Week 2 - Development of the Urinary System

Question 1

Which part of the mesoderm is involved in development of the genitourinary tract?

Answer 1

Intermediate mesoderm

Question 2

List the two membranes where there is no intervening mesoderm between the ectoderm and endoderm.

Answer 2

1. Buccopharyngeal membrane

2. Cloacal membrane

Question 3

Which region does the pronephros appear in?

Answer 3

Cervical region

Question 4

Which region does the metanephros appear in?

Answer 4

Pelvic region

Question 5

What is the main function of the pronephros?

Answer 5

Gives rise to a duct which extends from the cervical region to the cloaca and drives development of the next developmental stage

Question 6

What is the urogenital ridge?

Answer 6

A region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad

Question 7

What are the functions of the mesonephric duct?

Answer 7

1. Sprouts the ureteric bud which drives the development of the definitive kidney
2. Important role in development of the male reproductive system

Question 8

What causes renal agenesis?

Answer 8

Failure of the ureteric bud to interact with intermediate mesoderm

Question 9

What structures lie anterior to peri-renal/perinephritic fat?

Answer 9

1. Gerota’s fascia

2. Anterior capsule

Question 10

What is the embryological derivative of the bladder?

Answer 10

Hind gut

Question 11

What is the embryological basis for a pelvic kidney?

Answer 11

Failure of cranial migration

Question 12

What structure is the collecting system derived from?

Answer 12

Ureteric bud

Question 13

What is the excretory component of the kidney derived from?

Answer 13

Intermediate mesoderm under the influence of the ureteric bud

Question 14

What is the role of the ureteric bud?

Answer 14

Induces development of the definitive kidney

Question 15

Where does the metanephric kidney first appear?

Answer 15

The pelvic region

Question 16

What important structure does the kidney cross during its ascent?

Answer 16

Arterial fork formed by vessels returning blood from the foetus to the placenta

Question 17

What is the final position of the kidney?

Answer 17

Lumbar region

Question 18

Outline the embryological basis of accessory renal arteries.

Answer 18

1. When the kidneys ascend from the pelvic region, they sprout new vessels from the abdominal aorta
2. Other vessels normally regress
3. Some vessels don’t regress: accessory renal arteries which are end arteries

Question 19

What is the embryological basis of duplication of the ureters?

Answer 19

Splitting of the ureteric bud - partial or complete

Question 20

What are the symptoms of duplication of the ureter?

Answer 20

Ectopic ureteral orifices –> incontinence: no control over urinary sphincter

Question 21

Outline the main features of polycystic kidney disease.

Answer 21

1. Recessive
2. Presents early
3. Poor prognosis

Question 22

What can multi cystic kidney disease cause?

Answer 22

Atresia of the ureter

Question 23

How is the urogenital sinus formed?

Answer 23

Formed from the hindgut by the urorectal septum

Question 24

What is the urorectal septum?

Answer 24

A wedge of mesoderm which grows down towards the cloacal membrane to separate the urinary and gastrointestinal tracts

Question 25

What is the female urethra formed by?

Answer 25

Pelvic part of urogenital sinus

Question 26

What is the male urethra formed by?

Answer 26

Pre-prostatic, prostatic and membranous: pelvic part of urogenital sinus Phallic: spongy part of the urogenital sinus

Question 27

What are the basic components of external genitalia?

Answer 27

1. Genital tubercles 2. Genital folds 3. Genital swellings

Question 28

Outline the formation of external genitalia in males.

Answer 28

- GT elongates | - Fusion of genital folds produces the spongy urethra: driven by sex hormones (androgens)

Question 29

Outline the formation of external genitalia in females.

Answer 29

- No fusion occurs in females | - Urethra opens into the vestibule

Question 30

Outline the main features of hypospadias.

Answer 30

1. Defect in fusion of urethral folds 2. Urethra opens onto the ventral surface, rather than at the end of the glans 3. Increasing incidence

Question 31

Outline features of the filtration barrier.

Answer 31

1. Capillary endothelium is fenestrated 2. Podocytes invest the capillary endothelium 3. Making filtration slits: spaces between podocyte processes 4. Podocytes and endothelium share a basement membrane 5. Very leaky

Question 32

Outline the main features of the PCT.

Answer 32

1. Longest, most convoluted section 2. Reabsorption begins 3. Simple cuboidal epithelium with pronounced brush border

Question 33

State the components of the juxtaglomerular apparatus.

Answer 33

1. Macula densa - DCT 2. Juxtaglomerular cells of the afferent arteriole of the glomerulus 3. Extraglomerular mesangial cells (aka Lacis cells)

Question 34

What is the collecting duct?

Answer 34

Continuation of the DCT via the collecting tubule

Question 35

How does the collecting tubule differ from the thick limb of Henle's loop histologically?

Answer 35

1. Larger lumen | 2. Lumen is more irregular rather than circular

Question 36

How many smooth muscle layers are present in the ureter?

Answer 36

- 2 layers | - A third appears in the lower 1/3 of the ureter

Question 37

What is the function of the transitional epithelium lining the urinary bladder?

Answer 37

Umbrella cells on the surface layer make the epithelium impermeable to the fluid collected, especially when the urinary bladder is distended

Question 38

Why does the proximal convoluted tubule have so many mitochondria?

Answer 38

To energise active transport of sodium ions mainly by the 3 Na 2 K ATPase transporter

Question 39

Why does the descending limb have such few mitochondria?

Answer 39

Water moves by osmosis which is a passive process

Question 40

What distinguishes the PCT from the collecting duct?

Answer 40

Collecting duct has a wider lumen and no brush border

Question 41

What structure is formed from the merging of collecting ducts, and acts as the gateway to the cavity known as the minor calyx?

Answer 41

Collecting ducts merge and terminate to form the papillary ducts of Bellini which open sieve like at the area cribosa

Question 42

In which structures in the urinary tract can you find transitional epithelium?

Answer 42

1. Cavity of the minor calyx 2. Urinary bladder 3. Ureters 4. Superior urethra

Question 43

Interaction between which structures is key to development of the definitive kidney?

Answer 43

Ureteric bud and metanephric tissue cap

Question 44

What foetal abnormality might you suspect if you examined a pregnant patient and discovered that there was an abnormally Low amniotic fluid volume?

Answer 44

Bilateral renal agenesis

Question 45

Explain the embryological basis for a pelvic kidney.

Answer 45

Sometimes, 1 or both kidneys fail to ascend to their normal position in the lumbar region of the abdomen

Question 46

Explain the embryological basis of horseshoe kidney (seen in 1/600 births).

Answer 46

If the 2 developing kidneys become too close to each other as they begin to move out of the pelvis, their lower poles can fuse as they undergo lateral rotation. The fused kidney is caught on the inferior mesenteric artery (the first midline unpaired branch of the aorta that it meets during ascent). Therefore, a horseshoe kidney is typically found at the pelvic brim.

Question 47

Explain the embryological basis for accessory/suprarenal arteries.

Answer 47

Accessory renal arteries can arise because of the ascent of the kidney during development. As kidneys rise from the pelvis to the lumbar region of the abdomen, they acquire new branches from the aorta. They normally disappear, but can remain producing a variant blood supply