Development of the heart Flashcards
What is a blastocyst? [1 mark]
A cell 5 days after fertilisation with around 100 cells
What does the ectoderm form? [3 marks]
- Skin
- CNS
- Sensory organs
What will the mesoderm form? [5 marks]
- Heart
- Skeletal muscle
- Kidneys
- Urogenital tissue
- Connective tissue
What will the endoderm form? [3 marks]
- Lining of GI tract and lungs
- Pancreas
- Liver
What does the notochord give? [2 marks]
- Gives stability to the embryos before the vertebrae form
- Source of signalling molecules
How is the heart tube developed? [3 marks]
- From primitive streaks in blood islands
- Tubes fuse together
- Form truncus arteriosus and sinus venosus
Why is the truncus arteriosus bulgy on the left side? [1 marks]
The nortochord sending different signals to the left and right side of the body.
What happens in cardiac looping? [1 mark]
Tubes become longer and fold in on themselves to form ventricles and LA
What happens in dextrocardia? [2 marks]
- Heart is on the wrong side of the heart
- Due to incorrect looping
How are the atria and ventricles divided? [1 mark]
From the fusion of the posterior and anterior endocardial cushions
What does the septum primum do? [1 mark]
Divides atria (except for hole for foramen primum)
What are the effects of a ventricular septal defect? [2 marks]
- Systemic circulation doesn’t receive all the blood being pumped by the left ventricle.
- Leakage of blood into the right ventricle elevates right ventricular pressure and volume, causing pulmonary hypertension.
What can cause a ventricular septal defect? [1 mark]
The failure of the endocardial cushions to provide an anchor point for the developing ventricular septum.
What does the foramen primum do? [1 mark]
It permits the right to left shunt of foetal blood, because there is no pulmonary circulation.
What does the foramen ovale do in the foetal heart? [1 mark]
Bypass pulmonary circulation during development (blood can go from left to right atrium)
How are the septums fused and how does the foramen ovale close? [2 marks]
- Pressure in lungs at birth decreases so the veins and arteries in lungs open so blood flows through them.
- Pressure in right atrium and ventricle decreases and pressure in left atrium increases.
What results from the separation of the ventricles? [3 marks]
Union of:
- Conotruncal septum (grows as a spiral)
- Endocardial cushions (meets with CS and VS)
- Ventricular septum (meets with CS and ECs)
What happens if the conotruncal septum is misaligned? [1 mark]
Different sized aorta and pulmonary artery (causing tetralogy of Fallot)
What are the signs in the tetralogy of Fallot? [4 marks]
- Pulmonary stenosis
- Overriding aorta
- Ventricular septal defect
- Right ventricular hypertrophy
What does the ductus arteriosis do? [1 mark]
Bypass pulmonary circulation (closes at birth)
