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CVS > Session 3 Embryology > Flashcards

Session 3 Embryology Flashcards

1
Q

What develops from the cardiogenic field?

In what process is the field created?

Initially, where is it in the embryo?

A

The heart, blood vessels and blood cells

gastrulation

Cranial end (before folding)

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2
Q

When forms in the cardiogenic field in the 3rd week of development?

A

two endocardial tubes

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3
Q

Describe the folding in the embryo

A

lateral folding- fuses the two endocardial tubes into the primitive heart tube

cephalocaudal folding- moves the tube into the thoracic region

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4
Q

What does looping achieve?

What prompts it to occur?

Which sinus does looping create?

A

Looping of the heart tube places both the inflow and outflow at the cranial end of the heart as seen in the adult heart
(inflow is behind (dorsal) to outflow)

The tube is getting bigger and must rearrange to fit the pericardial sac

the transverse sinus

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5
Q

By what day in development is the primitive heart tube beating?

A

Day 22

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6
Q

Which primitive structure drains blood returning from the embryo into the primitive atrium?

A

sinus venosus

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7
Q

What does the right atrium form from?

How does it form?

A
  • primitive atrium (heart tube) MAJOR
  • sinus venosus
    (R atrium enlarges to include the R sinus horn)
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8
Q

How does the sinus venosus develop?

A

Initially two inflow horns
Venous return shifts to the right horn and left recedes
(R horn included in R atrium)

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9
Q

How does the L atrium develop?
What is it formed from?

Which sinus does it create?

A

Pulmonary veins begin to develop and the enlarging left ventricle absorbs them

  • pulmonary veins MAJOR
  • small part of the primitive atrium

oblique sinus

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10
Q

Why are the R and L atrium structurally different?

A

R - trabecular appearance bc it derives from neural tube

L- smooth walls due to development from the pulmonary veins

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11
Q

Where is the oblique sinus?

A

Posterior of the heart between the pulmonary veins

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12
Q

Name the three shunts in foetal circulation

Explain what they do

A
  • Formaen ovale
    shunts blood from right atrium to L
  • Ductus arteriosus
    shunts blood from pulmonary trunk to aorta
  • Ductus venosus
    shunts a portion of blood from the umbilical vein to the IVC
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13
Q

How do the foetal shunts close?

A

Foramen ovale closes when respiration begins and a huge venous return causes R atrium pressures to rise

Ductus arteriosus wall muscle is very sensitive to changes in pO2; it contracts and closes

Ductus venosus becomes flaccid and closed as there’s no blood entering from the umbilical vein anymore

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14
Q

Describe the primitive arterial system which the great vessels develop from?

A

The aortic arches

- symmetrical bilateral system of arched vessels

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15
Q

Which arches of the primitive structure are important?

A

4th branch

6th branch

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16
Q

What does the 4th branch of the aortic arches develop into?

A

L side- aorta

R side- subclavian vein

17
Q

What does the 6th branch of the aortic arches develop into?

Hint; what is the 6th arch known as?

A

Pulmonary arch

L- L pulmonary artery and ductus arteriosus
R- R pulmonary artery

18
Q

Which nerve descends with the 6th aortic arch? (Left branch)

What is it hooked around?

A

the left recurrent laryngeal nerve

the ductus arteriosus

19
Q

What happens in septation?

A

The heart tube is divided into 4 chambers and the outflow tract divided into the aorta and pulmonary trunk

20
Q

Septi grow towards the endocardial cushions in the heart tube. Where are they located?

Where does the cushion tissue come from?

A

At the junction between atrium and ventricles

Endocardial cushion tissue migrates in (not from primitive heart) thus this process can go wrong

21
Q

Which septum forms the foramen ovale in the atria?

What feature of the septum allows this?

Which atrium is it closest to?

A

septum secundum

crescent shaped

right atrium

22
Q

How does atrial septation occur?

A
  • Septum primum grows downwards towards the endocardial cushions
  • Ostium secundum appears in the septum before ostium primum disappears to allow continuous blood flow
  • Septum secundum forms the foramen ovale due to crescent shape
23
Q

The foramen ovale becomes the ____ ____ after birth?

How does the shunt close?

A

Fossa ovalis

After birth, pressure in the left atrium exceeds that of the right atrium. The septum primum is pushed against secundum, stopping blood flow between. They eventually become fused by fibrous tissue

24
Q

Describe the ostium secundum in hypoplastic left heart syndrome

What does this syndrome mean?

A

It’s too small

The left side of the heart doesn’t develop properly

25
Q

Why are the ventricular septi prone to defects?

Which ventricular septum is most commonly defective?

A

Septal tissue is derived from endocardial cushions rather than the primitive heart tube

Membranous septum

26
Q

Describe how ventricular septation occurs

A
  • Muscular septum grows upwards towards the endocardial cushions, but doesn’t reach them
  • Primary interventricular foramen is filled by the membranous septum
27
Q

Which septum splits the outflow tract of the heart tube into the aorta and pulmonary trunk?

The septum shape explain what about the 2 vessels?

A

The aorticopulmonary septum

Spiral shaped septum which explains why they twist around each other upon exiting the ventricles- rather than being in parallel

28
Q

How are the 2 outflow tracts from the ventricles created?

In what region of the heart tube does this begin?

A
  • Endocardial cushions grow into the lumen of the truncus arteriosus
  • They’re slightly offset so that they twist around each other upon meeting
  • Spiral septum divides the outflow tract into the aorta and pulmonary trunk

truncus arteriosus

29
Q

Why are congenital heart defects a common form of congenital birth defect?

A

Heart development is very complex because the foetal circulation is different to the newborn circulation; thus there are many opportunities for error to occur

30
Q

How can drugs for heart disease harm the foetus?

A

Highly teratogenic which means they disturb the development of the embryo/ foetus

31
Q

In which condition does the aorta emerge from the right ventricle?

What does the baby look like? Why?

A

Transposition of the great arteries

Blue skin and mucous membranes - cyanosis
Because deoxygenated blood is pumped into systemic circulation

32
Q

Which congenital heart condition is categorised by 4 abnormalities?

What are the 4?

A

Tetralogy of fallot

  • Overriding aorta
  • Ventricular septal defect (septum is missing)
  • Right ventricular hypertrophy
  • Pulmonary valve stenosis
33
Q

Which septum doesn’t form correctly in tetralogy of fallot ?

Which cells does this septum derive from?

A

The conotruncal septum
(cranial end of bulbus caudis)

neural crest cells

CVS (7 decks)

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