Cardiovascular System DEVELOPMENTAL ANATOMY Cardiovascular System Dr. Sukumal Chongthammakun Department of Anatomy, Faculty of Science Mahidol University http://intranet.sc.mahidol/AN

Development of Blood Vessels

Development of Blood Vessels Location: Body, Connecting Stalk, Yolk Sac, Chorion

(Splanchnic mesoderm) Development of Cardiogenic Area Late presomite embryo (3rd week) Mesenchymal cells (Splanchnic mesoderm) Angiogenic clusters plexus of small blood vessels ant. portion = cardiogenic area

Development of cardiogenic area and pericardial cavity 18 days

intraembryonic coelom = pericardial cavity Development of cardiogenic area and pericardial cavity 18 days intraembryonic coelom = pericardial cavity

Fusion of the Heart Tubes Head Flexion Rotation of cardiogenic area - caudal to prochordal plate - dorsal to septum transversum(diaphragm) & intraembryonic coelom (pericardial cavity) Fusion of paired tubes single tube

Rotation of cardiogenic area & pericardial cavity 180o rotation along a transverse axis 21 days 22 days 19-20 days

Formation of a single heart tube late presomite embryo (18 days) early presomite embryo (17 days)

Formation of a single heart tube 21 days (at 4 somites) Fusion of endocardial tubes 22 days (at 8 somites) Single endocardial tube

Formation of Myoepicardial Mantle Splanchnic mesoderm surrounds the heart Cardiac jelly (extracellular matrix) - rich in collagen & glycoproteins - play role in cardiac morphogenesis Myoepicardial Mantle Myocardium Epicardium

Formation of a single heart tube 21 days 22 days Atrium is the last to fuse. Sinus horns are embedded in the septum transversum.

Subdivisions of the Primitive Heart (26 days) Lt. & Rt. Aortic arches Aortic root Truncus arteriosus Bulbus cordis Ventricle Atrium Lt. & Rt. horns of Sinus venosus

Formation 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.

Formation of the Cardiac Loop U-shaped & convexed forward and to the right Ventricular growth S-shaped & bulboventricular sulcus in concaved loop 23 days (11 somites) 22 days (8 somites)

Formation of the Cardiac Loop Primitive atrium moves up into the pericardial cavity 24 days (16 somites)

Formation of the Cardiac Loop Atrium grows dorsally to the left Ventricle & bulbus cordis grows ventrally & to the right 28 days

Formation of the Cardiac Loop 28days 1. 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.

At the end of the loop formation 30 days

Septum 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.

Septum 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.

Septum Formation in Common Atrium Newborn 37 days (14 mm.)

Septum Formation in Common Atrium 1. Septum secundum is never completed. 2. Left venous & septum spurium fuse with septum secundum 3. Oval foramen is formed. 4. Septum primum = valve of oval foramen.

Differentiation of Atria 35 days (7- to 8- mm) Newborn 1. Right sinus horn incorporates into right atrial wall = smooth wall of right atrium = sinus venarum 2. Pulmonary vein develops as outgrowth of left atrial wall = smooth wall of left atrium

Development of Venous Valves Newborn 35 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 sinus 4. Crista terminalis = dividing line

Changes in Sinus Venosus 35 days 1. The veins to left sinus horn degenerates. 2. Right sinus horn moves to the right side. 8 week 1. 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 septum Right venous valves : Valve of IVC & Valve of Coronary sinus

Development of Sinus Venosus

Development of Sinus Venosus The remains of left sinus horn = oblique vein of left atrium & coronary sinus

Formation of Ventricular Septum 1. Growth of Endocardial cushions

Septum Formation in A-V Canal 1. Endocardial cushions appear. 2. AV canal enlarges to the right. 3. Fusion of sup. & inf. Endocardial cushions (10 mm. stage) 4. Rt. & Lt. AV orifices are formed.

Formation of Ventricular Septum 2. Growth of ventricular wall to form Muscular ventricular septum

1. Medial wall of ventricles form muscular intervent. septum 2. Outgrowth of inf. EC to close interventricular foramen. (= membranous interventricular septum)

Formation of Ventricular Septum 3. Growth of Trunco-conal ridges & fusion with endocardial cushion

Formation of Ventricular Septum 3. Growth of Trunco-conal ridges & fusion with endocardial cushion

Septum Formation in Truncus & Conus Fusion of Rt. & Lt. conus swelling = outflow tracts of Rt. & Lt. ventricle.

Formation of Cardiac valves 1. Aortic valves & Pulmonary valves (Semilunar valves) 5 wk. 6 wk. 7 wk. 6 wk. 7 wk. 9 wk.

Formation 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

Arterial System 4 wk (4 mm.)

Fate of Truncus Arteriosus & Aortic Sac

Fate of Aortic Arches

Fate of Aortic Arches

Aortic arches 4 mm. I disappear : rem. = Maxillary a. II disappear : rem. = Hyoid a. & Stapidial a. III, IV & VI become larger. Primitive pulmonary a. is formed.

