CVS Embryology

Question 0

What does cephalocaudal folding achieve?

Answer 0

Brings heart tube into the thoracic region

Question 1

What does lateral folding achieve?

Answer 1

Creates the heart tube

Question 2

What forms the primitive heart tube?

Answer 2

Fusion of the paired endocardial tubes in lateral folding

Question 3

How is the heart tube suspended in the pericardial cavity?

Answer 3

By a fold of mesodermal tissue (dorsal mesocardium)

Question 4

How is the transverse pericardial sinus formed?

Answer 4

Dorsal mesoderm (which primitively suspends the heart tube in the pericardial cavity) disappears creating the transverse pericardial sinus

Question 5

How does the heart tube continue to elongate in an embryo?

Answer 5

Cells are added from the secondary heart field to it’s cranial end causing elongation

Question 6

Why does looping occur?

Answer 6

Heart tube elongates within the pericardial sac which remains the same size so bending of the tube occurs

Question 7

Around what day does looping occur?

Answer 7

Day 23- 28

Question 8

In looping what happens to the cephalic and caudal portions of the heart tube?

Answer 8

Cephalic portion- moves ventrally, caudally and to the right

Caudal portion- moves dorsally, cranially and to the left

Question 9

What is the outcome of looping?

Answer 9

It achieves putting the primordium of the right ventricle closest to the outflow tract
It achieves putting the primordium of the left ventricle closest to the inflow tract
It achieves putting the atrium dorsal to the bulbus cordis (inflow dorsal to outflow)

Question 10

What are the five regions of the primitive heart tube?

Answer 10

Truncus arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus

Question 11

After looping has occurred what allows the atrium to communicate with the ventricle?

Answer 11

Atrioventricular canal

Question 12

What region of the primitive heart tube is first to receive venous blood?

Answer 12

The right and left horns of the sinus venosus (inflow tract)

Question 13

What veins make up the sinus horns of the sinus venosus?

Answer 13

Vitelline vein
Umbilical vein
Common cardinal vein

Question 14

Why does the entrance of the sinus venosus shift to the right?

Answer 14

Due to the presence of left to right shunts in the heart
Left sinus horn recedes and loses its importance
Right sinus horns enlarge greatl
(Right sinus horn which now forms the only communication between the original sinus venosus and atrium is incorporated into the RA to form the smooth wall- sinus venarum

Question 15

What does obliteration of the left sinus horn result in?

Answer 15

Oblique vein of the left atrium and coronary sinus

Question 16

What is septation?

Answer 16

Division of the primitive heart tube into 4 distinctive chambers and the division of the ventricular outflow tract into the pulmonary trunk and aorta

Question 17

What three septi form during septation?

Answer 17

Interatrial septum
Interventricular septum
Conotruncal septum

Question 18

Where are endocardial cushions derived from?

Answer 18

Neural crest cells (which were found in the neuroectoderm and did not form the neural tube) that migrate into the primitive heart tube

Question 19

What is the importance of the endocardial cushion?

Answer 19

It develops in to the atrioventricular region and divides the developing heart into left and right channels

Question 20

How does atrial septation occur?

Answer 20

Septum primum grows downwards towards the fused endocardial cushions
Ostium primum is the hole present before the septum primum fuses with the endocardial cushions
Before the optimum primum closes a second hole the ostium secundum appears in the septum primum
Finally a second crescent shaped septum, the septum secundum grows. The hole in the septum secundum is known as the foramen ovale

Question 21

What is the derivative of the right atrium?

Answer 21

Most of the primitive atrium- muscular wall

Absorption of Sinus venosus - smooth wall

Question 22

Where does the right atrium receive venous drainage from?

Answer 22

Receives venous drainage from the body (vena cava) and heart (coronary sinus)

Question 23

What is the derivative of the left atrium?

Answer 23

Small portion of the primitive atrium- muscular wall

Absorption of proximal parts of pulmonary veins (4 branches)

Question 24

Where does the left atrium receive venous drainage from?

Answer 24

Receives oxygenated blood from the lungs via the pulmonary veins

Question 25

How does ventricular septation occur?

Answer 25

Septum has a muscular and membranous component - muscular portion forms most of the septum - grows upwards towards the fused endocardial tissues leaving a small gap = primary inter ventricular foramen - membranous portion of interventricular septum is formed by the connective tissue derived from the endocardial cushions to fill the gap

Question 26

How does septation of the out flow tract (conotruncal septum) occur?

Answer 26

Endocardial cushions also appear in the truncus arteriosus As they grow towards one another they will twist around one another and form a spiral septum between aorta and pulmonary artery ***

Question 27

Are the lungs functional in fetal circulation?

Answer 27

No

Question 28

Where and how does the foetus receive oxygenated blood?

Answer 28

From the mother via the placenta and umbilical vein

Question 29

Where and how does the foetus get rid of deoxygenated blood?

Answer 29

Via the placenta and umbilical arteries to the mother

Question 30

What do foetuses have that allows them to bypass the non functional regions of their bodies?

Answer 30

Shunts

Question 31

What are the three main shunts in a foetus and what do they bypass?

Answer 31

Foramen ovale- bypasses the lungs (RA to LA) Ductus arteriosus- bypasses the lungs (L to R ?)- ensures as little blood as possible goes to the non functioning lungs by shifting the last drabs from the pulmonary artery into the aorta for systemic circulation) Ductus venosus- (bypasses the liver??)

Question 32

What is the remnant of the foramen ovale in an adult?

Answer 32

Fossa ovalis

Question 33

What is the remnant of the ductus arteriosus in an adult?

Answer 33

Ligamentum arteriosum

Question 34

What is the remnant of the ductus venosus?

Answer 34

Ligamentum venosum

Question 35

What is the remnant of the umbilical vein in an adult?

Answer 35

Ligamentum teres (hepatis)

Question 36

What is the structure of the early arteries in a foetus?

Answer 36

Bilaterally symmetrical system of of arched vessels (undergo extensive remodelling to create the major arteries leaving the heart)

Question 37

What two arches if the early arteries are involved in the formation of the great vessels and how?

Answer 37

4th arch - right- proximal part of R subclavian artery - left- arch of aorta 6th arch - right- R pulmonary artery - left-L pulmonary artery and ductus arteriosus

Question 38

(Each aortic arch has a corresponding nerve) What nerve corresponds to the 6th arch?

Answer 38

Recurrent laryngeal nerve | R T1 and T2) (L T4 and T5

Question 39

What two factors influence the course of the nerve on the L and R sides?

Answer 39

The caudal shift of the developing heart and expansion of the developing neck region Need for a fetal shunt between the pulmonary trunk and aorta

Question 40

What is the course of the recurrent laryngeal nerve on the L and R sides?

Answer 40

As the heart descends the nerve hooks around the 6th aortic arch and turns back on itself Left recurrent laryngeal nerve becomes hooked around the shunt between the pulmonary trunk and the aorta ***

Question 41

How is the oblique pericardial sinus formed?

Answer 41

Created as left atrium expands and absorbs pulmonary veins