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Flashcards in Development 2 Deck (27):
1

Which organs does the endoderm provide epithelial lining for?

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

2

What is the coelom?

A hollow tube which surrounds the viscera

3

How does the coelom form?

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

4

What does the somatic mesoderm give rise to?

Muscle and connective tissue

5

What does the splanchnic mesoderm give rise to?

Viscera

6

What forms the primitive gut tube?

The space enclosed by the splanchnic mesoderm coming together

7

What forms the body wall?

The somatic mesoderm coming together

8

What connects the gut to the yolk sac?

the yolk stalk - which remains persistent for a long time

9

What is the stomodeum?

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

10

At what age does the oral cavity form?

3 weeks

11

What is the proctodeum?

A thin membrane across the rear end of the gut tube

12

What is the allantois?

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

13

What divides the allatnois from the gut?

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

14

What is the heart derived from?

Lateral splanchnic mesoderm

15

How does the heart develop?

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

16

What is the commonest heart defect?

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

17

What is an atrial defect?

Where the foramen ovale doesn’t close

18

What is omphalocoele?

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

19

Which organs are derivates of the gut wall?

The lungs, liver, pancreas and thymus gland

20

What is situs invertus?

mirror image of organ positions

21

What causes situs invertus?

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

22

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

The intermediate mesoderm

23

Which forms first the urinary system or the genitals?

The urinary system

24

How do the kidneys develop?

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

25

How does the penis form?

by fusion of urogenital folds

26

What is hypospadiasis?

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

27

When is all major organogenesis completed?

By three months