15 Development of the heart, fetal circulation Flashcards
Development of the heart includes:
- formation of the heart tube
- looping and further differentiation of the heart tube,
- partitioning of the heart – complete isolation of the leftand right halves
- formation of the valves.
Early development of the heart: appearance of the heart tube
____ appears on the 18th-19th days (the end of the third week).
Heart primordium
Early development of the heart: appearance of the heart tube
____ appears on the 18th-19th days (the end of the third week).
Heart primordium
Early development of the heart: appearance of the heart tube
Heart primordium appears on the 18th-19th days (the end of the third week).
At this stage the embryo is a flat, trilaminar disc and the differentiation of the three germ layers has just begun.
→ Heart develops from the _____, a part of the intraembryonic mesoderm anterior to the oropharyngeal membrane.
cardiogenic area
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to inductive and permissive signals emanating from the endoderm, ectoderm, and midlinemesoderm
→ cardiogenic precursors form ____ within the splanchnic mesoderm at the cranial end of the embryonic disc called the cardiac crescent, or primary heart field.
a cardiac primordium
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
What is the primary heart field (PHF)?
a horseshoe-shaped region in the visceral layer of lateral plate mesoderm called the primary heart field (PHF)
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to inductive and permissive signals emanating from the endoderm, ectoderm, and midlinemesoderm
→ cardiogenic precursors form a cardiac primordium within the splanchnic mesoderm at the cranial end of the embryonic disc called ______
the cardiac crescent, or primary heart field.
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to inductive and permissive signals emanating from the endoderm, ectoderm, and midlinemesoderm
→ cardiogenic precursors form a cardiac primordium within____ at the cranial end of the embryonic disc called the cardiac crescent, or primary heart field.
the splanchnic mesoderm
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to signals from the underlying endoderm, a subpopulation of cells within the cardiac crescent form ___ through the process of vasculogenesis
a pair lateral endocardial tubes
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to signals from the underlying endoderm, a subpopulation of cells within the cardiac crescent form a pair lateral endocardial tubes through the process of ___
vasculogenesis
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
In response to signals from ____, a subpopulation of cells within the cardiac crescent form a pair lateral endocardial tubes through the process of vasculogenesis
the underlying endoderm
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
The cardiac cresent, primary heart field PHF) develops in the splanchnopleura at ___ (which position of the embryo?)
the cranial end of the embryo.
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
The cardiac cresent, primary heart field PHF) develops in____ at the cranial end of the embryo.
the splanchnopleura
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
By ____, an endothelial tube is formed on each side, surrounded by the mesoderm of the splanchnopleura.
fusing the primitive blood vessels (vasculogenesis)
Paths of migration of mesoderm during gastrulation
The most cranially migrating of these cells form the cardiogenic mesoderm, which moves cranial to the future position of ____
the oropharyngeal membrane (oval structures).
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
During folding of the embryo, the two endothelial tubes migrate toward the midline in the ventral-caudal direction and then converge at the midline to form____
the primitive heart tube.
Structure of the vasculature at the beginning of the 4th embryonic week - Position of the heart tube
During folding of the embryo, _____ migrate toward the midline in the ventral-caudal direction and then converge at the midline to form the primitive heart tube.
the two endothelial tubes
How is the cardiac present formed?
The cardiac crescent is formed by the cranially bilateral heart fields fusion at the midline (in mammals)
Formation of the pericardium/cavities open inthe splanchic mesoderm
Around the cardiac crescent, the formation of the prospective ___ in the splanchnopleura also begins
pericardial cavity
Formation of the pericardium/cavities open inthe splanchic mesoderm
Around the cardiac crescent, the formation of the prospective pericardial cavity in the splanchnopleura also begins
→ as shown in Figure B, cavities are formed in ____
the splanchic mesoderm
Formation of the pericardium/cavities open inthe splanchic mesoderm
Around the cardiac crescent, the formation of the prospective pericardial cavity in the splanchnopleura also begins
→ as shown in Figure B, cavities are formed in the splanchic mesoderm
→ . Figure C shows in longitudinal section the relationship of the heart tube to other structures: in front of it is (1)____ and behind it is (2)_____
- the septum transversum (the primordium of thediaphragm)
- the oro (bucco) pharyngeal membrane.
Further development of the heart is mainlydetermined by the folding of the embryo (4thweek)
The folding includes 2 things which are ___
1) folding around transverse axes – this will explain, how the heart primordium moves from „above the head” into the chest occupying its final position.
