chapter 27 development of circulatory...

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Human Embryology

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Department of Histology and EmbryologySchool of Basic Medical science School of International Education

Anhui Medical University

Dr. Lijie Feng

Development of the Circulatory System

Department of Histology and EmbryologySchool of Basic Medical science School of International Education


Dr. Lijie Feng


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Question: How embryos receive oxygen and nutrients?

zygote

Development process of an embryo

blastocyst implantation

3 weeks 4 weeks 20 weeks

amnion cavity umbilicalcord amnionchorion

amnion

umbilical cord

amnion

body stalk body stalk

chorion

yolk sac yolk sac

exocoelom

blastoderm


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Maternal blood diffusion Circulatory system development


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Content

Establishment of the primordial cardiovascular system

* Development of the heart

Fetal blood circulation and changes in the circulation

after birth

Congenital defects of the cardiovascular system


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Content


Development of the heart


after birth



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Period: in the 3rd-7th weeks of embryonic development

Origin: mesoderm

Significance: provide nutrition and

oxygen and remove wastes and

carbon dioxide

Establishment of the primordial cardiovascular systemAnhui Medical University

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The 15th day, mesenchymal cells in the wall of yolk sac

proliferate to form isolated cell clusters ----blood islands

1) Extra-embryonic blood vessels

Establishment of the promordial cardiovasular system

Blood islands

Yolk sac

Primordial heart

body stalk

extra embryonic mesoderm

ectodermendoderm

amnion cavity


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Peripheral cells endothelial cells endothelial tube

Central cells primitive blood cells (blood stem cell)

Endothelial tube approach and fuse with each other to form an endothelial tube network

Mesenchymal cell

endothelial cell

primitive blood cell

Establishment of the promordial cardiovasular systemAnhui Medical University

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• Endothelial tube network appears in chorionic membraneand body stalk, and connect to vitelline circulation.

chorionic membrane

body stalk


Blood islands

Yolk sac

Primordial heart

amnion cavity

Blood vessel

Blood vessel

villi

Allantois

amnion


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2) Intra-embryonic blood vessels

The 18-20th days, blood island appears in the

mesenchyma of intraembryonic splanchnic mesoderm to

form intraembryonic endothelial tube network

By the end of 3rd week, intraembryonic and extra-embryonic endothelial tube networks connect to eachother to form primitive cardiovascular system


Blood circulation begins at the end of 4nd week


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Blood island

Central cells

Primitive blood cells

Endothelial tube networkPrimitive cardiovascular system (later of 3rd weeks)

Formation and variation of blood islandsD15, mesenchymal cells in the wall of yolk sac

D18-20 intraembryonic mesenchymal cells

Peripheral cells

Endothelial cells

Blood cells Endothelial tube


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Establishment of the primordial cardiovasular system Mesenchyme near the endothelial tube differentiate into

smooth muscles and CT, form the vascular medial and adventitia, evolve into artery and vein.


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Primitive cardiovascular system include:3) Components of the primordial cardiovascular system

Model of primitive cardiovascular system (4th weeks)

- Cardiac tubes

- Artery

- Vein


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3) Components of the primordial cardiovascular system

Cardiac tube: paired, fuse into a single cardiac tube atthe 4th week.

d20 Early of 4w Later of 4w

Cardiac tube Primitive heartCardiac tube


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Arteries At the end of 3rd weeks Paired, the head end connect to cardiac tube Composition:

-- Abdominal aorta

-- Dorsal aorta

-- Aortic arch


d20

artery

Cardiac tube


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ArteriesAbdominal aorta: paired, the head end connect to cardiac tube, fused to form an aortic sac.



