3.1.3. Cardiovascular System Development Flashcards
Define Splanchnic mesoderm
mesoderm that overlies the endoderm and is a layer continuous with the mesoderm covering the yolk sac; gives rise to the mesothelial covering of viscera
Define Crista terminalis
the junction between the sinus venosus and the heart in the embryo; ridge of tissue in the right atrium
Define the Cardiogenic field (area)
a horseshoe shaped area in the splanchnic mesoderm on either side of the neural plate
Define Septum primum
the septum that separates the cavity of the primitive atrium into right and left chambers
Define Angiogenesis
physiological process through which new blood vessels form from pre-existing vessels
Define Septum secundum
semilunar in shape, grows downward from the upper wall of the atrium immediately to the right of the septum primum, with which it will fuse to close the foramen ovale
What are the Blood islands?
embryological structures which lead to the development of many different parts of the circulatory system; often seen on the umbilical vesicle, allantois, connecting stalk, or chorion
Define Ostium primum
an opening between the free edge of the septum primum and the AV cushions
What are the Vitelline veins?
veins which drain blood from the yolk sac
Define Ostium secundum
a foramen in the septum primum; precursor to the interatrial septum of the embryological heart
What are the Cardinal veins?
two short transverse veins which open on either side of the sinus venosus
Define Foramen ovale
hole in the fetal heart that allows blood to enter the left atrium from the right atrium; a cardiac shunt, which allows the blood to bypass pulmonary circulation
What are the Umbilical veins?
veins present in fetal development that carries oxygenated blood from the placenta to the fetus
The bulbus cordis gives rise to what structures?
together with the primitive ventricle will give rise to the developed ventricles
Define Ductus venosus
a fetal shunt that allows a portion of the umbilical blood flow to pass directly to the inferior vena cava, thereby allowing oxygenated blood from the placenta to bypass the liver
What is the Truncus arteriosus?
an embryologic trunk that originates from both ventricles and then differentiates into the aorta and pulmonary trunk
What is the Dorsal mesocardium?
part of the mesocardium of the fetal heart that breaks down to form the transverse sinus of the pericardium
What is the Aortic sac?
a dilated structure lined by endothelial cells located just above the truncus arteriosus, will give rise to the aortic arches
Define Transverse sinus
pericardial sinus from the mesoderm that will connect with the oblique sinus to form the pericardial sac
What is the Bulboventricular sulcus?
the junction between the ventricle and the bulbus cordis in the fetal heart
Define Epicardium
a serous membrane that forms the innermost layer of the pericardium and outermost surface of the heart
What are the Sinus horns?
right and left horns which supply the sinus venosus with venous blood from the vitelline, umbilical, and common cardinal veins
Define Mesocardium
embryonic mesentery supporting the embryonic heart in the pericardial cavity
What is the Oblique vein?
the remnants of the left sinus horn at 10 weeks gestation; supplies the left atrium
Define Endocardium
innermost layer of tissue that lines the chambers of the heart; similar to endothelium
What is the Coronary sinus?
a collection of veins joined together to form a large vessel that collects blood from the heart muscle; delivers deoxygenated blood to the right atrium
What is the Cardiac loop?
the term for the embryonic heart formed by the bending and twisting of the cardiac tube
What are the Endocardial cushions?
cells that play a vital role in proper heart septation; will give rise to the heart’s valves and septa
What is the Sinus venosus?
the large quadrangular cavity which proceeds the atrium on the venous side of the fetal heart; will be incorporated into the wall of the right atrium and give rise to the SA node
What are BMP 2, 4?
secretions from the endoderm and lateral plate mesoderm which induce the transcription factor NKX2.5 to produce heart-forming region
What are WNT inhibitors?
proteins that are secreted by the neural tube and block WNT proteins, which would inhibit normal heart development
What is NKX-2.5?
transcription factor for heart formation
When does the vascular system appear in embryonic development?
