1.2.2 Embryology and Development of Kidney and Urinary Tract

Question 1

What are some potential malformations of the bladder and urethra?

Answer 1

Extrophy of the bladder - exposure and protrustion of the posterior wall of the bladder through the abdominal wall

Epispadias - Urethra opens on the dorsal surface of the penis

Hypospadias - Urethra opens on the ventral side of the penis

Question 2

What is this an image of?

Answer 2

Wilms tumor - blastema

Question 3

What is the origin of the metanephric kidney?

Answer 3

It forms from the metanephric blastema which forms from the intermediate mesoderm

The Ureteric bud comes from the mesonephric duct and penetrates the metanephric blastema.

Question 4

Does the kidney ascend?

Answer 4

Question 5

What is congenital virilizing hyperplasia?

Answer 5

This is and Adrenogenital syndrome that can cause female pseudohermaphroditism

Question 6

What are three types of urachal malformation?

Answer 6

Urachal malformations: A. Urachal Fistula, B. Urachal Cyst, C. Urachal Sinus

Question 7

Describe the relationship of the ureters and the mesonephric ducts during development.

Answer 7

Dorsal views of the bladder showing the relationship of the ureters and mesonephric ducts during development. Initially, the ureters are formed by an outgrowth of the mesonephric duct (A), but with time they assume a separate entrance into the urinary bladder (B⇒D). Note the trigone of the bladder formed by the incorporation of the mesonephric ducts (C,D).

Question 8

Describe the development of the Metanephric Excretory Unit. (This is a picture of a slide)

Answer 8

Question 9

Is kidney development complete at birth?

Answer 9

Question 10

What cells form the medulla of the adrenal cortex?

Answer 10

Chromaffin cells

Question 11

Describe the development of the Urethra.

Answer 11

Question 12

What is this an image of and describe the process that is occuring.

Answer 12

Ureteric bud and induction of Vesicles in the metanephric blastema’

Nephron development in the metanephros (57 days): Ureteric bud has induced a change in the surrounding mesenchyme of the metanephric blastema to convert the mesenchyme to an epithelium and form the S-shaped nephric (renal) vesicle seen in what was metanephric blastema. Concomitant, with the change there is a conversion of intermediate filament protein markers and the production of laminin and type IV collagen instead of fibronectin and type I collagen. The arrow shows the junction of the collecting tubule and the nephron portion

Question 13

What is Potter Sequence/Syndrome?

Answer 13

These features are secondary to prolonged oligohydramnios secondary to bilateral renal agenesis, or anomalies in which the kidneys are present but there is an obstructed urethra, prolonged rupture of membranes, or severe growth retardation.

Question 14

What is the medulla derived from?

Answer 14

Neural crest cells

Question 15

What are the important genes involved in Metanephros differentiation?

Answer 15

WT1 - The only one he talked about

GDNF, HGF, BMP7 and WNT4

Question 16

What is this an image of?

Answer 16

Wilms tumor - pointing at tubules

Question 17

What does the Cloaca divide into?

Answer 17

Division of the cloaca into the urogenital sinus and anorectal canal. The mesoneprhic duct is gradually absorbed into the wall of the urogenital sinus, and the ureters enter separately. A. At the end of the 5th week. B. 7 weeks. C. 8 weeks.

Question 18

What are the characteristics of the mesonephros?

Answer 18

This is functional during the development of the permanent, metanephric kidney

The mesonephric duct contributes to the developing testis, the male genital system and vestigal remnants of the female

The mesonephros is important in the production of urine which is added to the amniotic fluid.

Question 19

What are the three types of kidneys during development?

Answer 19

Pronephros

Mesonephros

Metanephros

Question 20

What is the role of WT1?

Answer 20

WT1, expressed by the mesenchyme, enables the tissue to respond to induction by the ureteric bud.

Question 21

What are the histopathological characteristics of Wilms Tumor?

Answer 21

1. Tightly packed cells
2. Presence of fibrocytic or spindle shaped cells
3. Presence of poorly formed tubules**
4. Triphasic combination - blastemic, stromal, and epithelial

Question 22

Describe the development of the bladder.

Answer 22

Also know:

Mesonephric ducts and attached ureteric buds are intercalated into the posterior wall of the bladder - Exstrophy

Initially, the bladder is continuous with the allantois which forms the urachus which is know in the adult as the median umbilical ligament

The bladder is an abdominal organ in infants

Question 23

What are the types of renal angenesis?