Abdominal aorta Abdominal aorta Abdominal aorta


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ArteriesAbdominal aorta: paired, the head end connect to cardiac tube, fused to form a aortic sac

Dorsal aorta: paired, fused to form a single vessel at the 4th week

- vitelline artery: several paired, supply the yolk sac- umbilical artery: paired, allantoic artery, supply chorionic membrane


Dorsal aortaUmbilical artery

Vitelline artery

Dorsal aorta Dorsal aorta


vitelline artery

umbilical artery


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ArteriesAbdominal aorta: paired, the head end connect to cardiac tube, fused to form

a aortic sac

Dorsal aorta: paired, fused to form a single vessel at the 4th week

Aortic arch: 6 pairs, connect dorsal aorta to aortic sac


Aortic arch


Aortic arch


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Veins:Anterior cardinal vein: paired, from upper part of the body

Posterior cardinal vein : paired, from lower part of the body

--- common cardinal vein sinus venosus (cardiac tube)


4 weeks

d20

anterior cardinal veinposterior cardinal vein


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Veins:- common cardinal vein

- vitelline vein : paired, from yolk sac

- umbilical vein : paired, from chorionic membrane


sinus venosus


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Model of primitive cardiovascular system (4th weeks)

Vitelline circulation

Umbilical circulation

Embryonic circulation

Three sets of blood circulation existed at the end of 3rd week


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Content




after birth

Congenital defects of the cardiovasular system


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-- Formation of primitive heart

-- Establishing of the heart shape

-- Partitioning of the heart


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1. Formation of primitive heart

2. Establishing of the heart shape

3. Partitioning of the heart


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1) Formation of primitive heart

The heart arises from cardiogenic area, which located in

mesoderm situated cephalic of oropharyngeal membrane

oropharyngeal membrane

cloacal membrane

body stalk

Yolk sac Allantois

amnionbrain


Cardiogenic area


cardiogenic area


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Cardiogenic plate


pericardiac coelom


Pericardiac coelom: space in cardiogenic area

Cardiogenic plate: mesodermal cells ventral to the pericardiac

coelom aggregate and form two longitudinal, paired cell cords.

d19

D18-19


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Cardiac tubes: The cardiogenic plate become canalized to

form two cardiac tubes.

cardiac tube

pericardiac coelom

1) Formation of primitive heart D20Anhui Medical University

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Cephalic fold of the embryo pulls the cardiac tube and pericardiac

coelom forward and located in ventral of pharynx


cardiac tube

pericardiac coelomd22

head folds

Tail folds

notochord

d20


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Cardiac tube

pericardiac coelom

d28

Cephalic folds of the embryo pulls the cardiac tube and

pericardiac coelom forward and located in ventral of pharynx


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Lateral folds of the embryo make the two cardiac tubes close

together, then fused into a single layer in the midline.

dorsal aorta


cardiac tube

d21 d22

d20d19 pericardiac coelom Cardiogenic

plate

pericardiac coelom

cardiac tube

pericardial cavity

foregut

neural tube

neural groove

amnion yolk sac

dorsal mesocardium


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Dorsal mesocardium: cardiac tube invaginate into

pericardiac coelom and connect to it by dorsal mesocardium


d22

pericardiac coelomcardiac tube

Pericardiac coelom turns into the pericardial cavity

cardiac tube

pericardial cavity

foregut

neural tube

dorsal mesocardium

dorsal mesocardium


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Mesenchyme adjacent to endothelium of cardiac tube proliferate and

differentiate into subendothelium of endocardium, myocardium and

epicardium.


pericardial cavity

The wall of heart is formed

foregut

cardiac wall

atrium

venous sinus

Transverse sinus

truncus artiriosus

D28 Lateral view D28 transection

section

thoracic wall


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3. Partitioning of the heart


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2) Formation of the heart shape Single cardiac tube connected caudally to the vein; cephalically

connected to the artery, two ends fixed with pericardial cavity.

D21

Vein end

Fused cardiac tube

artery end

transversum

Unfused cardiac tubepericardial cavity

atrium

venous sinus

Transverse sinus

truncus artiriosus

D28 Lateral view


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Three dilatations:

bulbus cordis

ventricle

atrium

d22

2) Formation of the heart shapeTwo constriction:

bulboventricular sulcus

atrioventricular groove

cardiac atrium

cardiac ventricle

bulbus cordis

Truncus arteriosus

Sinus venosustransversum transversum

cardiac atrium

cardiac ventricle


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Sinus venosus: the 4th dilatation. Left and right horns whichreceives the umbilical, vitelline and common cardinal veins.

