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Y1 TP2 Cardiovascular (topic 4 Onwards) > 3. Embryology Of The Heart > Flashcards

3. Embryology Of The Heart Flashcards

1
Q

Inner cell mass differentiates – into 2 discs

A
  • Epiblast

* Hypoblast

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2
Q

Prechordal plate

A

where epiblast and hypoblast fuse together

• Cranial and caudal part

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3
Q

Gastrulation steps - 4 steps

A

Inner cell mass differentiates
Prechordial plate formation
Form primitive groove
Form germ layers

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4
Q

Formation of primitive groove

A

Some cells in epiblast – differentiate, proliferate, disintergrate to form the primitive groove

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5
Q

Formation of germ layers

A
  • Cells near primitive groove start to migrate into the groove down into the hypoblast layers
    • Migrating cells replace the hypoblast anf form the the first gem layer – endoderm
    • More migrating cells from mesoderm
    • More migrating cells form ectoderm
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6
Q

Formation of notochord

A

—> near primitaive groove more cells migrate down and form the tube = notochord
• Notochord is pushed into mesoderm layer

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7
Q

Formation of neural groove

A

—> near primitaive groove more cells migrate down and form the tube = notochord
• Notochord is pushed into mesoderm layer

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8
Q

What does the heart develop from

A

Mesoderm

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9
Q

Heart develops from

A

Splanchnic mesoderm

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10
Q

VEGF– vascular endothelial growth factor

A
  • Released by endodermal cells

* Differentiates mesodermal cells, specifically in lateral splanchnic part of mesoderm

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11
Q

Splanchnic mesoderm

- structure

A

= 2 pericardial cavities
= 2 heart tubes
• One of each on each side
• 2 heart tubes fuse together
• 2 pericardial cavities fuse together
○ Heart tube (fused) is pushed inside pericardial cavity, endoderm lines the organs
○ Dorsal mesocardium = structure that anchors heart tube to pericardial cavity

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12
Q

Dorsal mesocardium

A

structure that anchors heart tube to pericardial cavity

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13
Q

Layers of heart week 3

Medial → lateral

A

Endocardium
Cardiac jelly
Myocardium
Dorsal mesocardium

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14
Q

How does heart develop - location

A

• Heart develops on the top of your head, then it moves down into chest cavity (when cranial caudal folding of embryo occurs)

Cranial → caudal

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15
Q

6 parts of heart tube

A 
AS: Aortic Sac 
TA: Truncus Arteriosus
BC: Bulbus Cordis 
PV: Primitive Ventricle 
PA: Primitive Atria 
SV: Sinus Venosus
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16
Q

3 structures of sinus venomous

A
  • CCV: Common Cardinal Vein
    • UV: Umbilical Vein
    • VV: Vitelline Vein
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17
Q

How does blood pass through heart tube

A

Blood comes from bottom and out from top

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18
Q

Looping of the heart

  • what happens
A

• Form s shaped loop
PA and SV = pushed to back

* PA at back (top)
* TA, BC,PV - middle triangle (Ta middle)
* SV hanging from PA (back bottom)
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19
Q

Looping of the heart - when it happens and duration

A

Looping takes 45 days

22nd - 23rd day

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20
Q

Formation of visceral pericardium around the recent

A

Special cells migrate from sinous venossus – and produces visceral pericardium around the heart

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21
Q

Cells that form pacemaker

A
  • Spinous venossus cells from the spinous venossus also acts as the pacemaker
    • Heart starts to beat at day 22
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22
Q

Location of primitive heart tube pacemaker

A

• The pacemaker of the primitive heart tube is located in the caudal portion

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23
Q

AS: Aortic Sac -forms

A

Ascending aorta+ (aortic arch specifically) right brachiocephalic trunk

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24
Q

TA: Truncus Arteriosus - forms

A

Pulmonary trunk+ Ascending aorta

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25
Q

BC: Bulbus Cordis - forms

A

Right ventricle + outflow tracts

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26
Q

PV: Primitive Ventricle - forms

A

Left ventricle

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27
Q

PA: Primitive Atria→ forms

A

Left atrium (have cells coming from outside the heart from lung bud) + Right atrium

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28
Q

Sepation of the heart

A

• Endocardial cushions start to form = from neural crest cells
Endocardial cushions fuse to form septum intermedium seperating heart tube into 2 corrals

