Embryo/Teratogenesis

Question 1

Where does the urinary system develop from?

Answer 1

Intermediate mesoderm along posterior wall of abdominal cavity

Question 2

What are the 3 developmental kidney systems (cranial to caudal)?

Answer 2

1) Pronephros
2) Mesonephros
3) Metanephros

Question 3

Is the pronephros functional?

Answer 3

No, it is rudimentary and non-functional

Question 4

How long does the pronephros exist for?

Answer 4

1 week (beginning to end of 4th week)

Question 5

What arises from the pronephros?

Answer 5

Vestigial excretory units (nephrotomes)

Question 6

When does the pronephros develop?

Answer 6

Beginning of 4th week

Question 7

When does the mesonephros develop?

Answer 7

Middle of 2nd month

Question 8

Where are both the mesonephros and mesonephric ducts derived from?

Answer 8

Intermediate mesoderm from Upper thoracic to L3 segment

Question 9

The mesonephros form ______ on each side of the midline and the ________ ridge.

Answer 9

Form large ovoid organ
and urogenital ridge

Question 10

When do the 1st excretory tubules of the mesonephros appear?

Answer 10

Early in 4th week

Question 11

The 1st excretory tubules of mesonephros acquire _____________ at the _____ end. Tubules enter the ______________.

Answer 11

Acquire glomerular capillary tuft at medial end

Tubules enter longitudinal mesonephric (wolffian) duct laterally

Question 12

True or false: Caudal tubules will differentiate into functional tubules before the cranial tubules degenerate.

Answer 12

False.
Cranial tubules start degenerating while caudal tubules are still differentiating

Most disappear by end of 2nd month

Question 13

The metanephros forms the permanent kidney and appears in the ____ week.

Answer 13

5th week

Question 14

Where do nephrons develop from?

Answer 14

Metanephric mesoderm

Question 15

Where does the collecting system of kidneys develop from?

Answer 15

Ureteric bud

Question 16

How are metanephric tubules formed?

Answer 16

From metanephric tissue cap (induced by collecting tubule)
- forms small renal vesicles
→ comma-shaped → S-shaped
→ metanephric tubules

Question 17

How do metanephric tubules develop into functional nephrons?

Answer 17

Proximal end deeply indented by glomerulus and forms Bowman’s capsule

Distal end in open connection with collecting tubules

Nephron lengthen → PCT, LOH, DCT

Question 18

How does the collecting system of the kidneys form?

Answer 18

From ureteric bud
1) Bud penetrates metanephric tissue
2) Dilates to form renal pelvis
3) Branches repeatedly → Ureter, pelvis, major/minor, calyces, collecting tubules

Question 19

True or false: The maximum number of nephrons a person has is determined at birth.

Answer 19

True.
There is no increase in number of nephrons postnatally. (~1 mil)

Question 20

True or false: The kidneys are lobulated only at birth.

Answer 20

True.
The lobulations disappear with the growth of nephrons (gaps filled with tissue)

Question 21

True or false: The kidneys are located in the pelvic region throughout life.

Answer 21

False.
Kidneys initially located in pelvic region but ascend to more cranial position in abdomen.

Question 22

How does the blood supply of the kidneys change throughout development?

Answer 22

1) Initially supplied by pelvic branch of aorta
2) Shifts to more cranial position in abdomen
3) Supplied by arteries from higher levels of aorta → lower vessels degenerate

Question 23

What causes the ascent of the kidneys?

Answer 23

1) Diminution of body curvature
2) Growth of body in lumbar and sacral regions

Question 24

When does the metanephros become functional?

Answer 24

End of 1st trimester

Question 25

Where is fetal urine passed into after the 1st trimester?

Answer 25

Amniotic cavity
(mixes with amniotic fluid and swallowed to be excreted over and over)

Question 26

True or false: The kidneys are functional by the end of the 1st trimester and are responsible for homeostasis of ions, water, blood pressure, excretion of waste products etc.

Answer 26

False.
Excretion of waste products is done by placenta

Question 27

What are the forms of renal agenesis?

Answer 27

1) Unilateral (1 functional)
2) Bilateral (die)

Question 28

What is an ectopic kidney?

Answer 28

Pelvic kidney (did not ascend)

Question 29

What is a horseshoe kidney?

Answer 29

Fusion of kidneys

Question 30

In which condition would more than 2 renal pelvises be seen?

Answer 30

Duplication of urinary tract (eg. complete division of ureteric bud)

Question 31

What is a possible complication of accessory renal arteries formed as a result of developmental anormalities?

Answer 31

Compression/obstruction of ureter

Question 32

Where does the urinary bladder form from?

Answer 32

The upper (largest) part of urogenital sinus

Question 33

What does the pelvic part of the urogenital sinus form?

Answer 33

Forms prostatic and membranous parts of urethra in males

Question 34

What is the urorectal septum?

Answer 34

Divides cloaca into anorectal canal and urogenital sinus

Question 35

When does the cloaca divide into the anorectal canal and urogenital sinus?

Answer 35

Between 4th-7th week

Question 36

The _______ membrane divides into the urogenital and anal membrane.

Answer 36

Cloacal

Question 37

What are 2 structures that the urogenital sinus gives rise to?

Answer 37

Bladder and urethra

Question 38

The caudal portions of the mesonephric duct are absorbed into _________.

Answer 38

The urinary bladder wall

Question 39

What forms the ejaculatory ducts in males?

Answer 39

Orifices of the mesonephric ducts that move close together and enter the prostatic urethra

Question 40

What is the embryological origin of the mesonephric ducts and ureters?

Answer 40

Mesoderm

Question 41

What is the embryological origin of the trigone?

Answer 41

Mesoderm

Question 42

What is the embryological origin of the bladder lining?

Answer 42

Mostly endoderm
(only trigone mesoderm left, rest replaced)