Development Of The Urinary System

Question 1

How many seperate kidney systems form and what re they

Answer 1

3 systems develop sequentially 
• Disappearance of one system marks the onset of development of the next
developmental stage 
• 1st appears in the cervical region
– the pronephros

Mesonephros
Metanephros

Question 2

What is he pronephros?

Answer 2

Step 1: the pronephros
• First kidney system, never functions in
humans
– provided useful data on kidney
development
• So why bother?
– its DUCT
– pronephric duct extends from the cervical
region to the cloaca and drives the development of the next developmental stage
Duct is common to mesonephros

Question 3

\\what is the urogenital ridge

Answer 3

Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
See slide for diagram

Question 4

What is the embryonic kidney (mesonephros)

Answer 4

Mesonephric tubules + mesonephric duct

Question 5

Describe the development of the mesonephros and why it needs to be “upgraded”

Answer 5

Step 2: the mesonephros
• Mesonephric tubules develop caudal
to the pronephric region 
• Mesonephric tubules PLUS
mesonephric duct = embryonic kidney • No water conserving function
so….need to upgrade

Question 6

What is the function of the mesonephric duct

Answer 6

• Mesonephric duct has important role in the development of the reproductive system in the male (remains if androgens are present0
• Mesonephric duct sprouts the ureteric bud which induces development of the definitive kidney

Question 7

Describe the importance of the ureteric bu

Answer 7

• Undifferentiated intermediate mesoderm, caudal to the mesonephros
• Ureteric bud induces
development of the true kidney,
metanephros in this tissue
Bud releases signals, causing undifferentiated mesoderm to bone metanephros. If signals not received or produced properly, then no true kidneys form

Question 8

Describe the development of the ureteric bud

Answer 8

ureteric bud contacts metanephric blastema
Bud expands and branches
The ureteric bud drives the development of the definitive kidney
– The collecting system is derived from the ureteric bud itself
– The excretory component is derived from intermediate mesoderm under the influence of the ureteric bud

Question 9

Describe the “ascent” of the kidney

Answer 9

• The metanephric kidney first appears in the pelvic region
• Undergoes an apparent caudal to cranial shift, crossing the arterial fork
formed by vessels returning blood from the fetus to the placenta
Supplied by unpaid brain cells of abdominal aorta. When kidneys ascend, new blood supply comes of abdominal aorta . Renal arteries are end arteries. Occasional remnants of pre existing arteries remain ad accessory renal arteries
Down in caudal regions. Sitting in whatwil become embryonic cavity. As embryonic body changes in l enth. Apaprat caudalto cranial shift

Question 10

What happens when the ureteric bud fails to interact with the intermediate mesoderm

Answer 10

• Ureteric bud fails to interact with intermediate mesoderm
– renal agenesis
• Migration goes awry
• Duplication defects
• Ectopic ureter
• Cystic disease
If unilateral - compatible with lie. Bilateral is not compatible with life

Question 11

Describe to structural anomalies related to migration

Answer 11

Structural development associated with development, kidneys atays in starting pos - signal disrupted

horshoe = pair of kidneys - as they are moving up through the abdomen, the causal poles got close and fused , blocked by abdominal aorta

Question 12

Describe defects / ectopic urethral orifices

Answer 12

Splitting of the ureteric bud • Partial or complete • Symptomatic consequence is ectopic ureteral opening
Opening into vagina - inconteance

Question 13

What is the cloaca?

Answer 13

• The development of the three systems is closely linked
• To begin with, the reproductive tract, urinary tract and GI tract share a common caudal opening
• Hindgut ends in a dilated structure
– the cloaca
• Closed to the outside by the cloacal membrane
– no mesoderm

Question 14

What is the urogenital sinus?

Answer 14

• Created from hindgut by urorectal septum
• UGS is continuous with umbilicus
– Urachus
• Closes to become the median umbilical ligament

Question 15

Describe the urorectal septum

Answer 15

Grows down splitting cloaca. Ugs and anorectal canal form. See slide

Question 16

What does the UGS develop into?

Answer 16

• Superior part connects to umbilicus
• Majority differentiates to form the urinary bladder
• Inferior part develops into the urethra
– Sex differences in structural
development of the urethra, depends on karyotype of germ cells

Question 17

Describe the development of the UGS and MD in females

Answer 17

MD reach UGS, ureteric bud sprouts from MD, UGS begins to expand, MD begins to regress.

MD regression continues, ureteric bud opened into UGS. See slide

Question 18

Describe the development of the UGS and MD in males

Answer 18

MD reach UGS, ureteric bud sprouts from MD, UGS begins to expand, MD begins to regress

UBS and MDs make independent openings in UGS, prostate and prostatic urethra formed where the MDs contact. MDs go on to deelopinto duct system - develop into vas deferens and epididymis.

Question 19

What are the 4 parts of the male urethra

Answer 19

– Pre-prostatic
– Prostatic
– Membranous
– Spongy

Question 20

What is the male urethra formed from

Answer 20

Pelvic part of the urogenital sinus

Question 21

Describe the development of the male urethra

Answer 21

In the male the GT
elongates & genital folds
fuse to form the spongy
urethra
Need to be fusion - communication needs to be uninterrupted

Question 22

What is hypospadias

Answer 22

• Defect in fusion of urethral folds • Urethra opens onto the ventral
surface rather than at the end of
the glans • Incidence increasing