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29
Q

2 canals formed during Sepation of the heart

A

○ Right atrioventricular canal

○ Left atrioventricular canal

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30
Q

Formation of av values - week 4

A
  • Septum intermedium starts to produce valves that are conencted in little rings = valvular annulus
    • Chordae tendinae also formed and they attach to papilalry muscles
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31
Q

Formation of Interatrial septum

A

Ridge appears between 2 primitve atria PA = ridge is called septum primum
• Osteum primum is the space/ cavity between septium primum and septum intermedium
• Septum primum moves down to attach to septum intermdium
• Second space forms = ostium secundum (channel foramen ovale)
• Septum secundum forms

32
Q

Septum primum

A

Ridge between 2 primitive atria

33
Q

Osteum primum

A

is the space/ cavity between septium primum and septum intermedium

34
Q

Formation of Interventricular septum

A

Ridge forms = muscular portion of interventricular septum (not attached to septum intemedium yet)
• Membraneous portion of intraventricular septum is formed that attaches to septum intermedium

35
Q

Venticular septum defecst

A

○ Venticular septum defecst = the memrnaeous portion of intraventricular septum is not formed

36
Q

2 parts of Interventricular septum

A

muscular portion of interventricular septum ‘ (not attached to septum intemedium yet)

Membraneous portion of intraventricular septum is formed that attaches to septum intermedium
37
Q

3 inflow tracts to right citrus

A
  • Inferior vena cava
    • Superior vena cava
    • Coronary sinus
38
Q

3 veins in left horn of sinus venosous

A
  • All veins in left horn degenerate
  • Sinus venosus gets absorbed into right atrium
  • Remaining left horn gets absorbed into right atrium becomes coronary sinus
39
Q

3 veins in right horn of sinus venomous

A
  • Umbilical vein degernates
    • Only CCV and VV remain
    • CCV forms superior vena cava
    • VV forms inferior vena cava
40
Q

What forms coronary sinus

A

• Remaining left horn of sinus venous gets absorbed into right atrium becomes coronary sinus

41
Q

What forms superior vena cava

A

CCV - common cardinal vein from right horn of sinus venous

42
Q

What forms inferior vena cava

A

V V - vitelline vein from right horn of sinus venous

43
Q

Formation of outflow tracts

A

TA trunkus airteriosis and BC bulbus cordis form outflow tracts

* Neural crest cells migrate and form ridges on truncal and bulbar part (top and bottom) form truncal ridges and bulbar ridges
* Bulbar ridges and truncal ridges fuse, create 2 tracts that twist and rotate
* Aortic pulmonary septum rotates and differentiates into pulmonary trunk and aorta

Central part of BC forms ridges that fuse to form semi lunar valves

44
Q

2 outflow tracts

A

• Pulmonary artery

Aorta

45
Q

What happens to dorsal mesocardium when outflow tracts are formed

A

• Dorsal mesocardium disintegrates/ degenerates

46
Q

Pressure in utero

A

• In foetus pressure is higher in left side rather than right side

-– Lung is not functional – very constricted in foetus
– Hypoxic vasoconstriction of pulmonary arteries

47
Q

Hypoxic vasoconstriction

A
  • Partial pressure of oxygen is very very low in foetus , so pulmonary arteries and veins constrict
    • Increase in pressure as the vessels constrict
48
Q

Foetal circulation - where does oxygenated blood come from

A

Placenta = oxygenated blood from mum

49
Q

Foetal circulation - flow of oxygenated blood

A

• Oxygenated blood from placenta carried by umbilical vein into the liver
• In liver – the ductus venosus – shunts blood from umbilical vein into inferior vena cava
• Blood passes from IVC to right atrium→ Foramen Ovale→ Left atrium
○ Due to pressure gradient as pressure in right side > left side pressure
• Blood passes from left atrium→ Left ventricle→ Aorta→ Body

50
Q

ductus venosus

A

shunts blood from umbilical vein into inferior vena cava

51
Q

Foremen ovale

A

Gap between right atrium, and left atrium

- ra pressure > La pressure

52
Q

Effect of gravity on oxygenated blood in foetal circulation

A

• Some blood (10-20%) from right atria passes into right ventricle-> pulmonary trunk→ Ductus arteriosus (shant between pulmonary artery and arch of aorta)→ Aorta

53
Q

Ductus arteriosus

A

shant between pulmonary artery and arch of aorta)

