4(Splanchnic mesoderm) Development of Cardiogenic AreaLate presomite embryo (3rd week)Mesenchymal cells(Splanchnic mesoderm)Angiogenic clustersplexus of small blood vesselsant. portion = cardiogenic area
5Development of cardiogenic area and pericardial cavity 18 days
6intraembryonic coelom = pericardial cavity Development of cardiogenic area and pericardial cavity18 daysintraembryonic coelom = pericardial cavity
7Fusion of the Heart Tubes Head FlexionRotation of cardiogenic area- caudal to prochordal plate- dorsal to septum transversum(diaphragm) & intraembryonic coelom (pericardial cavity)Fusion of paired tubessingle tube
8Rotation of cardiogenic area & pericardial cavity 180o rotation along a transverse axis21 days22 daysdays
9Formation of a single heart tube late presomite embryo(18 days)early presomite embryo(17 days)
10Formation of a single heart tube 21 days (at 4 somites)Fusion of endocardial tubes22 days (at 8 somites)Single endocardial tube
11Formation of Myoepicardial Mantle Splanchnic mesoderm surrounds the heartCardiac jelly (extracellular matrix)- rich in collagen & glycoproteins- play role in cardiac morphogenesisMyoepicardial MantleMyocardiumEpicardium
12Formation of a single heart tube 21 days22 daysAtrium is the last to fuse.Sinus horns are embedded in the septum transversum.
13Subdivisions of the Primitive Heart (26 days) Lt. & Rt. Aortic archesAortic rootTruncus arteriosusBulbus cordisVentricleAtriumLt. & Rt. horns of Sinus venosus
14Formation of the Cardiac Loop 1. Bulbus cordis bends in ventral & caudal & to the right.2. Atrium shifts in a dorsal & cranial direction.3. Bulboventricular sulcus is created.
15Formation of the Cardiac Loop U-shaped & convexed forward and to the rightVentricular growthS-shaped & bulboventricular sulcus in concaved loop23 days(11 somites)22 days(8 somites)
16Formation of the Cardiac Loop Primitive atrium moves up into the pericardial cavity24 days(16 somites)
17Formation of the Cardiac Loop Atrium grows dorsally to the leftVentricle & bulbus cordis grows ventrally & to the right28 days
18Formation of the Cardiac Loop 28days1. Common atrium incorporated into pericardial cavity.2. Atrioventricular canal is narrowed.3. Bulbus cordis is narrowed, except trabeculated part of right ventricle.4. Conus cordis will form outflow tracts of ventricles.5. Truncus cordis will form roots of aorta & pulmonary artery.6. Bulboventricular sulcus = primary interventricular foramen.
20Septum Formation in Common Atrium 30 days(6 mm.)1. Endocardial cushions are formed in the AV canal.2. Septum primum grows from the roof of common atrium.3. Foramen (Ostium) primum is formed.4. Perforation appears in septum primum.
21Septum Formation in Common Atrium 33 days(9 mm.)1. Endocardial cushion extends to close Foramen primum.2. Foramen (Ostium) secundum is formed.3. Fusion of endocardial cushions.4. Septum secundum grows downward/toward endocardial cushion.5. Foramen ovale is remained on the inf. border of Septum secundum.
22Septum Formation in Common Atrium Newborn37 days(14 mm.)
23Septum Formation in Common Atrium 1. Septum secundum is never completed.2. Left venous & septum spurium fuse with septum secundum3. Oval foramen is formed.4. Septum primum = valve of oval foramen.
24Differentiation of Atria 35 days (7- to 8- mm)Newborn1. Right sinus horn incorporates into right atrial wall= smooth wall of right atrium = sinus venarum2. Pulmonary vein develops as outgrowth of left atrial wall= smooth wall of left atrium
25Development of Venous Valves Newborn35 days (7- to 8- mm)1. Septum spurium = fusion of Rt. & Lt. venous valves.2. Sup. portion of Rt. venous valve disappears.3. Inf. portion of Rt. venous valve = valve of IVC & valve of coronary sinus4. Crista terminalis = dividing line
26Changes in Sinus Venosus 35 days1. The veins to left sinus horn degenerates.2. Right sinus horn moves to the right side.8 week1. Left sinus horn becomes coronary sinus & oblique vein of the left atrium.2. Right sinus horn incorporates into the wall of left atrium.3. Sinuatrial orifice shifts to the right and is bordered by right & left venous valves (Septum spurium).Left venous valves : fuse with atrial septumRight venous valves : Valve of IVC & Valve of Coronary sinus
37Formation of Cardiac valves 2. Mitral valves & Tricuspid valves (Atrioventricular Valves)1. Proliferation of mesenchyme in A-V orifice.2. The cords becomes hollowed out by bloodstream.3. The muscular tissue degenerates, replaced by dense CNT.4. A-V valves = CNT covered by endocardium connected to papillary muscles by chordae tendineae.5. Right = tricuspid valves Left = bicuspid (Mitral) valves
48Other Changes in the Arch System 1. Obturation of Carotid duct (Dorsal aorta between III & IV)2. Obturation of Rt. dorsal aorta (at 7th intersegmental a.)3. Lt. subclavian a. shifts to higher point.4. Recurrent laryngeal n Rt = hook at Subclavian a Lt = hook at Ligamentum arteriosum
49Derivatives of Dorsal Aorta Intersegmental a.supply ribs, intercostal m. & spinal cordC & L segments - supply limbsLateral splanchnic a.supply kidneys & gonads (intermediate mesoderm)
50Derivatives of Dorsal Aorta Ventral splanchnic a.With yolk sacVitelline a. : supply yolk sacUmbilical a.: supply placenta & developing visceral organWithout yolk sacCeliac a. : supply foregut eg stomachSup. mesenteric a.: supply midgut eg duodenum & ileumInf. Mesenteric a.: supply hind gut eg colon & rectum
59Umbilical Veins Ductus venosus is formed. Lt. umbilical vein enlarges. wkDuctus venosus is formed.Lt. umbilical vein enlarges.
60Anterior Cardinal Veins 1231. Anastomosis of ACV shunts blood from LACV to RACV& form Left Brachiocephalic v.2. LACV(caudal) degenerates.3. RACV & RCCV form SVC7 wk.
61Posterior Cardinal Veins 1. Degenerate with the development of metanephric kidney2. Persists as common iliac v. & Root of Azygos v.3. Two temporary venous system developa.) Subcardinal v. develops intoLRV, Gonadal v., Suprarenal v., IVC (hepatic segment)b) Supracardinal vein develops intoAzygos v.Hemiazygos v.IVC (lower)
68Formation of Conducting System 1. Pacemaker lies in- initially : left cardiac tube- later : sinus venosus
69Formation of Conducting System 2. Incorporation of sinus into Rt. atrium.3. Sinuatrial node is formed.4. A-V node & Bundle of His are derived from cells ofa. left wall of sinus venosus (base of interatrial septum)b. A-V canal
70Abnormalities of Heart Position Dextrocardia : cardiac loop to the left.= Heart in the right thorax associated with situs inversus (transposition of the viscera)Ectopia cordis= Heart on the surface of chest caused by failure to close the midline