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35 Cards in this Set

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  • Back

septum primum
- from the roof of the primitive right atrium, a thin layer of tissue known as the septum primum extends inferiorly toward the base of the atrium but does not close all the way. The small opening that remains is called the ostium primum.

ostium secundum
- blood is flowing through the inferior vena cava into the atrium but is stopped by the newly formed septum.
- the pressure builds and the septum develops small holes that grow into one large hole known as the ostium secundum, which forms as ostium primum closes

septum secundum
- a stronger, fibrous layer of tissue descends from the roof of the right atrium and covers the ostium secundum.
- this second layer doesn't close fully and leaves a posterior opening. Blood continues to flow into the RA from the IVC at high pressure and passes through the hole in the septum secundum, pushes against the thin septum primum, and exits through the ostium secundum.

foramen ovale
- this opening through the multiple septa is called the foramen ovale. Thus there remains a shunt of blood from the right to left atria that is appropriate for the growing fetus since respiration happens through diffusion with the mother's blood and not with the fetal lungs

fossa ovalis
- when the fetus comes to term, the first breath will increase the blood pressure in the left atria and force the foramen ovale closed leaving only a small dimple in the atrial septum known as the fossa ovalis.
- fusion is completed in 75-80% of babies within the first month or so.

3 sets of veins in the embryo
- cardinal vein
- vitelline vein
- umbilical vein

cardinal veins
- anterior cardinal veins drain the head region
- posterior cardinal vein drain the trunk of the body
- they come together at the common cardinal vein
- carries deoxygenated blood

vitelline vein
- drains the yolk sac
- carries deoxygenated blood

umbilical vein
- carries oxygenated blood
- comes from the placenta

sinus venosus
- blood from the three pairs of veins drain into the sinus venosus
- eventually, the right side (common cardinal vein, posterior cardinal vein) of the sinus venosus becomes the right atrium and the left side (vitelline vein and umbilical vein) becomes the coronary sinus

pulmonary veins
- drains into the left atrium
- formed by intussusception

- when an organ absorbs the venous wall.
- this is why the left atrium is smooth.
- In the embryo, there is initially one vein that drains the blood from the lung into the left atrium but as the heart expands, it branches into 4 pulmonary veins

primitive vascular system: like a swamp
- the venous portion is at a much lower pressure than the arterial system so it will form later.
- b/c it is an intricate system, people can survive without major vessels such as the inferior vena cava. The blood just finds another way around to get to the right atrium

- cells in the epimyocardium secrete particles called adherons. These are particles that contain many signaling molecules that coax cells to migrate towards the endocardial cushions.
- These occur in the region that forms the atrioventricular valves.

endocardial cushions
- push down and fuse and there will be two atrioventricular openings left (which eventually become the mitral and tricuspid valves)

interventricular septum
- just a group of muscular cells that are growing superiorly in between the two ventricles

valves between the atria and ventricles
- when tissue erodes away, leaving flaps of tissue attachede to the papillary muscle of the ventricle.
- these flaps become the atrioventricular valves

truncus arteriosus
- at first, we only have one outflow tract coming from the heart, known as the truncus arteriosus.
- However, we know that in humans, we need two outflow tracts, one coming out of the right ventricle (pulmonary trunk) and one coming out of the left ventricle (aorta)

neural crest cells
- they migrate into the truncus arteriosus and form a division that longitudinally separates the tube into two compartments.
- spiral shaped. This happens due to pressure differences in the outflow tract.

aortic arches
- connections between the outflow tract of the heart (ventral aorta) with the dorsal aorta.
- the aorta has these arches as a result of cephalocaudal folding, during which time the heart was folded from the cranial end ventrally.
- folding resulted in a ventral portion and a dorsal portion of the resulting cardiovascular system, which are connected by the aortic arches

terminal part of maxillary artery

stapedial artery

common carotid and internal carotid

left arch of aorta and right brachiocephalic artery

- proximal part of the right and left pulmonary artery
- in the embryo the distal left 6th aortic arch becomes the ductus arteriosus, which provides a passage between the aorta and the pulmonary arteries. This constricts at birth to become the ligamentum arteriosum

foramen ovale
- in the embryo oxygenated blood goes from the right atrium to the left atrium through the foramen ovale.
- This can occur because the left atrium is at such a low pressure due to the absence of blood flow through the immature lungs

fossa ovalis
- when baby is born and the lungs open up, the left atrium pressure becomes higher and pushes the foramen ovale closed, which is called the fossa ovalis
- the ductus arteriosus is closed off and becomes the ligamentum arteriosum.

major processes that drive cardiovascular development:
1) cellular migration - neural crest cells and adherons
2) extracellular matrix - cardiac jelly
3) hemodynamics - differing pressures for growing septa
4) targeted growth - septa growing in certain directions
5) cell death - in spetum primum to form ostium secundum
6) visceral situs - heart bending in appropriate directions

persistent truncus arteriosus
- spinal septum doesn't form and a cmmon truncus arteriosus results.
- no separation between aorta and pulmonary trunks. Therefore the blood mixes
- usually not fatal, but will not be in the best shape. Usually associated with an interventricular septal defect.

transposition of great vessels
- spiral septum spirals the wrong way
- oxygenated blood is sent back to the lungs, and deoxygenated blood is sent to the body.
- it will be fatal unless there is an interventricular septal defect, so the oxygentated and the deoxygenated blood can mix.

tetralogy of fallot
- if the spiral septum is displaced ot one side.
- 4 characteristics:
1) overriding aorta
2) pulmonary stenosis
3) interventricular septal defect
4) right ventricualar hypertrophy

children with this condition will stay crounched down to give them better circulation. It is also associated with decreased VEGF.

malformation due to extracellular matrix abnormalities
the foramen ovale may not develop correctly, which will lead to an open fossa ovalis, which isn't necessarily detrimental. There can also be problems in the valves of the heart. Instead of two valves, we may only see one common opening.
- not fatal

abnormal blood flow - coarctation of the aorta
- the aorta gets pinched down, restricting flow. It can be either pre- or post- ductus arteriosus.
- may not be fatal, but can affect level of activity

aberrant cell death
- muscular ventricular septal defect is a result of cells dying in the interventricular septum

abnormal visceral situs
- if heart tube bends the wrong way, situs inversus is the result. The apex of th heart is on the right side of the body.