Development of urinary system Flashcards by Ibtihal Balubaid

The kidneys, ureters & trigone of urinary
bladder develop from the———-while the rest of urinary
bladder & urethra develop from the —————–

intermediate mesoderm

endoderm of the urogenital sinus (cloaca)

How well did you know this?

Not at all

Perfectly

The development of the kidneys in the
human embryo occur in ---- successive,
overlapping kidney systems, which are:
•----------
•---------
•---------

3
Pronephros
Mesonephros
Metanephros

How well did you know this?

Not at all

Perfectly

————-It is the 1st & simplest kidney system which appear in the embryo.
Site:
Structure:
Function:
Fate:

PRONEPHROS
• It is developed in the cervical part of intermediate mesoderm (early in 4th week), as series of 7-10 solid masses of cells, called ➔ nephrotomes.

• These masses form a 7-10 excretory tubules called pronephric tubules
(one tubule from each segment of intermediate mesoderm).
• These tubules end medially into coelomic cavity, where each tubule
overlies a tuft of capillaries, “external glomerulus”.
• Each tubule ends laterally by joining the lateral end of next one ➔ a longitudinal collecting duct called pronephric duct, which extends to open into the cloaca, by 24th day

No function in the human embryo. Thus, the pronephros is rudimentary & non functioning, analogous to kidney of some fish.
The tubules degenerate completely by the end of the 4th week, while the pronephric duct persists to become the mesonephric duct.

How well did you know this?

Not at all

Perfectly

•Excretory tubules of the pronephric and mesonephric systems in a ———weekold embryo

intermediate mesoderm 
nephrogenic cord
pronephros
mesonephros.
5

How well did you know this?

Not at all

Perfectly

• -----------: is formed by an
invagination of small branch of dorsal
aorta into coelomic cavity ➔ --------------, or into wall of nephric tubules
➔ --------------
• Excretory unit = --------- + nephric
tubule.

The glomerulus
external
glomerulus
internal glomerulus.
glomerulus

How well did you know this?

Not at all

Perfectly

what is the site of Mesonephros ?structure?

• It extends from lower cervical to upper lumbar segments of the intermediate mesoderm
• Each segment of the intermediate mesoderm develops 2-3 or more of excretory tubules called “mesonephric tubules (There are about
70 nephrotomes on each side).
• These tubules are not connected with intraembryonic coelum. Each
tubule is S-shaped that has:
• Medial end: acquires a glomerulus, where it forms a Bowman’s
capsule, which is invaginated by capillary tuft, internal
glomerulus.
• Lateral end: opens into the longitudinal mesonephric (Wolffian) duct, which opens caudally into primitive urogenital sinus.

How well did you know this?

Not at all

Perfectly

• In middle of ——- nd month, the mesonephros forms a large —– swelling (urogenital ridge) on sides of midline, attached dorsally
by a broad urogenital mesentery.
• The developing gonad lies medial to the mesonephros.

ovoid

How well did you know this?

Not at all

Perfectly

what is the fate of mesonephros ?

• While caudal tubules still
formed: cranial ones &amp; their
glomeruli start to
degenerate.
• The majority of the tubules
disappear by end of 2
nd
month, while a few tubules
persist near the gonads.
• The mesonephric duct
disappears in the female,
while in the male it forms the
vas deferens.

How well did you know this?

Not at all

Perfectly

what is the fate of Mesonephric tubules in male ?

◼ The upper tubules degenerate.
◼ The middle & lower tubules form the efferent
ductules of testis, head of epididymis & paradidymis.

How well did you know this?

Not at all

Perfectly

what is the fate of Mesonephric tubules in female ?

◼ Degenerates, few
rudimentary tubules
remain forming the
epoophoron &amp;
paroophoron in the broad
ligament.

How well did you know this?

Not at all

Perfectly

what is the fate of Mesonephric duct in male ? 6

It gives: male ducts
◼ Body &amp; tail of epididymis.
◼ Vas deferens.
◼ Ejaculatory duct.
◼ Seminal vesicle.
◼ Ureteric bud.
◼ Trigone of the bladder.

How well did you know this?

Not at all

Perfectly

what is the fate of Mesonephric duct in female ?3

It gives:
◼ Ureteric bud.
◼ Trigone of the bladder.
◼ A rudimentary duct called Gartner’s duct.

How well did you know this?