The vascular system appears in the middle of the third week, when the embryo is no longer able to satisfy its nutritional requirements by diffusion alone
What are the tree primary vascular systems
- Vitelline (will become blood vessels of digestive tract)
- Cardinal
- Umbilical
Throughout the development of the heart, blood must be able to flow through the heart _ ._
Throughout the development of the heart, blood must be able to flow through the heart continuously.
Four chambered heart functions as one chamber by using two shunts, _ _ and the _ _, because the lungs are not functioning.
Four chambered heart functions as one chamber by using two shunts, inter-atrial and the ductus arteriosus (from pulmonary trunk to aortic arch), because the lungs are not functioning.
In the embryo, pressure on the right side of heart is (higher/lower) than on the left.
In the embryo, pressure on the right side of heart is HIGHER than on the left.
Circulation resistance is high in pulmonary system because the lungs are not functioning; systemic circulation resistance low because it includes the placenta that is low pressure.
After _ _ (what event) the two shunts close, blood pumps into lungs and left side empties into systemic circulation so now the pressure on the right side is LOWER than on the left side.
After BIRTH the two shunts close, blood pumps into lungs and left side empties into systemic circulation so now the pressure on the right side is LOWER than on the left side.
When does the cardiac field (cardiogenic area) appear?
Appears around 18 days (in utero)
Where is the cardiogenic field in the embryo?
What factors help induce formation of the cardiogenic area?
- Induced by the combination of specific factors:
- BMP 2,4
- WNT inhibitors
- NKX-2.5 (specific transcription factor expressed in cardiac progenitor cells)
Angiogenic cells cluster on either side of the notochord to form the _ _ _ _ _ ._
Angiogenic cells cluster on either side of the notochord to form the primary heart field
_ _ _ _ _ _ is formed by the lateral folding and fusion of the endocardial heart tubes
PRIMITIVE HEART TUBE is formed by the lateral folding and fusion of the endocardial heart tubes
Lateral plate mesoderm located at the cephalic area of the embryo splits into a somatic layer and a splanchnic, thus formed the _ _ _ _
Lateral plate mesoderm located at the cephalic area of the embryo splits into a somatic layer and a splanchnic, thus formed the pericardial cavity
precardiac mesoderm preferentially migrates into the splanchnic layer and forms the _ _ _ _ _ _
precardiac mesoderm preferentially migrates into the splanchnic layer and forms the heart forming regions (HFRs)
hypertrophied foregut endoderm secretes _ _, which induces the sheet of mesoderm to form discontinuous vascular channels that remodel into a single endocardial tube (endocardium)
hypertrophied foregut endoderm secretes VEGF, which induces the sheet of mesoderm to form discontinuous vascular channels that remodel into a single endocardial tube (endocardium)
mesoderm around the endocardium forms the myocardium, which secretes a layer of extracellular matrix proteins called
mesoderm around the endocardium forms the myocardium, which secretes a layer of extracellular matrix proteins called cardiac jelly
the septum transversum will form portions of the _ _ and the _ _
the septum transversum will form portions of the diaphragm and the liver
Mesothelial cells on the surface of the septum transversum form the _ - _ near the sinus venosus
Mesothelial cells on the surface of the septum transversum form the pro-epicardium near the sinus venosus
Mesothelial cells on the surface of the septum transversum migrate over the heart to form most of the _ _
Mesothelial cells on the surface of the septum transversum migrate over the heart to form most of the epicardium.
This mesothelial cell layer on the surface of the septum transversum is responsible for formation of the _ _ _ ._
This mesothelial cell layer on the surface of the septum transversum is responsible for formation of the coronary arteries. (endothelial lining and smooth muscle)
The _ _ _ _ will then break down to initiate the segmentation and subdivision of the single cardiac tube
(around 22 days)
The dorsal mesocardium will then break down to initiate the segmentation and subdivision of the single cardiac tube
What is the function of cardiac looping in embryos before the heart is fully formed?
