Heart Development

Question 1

what is the cariogenic field?

Answer 1

most cranial structure before folding. Develops at cranial end. Two arms of cariogenic field during folding fuse together to form.

Question 2

what is lateral folding?

Answer 2

Ectoderm with neural crest cells migrates downwards around foregut tube. Endocardial tube forms and myocardial cells form outer myocardium layer.

Question 3

what is cardiac jelly?

Answer 3

in-between myocardium and endocardium tube= layer of connective tissue

Question 4

what happens during cranial caudal folding?

Answer 4

pericardial cavity moves into thorax. As lateral folding is taking place at same time the heart tube has formed by the time it is in correct place.

Question 5

in what direction does blood flow through the heart.

Answer 5

caudal to cranial

Question 6

describe features of the sinus venous

Answer 6

• smooth part of R.atrium
• coronary sinus
• oblique vein of L atrium (remnant of left common cardinal vein)

Question 7

what is the primitive atrium?

Answer 7

Trabeculated parts of R. and L. atrium

Question 8

what is the primitive ventricle?

Answer 8

Trabeculated part of L. Ventricle

Question 9

what is the bulbus cordis

Answer 9

• Trabeculated part of R. ventricle

- outflow part of both ventricles

Question 10

what are the 3 layers of the heart tube?

Answer 10

• Endocardium
• Myocardium
• Epicardium

Question 11

what is the endocardium?

Answer 11

endothelial lining

Question 12

what is the myocardium?

Answer 12

Muscular wall

Question 13

what is the epicardium?

Answer 13

visceral pericardium

Question 14

what happens during differential growth?

Answer 14

5 dilatations become apparent in the heart tube. These will develop into the adult structures of the heart.

Question 15

what are the cells that beat?

Answer 15

myocardial cells

Question 16

what do myocardial cells help with?

Answer 16

when you have myocardial cells your heart is beating synchronously.

Question 17

what happens on day 23 of folding of the heart tube?

Answer 17

the heart begins to loop and fold

Question 18

what are the steps involved in folding of the heart tube?

Answer 18

1) atrium moves dorsally and cranially
2) Ventricles are displaced down to the left.
3) Bulbus cordis is pulled inferiorly, ventrally to the right

Question 19

how does the septum form during folding?

Answer 19

Indentation caused by truncus arteriosis will be where the septum forms

Question 20

what forms the right ventricle?

Answer 20

base of truncus arteriosis will form the R. ventricle

Question 21

where does the atrium develop to?

Answer 21

dorsal and cranial

Question 22

where does the ventricle develop to?

Answer 22

displaced left

Question 23

where does the bulbus cords develop to?

Answer 23

Inferiorly ventrally to the right

Question 24

What is the atrioventricular canal?

Answer 24

Allows a clear division of four compartments of the heart. Initially the AV canal gives access only to the primitive L.V and is separated from bulbs cordis by bulbs V flange. At the fifth week the posterior of BVF terminates.

Question 25

AV canal and opening migrate where?

Answer 25

Right

Question 26

what happens during folding?

Answer 26

Anterior and posterior cushions fuse together as they migrate further into lumen; completely divide canal into R and L orifices

Question 27

What is ventricle septation?

Answer 27

• ventricles grow downwards around muscular bulge if septum

- creates papillary muscle and increases size of septum.

Question 28

what is the first step in atrial septation?

Answer 28

• septum primum grows from roof of atria. Grows downwards and makes foramen premium smaller until closes completely.

Question 29

what is the second stage of atrial septation?

Answer 29

• foramen secundam= holes in septum primum (formed by apoptosis)
• septum secundum grows down beside septum premium and ovaries foramen secundum

Question 30

what happens after birth to the two septums?

Answer 30

they fuse and leave fossa ovals remenant

Question 31

what is the foramen ovale and what does it allow for?

Answer 31

New space forms in septum secundum.

Allows for staggered opening communication between right and left atria to bypass fluid filled lungs.

Question 32

If fusion doesn’t happen between the two septum after birth what happens?

Answer 32

If fusion doesn’t happen its ok because pressure will always be greater in left atria.

Question 33

What are conotruncal swellings?

Answer 33

growths of aorta and pulmonary trunk. They grow outwards and downwards and sprial at same time to give structure of aorta and pulmonary trunk.

Question 34

what are the 2 types of valves?

Answer 34

• semi lunar

- AV valves

Question 35

where are the AV valves formed?

Answer 35

in the myocardium

Question 36

how are AV valves formed?

Answer 36

Blood forces wear away myocardium tissue to create spaces. Muscular cord forms from dense mesenchymal tissue. cords thin out to become chord tendinae.

Question 37

Describe how the semi lunar valves are formed.

Answer 37

• Truncus swellings grow outwards in aorta and pulmonary trunk.
• These are thinned out by pressure from blood.
• valves formed