CVS Session 2 (Lecutre 2.2)

Question 1

What does lateral folding achieve?

Answer 1

Creates the primitve heart tube

Question 2

What does cephalocaudal folding achieve?

Answer 2

Brings the heart tube into the thoracic region

Question 3

What lies near the cardiogenic field?

Answer 3

Pericardial cavity

Question 4

Why is the cardiovascular system the first to develop?

Answer 4

The neccessity for the rapidly growing embryo to obtain oxygen and nutrients and get rid of waste material.

Question 5

What is the structure that suspends the primitve heart in the pericardial cavity? What occurs to it eventually?

Answer 5

Dorsal mesocardium which degrades and leaves the heart suspended in the PC by the great vessels

Question 6

How do the cardiogenic cords develop?

Answer 6

Response from signals from the underlying endoderm cause the mesoderm in the cardiogenic area to form a pair of elongated strands.

Question 7

What do the cardiogenic cords give rise to?

Answer 7

Cords develop a hollow centre becoming the endocardial tubes.

Question 8

What do the endocardial tubes give rise to?

Answer 8

Lateral folding causes fusion of the two tubes to fuse forming the primitve heart tube.

Question 9

What are the 6 distinct regions that are developed and being to pump blood?

Answer 9

From caudal to cephalic (tail to head)

1) Sinus venosus
2) Primitve atrium
3) Primive ventricle
4) Bulbus cordis
5) Truncus arteriosus
6) Aortic roots

Question 10

What direction is the blood flow through the primitive heart tube?

Answer 10

From tail to head

Question 11

What do the 5/6 regions develop into?

Answer 11

1) Sinus venosus - part of RA (posterior wall), coronary sinus and SAN
2) Primitve atrium - part of RA (ant wall) right auricle, part of LA (ant wall) and left auricle
3) Primitive ventricle - LV
4) Bulbis cordis - RV
5) Truncus arteriosus - ascending aorta and pulmonary trunk

Question 12

When does looping start and finish? Which directions do the cephalic and caudal portion move in?

Answer 12

1) Day 23-28

2) Cephalic - ventrally, caudally, right
3) Caudal - dorsal, crainially, left

Question 13

Why does looping occur?

Answer 13

Enlargement of the heart structures with limited space to move in as the pericardial cavity is a fixed space.

Question 14

What happens after looping?

Answer 14

Atrium communicates with ventricle via the atrioventricular canal

Question 15

How do the sinus venosus develop?

Answer 15

1) R & L horns equal in size
2) Venous return shifts to RHS, L sinus horn recedes
3) Rt sinus horn is absorbed by enlarging RA

Question 16

How is the oblique sinus formed?

Answer 16

LA expands absorbing the pulmonary veins

Question 17

What are the fetal circulatory shunts?

Answer 17

1) By pass the liver to reach the RA&raquo_space;» majority bypasses lungs and reaches LA&raquo_space;> LV&raquo_space;» aorta
2) Small amount RA&raquo_space;> RV&raquo_space;> PT&raquo_space;» bypass lungs via ductus arteriosus (trains RV)

Question 18

What do the early arterial system begin as? How do they create the major arteries leaving the heart?

Answer 18

Bilaterally symmetrical system of arched vessels which undergo extensive remodelling.

Question 19

What do the 4th and 6th archers give rise to?

Answer 19

4th - R = prox part of R subclavian art
L = arch of aorta

6th - R = R pulmonary art
L = L pul art + DUCTUS ARTERIOSUS

Question 20

What is noted about each aortic arch?

Answer 20

Each arch is associated with a corresponding nerve

Question 21

Which nerve is corresponds with the 6th arch?

Answer 21

Recurrent laryngeal nerve (branch of vagus)

Question 22

Describe the course of the right and left RLN.

Answer 22

Right - descends to T1-T2 before returning

Left - descends to T4-T5

Question 23

Which two factors influence the course of the nerves?

Answer 23

1) Caudal shift of developing heart + expansion of the developing neck region
2) Need for a fetal shunt between PT & aorta

Question 24

What structures do the LRLN become hooked around?

Answer 24

Shunt between PT and aorta = DA