Podcast
Questions and Answers
What structure forms from the fusion of the endocardial cushions during the septation of the heart?
Which cells are responsible for the formation of the endocardial cushions during the septation of the heart?
What is the purpose of the chordae tendinae during the formation of the AV valves?
What is the result of the fusion of the septum primum and the septum intermedium?
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What is the function of the Foramen Ovale during fetal development?
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What is the name of the cavity formed by the septum primum before it fuses with the septum intermedium?
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What is the final structure formed by the septum secundum during the formation of the interatrial septum?
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Which of the following structures is NOT formed from the heart tube during embryonic development?
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During which stage of development does the heart form?
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What is the primary function of VEGF during heart development?
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What is the term for the structure that gives the heart tube stability and suspends the heart?
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What is the fate of the sinus venosus during heart development?
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What is the term for the process that occurs between the 22nd and 23rd day of development?
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What is the location of the pacemaker of the primitive heart tube?
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What is the term for the structure that forms around the heart during looping?
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What is the direction of blood flow in the heart tube during development?
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What is the purpose of the membranous portion of interventricular septum?
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What becomes the coronary sinus in the right atrium?
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What is formed from the cells that migrate and form ridges from neural crest cells?
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What is the region above the Bulbus cordis (BC) that later forms the semi-lunar valves?
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What happens to the dorsal mesocardium after the outflow tracts are formed?
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What is the result of the formation of the aortico-pulmonary septum?
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Study Notes
Blastulation (Week 1)
- No specific heart development during this stage
Gastrulation (Week 2)
- No specific heart development during this stage
Neurulation (Week 3)
- Development of the heart begins
- Splanchnic part of the mesoderm gives rise to the heart
- Endodermal cells secrete VEGF, which stimulates the splanchnic part of the mesoderm
- Splanchnic part differentiates and forms two pericardial cavities and two heart tubes
Development of the Heart (Week 3)
- The two pericardial cavities and heart tubes fuse together
- Heart tubes get pushed into the pericardial cavities
- Dorsal mesocardium gives the heart tube stability and suspends the heart
- Heart forms in the head and moves down towards the chest cavity
- Mesodermal structure gets pushed down into the chest cavity (pericardial cavity)
Heart Tube Structure
- Aortic sac (AS)
- Truncus arteriosus (TA)
- Bulbus cordis (BC)
- Primitive ventricle (PV)
- Primitive atria (PA)
- Sinus venosus (SV) - 3 inflow tracts (right and left horn, plus the veins)
- Common cardinal vein (CCV)
- Umbilical vein (UV)
- Vitelline vein (VV)
Looping of the Heart (22nd-23rd Day)
- Looping takes place, and the structures get pushed around
- PA gets pushed to the back of the heart and SV follows slightly
- Causes the atria to take final position above the ventricles
- Cells from SV migrate and form a layer around the heart - formation of visceral pericardium around the heart
- Heart starts to beat at day 22 - beating cells are from the SV
- The pacemaker of the primitive heart tube is located in the caudal portion
- Sinus venosus assumes the pacemaker's role of the embryonic heart (SA node) - located more to the caudal part of the embryo
Heart Tube Development
- Aortic sac -> ascending aorta + right brachiocephalic trunk
- Truncus arteriosus -> pulmonary trunk + ascending aorta
- Bulbus cordis -> right ventricle + outflow tracts
- Primitive ventricle -> left ventricle
- Primitive atria -> left atrium + right atrium
- Cells outside the heart (cells that form the lung buds) are used to form the tracts (pulmonary veins) going into the left atrium
Septation of the Heart (~27th Day)
- Neural crest cells migrate and form the endocardial cushions in the heart tube
- Fuse together and form a septum (septum intermedium)
- Separates into the right and left AV canals
Formation of AV Valves (Week 4)
- Neural crest cells differentiate and migrate to form a ring-like structure
- Forms the valves
- Forms the Valvular annulus which connects to the valves
- Chordae tendinae is formed in this process - used to keep valves shut
- Mitral and Tricuspid valves formed
Formation of Interatrial Septum
- Chambers and valves have been made at this point
- Septum primum is formed from tissue - doesn't touch the septum intermedium yet, and this cavity produced is known as the Ostium Primum
- Septum primum fuses with the intermedium
- Another gap forms - ostium secundum
- Another tissue known as the septum secundum forms next to the septum primum
- Foramen Ovale then forms - a form of bypassing the lungs through separation of oxygenated and deoxygenated blood (communication between right and left sides of the heart)
Formation of Interventricular Septum
- Another septum develops in the ventricles - muscular portion of interventricular septum
- Membranous portion of interventricular septum forms, which connects the muscular portion of interventricular septum to the septum intermedium
Formation of Inflow Tracts to Right Atrium
- Sinus venosus (from the side of the left horn) gets absorbed into right atrium
- All veins in left horn degenerate
- Remaining left horn becomes coronary sinus in right atrium
- CCV becomes superior vena cava on the right atrium
- VV becomes inferior vena cava on right atrium
- Umbilical vein (UV) degenerates
Formation of Outflow Tracts
- Cells migrate and form ridges (Truncal and Bulbar ridges) from neural crest cells
- The structure twists - aortico-pulmonary septum forms
- Forms pulmonary tracts and aorta
- There is a region above the BC known as the conus cordis, which later forms the semi-lunar valves
- Once the outflow tracts are formed, the dorsal mesocardium disintegrates and is taken over by the new outflow tracts - leads to formation of transverse and oblique sinus
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Description
This quiz covers the early stages of human development, including blastulation, gastrulation, and neurulation, as well as the formation of the heart. Understand the key processes and structures involved in these critical weeks.
