Session 2 - Early development of the heart Flashcards

0
Q

What is the cardiogenic field?

A

-An undifferentiated area within an embryo from which the heart, vessels and blood cells arise from

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1
Q

What happens to the cardiogenic field to produce the primitive heart tube?

A

-Pair of endocardial tubes form in the cardiogenic field by week 3 -Lateral folding of the embryo results in fusion of the endocardial tubes at the midline, forming the primitive heart tube

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2
Q

Where is the primitive heart tube after lateral folding?

A

-Initially suspended in the pericardial cavity by a membrane, membrane breaks down and primitive heart tube is free within the cavity

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3
Q

What is the effect of cephalocaudal folding on the heart tube?

A

-Relocates the primitive heart tube, within the pericardial cavity, to the correct anatomical location

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4
Q

At what point in the pregnancy does the primitive heart tube form?

A

-Approx. day 25

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5
Q

Describe the primitive heart tube initially

A

-Linear pulsatile sturcture consisting of sinus venosus, primitive atrium, primitive ventricle, bulbus cordis, truncus arteriosus and aortic roots

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6
Q

Where, initially, is the inflow of the primitive heart tube?

A

-At the caudal end -> sinus venosus

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7
Q

Where, initially, is the outflow of the primitive heart tube?

A

-At the cranial end -> throughout the aortic roots

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8
Q

In what direction is bloodflow through the primitive heart tube?

A

-From caudal to cranial

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9
Q

Why does the primitive heart tube need to develop from its original linear structure?

A

-The linear structure is sufficient to supply the embryo at first, but as the embryo develops, the primitive heart tube needs to change to meet demand

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10
Q

Why is looping a key developmental event?

A

-Ensures septation of chambers and outflow tract -Development of transverse sinus -Optimises space for growth

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11
Q

What is looping of the primitive heart tube?

A

-Continued elongation of the primitive heart tube results in the tube bending and folding upon itself -The primitive ventricle pushes ventrally, caudally and right -The primitive atrium pushes dorsally, cranially and left

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12
Q

When does looping occur?

A

-Approximately day 23-day 28

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13
Q

What does looping achieve?

A

-Primordium of right ventricle closest to its outflow -Primordium of LV closest to its inflow -Atrium dorsal to bulbis cordis (inflow dorsal to outflow) -Both inflow and outflow are cranial

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14
Q

What does the development of the transverse sinus ensure?

A

-The great arteries are in front of the great veins

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15
Q

What is the atrioventricular canal?

A

-A constriction between the primitive atrium and the primitive ventricle which is the first division between the two zones

16
Q

What is the purpose of the atrioventricular canal?

A

-Allows communication between the atria and ventricles -Contributes to the asymmetrical development of the heart, allowing the ventricles to enlarge more than the atria

17
Q

When is the oblique sinus formed?

A

-During formation of the left atrium when the LA absorbs the pulmonary veins and expands

18
Q

What happens to the sinus venosus during atrial development?

A

-As venous return shifts to the right side of the heart, the left horn of sinus venosus recedes and the right atrium absorbs the right sinus horn

19
Q

Where does the right atria develop from?

A

-Most of the primitive atrium and the right sinus horn

20
Q

Where does the left atrium develop from?

A

-A small portion of the primitive atrium but mostly from pulmonary veins

21
Q

Describe development of the left atrium

A

-LA sprouts pulmonary veins which branches into 4 veins -LA absorbs the proximal portions of these branches and expands to form complete LA

22
Q

Name the shunts in the feotal system

A

-Ductus arteriosus -Ductus venosus -Foramen ovale

23
Q

What is the function of ductus arteriosus?

A

-Shunt blood from the pulmonary trunk to aorta in order to bypass the lungs

24
Q

What is the function of ductus venosus?

A

-A shunt from umbilical vein to inferior vena cava to bypass the liver, as it is the first organ to be reached, and it is a very demanding one which would use all the oxygen and nutrients

25
Q

What is the function of foramen ovale?

A

-A shunt from the RA to the LA in order to bypass the right heart as it is not needed

26
Q

Why is there a ductus arteriosus if the right heart is bypassed?

A

-Because a small amount of blood does pass into the right ventricle in order to support its development and the development of the lungs

27
Q

Why does blood pass through the ductus arteriosus instead of continuing to the lungs?

A

-The resistance in the lungs is very high as they are collapsed, so flows through DA where pressure is lower

28
Q

What are the aortic arches?

A

-A bilateral system of arched vessels, connected to the primitive heart, which undergo extensive remodelling to create the major arteries leaving the heart

29
Q

What are the derivatives of the 4th aortic arch?

A

-Right -> right subclavian artery -Left -> arch of aorta

30
Q

What are the derivatives of the 6th aortic arch?

A

-R-> Right pulmonary artery -L->Left pulmonary artery and ductus arteriosus

31
Q

Which arch does the recurrent laryngeal nerve correspond to?

A

-6th

32
Q

What is the function of the recurrent laryngeal nerve?

A

-Innervate the intrinsic muscles of the larynx

33
Q

Where do the left and right recurrent laryngeal nerve loop?

A

-Left loops around aorta as it is hooked around the ductus arteriosus -Right loops around the right subclavian artery due to remodelling of the arches