Not at all

Perfectly

in —————-Situated in cervical and upper

thoracic regions

Pronephros

How well did you know this?

Not at all

Perfectly

in ————Consists of 7-8 segmentally

arranged pronephric tubules

Pronephros

How well did you know this?

Not at all

Perfectly

in -----------Each tubule is provided with one
external glomerulus; sometimes
both external and internal
glomeruli are connected with the
tubule

Pronephros

How well did you know this?

Not at all

Perfectly

in ————- Each tubule is connected to the
coelomic cavity by- a peritoneal
funnel

Pronephros

How well did you know this?

Not at all

Perfectly

————-Situated in lower thoracic and

lumbar regions

Mesonephros

How well did you know this?

Not at all

Perfectly

—————Consists of 70-80 non-segmental

mesonephric tubules

Mesonephros

—————Each tubule is provided with one

internal glomerulus only

Mesonephros

————The mesonephric tubules are not

connected to the coelomic cavity

Mesonephros

• ————- It is the 3rd kidney system (permanent kidney) to
develop.

Metanephros

Site of Metanephros ?

it arises in lower lumbar

& sacral regions.

Metanephros
• Structure: it appears in ——week, during regression of the mesonephros. It has a double origins:
•———————-:
• Begins at 28th day as an
outgrowth from —————wall
of mesonephric duct close to cloaca
➔ metanephric (ureteric) diverticulum.
➢ This diverticulum ——— &——— metanephros, which forms a cap on its distal end.
➢ The elongated stem will form the
———- its end dilates to form the
————— The later divides into
cranial & caudal branches (future
major calyces). Each subdivides until
more than ———- generations of collecting tubules are formed (— - —- millions).
➢ The 2nd order ——–&——– 3rd&4th generations to form the minor calyces by 7th week.
➢ The collecting tubules (10-25tubules) of 5th & successive generations elongate, converge on a minor calyx to form the ————–

5th 
Ureteric bud (collecting system)
dorso-medial 
elongates-penetrates
ureter
primitive pelvis
12
1-3
enlarges &amp; absorbs
renal pyramid

• Metanephric cap = metanephric blastema = renal vesicle = metanephric vesicle
(excretory system):
o While the collecting tubules penetrate the —————, the end of each one is covered by ——————- (in the form of a cell cluster).
o The cap moves with tubule distally and forms a cell cluster on each side of it. They form —————, which develop into small tubules (nephrons /
excretory tubule):
o Its proximal end invaginated by
————–, glomerulus(forming the —– capsule).
o Its distal end opens into
collecting tubule
o Continuous lengthening of the nephron gives proximal convoluted tubule, ———– & distal convoluted tubule.

metanephric blastema
metanephric tissue cap
renal vesicles
capillary loop
Bowman ’s
loop of Henle

• Ascent & rotation of kidney: • The metanephros shifts cranially, between 6 th-9th week, due to ---------------------, growth of lumbar & sacral regions & elongation of ureter. • At first, it is supplied by ------------- branches of aorta, then by ---------------- branches. • Its hilum directed ventrally at first then rotates medially. • The kidney is lobulated, then lobulation ------------ during 1st year of life. • The metanephros is functional during 10-13th week, and the urine passes to amniotic cavity (in renal agenesis, there is ---------------------). • Urine formation begins towards the end of the first trimester of fetal development and is excreted into the amniotic fluid

``` diminution of body curvature pelvic abdominal disappears oligohydramnios ```

* Urogenital sinus: * From 4-6th week, the primitive urogenital sinus is formed by growth of--------------- septum, which meats the cloacal membrane at the ------------------. * The sinus is closed by the ----------------- & is divided by the entrance of mesonephric ducts, into: * ---------------- part: It is the larger part above mesonephric ducts. It is continuous with allantois. It gives rise to: * Urinary bladder, except the --------------- * Upper ½ of prostatic urethra in male & whole urethra in female

``` urorectal perineal body urogenital membrane Vesico-urethral trigone. ```

• Definitive urogenital sinus: lies below ducts & is subdivides into: • -------- part: is narrow canal, it gives the lower ½ of prostatic urethra & membranous urethra in male. • ------------ part: is flattened from side to side, closed by urogenital membrane, it gives most of phallic (penile) urethra in male. N.B.: in female, the whole definitive urogenital sinus gives rise to -----------------.

