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51 Cards in this Set
- Front
- Back
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Initial precursor cells of the CV system:
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Angioblasts
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Precursor tissue of Angioblasts:
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Extraembryonic Mesoderm
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When do angioblasts first appear? Where?
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Day 13 in the wall of the Yolk Sac
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First thing that angioblasts do:
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Aggregate into Blood Islands
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Blood islands contain:
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Precursors for Blood cells and Endothelial cells.
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What do blood islands become?
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Primitive blood vessels, with progenitor blood cells inside.
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What do Angioblasts form other than Endothelial and Blood cells?
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Intraembryonic blood vessels
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What do intraembryonic blood vessels develop from?
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Angioblasts in the intraembryonic mesoderm
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Where does hematopoiesis occur
-At 1-2 months -At 1.5-7 months -At months 4-adult |
1-2 months: Yolk sac
1.5-7 months: Spleen/Liver 4 mo->Adult: Bone marrow |
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What is the Heart derived from?
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Splanchnic mesoderm
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What is the u-shaped region of splanchnic mesoderm from which the heart develops called?
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Cardiogenic plate
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What is the Cardiogenic Plate located within?
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Pericardial Coelom - an area ventral to the brain
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What is the 1st thing that happens in cardiac development?
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Splanchnic mesoderm from the cardiogenic plate migrates medially toward endoderm to form an ENDOTHELIAL PLEXUS.
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What will the endothelial plexus form?
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A layer of muscle that folds around a tube.
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What is the tube that muscle folds around? What does it come from?
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The Endocardium - comes from endothelial heart tube tissue.
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What happens to the two sides of the U-shaped Pericardial Coelom?
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They fuse together medially.
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What causes the heart to be located ventrally?
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Cranial-caudal folding of the embryo at weeks 3-4
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A special region of mesoderm-derived mesenchyme accumulates adjacent to the Transverse portion of U-shaped intraembryonic coelom: what is it?
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The septum transversum
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What does the septum transversum become?
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Diaphragm (part of it)
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What unites the bilateral heart primordia in the midline?
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Lateral folding of the embryo at weeks 3-4
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How many segments does the inital Tubular heart have?
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only 2
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In what order do the initial segments of the Heart Tube form?
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1-Primitive Right Ventricle and
Conus region (outflow) 2-Primitive Atrium 3-Truncus outflow region forms between Aortic Sac and Conus. |
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Important thing to remember re: the primitive tubular heart:
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Its segments are NOT equivalent to the adult heart chambers (duh)
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How are the 3 initial tissues of the heart arranged?
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As a tube within a tube.
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What is the outer tube?
What is the inner tube? What is between the 2 tubes? |
Outer = Myocardium
Inner = Endothelium Between = Cardiac Jelly |
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What does the dorsal mesocardium lying above the developing heart tube become?
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Epicardium - from the proepicardial organ
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What is the Epicardium?
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The visceral pericardium
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What IMPORTANT structures does the Proepicardial organ contribute to?
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CORONARY VESSELS
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Where does blood flow INTO the primitive tubular heart?
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At the Sinus Venosus
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What 3 vessels flow into the Sinus Venosus?
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1. Umbilical veins
2. Vitelline veins 3. Common Cardinal veins |
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What blood is carried by umbilical veins?
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Placental blood - oxygen rich
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What blood is carried by Vitelline veins?
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From the gut - oxygen poor
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What blood is carried by Common Cardinal veins?
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Blood from head/trunk - oxygen poor
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Where does blood flow out of the primitive heart?
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At the Bulbus Cordis (outflow) regionn
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What specific outflow structure is at the top of the Bulbus cordis? What will it become?
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Aortic sac - becomes Aortic arches.
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What region of the developing embryo is supplied by the Aortic arches?
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The pharyngeal arches
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What important process begins right after the heart tube segments begin to form?
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LOOPING AND TORSION
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In what direction does looping almost always occur?
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TO THE RIGHT
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Where does the loop form?
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Between Conus (PRV) and Ventricle (PLV) -> makes sense, because the apex forms between the R/L ventricles.
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What is the hinge point formed by looping called?
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Inner curvature
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What occurs simultaneously with the right looping of the heart?
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Right torsion of the heart
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What does the cranial leg of the loop contain?
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Bulbus (Primitive right ventricle)
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What does the caudal leg of the loop contain?
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Primitive left ventricle; later, AV canal, Atrium, and Sinus venosus.
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What are 3 consequences of Cardiac Looping and Torsion in the EARLY PHASE?
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1. Proper anatomic rltnships between heart segments establ.
2. Venous inflow & Arterial outflow regions come together 3. Outflow region elongates and subdivides. |
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What does the outflow region subdivide into during the early phase of looping?
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-Conus cordis (proximal)
-Truncus arteriosus (distal) |
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What are the consequences of cardiac looping in late phase?
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1. Both caudal/cranial legs contact at AV canal level
2. Inner curvature- contact pt 3. Conus outflow wedged into AV canal over both ventricles. |
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What changes in bloodflow are achieved during heart tube formation?
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1. Flow goes from sloshing back and forth to unidirectional
2. 2 separate streams, one from ea ventricle; no phys. separtn. |
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What does the bloodflow from the left ventricle enter?
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Left aortic arch #4 -> becomes the aorta.
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What does the bloodflow from the right ventricle enter?
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Left aortic arch #6 -> becomes Ductus arteriosus.
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What is the ductus arteriosus?
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A SHUNT that allows fetal circulation to bypass pulmonary circulation.
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By what day does the heart begin to beat?
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20-22
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