Untitled Quiz

Embryonic Development of the Cardiovascular System

• Embryonic development of the cardiovascular system is a crucial process.
• The embryo's nutritional and oxygen requirements are no longer met solely by diffusion.
• The cardiovascular system emerges first.
• Primordial heart and vascular system appear mid-week 3.
• The heart starts beating around days 22-23.

Lecture Outline

• Establishment of the cardiac lineage
• Establishment of laterality
• Brief anatomy of the heart
• Formation of the primary heart tube
• Formation of the pericardial cavity
• Embryonic origins of the adult heart
• Cardiac looping
• Circulation through the primordial heart
• Partitioning of the primordial heart
• Cardiac septation
• Valve development
• Formation of the conductive system of the heart
• Vascular development
• Circulation before and after birth

Establishment of the Cardiac Lineage

• The embryo's capacity to meet nutritional and oxygen needs through diffusion is limited.
• The cardiovascular system plays a fundamental role in the embryo.
• The cardiovascular system is the first significant system to function in the embryo.
• The primordial heart and vascular system commence forming around week 3.
• Heartbeat typically begins between days 22 and 23.

Establishment of Laterality

• Pathway is expressed in the lateral plate mesoderm on the left side.
• 5-HT: crucial factor for left-sidedness.
• PITX2: crucial factor for left-sidedness.
• Programs heart cells in the PHF and SHF.
• Disruption leads to laterality abnormalities (e.g., dextrocardia).

Brief Anatomy of the Heart

• A diagram of the heart with its various parts labeled is shown.
• The diagram displays the structure of the heart.
• Each part of the heart and its function is outlined in details.

Formation of the Primary Heart Tube

• Week 4: Embryonic folding, cranial and caudal folds, and lateral folds.
• Intraembryonic coelom/cavity
• Pericardial cavity, pleural cavity, peritoneal cavity
• Splanchnopleuric mesoderm
• Cardiogenic plate
• Angiogenic cell clusters
• Heart tube
• Two endocardial tubes merge.
• Each tube connects to a vitelline vein at the inferior end.
• Each tube connects to the ventral aorta at the superior end.

Embryonic Origins of the Adult Heart

• Bulbus cordis, outflow tracts.
• Bulboventricular sulcus
• Primitive ventricle
• Left ventricle
• Atrioventricular sulcus
• Right sinus horn
• Left sinus horn
• Sinus venosus.
• Sulcus: groove.
• Truncus arteriosus: arterial trunk dividing into aorta and pulmonary trunk.

Cardiac Looping

• Process causing the heart to fold on itself.
• Assuming its normal position in the thorax.
• Atria posteriorly, ventricles anteriorly.
• Cardiac tube begins to bend on day 23.
• Cardiac looping is completed by day 28.

Circulation through the Primordial Heart

• Blood enters the sinus venosus from the embryo, placenta, and umbilical vesicle.
• Blood flows through the common cardinal veins.
• Blood flows into the vitelline veins.
• The umbilical vesicle provides blood to fetus.

Partitioning of the Primordial Heart

• Septation (formation of septal structures).
• Partitioning of the atrioventricular canal.
• Partitioning of the atrium.
• Partitioning of the sinus venosus.
• Partitioning of the ventricles.
• Partitioning of the bulbus cordis and truncus arteriosus.
• Valvulogenesis (formation of valves).
• Atrioventricular valves.
• Semilunar valves.

Formation of the Pericardial Cavity

• A primitive pericardial cavity (pericardial coelom) appears on each side of the heart tube.
• Mesenchyme (embryonic connective tissue) surrounds the heart tube.
• The pleuropericardial membranes fuse.
• The two pericardial cavities merge to form a single pericardial cavity.
• Two pleural cavities are also formed.

Formation of the Conductive System of the Heart

• Network of nodes, specialized cells, and electrical signals regulates heartbeat.
• Conducting cells carry electrical signals.
• Muscle cells control heart contractions.
• Cardiac conduction system directs heartbeat initiation.
• Signal distribution throughout the heart regulates contractions and thus blood flow.
• Sinoatrial (SA) node creates excitation signal.

Vascular Development

• Blood vessel development (vasculogenesis and angiogenesis).
• Major vessels: Dorsal aorta, cardinal veins.
• Vascular endothelial growth factor (VEGF).
• Arterial system, including aortic arches, vitelline arteries, and umbilical arteries.
• Venous system, including vitelline veins, umbilical veins, and cardinal veins.

Fetal Circulation

• Blood from the placenta (80% oxygen) flows to the developing heart.
• Ductus venosus mixes returning blood from the portal system.
• Blood is shunted from the left atrium to right atrium in certain locations.
• Circulation modifications occur at birth to establish postnatal circulation.

Changes at Birth

• Cessation of placental blood flow reduces pressure in the right atrium.
• Increased blood flow to lungs begins respiration.
• Ductus arteriosus closes, forming the ligamentum arteriosum.
• Oval foramen closes.
• Umbilical arteries close.
• Umbilical vein and ductus venosus transform into ligaments.

Defects of Cardiovascular System

• Defects can arise in various stages of development
• Dextrocardia, DORV, Tetralogy of Fallot are examples where the circulatory system may not develop well.
• Other defects affecting valve development and the structures of the heart are shown as examples.

Bibliography

• Relevant bibliography for sources used is cited.