Embryology

Question 1

What are the 4 steps in heart deveolopment?

Answer 1

1) fusion of the L/R endocardial tubes into a primary heart tube
2)Folding/Looping of the heart tube on itself
3)Septation
4)remodeling of the venous pole

Question 2

Where does the heart tissue arrise from?

Answer 2

it arises from the splanchnic mesoderm

Question 3

What arises from the cardiogenic zone and where can we find it?

Answer 3

towards the head of the fetus and will give rise to the two primitive blood vessels known as the endocardial tubes

Question 4

How does the primitive heart tube form

Answer 4

forms from the endocardial tubes that merge together to form one tube

Question 5

Once the endocardial tubes merge, what are the 4 sections of the primitive heart (from venous to arterial flow)

Answer 5

Question 6

What are the 2 folds following the formation of the heart tube?

Answer 6

1) Lateral & Cranial Folding
Brings bilateral endocardial tubes together at the midline

2) Differential growth causes ventral/right bending of ventricle and dorsal/cranial shift of atrium
Creates heart’s chambered shape atria move posterior, ventricles anterior

Question 7

On this image on the primitive heart, identify:
Sinus venosus (L horn)
Sinus venosus (R horn)
R posterior cardinal v.
R umbilical v.
R vitelline v.

Answer 7

Question 8

Where does the blood that goes to the left and right horns come from?

Answer 8

the yolk sac
the placenta
the embryo itself

(from the inside and outside of the embryo)

Question 9

True or false?
The blood flow after the heart tube foldings is unidirectional and in series

Answer 9

true

Question 10

In this image of the heart after folding, identify:
bulbus cordis
primitive atrium (x2)
sinus venosus
atrio-ventricular groove and canal
primitive ventricle

Answer 10

Question 11

What are the 5 steps in partitioning (septation)

Answer 11

1) atrioventricular septation
2) septation of atria
3) septation of ventricles
4) septation of outflow tract into aorta and pulmonary trunk
5) reorganization of venous inflow

Question 12

How does Atrioventricular septation occur?

Answer 12

The atrio-ventricular canal will close in on itself (dorsally to ventrally) until there is formation of the AV septums

Question 13

What is the septum primum and what does it do in left and right atrial septation?

Answer 13

it’s a part of tissue that grows from dorsal to frontal until only a small hole is left called the foramen secundum

Question 14

What is the name of the tissue that grows over (on the right side) of the septum primum?

Answer 14

the septum secundum

Question 15

What is the name of the hole that the septum secundum will leave open?

Answer 15

the foramen ovale

Question 16

Why does the relation with the foramen ovale and foramen secundum only allow blood flow to pass from right to left but not vice versa?

Answer 16

because the septum primum can freely flap open towards the left side, but the septum secundum doesn’t allow it to be pushes into the right atrium so the blood can only pass from right to left

Question 17

What happens to the foramen ovale after birth?

Answer 17

Because of the pressure in the left atrium, it will stay closed and eventually seal shut

Question 18

What do you call the foramen ovale when it doesn’t successfully seal shut?

Answer 18

the patent foramen ovale

Question 19

true or false?
Just like the atrial septum, the ventricular septum is made up of a fine tissue

Answer 19

false, it is made of thick muscular tissue

Question 20

How does the ventricle septation happen? What tissues are used during this process

Answer 20

these 3 structures:
Muscular interventricular septum
Endocardial cushions (from the AV canal)
Conotruncal (bulbar) ridges (from the outflow tract)

will merge together to form the septum

Question 21

What 2 membranes are used to divide the aorta and pulmonary trunk?

Answer 21

Conotruncal ridges
aorticopulmonary septum

Question 22

True or false?
The conotruncal ridges and aorticopulmonary septum grow together in a straight line that clearly seperates the aorta and pulmonary trunkthe

Answer 22

false, they twist together (which is also the reason why the aorta and pulmonary trunk are criss-crossed)

Question 23

Which structure are continuous between the separation of the aorta/pulmonary trunk, but also in the formation of the ventricular septum?

Answer 23

THe conotruncal and bulbar ridges. So when one is affected the other often is as well

Question 24

What veins will disappear during the remodeling of the venous pole step?

Answer 24

The whole left side will disappear and only the vitelline v will remain (becomes the IVC) as well as the anterior cardinal v. (become the L and R brachiocephalic vv. and SVC)

Question 25

What will happen to the left horn of the sinus venosum?

Answer 25

it will become the coronary sinus

Question 26

What will happen to the right horn of the sinus venosus

Answer 26

it will become the sinus venarum (the part of the right atrium without the pectinate muscle/where the vena cavae will attach)

Question 27

What are the 3 shunts found in the fetal circulation?

Answer 27

ductus arteiosus = right atrium to aorta foramen ovale = right atrium to left atrium ductus venosus = mother circulation to IVC

Question 28

Are septal defects serious?

Answer 28

rarely, usually not even noticed

Question 29

What is an aorticopulmonary septum defect?

Answer 29

uneven septation of the truncus arteriosus by the conotruncal ridges causing stenosis of PT or aorta

Question 30

What is Tetralogy of fallot?

Answer 30

congenital heart defect that has: ventricular septal defects pulmonary valve stenosis R to L shunt (overriding aorta) hypertrophy of the right ventricle due to PT stenosis

Question 31

True or false? tetralogy of Fallot is always fatal

Answer 31

false, some people can live their whole lives with it