from the aorta for blood supply and the caudal ones disappear

partition of the cloaca

into dorsal ano-rectal canal and ventral urogenital sinus by formation of pro-rectal septum

allantois

a slim diverticulum of the cloaca extending into the connecting stalk

what forms the urinary bladder?

caudal allantois and urogenital sinus

what forms the urachus/median umbilical ligament in adults?

cranial allantois

what forms the trigone of the bladder?

incorporation of the mesonephric ducts into the posterior bladder wall

rectovesical fistula

anomaly in cloacal partitioning

genital ridge

ventromedial to the mesonephros

primordial germ cells migrate from yolk sac to the intermediate mesoderm in the thoracic region, this area

SRY gene on the Y chromosome

protein induces somatic support cells of gonad differentiation into sertoli cells and to secrete anti-Mullerian hormone, which in turn induces the degeneration of the mullerian ducts (paramesonephric duct)

in the absence of this, mullerian ducts develop into the female reproductive organs

in female, what does the cranial part of the paramesonephric ducts form?

the uterine tube and the caudal ends fuse to form the uterus, cervix, and cranial 1/3 of vagina

what happens to the paramesonephric ducts in males?

degenerates leaving few small remnants

what do male reproductive organs develop from?

the mesonephric duct

factors influencing descent of testis

androgens and pituitary hormones

gubernaculum of testis

intrabdominal pressure due to organ growth

formation of inguinal canal

caudal evagination of the abdominal wall

pathway taken by the testis as it descends into the scrotum

extends from the superficial to deep inguinal ring

males have higher incidence of inguinal hernias

cryptorchidism

undescended testis

failure of one or both testes to descend into the scrotum

most often testes descend spontaneously by 3 months, even if display this at birth

if not descended by 4-6 months, it is surgically brought down: orchiopexy

higher risk of testicular cancer