Development of the heart

Question 1

Where does the circulatory system arise from?

Answer 1

Mesoderm

Question 2

What is the first system to function?

Answer 2

The circulatory system

Question 3

When does blood begin to circulate?

Answer 3

By the end of the 3rd week

Question 4

When and where is heart development first indicated?

Answer 4

At 18 - 19 days in the cardiogenic area near the embryonic head

Question 5

What is the cardiogenic area derived from and when?

Answer 5

Splanchnic mesoderm cells - intra-embryonic mesoderm, 3rd week

Question 6

What is at either side of the neural plate?

Answer 6

Horse shoe area

Question 7

What occurs as folding takes place?

Answer 7

The heart tubes fuse to form a single medial endocardial heart tube.

Question 8

What does thickening mesenchyme around the heart tube thicken to form?

Answer 8

A myoepicardial mantle

Question 9

What does the myoepicardial mantle become?

Answer 9

Epicardium and myocardium

Question 10

What is the heart tube composed of? x3

Answer 10

1) Myoepicardial layer
2) Cardial jelly
3) Endocardium

Question 11

What is cardial jelly secreted by?

Answer 11

Cardiac myoblasts

Question 12

What does cardial jelly permit?

Answer 12

Permits twisting and diminishes until myocardium is adjacent to endocardium.

Question 13

What are the five heart regions?

Answer 13

• Truncus arteriosus
• Bulbus cordis
• Primitive ventricle
• Primitive atrium
• Sinus venosus

Question 14

What is the truncus arteriosus continuous with? x 2

Answer 14

• Caudally with the bulbus cordis

- Cranially with the aortic sac and the aortic arches

Question 15

What is the sinus venous and what does it receive?

Answer 15

A large venous sinus which receives the umbilical vein the vitelline vein and common cardinal veins.

Question 16

What are the fastest growing regions?

Answer 16

The bulbus cordis and ventricle

Question 17

What will the truncus arteriosus become?

Answer 17

Divide into ascending aorta and pulmonary trunk.

Question 18

What will the bulbus cordis develop into?

Answer 18

Right ventricle

Question 19

What does the primitive ventricle form?

Answer 19

Left ventricle

Question 20

What does the primitive atrium become?

Answer 20

The anterior portions of both the right and left atria, and the two auricles.

Question 21

What does the sinus venosus develop into?

Answer 21

The posterior portion of the right atrium, the SA node, and the coronary sinus.

Question 22

When do contractions begin?

Answer 22

At day 22

Question 23

Where do peristalsis-like waves begin?

Answer 23

In sinus venosus

Question 24

What is blood from sinus venosus controlled by?

Answer 24

SA valves

Question 25

What happens when ventricle contracts? (where does blood enter)

Answer 25

Enters bulbus cordis, into the aortic sac and then into the aortic arches (branchial arches) to the dorsal aorta

Question 26

When does septation occur?

Answer 26

From days 28-37

Question 27

What openings in septum primum and scundum allow?

Answer 27

Allow right-to-left shunting of blood throughout gestation

Question 28

What is the ostium secundum?

Answer 28

An invagination that arises from the roof of the atrium to the right of the septum primum making its way to the AV cushion

Question 29

What does foramen ovale allow?

Answer 29

Blood flow from right to left atrium

Question 30

Why does the foramen ovale close at birth?

Answer 30

Abrupt dilation of the pulmonary vasculature combined with cessation of umbilical flow reverses the pressure difference between the atria and pushes the flexible septum primum against the more rigid septum secundum

Question 31

When does the interventricular septum takes place?

Answer 31

Between the 4th and 7th week

Question 32

Summary - day 18/19 -

Answer 32

From the mesoderm – first organ to appear from cardiogenic region near the head.

Question 33

Summary - day 20/21

Answer 33

Cardiogenic cords transform to endocardial tubes which transform into a single heart tube

Question 34

Summary - day 21/22

Answer 34

Primitive heart begins beating and pumping blood.

Question 35

Summary - day 22

Answer 35

Heart tube transforms into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22.

Question 36

Summary - day 22-28

Answer 36

Developing heart is an S shape within the pericardium

Question 37

Summary - day 28

Answer 37

Internal septa begin to form

Question 38

Summary - weeks 5 and 8

Answer 38

The atrioventricular valves form.

Question 39

Summary - weeks five and nine

Answer 39

Semilunar valves form