2) folding around the longitudinal axis – this will mainly explain the fusion of the structures originally developing on the two sides of the embryo.
What happen to the heart primordial during Folding around transverse axes, Cranio-caudal folding?
The heart primordium, originally located in front of the oropharyngeal membrane, bends to its final thoracic position
Folding around the longitudinal axis, lateral folding of the heart
Folding of the embryo results in _____ in the midline.
the fusion of the two endocardial tubes
Folding around the longitudinal axis, lateral folding of the heart
Folding of the embryo results in the fusion of the two endocardial tubes in the midline.
Somewhat later ____ also unite and surround the endocardial tube.
the myoepicardial mantles
Folding around the longitudinal axis, lateral folding of the heart
Folding of the embryo results in the fusion of the two endocardial tubes in the midline.
Somewhat later the myoepicardial mantles also unite and surround the endocardial tube.
→ ____ fuse ventrally, and finally, the dorsal mesocardium disappears.
The intraembryonic coeloms
Folding around the longitudinal axis, lateral folding of the heart
Folding of the embryo results in the fusion of the two endocardial tubes in the midline.
Somewhat later the myoepicardial mantles also unite and surround the endocardial tube.
→ The intraembryonic coeloms fuse ventrally, and finally,___ disappears.
the dorsal mesocardium
Folding around the longitudinal axis, lateral folding of the heart
→ identify
Pericardium as part of the intraembryonic coelome
→ identify
The primitive heart tube
What is the position of the heart tube after fusion?
Caudal to the head region and ventral to the foregut.
The primitive heart tube
The fused primitive heart is lined with endothelium and differentiation of ___ begins.
myoblasts from the mesoderm also
3 Parts of the heart tube
Myocardium differentiates from ____ with cardiomyocytes
the splanchic mesoderm
3 Parts of the heart tube
Myocardium differentiates from the splanchic mesoderm with cardiomyocytes
→ These cells mainly secrete ___
The cardiac jelly (special ECM) (rich in hyaluronic acid)
3 Parts of the heart tube
epicardium (visceral pericardium)
→ Develops later from cells of the ___
secondary heart field, SHF
3 Parts of the heart tube
The SHF arises from cells that migrate through ____ and then reside in visceral mesoderm near the floor of the posterior part of the pharynx
the primitive streak
3 Parts of the heart tube
The SHF arises from cells that migrate through the primitive streak and then reside in ____ near the floor of the posterior part of the pharynx
visceral mesoderm
3 Parts of the heart tube
→ Identify
Septum transversum
What’s happening here?
The heart tube directs blood flow in thecaudocranial direction
Looping and further differentiation of the heart tube
Between weeks 4 and 8, the primitive heart tube undergoes _____ that transforms its single lumen into the four chambers of the definitive heart
→ laying down the basis for the separation of pulmonary and systemic circulations at birth.
a process of looping, remodeling, realignment, and septation
Looping and further differentiation of the heart tube
Between weeks 4 and 8, the primitive heart tube undergoes a process of looping, remodeling, realignment, and septation
→ The role of this process?
→ laying down the basis for the separation of pulmonary and systemic circulations at birth.
that transforms its single lumen into the four chambers of the definitive heart
→ laying down the basis for the separation of pulmonary and systemic circulations at birth
Looping and further differentiation of the heart tube
What is cardiac looping?
This process causes the heart to fold on itself and assume its normal position in the left part of the thorax with the atria posteriorly and the ventricles in a more anterior position.
Separation of pericardial cavity
Septum formation in the heart in part arises from development of endocardial cushion tissue in ____ and ____
the atrioventricular canal (atrioventricular cushions) and in the conotruncal region (conotruncal swellings)
Separation of pericardial cavity
Septum formation in the heart in part arises from development of ____ in the atrioventricular canal (atrioventricular cushions) and in the conotruncal region (conotruncal swellings)
endocardial cushion tissue
Separation of pericardial cavity
____ in part arises from development of endocardial cushion tissue in the atrioventricular canal (atrioventricular cushions) and in the conotruncal region (conotruncal swellings)
Septum formation in the heart
Mesocardium dorsale
The heart tube initially remains connected to the posterior body wall through ____
Dorsal mesocardium
Mesocardium dorsale
The heart tube initially remains connected to the posterior body wall through the mesocardium dorsale.
→ Over time, cavities form in ____, resulting in the formation of pericardial sinuses.
the dorsal mesocardium
Mesocardium dorsale
The heart tube initially remains connected to the posterior body wall through the mesocardium dorsale.