Answer 23

Unilateral - occurs 1/1,000 and only a major problem if other defects are present

Bilateral - occurs 1/3,000, oligohydramnios during gestation and is incompatible with postnatal life

Question 24

How do ectopic ureters occur?

Answer 24

Duplications of the ureteric buds

Question 25

What is the pronephros?

Answer 25

This is a transitory kidney and is regarded by most developmental biologist as a non-functional kidney

Question 26

What is this an image of?

Answer 26

Wilms tumor - stromal component

Question 27

What are these images of?

Answer 27

Hypoplasia of the lung due to oligohydramnios

Question 28

What does the Urogenital sinus develope into?

Answer 28

A. **Development of the urogenital sinus into the urinary bladder and definitive urogenital sinus**. B. In the male, the definitive urogenital sinus develops into the penile urethra. The prostate gland develops from outgrowths of the urethra and the seminal vesicles are formed as outgrowths of the developing ductus deferens.

Question 29

What is the common origin of the urinary and genital systems?

Answer 29

Intermediate mesoderm

Question 30

What is this an image of?

Answer 30

Formation of the metanephros and continuing inductions

Question 31

What is a horseshoe kidney and what can cause it?

Answer 31

Inferior poles of kidneys are fused, and ascent is blocked by the inferior mesenteric artery

Question 32

What is this an image of?

Answer 32

Ureteric bud and metanephric blastema

Question 33

Describe the dysregulation of the fetal adrenal gland in congenital virilizing hyperplasia (Adrenogenital syndrome)

Answer 33

Normal feedback control of the adrenal cortex is lost in adrenogenital syndrome (congenital virilizing hyperplasia). Most often the cause is a mutation in the C21 hydroxylase enzyme resulting in an inability to synthesize corticosteroids. **ACTH and CRH become elevated and increase secretion of dehydroepiandrosterone from the fetal adrenal cortex leading to elevated hydroxyprogesterone (precursor to cortisol) levels. The elevated dehydroepiandrosterone levels lead to masculinization of the female genitalia.**

Question 34

Describe the relation of the gonad and the mesonephros.

Answer 34

A. Transverse section through the urogenital ridge in the lower thoracic region of a 5-week-old embryo showing formation of an excretory tubule of the mesonephric system. Note the appearance of Bowman’s capsule and the gonadal ridge. The mesonephros and the gonad are attached to the posterior abdominal wall by a broad urogenital mesentery. B. Relation of the gonad and the mesonephros. The mesoneprhic (Wolffian) duct runs along the lateral side of the mesonephros.

Question 35

What is the adrenal cortex formed from?

Answer 35

Intermediate mesoderm

Question 36

What are the characteristics of the metanephros?

Answer 36

Permanent kidney, appears in the 5th week It produces urine when the fetus is 11 to 13 weeks old Urine formation continues throughout intrauterine life

Question 37

What is the Dr. Klein key to success when determining the difference of oligohydramnios and polyhydramnios?

Answer 37

Less urine output = less fluid - oligohydramnios Less swallowing = more fluid - polyhydramnios

Question 38

Describe the regulation of the adrenal gland

Answer 38

Normal feedback control of the adrenal cortex occurs from the anterior pituitary through the secretion of adrencorticotrophic hormone (ACTH) with oversight from a higher authority—the hypothalamus (CRH, corticotrophic releasing hormone. Increased secretion of cortisol feeds back on the anterior pituitary resulting in decreased ACTH secretion and decreased secretion of the releasing hormone from the hypothalamus.

Question 39

The pronephric system starts as what?

Answer 39

Segmented intermediate mesoderm which will then become the vestigal pronephric system

Question 40

What disease will result from a mutation in the WT-1 gene?

Answer 40

Wilms Tumor - nephroblastoma

Question 41

What is the importance of urine production in the embryo?

Answer 41

Included in this list are: Placenta is the primary waste disposal system for fetus Kidneys are essential organs at birth **Oligohydramnios**

Question 42

Describe the ascent of the kidney.

Answer 42

A ⇒ C. Ascent of the Kidneys. Note the change in position between the mesonephric and metanephric systems. The mesonephric system degenerates almost entirely, and only a few remnants persist in close contact with the gonad. In both male and female embryos, the gonads descend from their original level to a much lower position.