Heart Devo And Defects

Front 1

What are the original precursors for teh cardiovascular system (not the heart)? What tissue layer are they from? When and where do they first appear?

Back 1

ANgioblasts/ Hemangioblasts are mesenchyme cells withing the extra and intraembryonic mesoderm. They are first observed at day 17 in the wall of the yolk sac.

Front 2

What is a blood island? Where do they form? What occurs here?

Back 2

A blood island is an aggregation of angioblasts within the yolk sac. In the blood island the angioblasts differntiate into endothelial cells and hematopoietic stem cells.

Front 3

List in order the sites of hematopoiesis during development

Back 3

1. yolk sac (mo. 1-2)
2. spleen/liver (mo. 1.5-7)
3. bone marrow (mo. 4-adult)

Front 4

From what tissue is the heart derived? Where is this tissue?

Back 4

Heart is derived from cradiogenic cresent within the splanchnic mesoderm. The cardiogenic cresent is found in the medial wall of the IEC at the cranial end.

Front 5

Describe the formation of the heart tube up to cranial caudal folding

Back 5

-Cells from the cardiac cresent migrate into the space between the foregut endoderm and the cardiogenic cresent to form and endothelial plexus
-within the plexus,the endocardium (endothelial tube) forms, this will become the epithelial linging inside the heart
-the mesoderm of the cardiac cresent molds around the developing endocardium, forming the myocardium

Front 6

What is the origin of the cardiac endothelium (epithelial lining inside the heart)

Back 6

The endocardium forms as a tube within the endothelial plexus which was formed when cells from the cardiac crescent migrated into the space between the foregut endoderm and the crescent

Front 7

What is the origin of the myocardium (muscle layer of the heart)

Back 7

Myocardium comes from the mesoderm of the cardiogenic crescent that molded around the developing endocardium

Front 8

What is the role of lateral folding in heart development?

Back 8

Lateral folding unites the limbs of the cardiac cresent resulting in the formation of a prmitive heart tube (two tubes become one tube)

Front 9

What is the embryologic origin of the transverse pericardial sinus

Back 9

After the embryo folds laterally, the primitive heart tube is suspended in the cranial portion of the embryonic celom by the dorsal mesocardium. After the formation of teh pericardial cavity, the dorsal mesocardium disappears leaving a communication between the sides of the pericardial cavity. This communication is the transverse pericardial sinus.

Front 10

what is the secondary heart field

Back 10

Contribues cells used for the elongation of the heart tube as an additional source of cardiac progenitor cells. IT is a cresecent shaped area located and dorsal and medial to the primary heart field

Front 11

What are the four tissues involved with the primitive heart

Back 11

1. Cardiac endothelium (endocardium)= epithelium linging the lumen of the heart
2. myocardium= muscle layer
3. Cardiac Jelly= between endocardium and myocardium, accumulation of ECM
4. epicardium= epithelial layer over myocardium

Front 12

Swellings of cardiac jelly contribute to the formation of which two structures

Back 12

1. endocardial cushions in the AV canal
2. Bulbar/ Conotruncal Ridges in the outflow region

Front 13

From what structures does the fiberous connetive tissue of the visceral pericardium develop?

Back 13

proepicardial organ (cluster of coelomic epithelial cells adjacent to sinus venosus)=>epicardium=> visceral pericardium and coronary vessels

Front 14

What are the three venous channels that enter the sinus venousus region of the primtive heart tube?

Back 14

1. umbilical veins (oxygenated blood from mom)
2. Vitelline Veins (deoxy blood from gut)
3. Common Cardinal veins (deoxy blood from head and trunk via anterior and posterior common cardinal)

Front 15

Which direction does the heart normally loop? WHere is the bend of the loop?

Back 15

to the right, the ben is between the primitive left and right ventricles

Front 16

What occurs during the early stage of cardiac looping

Back 16

-establish proper anatomical relationships between heart segments
-venous inflow and arterial outflow regions are aproximated
-the outflow region becomes subdivided into the conus arteriousus (proximal) and the truncus arteriosis (distal, connects to aortic sac)

Front 17

What occurs during the late phase of cardiac looping?

