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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 Angioblasts AKA hemopoietic mesenchyme differentiates into the blood islands –Central cells of blood islands differentiate into blood and blood cells Lined with endothelium

3 Formation of blood cells Yolk sac-4 th week Body mesenchyme & blood vessels-5 th week Liver-6 th week Spleen, thymus, lymph glands-2-3 months Bone marrow- 4 th month There is overlap in production sites

4 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

5 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

6 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

7 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)heart development (adam) –development of the heartdevelopment of the heart –actual mouse embryoactual mouse embryo

8 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 animationanimation –Atrium –Sinus Receives venous return from –Umbilical, Vitelline & Common cardinal veins

9 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

10 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 4 th week, rhythmic contraction

11 Formation of cardiac septa Begins around middle of 4 th week & completed by end of 6 th 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

12 Cardiac Septum Atrioventricular septum (during 4 th week) –Bulges form on dorsal & ventral walls of AV canal AKA endocardial cushion septum Atrial septa (end of 4 th 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

13 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

14 Septal formation Ventricular septum (starts by end of 4 th 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 7 th 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

15 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

16 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)

17 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

18 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

19 Trilogy of Fallot Pulmonary Stenosis ASD Right ventricular hypertrophy

20 Development of the arterial system Branchial/pharyngeal arches develop during 4 th & 5 th week –Each arch receives its own artery & nerve Arteries called aortic arches –Arise from the truncus –Terminate in dorsal aorta –6 pairs of aortic arches develop »By the time the 6 th pair has formed, the first two pairs have disappeared

21 Aortic Arches 1 st pair  largely disappears, small ventral portion persists to form maxillary artery 2 nd pair  largely disappears, dorsal portion remains to form parts of the hyoid & stapedial arteries 3 rd pair  forms the beginning of internal carotid artery 4 th pair  –right arch becomes proximal portion of right subclavian artery –left arch forms part of arch of aorta 5 th pair  rudimentary (50%) or never develops (50%) 6 th pair  –Proximal part of each pair becomes a pulmonary artery –Distal part of left persists as ductus arteriosis, distal right regresses –diagramdiagram

22 Development of Venous System In 5 th week of development 3 major pairs –Vitelline veins  Portal vein and superior mesenteric from right VV –Umbilical veins  Left umbilical vein connects to right hepatocardiac channel via ductus venosus (bypass liver sinusoids) After birth –Ductus venosus closes  ligamentum venosus –Left umbilical vein is obliterated  ligamentum teres hepatis –Cardinal veins  main venous drainage of fetus

23 Cardinal veins (CV) Ant. cardinal veins drain anterior region –Anatomose btw ant CV  left brachiocephalic V Post. cardinal V drain rest During 5 th – 7 th weeks more veins formed –Subcardinal V Mainly drains the kidneys Anatomose  left renal vein –Supracardinal V Drains the body wall by way of intercostal veins Superior vena cava –From rt. common & proximal part of rt. ant. CV

24 Vena Cava, Azygous, Hemizygous Superior vena cava –Formed by the right common CV & proximal part of right common CV Inferior vena cava –Formed from right subcardinal vein Azygous –Formed from right supracardinal veins Hemizygous –Formed from part of left supracardinal veins


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