→ Over time, cavities form in the dorsal mesocardium, resulting in ____
the formation of pericardial sinuses.
Formation of pericardial sinuses
Which structure will disappear during this process?
Mesocardium dorsale - disappears quickly
Formation of pericardial sinuses
Mesocardium dorsale - disappears quickly → Causing Two inflection points at the arterial and venous ends of the heart
With the formation of an S-shaped curvature, the pericardial cavity closes into a channel between the two orifices
→ This channel is called?
the sinus transversus
Formation of pericardial sinuses
The visceral layer of the pericardium holds the arteries and veins together
→ then create an originally a common bending point which is called ___
sinus obliquus
Formation of pericardial sinuses
____ holds the arteries and veins together
→ then create an originally a common bending point which is called sinus obliquus
The visceral layer of the pericardium
Formation of pericardial sinuses
The visceral layer of the pericardium holds ___ and ___ together
→ then create an originally a common bending point which is called sinus obliquus
the arteries and veins
Parts of the developing heart tube 1.
As the heart tube lengthens, it develops a series of expansions and shallow sulci that subdivide it into _____
primordial heart chambers.
Parts of the developing heart tube 1.
As the heart tube lengthens, it develops a series of expansions and shallow sulci that subdivide it into primordial heart chambers.
→ Starting at the inflow end, these are _____ (6)
- the left and right horns of the sinus venosus
- the primitive atrium
- the primitive ventricle
- the bulbus cordis
- the outflow tract (truncusarteriosus).
Parts of the developing heart tube 1.
As the heart tube lengthens, it develops a series of expansions and shallow sulci that subdivide it into primordial heart chambers.
- The bulbus cordis forms ____
- The primitive ventricle gives rise to ____
- much of the right ventricle
- the left ventricle.
Parts of the developing heart tube 1.
As the heart tube lengthens, it develops a series of expansions and shallow sulci that subdivide it into primordial heart chambers.
→ The outflow tract (the conotruncus) will form ___ and __
the conus arteriosus and the truncus arteriosus
Parts of the developing heart tube 1.
As the heart tube lengthens, it develops a series of expansions and shallow sulci that subdivide it into primordial heart chambers.
→ The outflow tract (the conotruncus) will form the conus arteriosus and the truncus arteriosus
→ both of which split to become ___-(4)
- outflow regions of the two ventricles
- the ascending aorta
- pulmonary trunk.
Parts of the developing heart tube 1.
→ Identify
Parts of the developing heart tube 1.
→ Identify
Circulatory system at the end of 4th week
→ identify
Vessels in the head region at 4th week
→ Aortic arch systems begin at ___
6th week
List Vessels entering to sinus venosus
- vv. vitellinae
- vv. umbilicales
- vv. cardinales communes
The primitive heart tube lengthens at both ends, particularly the outflow (arterial) end,
→ through the addition of ___
cardiac progenitors from secondary heart field mesoderm
(Cells from these region will form the conus cordis, truncus arterious and parts of the right ventricle)
While myocardial cells within developing primitive heart tube continue to proliferate, there is a continued recruitment of cardiac progenitor cells from outside the original cardiac crescent at both (1)____ and ____
→ The source of these cells is referred to as (2)_____
- the arterial (cranial) pole and venous (caudal) pole.
- the secondary heart field.
Do Neural crest cells participate in heart development?
Yes
The heart tube grows rapidly and curves in an S-shape. Consequently, the originally caudal atria are at the same height as and behind ____
the cranial truncus arteriosus (sinus transversus!).
(By the 28-30th day the heart had taken its external shape but itslumene was still uniform, undivided.)
Parts of the developing heart tube 3.
As a result of the uneven growth and rotation of the heart
- the atria become ___
dorsocranial → the right-left asymmetry increases.
Development of atria
Venous blood initially enters the sinus horns through _____
paired, symmetrical common cardinal veins.
Development of atria
Venous blood initially enters the sinus horns through paired, symmetrical common cardinal veins.
→ Changes in the venous system rapidly shift (1)____ return to the right so that all blood from the body and umbilicus enters the future right atrium through (2)____ and ____
The left sinus horn becomes the coronary sinus, which drains the myocardium.
- the entire systemic venous
- the developing superior and inferior venae cavae.
Development of atria
Venous blood initially enters the sinus horns through paired, symmetrical common cardinal veins.
