Embryology

Question 1

What does the paraxial mesoderm form?

Answer 1

Somites

Question 2

What does the intermediate plate mesoderm form?

Answer 2

Urogenital system (kidneys + repro)

Question 3

What does the lateral plate mesoderm form?

Answer 3

Body cavity and coverings

Question 4

What is below the endoderm?

Answer 4

The yolk sac

Question 5

What is above the ectoderm?

Answer 5

The amniotic cavity

Question 6

Take a wee gander at this

Answer 6

Question 7

What is the allantois?

Answer 7

Allantois is an outpouching of endoderm at the hindgut that extends into the body stalk

(body stalk later forms the umbilical cord)

Question 8

What is the cloaca?

Answer 8

(noun) The cloaca is the single posterior opening for a bird’s digestive, urinary and reproductive tracts and is used to expel feces and lay eggs.

Question 9

Wat does the cloaca divide to form?

Answer 9

Rectum and anteriorly the urogenital sinus

Question 10

What drains into the urogenital sinus?

Answer 10

The mesonephric duct

Question 11

What does the urogenital sinus later form?

Answer 11

The urinary bladder and its caudal end forms the urethra

Question 12

How many sets of kidneys develop during nephrogenesis?

Answer 12

3

Question 13

Where does the first set of pronephrons form?

Answer 13

Early in the Week 4 the intermediate mesoderm in the neck region of the embryo becomes the pronephros

Question 14

What makes up pronephros?

Answer 14

•pronephric duct + rudimentary pronephric tubules

Question 15

Where does the pronephric duct drain?

Answer 15

Drains into the cloaca

Question 16

When do the pronephros normally degenerate?

Answer 16

•In humans, the pronephros mainly degenerates by Week 5 (except the pronephric duct)

Question 17

What does the mesonephros form?

Answer 17

•Mesonephros = Intermediate mesoderm in trunk region, late Week 4.

Question 18

What does the pronephric duct become?

Answer 18

•Pronephric duct now becomes the mesonephric duct

Question 19

Where do mesonephric tubules drain?

Answer 19

•Mesonephric tubules develop and drain into the mesonephric duct

Question 20

What does the metonephros develop from?

Answer 20

• A ureteric bud that develops off the mesonephric duct
• Metanephric mesoderm (the most caudal part of the intermediate mesoderm)

Question 21

What happens to the mesonephros?

Answer 21

Much of the mesonephros will be incorporated into the developing gonad.

(Undifferentiated cells from the yolk sac migrate in to form the spermatogonia/ oogonia)

Question 22

What forms from the mesonephric tubules and the mesonephric ducts?

Answer 22

The mesonephric tubules become the rete testis

The mesonephric duct becomes the vas deferens

(In females the mesnephros becomes the ovary but the tubules and mesonephric duct degenerate)

Question 23

What happens to the ureteric bud?

Answer 23

The ureteric bud undergoes repeated branching at its distal end. (Ureteric bud comes from the mesonephric duct)

The stalk becomes the ureter, the expanded cranial end becomes the renal pelvis.

The first 4 generations of branches become confluent to become the major calyces

The next 4 generations form the minor calyces

The remaining generations form the collecting tubules

Question 24

How are the ureteric bud and the metanephric mesoderm induced?

Answer 24

The ureteric bud and the metanephric mesoderm reciprocally induce each other

Question 25

What is the definition of a nephron and a uriniferous tubule?

Answer 25

Nephron = Renal corpuscle + PCT + Loop of Henle + DCT

Uriniferous tubule = Nephron + Collecting duct

Question 26

What do the metanephric mesoderm and the ureteric bud form respectively?

Answer 26

Metanephric mesoderm: Nephron

Ureteric bud: Collecting duct and calyces, pelvis and ureter

Question 27

Why do the kidneys appear to ascend into the abdomen?

Answer 27

Mainly due to differential growth of lower body inferiorly away from kidneys

Kidneys come to lie in the upper abdomen (T12 - L3)

Question 28

What direction do the kidneys rotate?

Answer 28

Hilum rotates from ventral to medial (~90degrees)

Question 29

When does the ascent of kidneys end?

Answer 29

Ascent stops when they come in contact with adrenal glands

Question 30

During ascent what happens to the vasculature?

Answer 30

Segmental breakdown and reform of vascular supply during ascent