Aortic arches 10 mm. I & II disappear VI connect to Pulmonary trunk

Transformation to Adult Arterial System

Transformation to Adult Arterial System

Transformation to Adult Arterial System

Other Changes in the Arch System 1 4 2 3

Other 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

Derivatives of Dorsal Aorta Intersegmental a. supply ribs, intercostal m. & spinal cord C & L segments - supply limbs Lateral splanchnic a. supply kidneys & gonads (intermediate mesoderm)

Derivatives of Dorsal Aorta Ventral splanchnic a. With yolk sac Vitelline a. : supply yolk sac Umbilical a.: supply placenta & developing visceral organ Without yolk sac Celiac a. : supply foregut eg stomach Sup. mesenteric a.: supply midgut eg. duodenum & ileum Inf. Mesenteric a.: supply hind gut eg. colon & rectum

Vitelline and Umbilical Arteries

Venous System

Venous System 1. Vitelline veins 2. Umbilical veins 3. Common cardinal veins Anterior cardinal veins Posterior cardinal veins

Vitelline veins 1. LVV are converted into Hepatic sinusoids, Hepatic v. and Portal v. 2. RVV persists as IVC (post-hepatic IVC)

Vitelline veins 4 - 5 wk 4 wk : form plexus to duodenum & septum transversum 5 wk : form hepatic sinusoid

Vitelline Veins 8 wk : Rt. hepatocardiac channel enlarges 12 wk: RVV is converted into IVC (hepatic portion)

Umbilical veins 1. Differentiation into Hepatic sinusoids 2. LUV & Ductus arteriosus form Ligamentum arteriosum 3. RUV degenerates 4. LUV (caudal) persists in fetal life

Umbilical veins 4 - 5 wk 5 wk = RUV & LUV connect to Hepatic sinusoid

Umbilical Veins Ductus venosus is formed. Lt. umbilical vein enlarges. 8 - 12 wk Ductus venosus is formed. Lt. umbilical vein enlarges.

Anterior Cardinal Veins 1 2 3 1. Anastomosis of ACV shunts blood from LACV to RACV& form Left Brachiocephalic v. 2. LACV(caudal) degenerates. 3. RACV & RCCV form SVC 7 wk.

Posterior Cardinal Veins 1. Degenerate with the development of metanephric kidney 2. Persists as common iliac v. & Root of Azygos v. 3. Two temporary venous system develop a.) Subcardinal v. develops into LRV, Gonadal v., Suprarenal v., IVC (hepatic segment) b) Supracardinal vein develops into Azygos v. Hemiazygos v. IVC (lower)

Fate of Fetal Circulatory Structures 1. Umbilical vein Ligamentum teres hepatis 2. Ductus venosus Ligamentum venosum 3. Umbilical artery Medial umbilical ligament

Fetal Circulation High oxygen content decreased in : I Liver II IVC III Rt. atrium IV Lt. atrium V Desc. Aorta (at the entrance of ductus arteriosus)

Changes at Birth 3 Causes : 4 Changes : 2 1 cessation of placental blood flow lung respiration 4 Changes : 1. Closure of umbilical a. & formation of med. umbilical lig. 2. Closure of UV & ductus venosus & formation of lig. teres & lig. venosum 3. Closure of ductus arteriosus by bradykinin & formation of lig. arteriosum 4. Closure of oval foramen 2 1

Lymphatic System 5 wk. origin : mesenchyme or out growth of endothelium of veins 6 primary lymph sacs are formed : - 2 jugular lymph sacs - 2 iliac lymph sacs - 1 retroperitoneal lymph sac - 1 cisterna chyli

Lymphatic System Rt. & LT. Lymphatic ducts Rt. & Lt. thoracic ducts Rt. lymphatic duct

Formation of Conducting System 1. Pacemaker lies in - initially : left cardiac tube - later : sinus venosus

Formation 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 of a. left wall of sinus venosus (base of interatrial septum) b. A-V canal

Abnormalities 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

Common Congenital Anomalies Etiologic factors: 1. Disorders of chromosome numbers eg. trisomy 21, 18 or 13 2. Familial disorders 3. Teratogenic viral infections : Rubella

Atrial Septal Defects (ASD) Probe patency of Foramen ovale Left to right shunt of blood

Atrial Septal Defects (ASD)

Ventricular Septal Defect 1 in 500 Trisomy syndrome 90% involve Membranous interventricular septum Shunted from left to right ventricle

Ventricular Septal Defects

Tetralogy of Fallot 1 in 8500 Four anomalies : 1. Ventricular septal defect 2. Pulmonary artery stenosis 3. Overiding aorta 4. Right ventricle hypertrophy

Tetralogy of Fallot

Tricuspid Atresia 1 in 5000 Fusion of tricuspid valves Patent oval foramen Ventricular septal defect Right ventricle atrophy Left ventricle hypertrophy

Tricuspid Atresia

Patent Ductus Arteriosus 1 in 3500 Shunting oxygenated blood to pulmonary artery Prostaglandin synthetase inhibitors eg. indomethacin can promote closure of Ductus arteriosus

Patent Ductus Arteriosus

Abnormalities of Semilunar Valves 1. Transposition of great vessels 2. Pulmonary valvular stenosis

Abnormalities of Semilunar Valves 3. Aortic valvular stenosis 4. Aortic valvular atresia

Abnormalities of Great Vessels 1. Patent ductus arteriosus 2. Preductal & Postductal coarctation of aorta

Abnormalities of Great Vessels 3. Abnormal origin of Right subclavian a. 4. Double aortic arch

Abnormalities of Great Vessels

Abnormalities of Venous Drainage

Abnormalities of Venous Drainage