The function of cardiac looping is to align the four presumptive chambers of the future heart so that their spatial relationships are correct
What are the five primitive heart tube dilations?
- Five appear along the length of the tube
- truncus arteriosus
- bulbus cordis
- primitive ventricle
- primitive atrium
- sinus venosus
The primitive cardiac dilations undergo _ _ looping and develop into the adult structures of the heart
They undergo dextral looping and develop into the adult structures of the heart
Cells are added to the _ _ _ _ and _ _ _ _ from the secondary heart field
Cells are added to the Truncus arteriosus and Bulbus cordis from the secondary heart field
Why (mechanical reason) does the cardiac tube end up looping?
Ends of the tube are fixed in length, causing looping of the tube
series of constrictions and expansions form in the heart tube; (constrictions/expansions) contribute to the different heart chambers
(which of the two)
series of constrictions and expansions form in the heart tube; expansions contribute to the different heart chambers
How are portions of the cardiac tube displaced so that the inflow and outflow regions come to lie next to each other.
- Bulbus cordis displaced – caudally, ventrally, and to the right
- Primitive ventricle displaced – to the left
- Sinus venosus displaced – dorsally and cranially
Try to imagine how the cardiac loop looks when it is colded completely.
About when does this occur?
Name one example of the cardiac loop folding incorrectly.
Dextrocardia => dextro means right; heart loops to the right rather than left
Describe Atrioventricular septum formation
Dorsal AV cushion and ventral AV cushion approach each other and fuse to form the AV septum
partitions the AV canal into the right and left AV canals
When the AV cushions fuse into the AV septum, how does blood continue to flow through the cardiac loop?
Septum primum will fold towards the endocardial cushions, and fuse, resulting in the closing of the _ _ _ _; ostium secundum forms via perforations in the septum primum
Septum primum will fold towards the endocardial cushions, and fuse, resulting in the closing of the ostium primum; ostium secundum forms via perforations in the septum primum
ostium secundum formed as tissue degenerates in the superior septum primum
most common ASD (atrial septal defect) is _ _ _ _ type due to excessive resorption of the septum primum or inadequate formation of the septum secundum
ostium secundum formed as tissue degenerates in the superior septum primum
most common ASD (atrial septal defect) is OSTIUM SECUNDUM type due to excessive resorption of the septum primum or inadequate formation of the septum secundum
About when does atrial septum form?
33 days
Septum secundum then folds towards the endocardial cushions and fuses; _ _ _ _ forms
Septum secundum then folds towards the endocardial cushions and fuses; foramen ovale forms
septum secundum forms alongside the right edge of the
septum secundum forms alongside the right edge of the septum primum
Foramen ovale (FO) allows blood to be shunted from _ _ _ _ to _ _ _ _ during fetal life
FO allows blood to be shunted from right atrium to left atrium during fetal life
The FO closes after birth due to…
The FO closes after birth due to pressure in the LA
How does pressure in the left atrium (LA) close the foramen ovale after birth?
How can a too large ostium secundum or foramen ovale cause an Atrial Septal Defect (ASD) after birth?
