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Cardiorespiratory 2 > Development of the Heart > Flashcards

Development of the Heart Flashcards

1
Q

what are the three germ layers

A
  • Ecotoderm
  • mesoderm
  • endoderm
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2
Q

what do the three germ layers develop into

A
  • Ectoderm – skin, CNS, PNS, eyes, internal ear (outside)
  • Mesoderm – bones, connective tissue, skeletal muscle, urogenital system, cardiovascular system
  • Endoderm – gut and associated derived tissues such as the liver, pancreas and lungs) (inside)
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3
Q

what does the heart originally develop from and where does this happen

A
  • Develops from cardiogenic mesoderm (lateral plate), originally lying above cranial end of developing neural tube
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4
Q

what are the two blood islands

A
  • haemangioblasts and myoblasts
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5
Q

describe how the endocardial tubes form

A
  • Angiogenic cell clusters coalesce forming right and left endocardial tubes
  • Lateral folding of embryo results in fusing of paired endocardial tubes into primitive heart tube
  • At 21 days there is a venous end and a atrial end, start to get different bulges along the tube that are associated with the end heart structures
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6
Q

name the parts of the congenial heart and what they develop into

A

At the top

  • truncus arteriosus - this develops into the proximal aorta and pulmonary artery
  • bulbs cordis - this forms the ventricular outflow tracts and right ventricle
  • primitive ventricle - left ventricle
  • primitive ratio - left and right atria
  • sinus venous - smooth part of the right atrium and coronary sinus
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7
Q

what covers the heart tube and why

A
  • there is a pericardium sac

- this helps shape the heart as the tube has to fold within the pericardium

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8
Q

how long does tube folding of the foetal heart into a alignment similar to the adult heart

A
  • process occurs between 23 and 28 days
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9
Q

what day does the foetal heart begin to resemble an adult heart

A

day 35

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10
Q

what is dextrocardia

A
  • this occurs when the heart is on the wrong side fo the chest
  • happens when cardia looping happens in the wrong direction
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11
Q

describe the process of foramen oval

A
  • this shunts the blood from the RA to LA
  • bypasses the lungs and thus pulmonary circulation, this is because the lungs are not fully developed and there is a lack of oxygen in the uterus
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12
Q

why does the foramen oval stay open before birth

A
  • There is higher pressure in the right atrium than in the left atrium therefore there is shunting from RA to LA
  • there is high pulmonary resistance
  • Therefore blood passes through the foramen ovale
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13
Q

why does the foramen oval close after birth

A
  • right atrium has lower pressure than the left atrium therefore this forces the valve to close
  • pulmonary resistance is reduced
  • therefore the Forman oval closes and form the fossa ovalis
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14
Q

what is a patent foramen ovale

A
  • In up to 25% of people a probe can be passed from one atrium to the other
  • Defect is usually small and is not significant
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15
Q

describe how the atria septum is created (wall between the two atria)

A
  • The septum starts to grow down from the top of the atria this is called the septum primum
  • As it is growing down towards the endocardial cushion the space between them is called the ostium primum
  • Before the ostium primum disappears completely a second hole forms this is called the ostium secundum
  • Once osteium secundum develops osteium primum then closes and ostium secundum develops
  • Once septum primum reaches endocardial cushions septum secundum starts to form and this goes down to the endocardial cushion
  • Septum secundum leaves a hole in it and this is the foramen ovale
  • Septum primum helps form this valve as well
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16
Q

what leaves a hole to form the foramen ovale

A
  • Septum secundum leaves a hole in it and this is the foramen ovale
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17
Q

when does the atria septum develop

A
  • Day 28/end of 4th week, two swellings of mesenchymal tissue appear from walls of the atria- endocardial cushsions
  • The endocardial cushsions grow and fuse together to divide canal into R and L
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18
Q

describe the perlevance of atrial septal defects

A
  • ASD incidence 7:10,000 births

* 2:1 prevalence in females versus males

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19
Q

name some atrial septal defects

A

• Septum primum and septum secundum defects

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20
Q

what does atrial septal defects lead to

A
  • large atrial septal detects with left to right shunting can result in pulmonary hypertension and thus right ventricular hypertrophy
21
Q

describe how ventricular septum develops

A
  • Has a muscular part that grows from the base of the heart to the endocardial cushions
  • And a membranous component that grows down from the endocardial cushions towards the muscular part
  • End of 4th week a muscular IVS develops from floor of primordial ventricle
  • Grows towards membranous IVS which develops from endocardial cushions
22
Q

what is the most common type of cardiac defect

A

• VSDs are most common type of cardiac defect accounting for 25% of congenital heart defects.