Back 17

-both limbs of the loop contact each other along the bulboventricular groove at the level of the AV canal, the inner curvature is the hinge for this contact
-the proximal portion of the outflow region is wedged into the AV cana

Front 18

In general, failure of complete looping results in...

Back 18

retention of the embryonic pattern of blood flow through the heart

Front 19

When does the heartbeat begin

Back 19

day 22
(two two, two two sounds like lub dub, lub dub)

Front 20

Describe how the flow of blood changes in the primitive heart tube between days 22-28 (during looping, before chamer formation)

Back 20

Initially the blood just sloshes back and forth but by day 26 it becomes unidirection from inflow to outflow. By day 28 left and right streams spiral around each other and are physically separated even though no sepation has occured. The stream from the LV enters into what will be the aorta and the stream from the right enters what will be the ductus arteriosus

Front 21

When does heart partitioning occur

Back 21

weeks 5-8

Front 22

What 4 types of tissue are involved in partitioning

Back 22

1. cardiac muscle
2. Cardiac mesenchyme (endocardial cushions)
3. extracardiac mesenchyme (mesoderm)
4. neural crest (aorticopulmonary septum and distal outflow valves)

Front 23

What two structures give rise to the definitive right atrium?

Back 23

1. primordial right atrium
2. portions of sinus venosus

Front 24

Explain how all of the systemic blood comes to empty into the right atrium rather than two separate enteries (horns of sinus venosus) into the common atrium

Back 24

-the left horn of the sinus venosus becomes a tributary of the right horn
-the left umbilical and vitelline as well as the right proximal umbilical veins atrophy
-the crainial portion of the R. vitelline vein becomes the IVC

Front 25

What structure of the primtive heart gives rise to the coronary sinus

Back 25

Right SV valve

Front 26

What structure of the primtive heart gives rise to the crista terminalis

Back 26

right SV valve

Front 27

What structure of the primtive heart gives rise to the valve of the IVC

Back 27

right SV valve

Front 28

What structure of the primtive heart gives rise to the valve of the valve of the conronary sinus

Back 28

right SV valve

Front 29

What structure of the primtive heart gives rise to the smooth area of the right atrium

Back 29

R. sinous venousus

Front 30

What structure of the primtive heart gives rise to the IVC terminal segment

Back 30

R. vitelline vein

Front 31

What structure of the primtive heart gives rise to the SVC

Back 31

R. anterior cardinal vein

Front 32

What structure of the primtive heart gives rise to the trabeculated part and auricle of the right atrium

Back 32

the right primitive atrium

Front 33

Describe the formation of the left primitive atrium

Back 33

Forms from absorbed pulomnary veins and the primitive left atrium

Front 34

What gives rises to the trabeculated portion of the definitive left atrium? Where is it located?

Back 34

Trabeculated portion is derived from the primordial left atrium. It is restricted to the auricle in the definitive chamber

Front 35

Explain how an inflow connection to the primitive right ventricle from the right side of the common atrium is established

Back 35

The common av canal is repositioned in order to create an opening from the right side of the common atrium to the primitive right ventricle. Endocardial cushion tissue along the innvercurvature of the heart is replaces with msucle which thins the heart wall. The AV canal is then shifted to the right.

Front 36

Where does the endocardial cushion tissue form? What tissue does it form from.

Back 36

Cushion tissue forms in the AV canal and the Outflow region. In these regions, endocardial epithelial cells become mesenchyme cells and mirgrate into the cardiac jelly.Note that in the outflow region these areas are called bulbar ridges

Front 37

What is the purpose of the septum intermedium

Back 37

The septum intermedium separateds the right and left AV canals This tissue is formed by fusion of dorsal and ventral endocardial cushions. This area is a guide and glue for positoning and attachment of the future septa when the heart chambers are formed

Front 38

Which mature heart structures derive from cardiac mesenchyme (endocardial cushions)?

