Download Formation of the Cardiac Loop

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
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
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
early presomite embryo
(17 days)
late presomite embryo
(18 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
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.
6 wk.
7 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
Structure
Truncus
Arteriosus
Aortic sac
Fate
Left
Right
Root of
Root of Aorta
Pulmonary Trunk (proximal)
(proximal)
Brachiocephalic
artery
Arch of Aorta
(proximal)
Fate of Aortic Arches
Structure
Fate
Right
Left
1st Aortic arches
Maxillary a.
Maxillary a.
2nd Aortic arches
Hyoid a. &
Stapedial a.
Hyoid a. &
Stapedial a.
3rd Aortic arches
1. Common carotid 1. Common carotid
a.
a.
2. Internal carotid 2. Internal carotid
a. (proximal)
a. (proximal)
3. External carotid 3. External carotid
a.
a.
Fate of Aortic Arches
Structure
Fate
Right
Left
4th Aortic arches
Subclavian a.
Arch of Aorta &
Subclavian a.
5th Aortic arches
-
-
6th Aortic arches
Right Pulmonary
a.
Ductus
arteriosus & Left
Pulmonary a.
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
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.
= hook at Subclavian a.
hook at Ligamentum arteriosum
Rt
Lt =
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 - 12 wk
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
8 - 12 wk
Ductus venosus is formed.
Lt. umbilical vein enlarges.
Anterior Cardinal Veins
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.
1
3
2
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 :
• 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
• Thoracic duct
• 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