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Development of the cardiovascular system. Begins to function by end of the 3 rd week Necessary in order to meet nutrient needs of rapidly growing embryo Angioblasts arise from: mesoderm Splanchnic & chorionic mesenchyme yolk sac & umbilical cord Give rise to blood & blood vessels.

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development of the cardiovascular system
Development of the cardiovascular system
  • Begins to function by end of the 3rd week
    • Necessary in order to meet nutrient needs of rapidly growing embryo
  • Angioblasts arise from:
    • mesoderm
      • Splanchnic & chorionic
    • mesenchyme
      • yolk sac & umbilical cord
    • Give rise to blood & blood vessels
angioblasts
Angioblasts
  • AKA hemopoietic mesenchyme differentiates into the blood islands
    • Central cells of blood islands differentiate into blood and blood cells
  • Lined with endothelium
formation of blood cells
Formation of blood cells
  • Yolk sac-4th week
  • Body mesenchyme & blood vessels-5th week
  • Liver-6th week
  • Spleen, thymus, lymph glands-2-3 months
  • Bone marrow- 4th month
  • There is overlap in production sites
development of main blood vessels
Development of Main Blood Vessels
  • First indication of paired blood vessels
    • 3 week old embryo
      • Embryonic period (4-8 weeks)
        • By end of embryonic period the main organ systems have been established
  • Appear as solid cell clusters which acquire a lumen & form a pair of longitudinal vessels
    • Dorsal aorta
    • Aortic arches
      • Continue anteriorly and run ventrally
    • Heart primordia
      • Continue posteriorly
venous system at 4 weeks
Venous system at 4 weeks
  • 3 systems of paired veins drain into heart
    • Vitelline veins
      • Returning blood from yolk sac
    • Umbilical veins
      • Bring blood from the chorion and placenta
    • Cardinal veins
      • Returning blood from various parts of the body
  • vascular system
arterial system at end of 4 weeks
Arterial system at end of 4 weeks
  • Four pairs of aortic arches have appeared
  • Dorsal aorta have fused throughout much of their length  descending aorta
development of the heart
Development of the heart
  • Starts as two thin walled endocardial tubes
    • Caudal continuation of the first aortic arches
      • Endocardial heart tubes
        • Begin to fuse to form a single tube
  • As heart tube fuses
    • Surrounding mesenchyme thickens to form
      • Myocardium
      • Epicardium
    • Tubular heart elongates and develops dilations or sacculations
      • Primordia of Truncus, Bulbus, Ventricle, Atrium, Sinus (SI)
        • heart development (adam)
        • development of the heart
        • actual mouse embryo
primitive heart
Primitive heart
  • Primordia (SI) (Cranially Caudally) (A V)
    • Truncus
      • Continuous cranially with first pair of aortic arches
    • Bulbus
    • Ventricle
      • Both bulbus and ventricle grow faster than other parts which causes S shape bend animation
    • Atrium
    • Sinus
      • Receives venous return from
        • Umbilical, Vitelline & Common cardinal veins
primitive heart9
Primitive heart
  • As primitive heart bends the atrium and sinus come to lie dorsal to the bulbus & ventricle
    • Reversal of original cranio-caudal relationship
  • Atrial portion being paired becomes one
  • Atrioventricular junction remains narrow
    • Form an atrioventricular canal
      • Connecting atrium with the ventricle
primitive heart cont
Primitive heart (cont)
  • At the end of loop formation, the smooth inner heart surface begins to form the primitive trabecullae in the ventricle
  • Atrium & bulbus remain temporarily smooth
  • Sinus maintains it’s paired condition longer than any other portion of heart tube
  • Contraction begins by day 22
    • Initially ebb & flow  unidirectional flow
      • By end of 4th week, rhythmic contraction
formation of cardiac septa
Formation of cardiac septa
  • Begins around middle of 4th week & completed by end of 6th week
    • Two methods
      • Tissue growth
        • Two of more actively growing masses of tissue which approach each other in the same plane, fuse to divide a single chamber into two
      • Overgrowth
        • Involves growth of a chamber at all points except for a narrow strip which fails to grow
        • Leaves a small canal connecting the two chambers
cardiac septum
Cardiac Septum
  • Atrioventricular septum (during 4th week)
    • Bulges form on dorsal & ventral walls of AV canal AKA endocardial cushion septum
  • Atrial septa (end of 4th week)
    • Sickle-shaped crest grows from roof of common atrium in the direction of the endocardial cushion
      • Septum primum
    • As right atrium grows & incorporates part of the sinus
      • Septum secundum associated with foramin ovale (oval foramin)
    • Ostium primum
      • Opening between septum and endocardial cushion which closes by growth of endocardial cushion
    • Ostium secundum superior in septum primum
foramin ovale fo
Foramin ovale (FO)
  • Shunts blood from Right to left atria via ostium secudum
    • Mostly blood returning via inferior vena cava
    • Bypasses lungs in fetus
  • Associtated with septum secundum
  • At birth FO pressed against septum primum which seals the opening
septal formation
Septal formation
  • Ventricular septum (starts by end of 4th week)
    • Expansive growth of ventricle laterally & ultimate fusion of the medial walls starts the formation of the Muscular Interventricular Septum near apex
    • Communication btw ventricles below cushion
      • Closed by membranous IV septum at end of 7th week
  • Septum of the truncus & bulbus
    • Continous paired ridges fuse
      • Form a spiral septum (aorticopulmonary septum)
        • Cavum aorticum  LV
        • Cavum pulmonare  RV
      • Two cava eventually separate forming acending aorta & pulmonary trunk
      • image
congential malformations
Congential malformations
  • Acardia
    • Absence of heart
      • Only occurs in conjoined monozygotic twins
      • 1:35,000
  • Ectopic Cordis
    • Heart is located through a sternal fissure into:
      • Into the neck
      • Down through a diaphragmatic hernia into a exomphalocoele
      • Protruding outside chest
        • Dextra thoracic ectopia
          • Limited life expectancy
congenital malformations
Congenital Malformations
  • Dextracardia
    • Heart is located in right hemithorax
    • Most cases associated with situs inversus
      • Heart, great vessels, other thoracic & abdominal organs may present a mirror image of the norm.
      • 1:10,000
    • Known to occur with other anomolies
      • Duodenal atresia
      • Agenesis of spleen
      • Spina bifida
    • Isolated cases rare (1:900,000)
septal defects
Septal Defects
  • Atrial Septal Defect
    • Well tolerated into adult life
    • Problem in old age
    • May be combined with rarity of other cardiac anomalies
  • Prenatal Closure of the interatrial shunt
    • Enlargement of right atrium & ventricle
    • Causes hypoplastic left side
    • Death soon after birth
  • Ventricular Septal Defect
    • About ½ of all cases of congestive heart failure show a VSD
    • Uncomplicated form considered harmless
      • Harsh systolic murmur with no cyanosis
    • 6:10,000
tetralogy of fallot
Tetralogy of Fallot
  • Pulmonary stenosis
  • VSD
  • Overriding Aorta
  • Right Ventricular hypertrophy
    • Life expectancy 12 years
    • Major symptom is cyanosis
    • Paroxysmal dyspnea on exertion is common
    • Above symptoms may lead to unconsciousness & paralysis
trilogy of fallot
Trilogy of Fallot
  • Pulmonary Stenosis
  • ASD
  • Right ventricular hypertrophy