Back 38

valve leaflets, mitral, tricuspid, aortic, and pulmonary valves, chordae tendinae, and cardiac skeleton

Front 39

The primitive ventricles are separated by an interventricular septum with muscular and membranous portions. Explain how each are formed

Back 39

1. muscular=the medial walls of the primitive right and left ventricles appose and result in a build of trabeculae
2. membranous= formed from cushion tissue of septum intermedium and bullbar ridges. The cushion tissue fuse together and also fuse with the suberior edge of the muscular IVS.

Front 40

The opening between the top of the muscular portion of the interventricular septum and the bottom of the cushion tissue septum intermedium is the primary interventricular foramen. Explain why this foramen never closes

Back 40

this foramen becomes the opening into the aortic vestible

Front 41

How does the secondary interventricular foramen (between wall of aortic cestibule and forming right ventricle) close

Back 41

It is closed by the membranous portion of the interventribular septum that is formed from cushion tissue of the bulbar ridges and septum intermedium

Front 42

Explain how the formation of the interatrial septa develops in such a way as to allow right to left shunting of the blood

Back 42

1. The septum primum extends from the roof of the common atrium towards the setum inermedium, does not go all the way but rather leaves an opening called the ostium primum
2. The dorsal mesocardial projection fills the ostium primum from the other side while the ostium secundum forms to keep blood moving.
3. The septum secundum forms to the right of the septum primum. It does not grow all the way and leaves the foramen ovale at its inferior border.
Since the two openings are each in a different septum and are offset, they act as a valve and allow for right to left shuting of the blood

Front 43

In which direction is blood allowed to shunt between the atria?

Back 43

Right to left

Front 44

The proximal outflow region (conous arteriosus), the distal outflow region (truncus arteriosus) and the aortic sac each develop into differnet ventricle strucutes in the adult. What are these structures.

Back 44

conus arteriosus=smooth portions of right and left ventricles
truncus arteriosus= pulmonary and aortic valves, and part of roots of aorta and pulm. trunk
aortic sac= parts of pulmonary and aortic root

Front 45

What is the conotruncal septum? What tissue forms it

Back 45

The conotruncal septum divides the outflow region into right and left channels. It is formed from paired ridges of endocardial cushion tisue aka "bulbar ridges"

Front 46

Why does the conotruncal septum spiral?

Back 46

During cardiac looping the region twists 90 degrees

Front 47

What happens to the proxmial outflow region? Distal?

Back 47

After the formation of the contotruncal septum which makes right and left halves, myocytes invade the proximal outflow region and turn it into a muscular structure. In the distal region, the cushion tissue contributes to the formation of the aortic and pulmonary vavles.

Front 48

What is the role of neural crests cells in the division of the proxmial and distal outflow regions.

Back 48

In the outflow region, neural crest cells contribute to the mesenchyme that will form the conotruncal septum.

In the aortic sac, neural crest cells give rise to the mesenchyme that forms the arterial spine that becomes the aorticopulmonary septum which fuses with the superior edge of the conotruncal seputm in order to divide the roots of the aorta and pulm. trunk

Front 49

Explain how the aortic sac is divided into the roots of the pulmonary trunk and aorta

Back 49

The arteria spine (mesenchyme derived from neural crest cells) extends from the dorsal wall of the aortic sac into the lumen forming the aorticopulmonary septum which fuses with the superior edge of the conotruncal septum. This divides the sac into ventral and dorsal components. Ventral becomes root of pulm. trunk and dorsal becomes root of aorta.

Front 50

What two components derived from endocardial cushion tissue are used to form the membraneous internventricular septum and close the secondary IVF.

Back 50

The inferior edge of the conotruncal septum (bulbar ridges,divides the outflow regions) and the ventral endocardial cushion of the septum intermedium.
To close the secondary IVF the membranous IVS fuses with the muscular IVS.