Pelvic Phallic vestibule of vagina

Development of urinary bladder • It develops from: •----------- part: -------------- in origin. Apex connected by allantois to umbilicus. Proximal part of allantois incorporated into -------------. Distal part narrowed into thick fibrous cord, -------- which gives median umbilical ligament after birth. •Caudal parts of mesonephric ducts: --------- in origin. During division of cloaca, their proximal parts absorbed into bladder wall, forming trigone of bladder

``` Vesico-urethral Endodermal bladder urachus Mesodermal ```

* Ureters, initially emerging from mesonephric ducts, enter bladder separately. Later, ureteric orifices move ----------; those of ducts move medially, become close together to enter prostatic urethra. Absorbed parts incorporate into the trigone of bladder, i.e. mesodermal. Rest of bladder is --------------. * ----------- lining of trigone is replaced by endodermal epithelium, so the bladder becomes lined completely by epithelium of endodermal origin. * Splanchnic mesoderm around cloaca gives------------

cranially endodermal Mesodermal muscle wall

•Development of urethra: (in male) •Prostatic part: •Upper ½: From ------------part (endodermal). Its post wall develops from absorbed ----------(mesodermal). •Lower ½: From pelvic part of definitive -------------- •Membranous part: From pelvic part of definitive urogenital sinus. It gives two endodermal outgrowths, the ---------------- •Spongy (penile) part: From ------------- part of definitive urogenital sinus & ----------- overlying glans penis.

``` vesico-urethral mesonephric ducts urogenital sinus. bulbo-urethral glands. phallic ectoderm ```

Anomalies of kidney ------------------------Bilateral / unilateral, due to early degeneration of ureteric bud. Unilateral agenesis occurs 1:1500, more in males. Bilateral agenesis associated with oligo-hydramnios, incompatible with life (transplantation)

Renal agenesis:

Anomalies of kidney ----------------------Due to inadequate branching of ureteric bud.

Hypoplasia of kidney

Anomalies of kidney -------------------------Nephrons are abnormally developed; consist of primitive ducts lined by undifferentiated epithelium surrounded by thick layers of connective tissue.

Dysplasia of kidney

Anomalies of kidney ------------------Results from extra-ureteric bud

Supernumerary kidney

Anomalies of kidney --------------------------- • Solitary or polycystic, due to non-union of a collecting tubule with an excretory tubule. Urine accumulated in excretory tubule causes its dilatation, followed by cyst formation, lined by cuboidal epithelium. Usually present in renal cortex. • Cysts may arise from abnormal development of collecting system, due to hyperplasia of their walls or abnormal differentiation of ureteric bud leads to dilatation, constriction or atretic tubules.

• Congenital cystic kidney:

``` Anomalies of kidney ------------------------ 1:600. Lower poles fuse together, usually located at lower lumbar vertebrae. Its ascent prevented by inferior mesenteric artery. Ureters arise from anterior surface of kidney, pass ventral to isthmus. ```

Horse-shoe kidney:

Anomalies of kidney ---------------Caused by fusion of upper & lower poles of both kidneys.

Rosette kidney

2 examples of Anomalies of kidney?

* Pelvic kidney | * Lobulated kidney

Anomalies of ureters ----------------------------• One ureter ends in bladder, other ends into vagina, urethra or vaginal vestibule or into prostatic urethra, ejaculatory duct, vas deferens or seminal vesicle. • Due to migration of one ureter downward with its mesonephric duct to open abnormally.

• Ectopic ureter

``` Anomalies of ureters ----------------------------------- • Due to splitting of ureteric bud, may be partial (bifid) or complete (cap may be divided). • In bifid (Y-shaped) ureter: contractions in its limbs may be asynchronous ➔ reflux of urine from one limb to other; i.e. stasis of urine & infection. ```

• Double ureter:

Anomalies of urinary bladder • Urachal fistula, cyst & sinus: * Fistula: Persistence of ------------------ * Cyst: Persistence of------------------ * Sinus: Persistence of its -----------

allantois localized part. distal (umbilical) end

``` Anomalies of urinary bladder ----------------------- • Bladder opens on the surface of anterior abdominal wall, due to failure of development of infra umbilical part of abdominal wall. ```

• Ectopia vesica:

Urethra abnormalities ------------------- • Urethra opens into dorsum of the penis

Epispadias

Urethra abnormalities -------------------------- • Urethra opens into ventral surface of the penis

Hypospadias