urogenital embryology

Question 1

urogenital development

Answer 1

develop from intermediate mesoderm along posterior abdominal cavity, are therefore primary retroperitoneal and initialy both systems enter the cloaca cavity, both nephrogenic and genital structures development from urogential ridge

Question 2

kidney development

Answer 2

three kidney systems develop (pronephros, mesonephros, and metanephros) from urogentia ridge (IM), nephrogenic ridge sequentially form

Question 3

pronephros

Answer 3

develop at week 4 in cervical region, clumps of im ball up and disappear, never become functional, form pronephric duct (a cord that extends down toward mesonephros and induce mesonephric duct formation

Question 4

mesonephros

Answer 4

week 4-10, from level T1-L3, clumps of im ball up and form functiona nephrons, filter embryonic blood and generate urine, create mesonephric ducts that drain urine into developing urinary bladder,

Question 5

metanephros

Answer 5

start to form at week 5 and begin to function at week 9-10, develop in the pelvic region, made up of two components ureteric bud and metanephric blastema

Question 6

ureteric bud

Answer 6

an outgrowth of the mesonephric duct close to the entrance of the cloaca, develop into ureter and kidney collecting ducts (renal pelvis, calyces, and tubules, also called mesonephric divirticulum, also produce factors to stimulate metanephric blastema

Question 7

metanephric blastema

Answer 7

develops from im at pelvic region, the caudal most region of metanephros, produces factors to stimulate ureteric bud to continue to branch and grow, give rise to nephrons

Question 8

ascent of kidneys

Answer 8

metanephric kidneys ascend from pelvic region to thoracolumbar level as embryonic body grows, sequential acquisition of new blood supply with the ascent, new cranial vessel grows into the kidney and the caudal vessels degenerate

Question 9

indefferent phase

Answer 9

can’t tell sex by morphology, up until week 6, both sexes possess the genital ridges that look the same and two sets of genital ducts, mesobephric duct (wolffian) and paramesonephric duct (mullerian)

Question 10

wolfian duct

Answer 10

mesonephric duct become epididymis and ductus defernce

Question 11

genital ridge

Answer 11

formed by proliferation of the epithelium and a condensation of underlying mesenchyme, also produces cord cells

Question 12

primordial germ cells

Answer 12

originate in the epiblast , migrate through the primitive streak, endoderm cells in the wall of the yolk sac close to the allantosis, and finaly arriving at primitive gonads in the genital ridges, if they fail to reach the ridge, gonads will not develop

Question 13

cord cells

Answer 13

budding mesoderm in genital ridges, forms cords when penetrate underlying mesenchyme (play a supportive role) and envelope arriving primordial germ cells in reciprocal induction, if primary germ cells don’t migrate, both pgc and cord degenerates

Question 14

sex determining region on y

Answer 14

SRY, produces testes determining factor

Question 15

testes determining factor

Answer 15

stimulates cord cells to defferentiate into sertoli cells, and mesenchyme to differentiate into leydig cells in males

Question 16

sertoli cells

Answer 16

important for spermtogensis in adults, also produces mullerian inhibiting factor which causes the degeneration of mullerian ducts

Question 17

leydig cells

Answer 17

produce male sex hormone testosterone, which influence sexual differentiation of external genitalia and male genital ducts

Question 18

development of ductus deferens

Answer 18

as the mesonephric kidneys degenerate, mesonephric ducts are repurposed and connect with seminiferous tubules to become epididymis and ductus deference, as testes descend, ductus deferens loops around ureter

Question 19

development of female genital system

Answer 19

no SRY-> no TDF, cord cells become follicular cells and mesenchyme become stromal cells (ovary), mesonephric duct degenerates, no MIF allows mullerian duct to develop into uterine tube

Question 20

mullerian ducts

Answer 20

caudal end fuses to become uterus and cervix, cranial end do not fuse to become uterine tubes

Question 21

sinovaginal bulbs

Answer 21

two envaginations that form from ventral part of cloaca (urethral plate), meets with uterin canal to form vagina

Question 22

transformation of cloaca

Answer 22

divides into ventral urogenital space continuous with allantois and dorsal rectal space

Question 23

bladder development

Answer 23

as bladder grows from urogentical sinus, caudal meonephric ducts are incorporated into dorsal wall to create trigone, ureters gain separate opening on dorsal cranial wall and in males, ductus deferens hooks over the ureter

Question 24

genital tubercle

Answer 24

mesenchyme outgrowth anterior to cloacal membrane, becomes either glan penis or clitoris

Question 25

urogenital folds

Answer 25

mesenchyme cloacal cells on either side of cloacal membrane, becomes shaft of penis or labia minora

Question 26

labioscrota folds

Answer 26

a pair of elevations on either side of urogenital folds, become either scrotum or labia majora

Question 27

urethral plate

Answer 27

derives from endoderm, replacing cloacal membrane after it breaks down, in males get enveloped in genital tubercle to become penile urethra or vestibule of vagina