Front 51

when is the heart completely divided into 4 separate chambers

Back 51

7-8th week

Front 52

Explain how and why blood is shunted around the liver in the fetus

Back 52

-The liver is not needed to detox because mom does this.
-In the fetus oxygen rich blood returns from the placenta throug the umbilical vein.
-The blood is directed around the liver via the ductus venosus which connects the umbilical vein with the IVC

Front 53

In which direction is blood shunted in the fetal heart? What structure does this? Why is this done?

Back 53

Blood is shunted from right ventricle to left ventricle via the foramen ovale. This occurs because we don't need to send the blood to the pulmonary circulation to reoxygenate.

Front 54

What is the function of the ductus arteriosus in the fetus

Back 54

Shunts blood leaving the right ventricle via the pulmonary trunk to the aorta to further avoid the pulmonary circulation

Front 55

Which side of the fetal heart is higher in pressure

Back 55

The right side because pulmonary vascular resistence is high
(this is why a right to left shunt through the forament ovale can work effectively

Front 56

What is the fate of the ductus venosus

Back 56

becomes the ligamentum venosum on the inferior surface of the liver

Front 57

What is the fate of the ductus arteriosus

Back 57

becomes the ligamentum arteriosum that tracks between the pulmonary trunk and the aorta

Front 58

WHihc side of the newborn heart is higher in pressure

Back 58

The left beceause the pulmonary resistence decreases and the filling of the pulmonary circulation

Front 59

What is the fate of the inferior portion of the left umbilical vein?

Back 59

The inferior portion of the left umbilical vein becomes the ductus venosus in the fetus which becomes ligamentum teres of the liver in adults

Front 60

What embryologic structures form the medial umbilical ligaments

Back 60

the distal portions of the umbilical arteries

Front 61

List 4 CHD's that cause left to right shunting

Back 61

1. Endocardial cushion defect
2. ASD
3. VSD
4. PDA

mnemonic: "Every Conservative Adult Votes PreDictAbily"
left=>right, the right is conservative

Front 62

Which type of shunting will causes cyanosis

Back 62

right to left

Hint: Left to right won't make you bright (blue)

Front 63

List 5 CHD's that lead to a right to left shunt/ cyanotic condition

Back 63

Definitely cyanotic
1.Persistent truncus arteriosus
2. Transposition of the great vessels
3. HLH
4. tetralogy of Fallot
mnemonic= 1,2,3,4: 1 opening, 2 switches, 3 letters, 4 things wrong

5.Pulmonary stenosis/ atresia may result in cyanosis if a right to left shunt is present

Front 64

List 4 CHD's that result from an obstructive process

Back 64

1. Coarctation of the aorta
2. aortic stenosis atresia
3. pulmonary stenosis/ atresia
4. HLH

Front 65

Explain the "progression" that occurs if a left to right shunt is not corrected. (why is it a problem)

Back 65

1. adding blood to the right side creates a volume overload in the pulmonary circulation
2. The wall of the pulmonary vessesl thickens causing pulmonary hypertensin
3. Pulmonary hypertension leads to right heart hypertrophy and failure
4. Right heart failure can lead to reversal of the shunt left to right to right to left.
5. A right to left shunt leads to cyanosis

Front 66

Why does a right to left shunt lead to cyanosis

Back 66

Dexoygenated blood entering the right atrium/ ventricle is shunted into the left side before it can be pumped into the lungs for oxygenation.