the offset angles of the foramen ovale and the ostium secundum are necessary for when the pressures of the heart shift following birth; if the angles were not offset, or the foramen/ostium were formed too large, it would result in an “atrial-septal defect” resulting in blood flowing from the left atrium to the right atrium
- The muscular interventricular septum folds toward the atrioventricular septum
- forms as an upward expansion of the base of the primitive ventricle; extends toward the AV septum but does not reach it; resulting gap is the _ _
_ _
- The muscular interventricular septum folds toward the atrioventricular septum
- forms as an upward expansion of the base of the primitive ventricle; extends toward the AV septum but does not reach it; resulting gap is the interventricular foramen
The interventricular septum (IVS) will not close initially; must have formation of the _ _ portion of the IV septum
This septum will not close initially; must have formation of the membranous portion of the IV septum
membranous IVS formed by the fusion of the _ _ septum with the muscular IVS; grows downward from the AV cushions and fuses with the muscular interventricular septum (obliterates the _ _ _ _)
membranous IVS formed by the fusion of the aorticopulmonary septum with the muscular IVS; grows downward from the AV cushions and fuses with the muscular interventricular septum (obliterates the interventricular foramen)
The membranous portion of the interventricular septum contributes to the AV cushions and the _ _
_ _
The membranous portion of the interventricular septum contributes to the AV cushions and the conotruncal bridges/septum
IV foramen is located between the free edge of the _ _ IV septum & the fused _ _ cushions
IV foramen is located between the free edge of the muscular IV septum & the fused AV cushions
- membranous IV septum forms by the proliferation & fusion of tissue from three sources. What are they?
- membranous IV septum forms by the proliferation & fusion of tissue from three sources
- right bulbar ridge
- left bulbar ridge
- AV cushions
What is the difference between a normal heart and a heart with a VSD (ventricular septal defect)?
In the _ _ (1st, 2nd, 3rd…) week, the AP septum will be remodelled to form the aorta and the pulmonary trunk
In the 9th week, the AP septum will be remodelled to form the aorta and the pulmonary trunk
AP septum derived from _ _ _ _ cells that migrate to the conotruncal ridges
AP derived from neural crest cells that migrate to the conotruncal ridges
What happens if the conotruncal septum doesn’t spiral?
If the conotruncal septum doesn’t spiral, results in “transposition of the great vessels” - results in the majority of blood bypassing the lungs;
treatment is to poke a hole in the right atrium, allows oxygenated and deoxygenated blood to mix more.
Describe blood flow in the fetus.
Blood originates in the umbilical veins, and circulates throughout the body and back to the mother via the umbilical arteries
How do the six pairs of aortic arches develop into their adult derivatives, i.e., what are the adult finalized forms of these primitive six initial aortic arch pairs?
Describe the role of neural crest cells in the development of the heart.
The cardiac neural crest cells have a number of functions including:
creation of the muscle and connective tissue walls of large arteries and parts of the cardiac septum
They may also contribute to the creation of the carotid body, the organ which monitors oxygen in the blood and regulates breathing
Explain the bilateral asymmetry of the recurrent laryngeal nerve
What kind of threat does this pose to hepatic surgery patients?
- Whereas the right side laryngeal nerve runs directly to the larynx, the left side nerve wraps around the ductus arteriosus in the fetus and the ligamentum arteriosus in the adult
- This poses an issue for hepatic surgery in the adult because accidental transection of the ligamentum arteriosus could result in damage to the left laryngeal nerve and paralysis of the larynx.
What are the three embryologic venous circuits?
Vitelline
Umbilical
Cardinal
What is the adult fate of the Vitelline veins?
Embryonic
Adult
Vitelline Veins
Right & Left
portion of the IVC, hepatic veins and sinusoids, ductus venosus, portal vein, inferior mesenteric vein, superior mesenteric vein, splenic vein
What is the adult fate of the Umbilical veins?
Embryonic
Adult
Umbilical
Right
degenerates early in fetal life
Left
ligamentum teres
What is the adult fate of the Cardinal veins?
Embryonic
Adult
Cardinal
Anterior
SVC, internal jugular veins
Posterior
portion of IVC, common iliac veins
Subcardinal
portion of IVC, renal veins, gonadal veins
Supracardinal
portion of IVC, intercostal veins, hemiazygos vein, azygos vein
In the fetus, why does the majority of the blood bypass the pulmonary system?
When organs are developing, they need some blood to supply the development, but too much can hinder development. The lungs receive a very large amount of blood in adults, which would be damaging to fetal lungs.
What changes in the vascular system must take place at birth so that a baby can live independently from her/his mother?
- Change in blood flow
- Closure of the ductus arteriosus
