Embryology: Application

Question 1

what happens during lateral folding

Answer 1

• open coelom becomes a closed cavity
• amniotic sac surrounds embryo by folding towards the yolk sac
• thoracic and abdominal cavities are formed
• mid and fore gut are closed

Question 2

what happens during cranial folding

Answer 2

• amniotic cavity folds up

- forms foregut and defines thoracic cavity

Question 3

what happens during caudal folding

Answer 3

• amniotic cavity folds in and caudally
• cloacal membrane and connecting stalk displaced ventrally beside yolk sac neck
• hindgut, anus and umbilical cord formed

Question 4

what are the 4 causes of embryological defects

Answer 4

unknown, genetic, environmental, multifactorial

Question 5

what period and week os the most ‘risky’ in terms of defects

Answer 5

embryological period, week 5

Question 6

describe the development of the heart

Answer 6

cardiac progenitor cell migrate through the primitive streak into visceral lateral plate mesoderm forming a right and left heart field

Question 7

describe the formation of the heart tube

Answer 7

• craniocaudal folding forms the first arch of the aorta
• mesocardium attaches to vitelline veins
• aorta attaches to umbillical arteries
• lateral folding brings endocardial tubes closer

Question 8

describe the septum primium

Answer 8

• flexible
• grows at 30 days
• between the primary atrium and ventricles

Question 9

describe the septum secondium

Answer 9

• rigid
• grows at 33 days
• between the atria

Question 10

what is the function if the foramen ovale

Answer 10

allows communication between the atria until birth

Question 11

function of foramen ovale before birth

Answer 11

shunt between higher RA pressure and lower LA pressure

Question 12

what happens to the foramen ovale after birth

Answer 12

septum primium shuts off the shunt due to pressure change

Question 13

what does the spetum primium do before birth

Answer 13

acts as a valve for the foramen ovale in the LA

Question 14

causes of pressure change at birth

Answer 14

umbilical vessels constrict and RA pressure decreases

Question 15

causes of pressure change during crying and first breath

Answer 15

• decrease pulmonary VR, circulation permitted in pulmonary system
• increased LA pressure, initially decreased RA pressure

Question 16

ASD

Answer 16

atrial spetal defects - defects in 1 or 2 atrial septae

Question 17

3 ASDs

Answer 17

• excessive resorption of septum primium
• absent septum secondum
• probe patent foramen ovale

Question 18

excessive resorption of septum primium

Answer 18

small septum primium, normal septum secondum - foramen ovale not closed

Question 19

probe patent foramen ovale

Answer 19

septum primium and secondum fail to fuse - blood mixing, hole between A

Question 20

what are the two parts of ventricular septation and when do they grow

Answer 20

• muscular and membranous portions

- 33 days

Question 21

muscular portion of V septation

Answer 21

grows up from expanding V

Question 22

membranous portion of V septation

Answer 22

grows from endocardial cushions

Question 23

what happens during septation of the outflow tract

Answer 23

bulbs grow on the outflow tract and eventually join with the V spetum to form a septum between the future aorta and pulmonary trunk

Question 24

VSDs

Answer 24

ventricular spetal defects - can form shunt and therefore mixing between Vs

Question 25

2 types VSDs and characteristics

Answer 25

• membranous - common, less severe

- muscular - uncommon, more severe

Question 26

patent ductus arteriosus

Answer 26

link between the aorta and pulnonary trunk

Question 27

what is tetralogy of fallot

Answer 27

4 congenital abnormailities

Question 28

tetralogy of fallot

Answer 28

• pulmonary stenosis
• VSD
• overriding aorta
• enlarged RV