Front 67

What are the physiological outcomes associated with left heart obstruction (both obstruction into the atrium/ventricle and out of the ventricle)

Back 67

1. the obstruction leads to an increase in pulmonary circulation pressure leading to pulmonary hypertension
2. pulmonary hypertension can lead to left heart failure

Front 68

What are the physiological outcomes associated with right heart obstruction (flow out of the right heart)

Back 68

-insufficient blood flow to the lungs leads to hypoxia and cyanosis if a right to left shunt is present
-right heart failure will occur

Front 69

What is the most common cause of CHD

Back 69

multifactorial/ unknown (90%)). Other causes include genetic and environemental

Front 70

Where are VSD's most commonly located

Back 70

menbranous portion of IV septum

Front 71

A VSD is most likely associated with which developmental tissue

Back 71

Since VSD's usually occur in the membranous portion, a defect in endocardial cushion tissue formation/processes may be involved

Front 72

What is the most common type of ASD

Back 72

secundum type, involves a patent oval foramen
note this type is most common seen in adults

Front 73

In general, when will a murmmur associated with a heart defect be heard

Back 73

A mummur will occur if there is shunting across the defect

Front 74

Endocardial cushion defects can result in shunting in which direction

Back 74

left to right
"Every Conservative Adult Votes PreDictabily"

Front 75

A patent ductus arteriosus is a left to right shunt condition.. What can be done to close the PDA

Back 75

antiprostaglandins

Front 76

What are the 5 defects associated with tetralogy/pentalogy of fallot, a right to left shunting defect

Back 76

1. Pulmonary stenosis
2. R. ventricular hypertrophy/ outflow defect
3. Overiding Aorta
4. VSD
and A+ if you can PROV pentalogy
A= ASD

Front 77

Tetralogy of fallot is secondary to a defect in which structure

Back 77

Anterior deviation of the infundibular (aorticopulmonary) septum that divides the great vessels

Front 78

Why does transposition of the great vessels result in cyanosis

Back 78

Oxygenated blood is trapped i nthe pulmonary circulation because the pulmonary vein does not enter the left atrium

Front 79

What can be done to temorarly fixed the problem associated with complete transposition of the great vessels

Back 79

give prostaglandins to keep the ductus arteriosus open which will shunt blood from the pulmonary trunk to the aorta

Front 80

A persisent truncus arteriosus results in right to left shunting of the blood and a cyanotic condition because a single vessel empties both ventricles. What embryological process was likely disturbed.

Back 80

In outer to partition the outflow region, bulbar ridges must fuse to form the conotruncal septum. Later on, the aorticopulmonary septum must form in order to create the pulmonary trunk and aorta.

Front 81

what is the cause of HLH

Back 81

the left ventricle and/or atrium were not filled during development. This is probably due to mitral stenosis or a foramen ovavle that closes too soon or is too small

Front 82

What are the clinical signs of coarctation of the aorta

Back 82

differential pulses in the extremeties, strong pulse in upper limb, weak in lower. A heart murmur may also occur. In females, the condition is often associated with turner's syndrome

mnemonic: "arched" pulses, and arched (webbed) neck

Front 83

Aortic stenosis/ atresia involving narrowing of the aortic vavle or absence of the aorta leads to failure of which heart structure

Back 83

left ventricle

Front 84

What is the cause of pulmonary stenosis? What heart structure is affected

Back 84

Caused by narrowing of the pulmonary vavle or outflow region of the right ventricle. Stenosis make sthe right ventricle work harder and results in right ventricular hypertrophy

Front 85

heart looping to the left results in a condition called

Back 85

dextrocardia or a right sided heart
this can occur in isolation or as part of other malformations. Situs inversus can also occur resulting in a complete reverse of the normal pattern

Front 86

Ectopic cardia is associated the the defective development of....

Back 86

ventral body wall

Front 87

Which structures give rise to the following segments of the IVC
terminal
liver=> kidenys
Kidney=> sacrum
sacrum

Back 87

terminal= R. vitelline vein
liver=> kidneys= R. subcardinal
Kidney=> sacrum= R. supracardinal
sacral= R. and L. posterior cardianl

Front 88

What does the 4th pharyngeal arch artery become

Back 88

L= aortic arch
R= right subclavian

Front 89

What does the 6th pharyngeal arch artery become

Back 89

L=L. pulmonary artery and ductus arteriosis
R.= R. pulmonary artery