20 Questions
What is the process called when the embryo transforms from a bilaminar disc to a trilaminar disc?
Gastrulation
What are the three parts of the mesoderm?
Paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm
What is the name of the cavity in the blastocyst?
Blastocele (blastocyst cavity)
What is the name of the structure that induces changes in the overlying ectoderm and forms the neural plate?
Notochord
What are the three shunts or bypasses in the foetal circulation?
The three shunts or bypasses in the foetal circulation are: 1) By-pass of the hepatic circulation via the ductus venosus, 2) By-pass of the pulmonary circulation via the foramen ovale, and 3) By-pass of the pulmonary circulation via the ductus arteriosus.
What is the function of the umbilical cord in the foetus?
The umbilical cord in the foetus is responsible for carrying oxygen- and nutrient-rich blood from the placenta to the foetus, and also removing waste products such as CO2 through the placenta.
What happens to the shunts in the foetal circulation after birth?
The shunts in the foetal circulation, including the ductus venosus, foramen ovale, and ductus arteriosus, must be obliterated after birth when the pulmonary circulation becomes fully functional.
Explain how blood circulates through the foetal heart.
Blood circulates through the foetal heart in the following steps:
- Deoxygenated blood enters the right atrium through the superior and inferior vena cava.
- Blood flows through the right atrium into the right ventricle.
- The right ventricle pumps the blood into the pulmonary artery.
- Instead of going to the lungs, a large portion of the blood is shunted through the foramen ovale to the left atrium.
- From the left atrium, the oxygenated blood is pumped into the left ventricle.
- The left ventricle then pumps the blood into the aorta, which distributes it to the rest of the body.
Explain the functions of the foramen ovale, ductus arteriosus, and ductus venosus.
The functions of the foramen ovale, ductus arteriosus, and ductus venosus in the foetal circulation are as follows:
- Foramen ovale: It is a hole between the atria that allows the majority of the blood to bypass the non-functional foetal lungs by shunting oxygenated blood from the right atrium to the left atrium.
- Ductus arteriosus: It is a blood vessel connecting the pulmonary artery to the aorta, bypassing the non-functional foetal lungs. It allows the majority of the blood to flow directly into the systemic circulation.
- Ductus venosus: It is a blood vessel connecting the umbilical vein to the inferior vena cava, bypassing the liver. It allows oxygenated blood from the placenta to travel directly to the heart.
What are the consequences of non-closure of foramen ovale and ductus arteriosus?
The consequences of non-closure of foramen ovale and ductus arteriosus are:
- Non-closure of foramen ovale: It can result in a condition called patent foramen ovale (PFO), where blood can continue to flow between the left and right atria even after birth. This can lead to complications such as paradoxical embolism and increased risk of stroke.
- Non-closure of ductus arteriosus: It can result in a condition called patent ductus arteriosus (PDA), where the ductus arteriosus remains open, causing abnormal blood flow between the aorta and the pulmonary artery. This can lead to symptoms such as difficulty breathing, poor growth, and increased risk of infections.
Which gene(s) are associated with the common defects in Down syndrome?
DSCAM and COL6A2
What is the cause of deletions in the 22q11.2 deletion syndrome?
Mutations in TBX1
What is the mode of inheritance for Long QT syndrome?
Channelopathy
What is the significance of identifying a mutation in Long QT syndrome?
Risk for life-threatening cardiac events by mutation location and β-blocker treatment
What is the gene associated with Familial Hypercholesterolemia?
Unknown
What are the Simon Broome criteria for diagnosing Familial Hypercholesterolemia?
The Simon Broome criteria for diagnosing Familial Hypercholesterolemia include cholesterol levels greater than 6.7mM (LDL>4mM) in children under 16 or greater than 7.5mM (LDL>4.9mM) in adults, along with either tendon xanthoma in the patient or a first/second degree relative, or a family history of myocardial infarction.
What are the possible causes of Familial Hypercholesterolemia?
Familial Hypercholesterolemia can be caused by various mutations, including those that result in the absence of synthesis, improper transport to the cell membrane, inadequate binding to LDL, improper internalization, or improper recycling of LDL. Specific mutations include ApoB - Arg3500Gln, LDL receptor associated protein - null mutations, and PCSK9 - Asp374Tyr.
What are the effects of gene dosage in Familial Hypercholesterolemia?