Truncus arteriosus: distal part of the bulbus cordis, connect withaortic sac cephalically.

d23

d22

cardiac atrium

cardiac ventricle

bulbus cordis

Truncus arteriosus

Sinus venosustransversum transversum


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Bulboventricular portion of cardiac tube grows rapidly, bends

forming a “U” shaped loop---- bulboventricular loop

d24d23

cardiac atrium

cardiac ventricle

bulbus cordis

Truncus arteriosus

Sinus venosustransversum

cardiac atrium

cardiac ventricle

bulbus cordis

Truncus arteriosus

Sinus venosus

transversum

bulboventricular loop


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“S”-shaped heart: the cardiac tube continues to grow and bend, atrium leave primitive transversum, shifts in dorso-cranial direction; sinus venosus located at back and caudal portion of atrium.

Atrium expand to the left and right, located on the both sides of the truncus arteriosus.

aortic arch

d35d24

cardiac atrium

cardiac ventricle

bulbus cordis

Truncus arteriosus

Sinus venosus

transversum

Truncus arteriosus

cardiac ventricle

cardiac atrium

bulbus cordis


pericardium


Truncus arteriosus

cardiac ventricle

cardiac atrium

bulbus cordis

bulboventricular groove

pericardium 40

Atrioventricular groove Atrioventricular canal

Proximal portion bulbus cordis right ventricle

Primary ventricle left ventricle

Interventricular groove

d35

At the early of 5th week, shape of heart is formed

Bulbus curds

Primitive ventricle

Truncus arteriosus

atrium

A.V canal

d23


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Formation of the heart shape

pericardiac coelom

midgut

foregut The first bow artery

Fused cardiac tube

fused cardiac tube

bulbus cordis

ventricle

atrium

The first bow artery

midgut

bulbus cordis

ventricle

atrium

venous sinus

atrium

ventricle

The second bow artery

truncus artiriosus

cardiac tube


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Truncus arteriosus

cardiac ventricle

cardiac atrium

bulbus cordis


pericardium

Formation of the heart shape


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Formation of the heart shapeAnhui Medical University

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3. Partitioning of the heart (from 4th to 7th weeks)

④ Division of truncus arteriosus and bulbus cordis

③ Partitioning of the primitive ventricle

① Partitioning of the atrioventricular canal

② Partitioning of the primitive atrium


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① Partitioning of the atrioventricular canal Endocardial cushion: thickenings of sub-endocardial tissue in the dorsal

and ventral walls of the atrioventricular canal (the 4th week)

Endocardial cushions grow toward each other and fuse, atrioventricular canal

is divided into left and right atrioventricular orifice (the end of 5th week)

Mesenchyme surround each orifice form atrioventricular valve.

Endocardiac cushion

septum primum

bulbus cordis

sinus venosus atrium

section

ventricle


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Bulbus cordis

Primitive ventricle

atrium

Truncus arteriosus

Fused endocardial cushions

atrium

ventricle

atrium

A.V canal

Left A.V orifice

dorsal the heartve

ntra

l of t

he h

eart

ventral

dorsal

endocardial cushions

venous sinus

d 23 d 26

d 31 d 35

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② Partitioning of the primitive atrium Septum primum: a thin sickle-shaped membrane appearing from dorso-

cranial wall of atrium (the end of 4th weeks).

Foramen primum: septum primum grows toward the endocardial

cushions, leaving a temporary opening between its lower edge and the

endocardial cushions

septum primum

Endocardiac cushion

Foramen primum

bulbus cordis

atrium

ventricle

venous sinus

section


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Foramen secundum: the upper part of the septum primum

perforated and form an opening

foramen secundum


septum secundum

foramen ovale

septum primum


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Septum secundum: another thicker membrane appears in the ventro-cranial wall in the right of the septum primum (the end of 5th week)

Foramen ovale: septum secundum grows toward the endocardial cushions, leaving an opening between its lower edge and endocardial cushions

