Heart Development, Congenital Defects Flashcards
What are the 2 effects of the 2 folding types
Lateral: Creates a heart tube
Cephalocaudal: brings tube into thoracic region
Name the 6 sections of the primitive heart tube
Use pneumonic
All The Best Vacuums Are Silver
Aortic roots Truncus Ateriosus Bulbus Cordis Ventricle Atrium Sinus Venosus
Describe the formation of the primitive heart tube in 3 steps
- Cardiogenic field lies at cranial end of embryo
- In week 3, endocardial tubes are formed
- Endocardial tubes bought together during folding, and fuse in mid-line to create the Primitive Heart Tube
Describe looping of the primitive heart tube
Both inflow and outflow vessels cranially, with inflow vessels dorsal to outflow
How does the Sinus Venosus develop in 3 steps
What does the Right sinus horn develop into
What does the Left sinus horn develop into
- Right and left sinus horns are equal in size
- Venous return shifts to Right side, so left Sinus horn recedes
- Right sinus horn is absorbed by the enlarging Right atrium
- Coronary Sinus
- Superior/ Inferior Vena Cava
What does the right atrium form from
- Most of the primitive atrium
- Sinus Venosus
What does the left atrium form from
- Small portion of primitive atrium
- Aborbs proximal parts of pulmonary veins
Which process forms the Transverse Pericardial Sinus
Which process forms the Oblique Pericardial Sinus
- Looping—> Transverse
- LA expands while absorbing pulmonary veins-> Oblique
Illustrate the route taken by blood in a fetus. Include the shunts involved.
Start at the Aorta
- Aorta
- Body
- Placenta
- DUCTUS VENOSUS - Inferior Vena Cava
- Right Atrium
A small amount of blood enters the RV then into PT then THROUGH DUCTUS ATERIOSUS into Aorta
Rest of blood from RA enters LA through FORAMEN OVALE. Then into LV into Aorta
Explain how the Fetal Circulatory Shunts change after birth
LA pressure increases
- Foramen Ovale closes
- Ductus Venosus closes
- Ductus Arteriosus contracts
Describe the development of the great vessels
Each arterial system begins as a bilaterally symmetrical system of arched vessels
Undergo extensive remodelling to create the major armies leaving the heart
Do humans have a 5th aortic arch?
No, but other animals do
What do the Right and Left 4th Aortic Arch derive into
Right: Proximal part of right subclavian artery
Left: Arch of Aorta
What do the Right and Left 6th Aortic Arch derive into
Right: Right pulmonary artery
Left: Left Pulmonary artery + Ductus Arteriosus
Which nerve corresponds to the 6th Aortic arch
Recurrent Laryngeal Nerve
Define Septation
The process in which the primitive heart tube is divided into chambers and outflow tract is split Ito aorta and pulmonary trunk
What is the first step in Septation
What is the heart divided into
Endocardial cushions form in the atrioventricular region
Right ad left channels
Explain formation of the Foramen Ovale
- Septum Primum grows down towards fused endocardial cushions. Ostium Primum is the hole already present
- Ostium Secundum grows in SP, before OP closes
- Septum Secundum grows downwards, with a hole in it called the Foramen Ovale
How is the Foramen Ovale opened
How is it closed
- LA pressure< RA pressure, so blood flows from RA to LA
2. At first breath, LA Pressure> RA pressure, so septum Primum s pushed against septum secundum
Name 4 Atrial Septal defects
- Ostium Secundum defect
- Resborbed septum primum
- Short septum primum
- Small Septum Secundum
What is Hypoplastic Left Heart Syndrome
What 2 shunts are needed for life
Left Ventricle is underdeveloped and ascending Aorta is small so right to left blood flow in Utero is inadequate
ASD/ PFO- for blood to enter Pulmonary Trunk
PDA- For blood to enter Aorta
Although the cause of hypolastic left hart syndrome isn’t known, suggest 2 possible causes
What does one of these cause
- Defect in Mitral and Aortic valve development (Causes limited flow and atresia)
- Ostium Secundum too small
How does ventricular Septation occur in 2 steps
- Muscular portion grows upwards towards fused endocardial cushions, but doesn’t go all the way leaving a gap (Primary inter-ventricular foramen)
- Membrane portion grows down from cushions to fill the gap
What is a patent foramen Ovale
A condition where the foramen Ovale doesn’t close and persists after birth
What is an Atrial Septal Defect, ASD
Why is it not life threatening
An opening in the septum between 2 atria that persists after birth
Blood flows left—>Right, so deoxygenated blood doesn’t mix with oxygenated
What is a Ventricular Septal Defect, VSD
An abnormal opening in the septum between ventricles, most commonly in membranous portion
Explain the separation of the outflow tract
What is formed
Endocardial cushions appear in the truncus Arteriosus, and twist around each other, while growing, forming a Spiral Septum
This causes one outflow tube to split into Aorta and Pulomary Trunk
What is Transposition of the Great Arteries
What is a symptom?
How can it be treated
When the Aorta arises from the RV and the Pulmonary trunk arises from the LV
Cyanosis
Surgery
What is Tetralogy of the Fallot?
A Ventricular Septal Defect where;
The Aorta is overriding (Sits on both ventricles)
RV outflow tract is obstructed (Pulmonary Stenosis)
RV Hypertrophy is present
What cells needed to make Endocardial cushions
Neural crest cells
What are 3 causes of congenital heart defects
Genetics
Environmental
Maternal infections
Explain 4 effects of an Atrial Septal Defect
Blood flows from left to right atrium , due to higher pressure
- Increased pulmonary flow
- RV Hypertrophy
- Pulmonary hypertension
- Eventual Right Heart Failure
Explain 3 effects of Ventral Septal Defects
- Blood enters right ventricle from left, eventually having a larger pressure than left, so eventually blood enters left from right, causing LV Hypertrophy, thus eventually becoming cyanotic
- Pulmonary Venous Extension
- Eventual Pulmonary Hypertension
What is an Atrioventricular-Ventricular Septal defect?
In who, is it common
Hole above and below valve
Common in Downs’ Syndrome patients
What is Tricupsid Atresia and what does it result in
What 2 things are needed for life
Lack of development of the tricuspid valve-> No RV inlet
Right to left shunt (ASD/ PFO) for blood to enter LA
VSD or PDA for blood to reach lungs
What is coarctation of the aorta
What can it lead to
Which parts of the body are affected/ not affected and why
- Narrowing of aortic lumen in the region of the Ligamentum Arteriosus.
- Leads to LV Hypertrophy
- Vessels to head and upper limbs are proximal to coarctation so not affected
- Blood flow to rest of body is reduced
Identify 2 symptoms of Coarctation of aorta
Hypertension in Upper Extremities
Hypotension in Lower Extremities