Familial Hypercholesterolemia exhibits autosomal dominant or recessive inheritance patterns, with gene dosage influencing the severity of the condition.
What is the difference between locus heterogeneity and allelic heterogeneity in Familial Hypercholesterolemia?
Locus heterogeneity refers to the presence of multiple genetic loci that can cause the disorder, while allelic heterogeneity refers to the existence of different mutations within the same gene that can result in the disorder.
What is the role of cascade testing in diagnosing Familial Hypercholesterolemia?
Cascade testing involves testing family members of an affected individual to identify others who may carry the same genetic mutation and be at risk for developing the condition. It is an important tool in diagnosing and managing Familial Hypercholesterolemia.
Study Notes
Blastocyst Development
- The blastocyst is a stage in embryonic development, characterized by a cavity called the blastocele.
- The inner cell mass at one pole of the blastocyst differentiates to form the primary germ layers: endoderm and ectoderm.
- This process is called gastrulation.
Morula to Blastocyst
- The morula stage precedes the blastocyst stage.
- During this stage, the embryo undergoes significant changes, including the formation of the blastocele and the differentiation of the inner cell mass.
Implantation
- The blastocyst implants in the uterine mucosa around day 9.
- At this stage, the embryo forms a bilaminar disc, consisting of the hypoblast and epiblast.
Gastrulation
- Gastrulation is the process of transforming the bilaminar disc into a tri-laminar disc.
- During gastrulation, epiblast cells migrate through the primitive streak, displacing the hypoblast cells and forming the endoderm and mesoderm layers.
Germ Layers
- The three germ layers are: ectoderm, endoderm, and mesoderm.
- These layers give rise to all tissues and organs in the body.
Notochord
- The notochord is a structure that forms from the primitive pit and induces changes in the overlying ectoderm, forming the neural plate.
- The notochord also induces the differentiation of the mesoderm into different layers.
Mesoderm
- The mesoderm has three parts: paraxial, intermediate, and lateral plate mesoderm.
- These parts differentiate into various tissues and organs, including the somites, urogenital system, and body cavities.
Foetal Circulation
- The foetal circulation is modified by three shunts to avoid the lungs and liver: the ductus venosus, foramen ovale, and ductus arteriosus.
- The foetal circulation is designed to meet the special needs of the developing foetus.
Placenta
- The placenta is a vital organ that supplies oxygen and nutrients to the foetus and removes waste products.
- The placenta is usually located posterior-fundally.
Umbilical Cord
- The umbilical cord is surrounded by the foetal membrane and contains two umbilical arteries and one umbilical vein.
- The umbilical cord is the lifeline of the foetus.
Ductus Venosus
- The ductus venosus is a shunt that bypasses the liver and drains into the inferior vena cava.
- The ductus venosus allows oxygenated blood to mix with venous blood from the lower limbs.
Foramen Ovale
- The foramen ovale is a shunt that allows blood to flow from the right atrium to the left atrium.
- The foramen ovale is a vital structure that allows the foetus to bypass the lungs and liver.
Ductus Arteriosus
- The ductus arteriosus is a shunt that allows blood to flow from the pulmonary trunk to the aorta.
- The ductus arteriosus is a vital structure that allows the foetus to bypass the lungs and liver.
Postnatal Circulation
- After birth, the shunts must be obliterated to establish the adult circulation.
- The umbilical cord is tied and cut, and the foramen ovale and ductus arteriosus close.
Patent Foramen Ovale
- A patent foramen ovale is a consequence of non-closure of the foramen ovale.
- This can cause paradoxical emboli.
Genetics in Cardiology
- Various genetic disorders can affect the heart, including Down syndrome, 22q11.2 deletion syndrome, and long QT syndrome.
- These disorders can be caused by mutations in specific genes, leading to cardiac abnormalities.
Cascade Testing
- Cascade testing is a genetic testing strategy that involves testing relatives of an individual with a genetic disorder.
- This approach can help identify individuals who are at risk of developing a genetic disorder.
Test your knowledge on fetal circulation and the functions of the foramen ovale, ductus arteriosus, and ductus venosus. This quiz will assess your understanding of how blood circulates through the fetal heart and the overall circulation in the fetus and placenta. Prepare yourself for a thorough examination of these crucial aspects of fetal development.
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