Valve of foramen ovale: the part of septum primum covers foramen ovale

foramen secundum


septum secundum

foramen ovale

membranous part of interventricular septum

Valve of foramen ovale


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Before birth, the pressure of left atrium is below right atrium, blood

can flow from right atrium to left atrium through foramen ovale

After birth, the pressure of left atrium increases, two septums fit

closely to separate atrium completely (foramen ovale functionally

closes)

foramen secundum

septum secundum

foramen ovale

membranous part of interventricular septum


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② Partitioning of the primitive atriumAnhui Medical University

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③ Partitioning of the primitive ventricle Muscular part of interventricular septum: by the end of 4th week,

tissue of ventricular bottom wall grows toward endocardial cushions, but left an opening so called interventricular foramen

muscular part of interventricular septum

ventricle

bulbus cordis

atrium

venous sinus

section

septum primum

Endocardiac cushion

Foramen primum

foramen secundum

interventricular foramen


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Membranous part of interventricular septum: made up of left and

right bulbar ridge in bulbus cordis, and endocardial cushion.

septum secundum

③ Partitioning of the primitive ventricle

Membranous part of interventricular septummuscular part of

interventricular septum

foramen secundum

septum secundum

foramen ovale

foramen secundum



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membranous ventricular septum

endocardial cushion

aorta

pulmonary trunk

Left bulbar ridge

right bulbar ridge


muscular part of interventricular septum

aortico-pulmonary septum

Model of formation of membranous interventricular septum


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Partitioning of the heart chambers foramen secundumforamen primum

septum primum

Endocardiac cushion

membranous ventricular septumMuscular

ventricular septum

Interventricularforamen

foramen secundum

septum secundum

septum secundum

Foramen secundum

foramen ovale

atrium

bulbus cordis

ventricle

Interventricularforamenmuscular

interventricular septum

sinus venosus

section

Valve of foramen ovale


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At the 5th week, two spiral mesodermal ridges grow from the inner

walls of the truncus arteriosus and bulbus cordis are termed truncal

ridges and bulbar ridges, respectively.


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Truncal ridges and bulbar ridges twist around each other

and fuse to form a spiral aortico-pulmonary septum.


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Truncus arteriosus and bulbus cordis are divides into pulmonary trunk and aorta. Pulmonary trunk connect to right ventricle, Aorta connect to left ventricle.


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aorta

pulmonary trunk

right pulmonary artery

④ Division of truncus arteriosus and bulbus cordisAnhui Medical University

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④ Division of truncus arteriosus and bulbus cordisAnhui Medical University

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⑤ Changes in the sinus venosus

Study by yourself


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Content




after birth



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1) Blood circulation of fetus

foramen ovale

aorta

descending aorta

left ventrical


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① umbilical V→ducts venosus or hepatic sinus → inferior vena cava → right atrium →foramen ovale →left atrium →left ventricle → aortic arch → upper region of the body/ descending aorta →umbilical A→ placenta

② head and neck region blood→superior vena cava →right atrium→right ventrical → pulmonary artery → ductus arteriosus → descending aorta →umbilical A→ placenta (lower region of the body)


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2) Circulatory changes after birth

Cutting off of the placental bloodstream

Establish of the pulmonary circulation of the function

of oxygenating the blood


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Closure of the umbilical vessels

Umbilical vein→ round ligament of the liver


Umbilical arteriesDistal portion

Proximal portions

→ lateral umbilical ligaments

→ superior vesical arteries


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Closure of the ductus arteriosus → ligamentum arteriosum

2) Circulatory changes after birthAnhui Medical University

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2) Circulatory changes after birth Closure of the Ductus venosus: ligamentum venosum


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Foremen ovale closed Right atrium Left atrium

Pulmonary venous return increase

the pressure of left atrium.

