CVS Development And Congetial Defects

Question 1

What are the 4 regions, listed from top to bottom, that make up the primative heart tube?

Answer 1

aortic roots 
truncus arteriosus 
bulbus cordis 
ventricle 
atrium 
sinus venosus 
(all the best vaginas are shaven)

Question 2

How does the primitive heart tube form?

Answer 2

the cardiogenic fields fuse after the embryo has folded to place the cardiogenic feilds in the correct place

Question 3

What occurs during looping of the primitive heart tube?

Answer 3

• The tube elongates until it runs out of room in the pericardial space
• Cephalic (top) portion goes forwards, down and right
• caudal goes back, up and left

Question 4

From what do the L and R atria develop?

Answer 4

Left is from the proximal parts of the pulmonary veins and a bit from the primative atrium
Right is mostly from primitive atrium and a bit of the sinus venosus

Question 5

How does the pump requirements in the foetus and baby differ?

Answer 5

in foetus the lungs dont work, oxygenated blood comes from the placenta, shunts are required and these shunts must be reversible

Question 6

Describe where blood flows in foetus, include the shunts the blood passes through

Answer 6

• blood in from placenta, enters inferior vena cava through ductus venosus shunt
• blood shunts from right to left atria via the foramen ovale, which then goes into the left ventricle and to the body via the aoerta
• any blood managing to get into the RV and pulmonary artery goes back into the aeorta via the ductus arteriosus

Question 7

How does the ductus arteriosus and venosus close?

Answer 7

physiological signals on birth causes contraction and then growth over the duct

Question 8

What is the name for a ductus arteriosus persisting after birth and causing mixing of oxygenated and deoxygenated blood?

Answer 8

patent ductus arteriosus

Question 9

Describe development of the foramen ovale

Answer 9

• First layer to develop between the atria is cresent shaped so allows blood flow underneath it. This is called the septum primum.
• Crescent closes off but hole appears near top due to apoptosis, this is called the ostium secundum
• Another layer develops called the septum secundum this has a hole in the bottom
• pressure in the LA is less than in the RA so blood flows through the foramen ovale as the two septal layers are kept apart

Question 10

Explain how the foramen ovale closes on birth.

Answer 10

• baby breaths in air
• fluid that was in alveoli moves into capillaries
• presence of 02 in alveoli causes vasodilation in pulmonary capillaries
• therefor more blood to LA and so LA pressure increases greater than RA
• causes septum primium to be pushed against septum secundum so blood can no longer flow through from RA to LA

Question 11

Describe the formation of the interventricular septum

Answer 11

The muscular portion of the septum grows up from the base of the hearts ventricles. The membranous portion grows down from the endocardial cushion which is in between the atria.

Question 12

Where is an inter ventricular defect most likely to occur and why?

Answer 12

nearer the top section where the membranous and muscular portions fuse during development

Question 13

How are the pulmonary artery and aorta formed from the tuncus arteriosus?

Answer 13

An endocardial cushion grows upwards and twists so that the aorta and pulmonary artery are correctly orientated together

Question 14

What are the systolic pressures from RA, LA, RV, LV in an adult?

Answer 14

6, 12, 24, 120

Question 15

What is the effect of a pathological left to right and right to left shunt?

Answer 15

right to left: cyanosis- deoxygented blood is skipping lungs and mixing with oxygenated blood
left to right: increased pulmonary pressure- oxygenated blood flowing back into pulmonary circulation

Question 16

What is an atrial septal defect? In what conditon is it common?

Answer 16

opening between the two atria persisting after birth, blood flows from LA- RA
common in downs syndrome

Question 17

What are the consequences of an atrial- septal defect?

Answer 17

right ventricle overloaded, eventually leading to right sided heart failure

Question 18

What is coarctation of the aorta and is its impact?

Answer 18

A narrowing of the aortic lumen in the region of the ligamentum arteriosus (former ductus arteriosus).
The narrowing is after the bracocepahilic trunk, left carotid and left subclavian arteries so the blood supply to the head and upperlimbs is normal however afterload increases on the heart and blood supply to lower limbs is impaired.

Question 19

What is a tetralogy of fallot?

Answer 19

4 lesions as a result of a developmental defect that places the outflow portion of the interventricular septum too far in front.

Question 20

What are the 3/4 defects in a tetralogy of fallow?

Answer 20

• ventricular septal hole
• overriding aeorta (most blood flows through it)
• pulmonary stenosis
• RV hypertrophy

Question 21

How does tetralogy of fallot lead to cyanosis?

Answer 21

Blood flows through aoerta because its overiding, there is a hole in the intraventricular septum and the RV has hypertophied to try and pump some blood to pulmonary circulation against a stenosis, meaning there is little pressure gradient between the left and right sides, meaning the deoxygenated blood from the right side will mix with the left side and go up aorta.

Question 22

What is tricuspid atresia?

Answer 22

Where the tricuspid valve doesnt develop. Blood moves from the RA to LA via foramen ovale as pressure in RA increases. This conditon is only compatable with life if there is a patent ductus arteriosus or ventricual septal defect to allow blood flow into pulmonary circulation.

Question 23

What is transposition of the great arteries?

Answer 23

RV is connected to the aorta and LV is connected to pulmonary artery. This is not compatible with life but they can live as foetus because blood shunts into aorta and to body by the ductus arteriosus and is oxygenated by the placenta.

Question 24

What is a hypoplasic left heart?

Answer 24

LV and ascending aorta fail to develop properly so blood little blood flows from LV to aorta so deoxygenated blood mainly flows from pulmonary artery into the aorta via ductus arteriosus

Question 25

What is the result of pulmonary atresia?

Answer 25

Blood backs up so RA pressure > LA, blood then flows from RA- LA and out through aorta. In foetus this is normal but after birth deoxygenated blood not going to lungs but to aorta so they’ll die if untreated.