54
Q

Foetal circulation: deoxygenated blood

A

• Deoxygenated blood carried by superior vena cava (SVC)→ Right atrium
• Blood passes from right atrium→ Right ventricle→ Pulmonary arteries→ Ductus arteriosus→ Aorta
○ Deoxygenated blood flows into right atrium and down into right ventricle as it flows down to enter to the heart
• Descending aorta→ Internal iliac artery (2 umbilical veins carrying deoxygenated blood back into placenta)→ Umbilical arteries→ Placenta

55
Q

Pressure after birth

A

– Pressure lower in the right side of the heart compared to the left side

56
Q

Fetal circulation: after birt

A

– Lung is functional
– No hypoxic vasoconstriction of pulmonary arteries
– Pressure lower in the right side of the heart compared to the left side
– Blood level in pulmonary arteries increase
– Pulmonary veins empty blood into left atrium

Partial pressure of oxygen in alveoli is high = no hypoxic vasoconstriction, pulmonary arteries and veins filled with blood

57
Q

6 foetal shunt s.

A
  • Umbilical vein
  • Umbilical arteries
  • Ductus venosus
  • Ductus venosus
  • Ductus arteriosus
58
Q

Fate of • Umbilical vein after birth

A

only one vein → becomes Ligamentum Teres

○ Ligamentum teres is in the liver

59
Q

Fate of • Umbilical arteries after birth

A

becomes medial umbilical ligament

60
Q

Fate of • ductous venous after birth

A

(in the liver) closes→ becomes Ligamentum Venosum

61
Q

Fate of • foreman vale after birth

A

closes→ becomes Fossa Ovalis

62
Q

Fate of • ductus arteriosus after birth

A

closes→ becomes Ligamentum Arteriosum

63
Q

Congenital heart defects - causes

A

• Significant majority of congenital heart defects occur due to genetic mutations that interfere with cardiac development

64
Q

Trisomy 21

A

• Common genetic cause of congenital heart disease is trisomy 21, (down syndrome) which often manifests itself as endocardial cushion defects

65
Q

Shunts

A
  • Malformations causing shunting – diverting the blood flow (right-to-left or left-to-right) or malformations causing an obstruction
    • Shunts are abnormal communications between systemic circulation (the left heart) and the pulmonary circulation (the right side)
    • These shunts permit non-physiologic blood flow along pressure gradients
66
Q

Right to left shunt - what is it

A

—-> Blood flowing abnormally from the right side of the heart to the left side

67
Q

Right to left shunt - effect

A
  • Circulation of deoxygenated blood (i.e., blood that has yet to reach the pulmonary system) to the systemic circulation – deoxygenated blood is pumped around the body
  • Patients with a right to left shunts present with cyanosis
68
Q

Left to right shunt - what is it

A

—> Blood flowing abnormally from the left side of the heart to the right side

69
Q

Left to right shunt - effect

A
  • The systemic circulation still receives oxygenated blood – oxygenated blood still leaves through aorta to go to the body
  • Patients with a left to right shunts do NOT present with cyanosis
70
Q

Reversal of left to right shunt

A
  • Pulmonary system is a “low-pressure” system incapable of withstanding the increased pressure
  • Pulmonary arteries typically respond to the increased blood flow and pressure via hypertrophy and vasoconstriction
  • Eventually, pulmonary vascular resistance approaches systemic levels, creating a shunt reversal (now right-to-left) to distribute deoxygenated blood into the systemic system
71
Q

• Atrial septal defects (ASD)

A

occur when there is a failure to close the communication between left and right atria = hole in atria blood passes from left to right

• Failure to close will cause mixing of blood in right and left atria

72
Q

• Defect in formation of interventricular septum

A

• Membranous portion of interventricular septum is most commonly involved

73
Q

2 examples of left to right shunt

A
  • Atrial septal defects (ASD)

* Defect in formation of interventricular septum

74
Q

• Transposition of the great arteries

A

○ Switching of the arteries as looping of the great vessels doesn’t occur properly they loop the wrong way round
• Aorta arises from right ventricle
• Pulmonary artery arises from left ventricle – Rotational failure

75
Q

Tetralogy of Fallot = 4 problems

A

• Characterised by FOUR structural defects of the heart
– Ventricular septal defect
– Pulmonary valve stenosis = blood cannot pass into pulmonary arteries so blood pushed back into left side
– Right ventricular hypertrophy = thickening of right ventricle
– Aorta displacement = aorta sit on the septum defect

76
Q

2 Right to left shunt – examples

A

• Transposition of the great arteries

Tetralogy of Fallot = 4 problems

Y1 TP2 Cardiovascular (topic 4 Onwards) (8 decks)

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