Cpm Lecture 5

Front 1

5.1

septum primum

Back 1

- 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.

Front 2

5.2

ostium secundum

Back 2

- 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

Front 3

5.3

septum secundum

Back 3

- 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.

Front 4

5.4

foramen ovale

Back 4

- 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

Front 5

5.5

fossa ovalis

Back 5

- 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.

Front 6

5.6

3 sets of veins in the embryo

Back 6

- cardinal vein
- vitelline vein
- umbilical vein

Front 7

5.7

cardinal veins

Back 7

- 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

Front 8

5.8

vitelline vein

Back 8

- drains the yolk sac
- carries deoxygenated blood

Front 9

5.9

umbilical vein

Back 9

- carries oxygenated blood
- comes from the placenta

Front 10

5.10

sinus venosus

Back 10

- 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

Front 11

5.11

pulmonary veins

Back 11

- drains into the left atrium
- formed by intussusception

Front 12

5.12

intussusception

Back 12

- 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

Front 13

5.13

primitive vascular system: like a swamp

Back 13

- 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

Front 14

5.14

adherons

Back 14

- 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.

Front 15

5.15

endocardial cushions

Back 15

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

Front 16

5.16

interventricular septum

Back 16

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

Front 17

5.17

valves between the atria and ventricles

Back 17

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

Front 18

5.18

truncus arteriosus

Back 18

- 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)

Front 19

5.19

neural crest cells

Back 19

- 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.

Front 20

5.20

aortic arches

Back 20

- 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

Front 21

5.21

AA1

Back 21

terminal part of maxillary artery

Front 22

5.22

AA2

Back 22

stapedial artery

Front 23

5.23

AA3

Back 23

common carotid and internal carotid

Front 24

5.24

AA4

Back 24

left arch of aorta and right brachiocephalic artery

Front 25

5.25

AA6

Back 25

- 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

Front 26

5.26

foramen ovale

Back 26

- 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

Front 27

5.27

fossa ovalis

Back 27

- 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.

Front 28

5.28

major processes that drive cardiovascular development:

Back 28

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

Front 29

5.29

persistent truncus arteriosus

Back 29

- 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.

Front 30

5.30

transposition of great vessels

Back 30

- 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.

Front 31

5.31

tetralogy of fallot

Back 31

- 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.

Front 32

5.32

malformation due to extracellular matrix abnormalities

Back 32

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

Front 33

5.33

abnormal blood flow - coarctation of the aorta

Back 33

- 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

Front 34

5.34

aberrant cell death

Back 34

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

Front 35

5.35

abnormal visceral situs

Back 35

- 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.