# 1 Angiogenesis Flashcards
Agiogenic cells clusters are known as?
Blood Islands because they start not connected to each other.
Angiogenisis begins AS what ?
formation of blood islands
The vascular system of the human embryo appears in ___ (___) because the embryo is ______?
- 3rd week (15-18 days)
- No longer able to satisfy its nutritional requirements by diffusion alone.
Clusters of mesenchymal cells in the yolk sac wall, chorion, and body atalk start to proliferate and form what ?
Angiogenic clusters (AKA: Blood Islands).
The peripheral cells of each island become flattened and form the endothelial lining of the vessels. Intercellular clefts appear between the centrally located cells that become detached and free and become the ?
Primitive Blood Cells
Fluid that has been accumulating makes up the?
blood plasma
As more blood islands form, they enlarge and fuse with each other and the endothelial-lined spaces are arranged into capillary plexuses, which eventually envelop the
entire yolk sac.
Gradually certain capillaries enlarge to create main blood vessels, including the
Vitelline Vessels &
Umbilical Vessels
Vitelline Vessels, form in the ?
wall of the yolk sac
Umbilical Vessels, form in the
chorion and body stalk
These extra-‐embryonic blood vessels now join blood vessels inside the embryo that have developed in a similar manner thereby establishing a
primitive vascular system.
What is the final position of the heart tube ?
ventral to the pharynx and dorsal to the developing pericardial cavity
The originally flat embryonic shield begins to fold in a transverse direction. As a result, the two lateral endothelial heart tubes come closer to each other and fuse.
This fusion begins at the cephalic end and extends in a caudal direction, forming what?
a single endocardial tube
What is the final placement of the cardiogenic area ?
caudal to the forebrain and the cranial opening of the gut; and dorsal to the pericardial cavity.
Once the heart tube has achieved the position illustrated on the previous card, it begins to bulge into the pericardial cavity. As the tube sinks deeper into the pericardial cavity, it becomes suspended from its dorsal wall by a
mesentery, the Dorsal Mesocardium
Meanwhile a thick layer of mesenchymal cells forming the Epimyocardial Mantle surrounds the endocardial tube. This layer is at first separated form the endothelial tube by the gelatinous substance, called the ?
Cardiac Jelly
Later cells derived from the endothelium invade the jelly. The cells of the _________ ________ differentiate into the muscle cells of the myocardium until, finally the wall on the heart tube consists of three layers;
1) the Endocardium, forming the internal endothelial lining of the heart;
2) the Myocardium, forming the muscular wall; and
3) the Epicardium or Visceral Pericardium, covering the outside of the tube.
epimyocardial mantle
The dorsal mesocardium now disappears; leaving the heart tube attached to the pericardium only at its cephalic and caudal ends. The primitive heart has been established and is situated ventral to the pharynx. The __1.)__ of the heart is the
arterial end and the __2.)__ end is the venous end.
- ) Cephalic end
2. ) Caudal end
At what day does the heart begin to beat ?
23rd
The arterial end of the heart is continuous beyond the pericardium with a large vessel, the Aortic Sac. From this sac extends two branches, the ______ , which run caudally along the posterior wall of the aorta.
Dorsal Aortae
The venous end of the primitive heart tube receives the ___ veins from the yolk sac and the ___ veins from the placenta, and the ____ veins from the body wall.
vitelline
umbilical
common cardinal
he segment receiving the venous return is generally termed the Sinus Venosus, and is symmetrical with two extensions, the Right and Left Sinus Horns. The sinus venosis drains into the ___ ___, which is generally recognized as the Primitive Atrium.
Atrial Primordium
he en@re ventricular por@on is known as the Bulboventricular Tube. This tube undergoes rapid growth, which because the heart is anchored at its arterial and venous poles, causes the heart tube to begin to fold and rotate inside the pericardial cavity to accommodate its increasing size. This growth process takes place mainly in the ________, so that the atrium appears to “climb up” the dorsal pericardial wall.
dorsocranial direction
These two segments are separated by a distinct fold or narrowing in the tube which is know as the Bulboventricular Flange on the inside of the loop (which will soon be called the Conoventricular Flange) and the Bulboventricular Sulcus on the outside of the loop. This narrowing is called the ____?