-- At birth, foramen ovale valve

closely to septum secundum

(functionally closed)

-- One year following birth the

septum primum fuses with the

septum secundum to seal the

foramen ovale (permanent closed).


septum secundum

foramen ovale

foramen secundum

membranous ventricular septum


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Content




after birth



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1) Atrial septal defect (ASD): open foramen ovale is most common

Small holes existing in the foramen ovale valve

Perforation of foramen ovale valve

Perf

orat

ion

foramen ovale valve

Tricuspid valve

Sinus venosus


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1) Atrial septal defect (ASD):

Excessive resorption of the septum primum Foremen ovale

isn’t sealed physically due to small valve of foremen ovale

Relative small size of foramen ovale valve

Small septum primum

septum primum

Normal foramen ovale


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1) Atrial septal defect (ASD): Incomplete development of the septum secundum too large

foramen ovale;

Too large foramen ovale, and too small valve of foramen ovale

Septum primum not fused with the endocardial cushions

large foramen ovale

normal septum primum

large foramen ovale

small septum primum

Incomplete development of the septum secundum


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1) Atrial septal defect (ASD): Permit blood to continue to flow across the septum after birth.

The higher blood pressures on the left side of the heart after birth cause left-to-right flow, overburden the right side of the heart and lead to cardiac failure and pulmonary hypertension .


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Atrial septal defect occluder device

Diagram of transcatheter closure of ASD with occlusion device

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2) Ventricular septal defect (VSD): Membranous ventricular septal defect (VSD): common, the

endocardial cushion, bulbar ridge and muscular septal portions fail to fused with each other.

Muscular ventricular septal defect ( Muscular VSDs): occasionally occur in the trabeculated regions of the lower muscular ventricular septum.


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2) Ventricular septal defect (VSD): The most commonly occurring congenital heart defects. In children with a VSD, blood usually flows through the defect from

the left ventricle to the right ventricle. This causes extra blood in the pulmonary arteries and lungs, lead to left ventricle hypertrophy and pulmonary hypertension.


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Aorta or pulmonary artery stenosis:

-- unequal divisions of truncus arterious and bulbus cordis leading to aorta or pulmonary artery stenosis or enlargment, usually with membranous ventricular septal defect.

-- Enlarged vessel overrides a ventricular septal defect resulting in oxygenated and deoxygenated blood mixture in the outflow tract.

3) Defects of truncus arterious and bulbus cordis septation

aorticopulmonary septum

aortic

pulmonary trunk


Right Ventricular Hypertrophy

pulmonary stenosis

aorta overriding

ventricular septal defect

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Transposition of the aorta and pulmonary artery ：forming a straight but not spiraling aortico-pulmonary septum. Thus, the aorta is transposed to the right ventricle, and the pulmonary artery to the left.


right atrium atrial septal defect

Aorta

pulmonary trunk


left ventricle


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Tetralogy of Fallot : unequal division of the truncus arterious and

bulbus cordis leading to narrow right ventricular out-flow tract

(pulmonary artery), overriding aorta, ventricular septal defect, and

right ventricular hypertrophy


aortic

pulmonary trunk


Right Ventricular Hypertrophy

pulmonary stenosis

aorta overriding


3) Defects of truncus arterious and bulbus cordis septation Anhui Medical University

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Persistent truncus arteriosus

Aorticopulmonary septum defect or

fail to form. Since pulmonary trunk

and aorta fail to form, the persistent

truncus overrides a ventricular

septal defect.

Oxygenated and deoxygenated

blood mix in the outflow tract,

resulting in a cyanotic defect. This

defect is difficult to fix surgically.


Aorta

pulmonary trunk

ventricular septaldefect

left ventricularhypertrophy

Permanent truncus arteriosus


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4) Patent ductus arteriosus (PDA) The ductus arterious doesn’t close after birth to keep the aorta connection with pulmonary artery leading to being shunted from aorta to the lung, eventually causing irreversible pulmonary hypertension.


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Key points1. Partitioning of the heart，especially the partitioning of

primitive atrium and ventricular

2. Mechanism of atrial septal defect, ventricular septal

defect, tetralogy of Fallot form.

3. Glossary: endocardial cushion


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Homework

1. Describe the partitioning of primitive atrium and

ventricular of heart

2. Describe the mechanism of atrial septal defect,

ventricular septal defect, tetralogy of Fallot formed

briefly.

3. Glossary: endocardial cushion


chapter 27 development of circulatory...

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