# 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