23
Q

describe the relevance of VSD (ventricular septal defects)

A
  • Many small VSD will close spontaneously (30-50%).
  • Isolated VSD are detected with an incidence of 10-12:10,000.
  • About 90% of VSD are in membranous septum and 10% in muscular septum.
24
Q

what does ventricular septal defects lead to

A
  • massive left to right shunting of blood and pulmonary hypertension
25
Q

what happens in the 5th week of the heart development

A
  • the aorta and pulmonary arteries separate
26
Q

describe how the aorta and pulmonary artery separates

A
  • Truncoconal swellings form in the truncus arteriosus and grow towards each other in a spiral structure
  • Therefore the aorta connects with the left ventricle and the pulmonary trunk with the right ventricle
27
Q

what are the things in foetal circulation that are different from adult circulation

A
  • ductus venous
  • foramen ovale
  • ductus arteriosus
28
Q

describe what ductus venous does

A

Ductus venosus - shunts blood from umbilical vein to IVC (bypassing liver)

29
Q

describe what Forman ovale does

A

• Foramen ovale - shunts blood from RA to LA (bypassing pulmonary circulation)

30
Q

describe what ductus arteriosus does

A

• Ductus arteriosus - shunts blood from pulmonary trunk to ascending aorta (bypassing lungs)

31
Q

what happens to the

  • ductus Venus
  • foramen ovale
  • ductus arteriosus at birth
A
  • Formane ovale closes because of increased pressure in LA compared to RA and this becomes the fossa ovalis
  • Ductus arteriosus and venosus – fibroses and becomes the ligamentum arteriosus and venosus
32
Q

what is an acynatoic heart lesions

A
  • this is when there is a left to right shunt or left heart abnormality which does not result in cyanosis (blue skin colour of the baby)
33
Q

what percentage of congenital heart diseases are acynaotic heart lesions

A

1/3

34
Q

name two types of heart defects

A

acynatoic heart lesions

cyanotic heart lesions

35
Q

name some acyanotic heart lesions

A

o ASD - Atrial Septal Defects
o VSD - Ventricular Septal Defects
o PDA - Patent Ductus Arteriosus
o Coarctation of the aorta

36
Q

what is a patent ductus arteriosus

A
  • Ductus Arteriosus connects the descending aorta to the main pulmonary trunk near the origin of the left subclavian
  • Normal postnatal closure results in fibrosis- which becomes the ligamentum arteriosum.
37
Q

what is the risk of a patent ductus arteriosus

A
  • Small PDA does not increase risk for heart failure- but does carry a risk for bacterial endocarditis
38
Q

what is the current treatment for a patent ductus arteriosus

A

prostaglandin inhibitor such as ibuprofen and if this fails to close then surgical closure with a clip is performed in infants older than 3 months

39
Q

what is coarction of the aorta

A
  • this is when the aorta narrows or thins

- the constriction may be above or below the ductus arteriosus (pre-ductal, post-ductal)

40
Q

what is the difference between pre-ductal and post-ductal coarction of the aorta

A
  • In pre-ductal types, ductus arteriosus persist allowing blood flow.
  • In Post-ductal collateral circulations must be established for proper perfusion of body and legs
41
Q

what does coarction of the aorta result in

A

• Have higher pressure in upper limbs than in the lower limbs as the lower limbs have low blood pressure below the coarction of the aorta

42
Q

what is cyanotic heart lesions

A

• Cyanotic congenital heart disease: a group of cardiac diseases which allow deoxygenated blood to bypass the lungs and enter the systemic circulation therefore the tissues of the body have less oxygen than they require and the baby is cyanosed (blue).

43
Q

what are the examples of cyanotic congenital heart disease

A

o Tetralogy of Fallot
o Persistent truncus arteriosus
o Transposition of the great vessels

44
Q

what is tetralogy of fallot

A
  • It is a cognetial heart defect that is comprised for 4 differnet defects
45
Q

what are the 4 different defects of the tetralogy of fallot

A
  1. Ventricular septal defect
  2. Overring aorta – aorta is not positioned coming out of the left ventricle but sits over the top of the ventricular septal defect therefore there is only mixed blood going into the aorta
  3. Pulmonary stenosis
  4. Right ventricular hypertrophy
46
Q

what is persistent trunks arteriosus

A

• Single artery (truncus) arises from the heart, supplying both aorta and pulmonary artery.
• A large VSD (ventricular septal defect) below the truncal valve allows mixing of right and left ventricular blood
- progressive heart failure

47
Q

what happens with transposition of the great vessels

A
  • Conotruncal septum fails to follow spiral course (runs straight down)
  • Usually accompanied by open ductus arteriosus
48
Q

what is the procedure for someone born with transposition of the great vessels

A

• Blue baby – immediate surgical intervention – catherterisation of fossa ovalis to increase mixing of pulmonary and systemic blood– buy time till infant can be operated on at later date

Cardiorespiratory 2 (43 decks)

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