Atrio-‐Ventricular Canal
Between the ____ and ___ days of development, diverticula appear along the ventral surface of two sharply defined areas of the bulboventricular loop. One area will develop into the left ventricle while the other area which is the most proximal section of the bulbus cordis, will develop into the right ventricle.
24th and 25th
At the ___ day the bulbus cordis can be differentiated into three different segments. Most proximally is the Right Ventricle; distal to that is the Conus Cordis, (which will become the out flow portions of both ventricles) and most distally is the Trunkus Arteriosis, (which will be partitioned and become the proximal portions of the Ascending Aorta and the Pulmonary Trunk).
25th
Initially, the sinus venosus is a bilaterally symmetrical structure receiving on each side cardinal, vitelline and umbilical veins. Atrial septation demands what ?
transfer of systemic venous return to the right side of the primitive atrium together with establishment of pulmonary venous circulation.
The three systems of venous tributaries, which drain to the sinus venosus, have no connection with the pulmonary circulation, which develops in situ in the developing lung buds posterior to the heart. Initially therefore the intrapulmonary venous system is in communication with the veins developed along the gut know as what ?
the splanchnic venous plexus
During incorporation to the sinus venosus into the Common Atrium, the Right Vitelline merges with what other vessel?
The Left Umbilical Vein
All venous tributaries entering the heart tube are systemic veins, draining the yolk sac (vitelline), the placenta (umbilical), and the embryo its self (cardinal). -‐See A-‐ these veins originally drain symmetrically into each sinus horn. However, during early development, there is drastic reorganization of the venous channels so that most leL-‐sided blood is diverted to right-‐sided veins. This is accomplished by formation of anastomotic channels. One in the head, the Left Brachiocephalic vein, transfers all left-‐sided cardinal blood to the ?
right cardinal vein
All venous tributaries entering the heart tube are systemic veins, draining the yolk sac (vitelline), the placenta (umbilical), and the embryo its self (cardinal). -‐See A-‐ these veins originally drain symmetrically into each sinus horn. However, during early development, there is drastic reorganization of the venous channels so that most left-‐sided blood is diverted to right-‐sided veins. This is accomplished by formation of anastomotic channels. Another in the trunk, the Ductus Venosus, transfers blood from the leL umbilical vein to the termination of the ?
right vitelline vein.
Concomitant with this, there is regression of both distal vitelline systems and the proximal leL vitelline vein along with the distal right umbilical vein and both proximal umbilical veins. The end result is that only two channels remain draining blood to the sinus venosus, what are they?
the right cardinal vein and the right vitelline vein.
obliteration of the left umbilical vein at approximately ?
27 days
obliteration of the left vitelline vein at approximately ?
29 days
the left sinus horn rapidly loses its importance. When finally the left common cardinal vein is obliterated during the
10th week
Is Cardiac Septation an active, passive, or both process?
Both
The partitioning of the heart tube into an organ consisting of 4 chambers and 2 pairs of valves and giving off 2 large arteries, is accomplished by the formation of seven septa by PASSIVE CARDIAC SEPTATION. Name 3 ?
- ) Septum Secundum
- ) Muscular portion of the ventricular septum
- ) Aorticopulmonary septum
The partitioning of the heart tube into an organ consisting of 4 chambers and 2 pairs of valves and giving off 2 large arteries, is accomplished by the formation of seven septa by ACTIVE CARDIAC SEPTATION. Name 3 ?
- ) Atrio-Ventricular Canal Septum
- ) Conus Septum
- ) Trunkus Septum
The 7th Cardiac Septation is unique because ?
The atrial septum primum starts as PASSIVE formation, but is later completed by ACTIVE septal formation derived from Atrioventricular Endocardial Cushins.
The majority of all septation of the heart takes place during the ?
27th and 37th day
All septation begins simultaneously at the ?
End of the 4th week
The development from day ____ to ____ has allowed the A-‐V Canal to assume a more centrally located position across the I-‐V foramen, providing an opening from the atrium into both the left and right ventricles.
27 to day 31
