Development 2

Question 1

Which organs does the endoderm provide epithelial lining for?

Answer 1

GIT tracts, respiratory tract, tonsils, thyroid, parathyroid, thymus, liver, pancreas

Question 2

What is the coelom?

Answer 2

A hollow tube which surrounds the viscera

Question 3

How does the coelom form?

Answer 3

The lateral mesoderm splits into two sheets - the somatic mesoderm and the splanchnic mesoderm which curve around and enclose a space - the coelom

Question 4

What does the somatic mesoderm give rise to?

Answer 4

Muscle and connective tissue

Question 5

What does the splanchnic mesoderm give rise to?

Answer 5

Viscera

Question 6

What forms the primitive gut tube?

Answer 6

The space enclosed by the splanchnic mesoderm coming together

Question 7

What forms the body wall?

Answer 7

The somatic mesoderm coming together

Question 8

What connects the gut to the yolk sac?

Answer 8

the yolk stalk - which remains persistent for a long time

Question 9

What is the stomodeum?

Answer 9

A thin layer of ectoderm which covers the mouth end of the gut tube

Question 10

At what age does the oral cavity form?

Answer 10

3 weeks

Question 11

What is the proctodeum?

Answer 11

A thin membrane across the rear end of the gut tube

Question 12

What is the allantois?

Answer 12

A branch off the gut that extends down into the body stalk - branches off at the proctodeum - will form the urogenital tract and bladder

Question 13

What divides the allatnois from the gut?

Answer 13

The urorectal septum - which will fuse with the cloacal membrane and form two separate openings for the urogenital tract and the gut

Question 14

What is the heart derived from?

Answer 14

Lateral splanchnic mesoderm

Question 15

How does the heart develop?

Answer 15

Two separate tubes develop in the thoracic cavity and then fuse in the midline - forms a single atrium and single ventricle each with two inflows and two outflows - then complex folding occurs to result in the two atria and two ventricles

Question 16

What is the commonest heart defect?

Answer 16

ventricular septal defect - where the left and right ventricles are not sealed off from one another

Question 17

What is an atrial defect?

Answer 17

Where the foramen ovale doesn’t close

Question 18

What is omphalocoele?

Answer 18

Failure of the gut to retract back into the coelom - fatal condition

Question 19

Which organs are derivates of the gut wall?

Answer 19

The lungs, liver, pancreas and thymus gland

Question 20

What is situs invertus?

Answer 20

mirror image of organ positions

Question 21

What causes situs invertus?

Answer 21

Failure of the primitive node to develop - no cilia to beat and create a current for the signalling molecules to follow

Question 22

What is urogenital system (apart from the bladder and urethra) derived from?

Answer 22

The intermediate mesoderm

Question 23

Which forms first the urinary system or the genitals?

Answer 23

The urinary system

Question 24

How do the kidneys develop?

Answer 24

First the pronephros and the pronephic duct grow and then the development of the pronephros is aborted, then the mesonephros forms and the pronephric becomes the mesonephric duct - then the mesonephros degenerates and the metanephros forms as bud that grows alongside the mesonephric duct - the metanephros becomes the kidney and ureters and then mesonephric duct becomes the vas deferens

Question 25

How does the penis form?

Answer 25

by fusion of urogenital folds

Question 26

What is hypospadiasis?

Answer 26

when partial fusion of the urogenital folds leaves a urethral opening on the base of the penis

Question 27

When is all major organogenesis completed?

Answer 27

By three months