→ Changes in the venous system rapidly shift the entire systemic venousreturn to the right so that all blood from the body and umbilicus enters the future right atrium through the developing superior and inferior venae cavae.
→ The left sinus horn becomes (1)_____, which drains (2)____
- the coronary sinus
- the myocardium.
Development of atria
Venous blood initially enters the sinus horns through paired, symmetrical common cardinal veins.
→ Changes in the venous system rapidly shift the entire systemic venous return to the right so that all blood from ___ and ____ enters the future right atrium through the developing superior and inferior venae cavae.
→ The left sinus horn becomes the coronary sinus, which drains the myocardium.
the body and umbilicus
Development of atria
A process of _____ incorporates the right sinus horn and the ostia of the venae cavae into the posterior wall of the future right atrium, displacing the original right half of the primitive atrium.
intussusception
Development of atria
A process of intussusception incorporates ____ and ____ into the posterior wall of the future right atrium, displacing the original right half of the primitive atrium.
the right sinus horn and the ostia of the venae cavae
Development of atria
A process of intussusception incorporates the right sinus horn and the ostia of the venae cavae into _____, displacing the original right half of the primitive atrium.
the posterior wall of the future right atrium
Development of atria
A process of intussusception incorporates the right sinus horn and the ostia of the venae cavae into the posterior wall of the future right atrium, displacing___
the original right half of the primitive atrium.
Development of atria
The pulmonary vein develops in the midline and then shifts to ____
→ the trunk of the pulmonary vein is subsequently incorporated by (2)____ to form most of the left atrium.
- the future left atrium
- intussusception
Development of atria
The pulmonary vein develops in the midline and then shifts to the future left atrium
→_____ is subsequently incorporated by intussusception to form most of the left atrium.
the trunk of the pulmonary vein
Development of atria
The pulmonary vein develops in the midline and then shifts to the future left atrium
→ the trunk of the pulmonary vein is subsequently incorporated by intussusception to form____
most of the left atrium.
Development of atria
Right and left venous valves: two semilunar structures at the sinu-atrial junction.
→ Postero-superiorly they unite and form _____
the septum spurium.
Development of atria
Right and left venous valves: two semilunar structures at the sinu-atrial junction.
→ Postero-superiorly they unite and form the septum spurium.
→ The left one later completly disappears by ____
fusing with the interatrial septum.
Development of atria
Right and left venous valves: two semilunar structures at the sinu-atrial junction.
→ Postero-superiorly they unite and form the septum spurium.
→ The left one latercompletly disappears by fusing with the interatrial septum.
→ The right one divides into two
- the upper part persists as ______
- the lower gives ____ and ___
- a part of the crista terminalis
- the mass of the Thebesian and the Eustachian valves.
Development of atria
As they are all derived from the same structure, valves of IVC and coronarysinus as well as the crista terminalis can be marked with one uninterrupted line!
(for reading)
(for reading)
Partitioning of the heart 4th to 5th week
- Septation of _____
- Formation of ______
- Formation of ____
- Appearance of the membranous interventricular septum and the spiral aorticopulmonary septum.
- the common atrioventricular (AV) orifice.
- the interatrial septum.
- the muscular interventricular septum.
Partitioning of the heart 4th to 5th week
- Septation of the common atrioventricular (AV) orifice.
- Formation of the interatrial septum.
- Formation of the muscular interventricular septum.
- Appearance of ___ and _____
the membranous interventricular septum and the spiral aorticopulmonary septum.
Partitioning of the heart 4th to 5th week
- ____ of the common atrioventricular (AV) orifice.
- ____ of the interatrial septum.
- ____ of the muscular interventricular septum.
- ____ of the membranous interventricular septum and the spiral aorticopulmonary septum.
- Septation
- Formation
- Formation
- Appearance
Septation of the common atrioventricular (AV) orifice
→ What happen?
Endocardial cushions → Placed to the right
Formation of the interatrial septum
In the 5th and 6th weeks,_____, grow to separate the right and left atria.
→ These septa are perforated by a staggered pair of foramina that allow right-to-left shunting of blood throughout gestation.
a pair of septa, the septum primum and the septum secundum
Formation of the interatrial septum
In the 5th and 6th weeks, a pair of septa, the septum primum and the septum secundum, grow to ___
→ These septa are perforated by a staggered pair of foramina that allow right-to-left shunting of blood throughout gestation.
separate the right and left atria.
Formation of the interatrial septum
In the 5th and 6th weeks, a pair of septa, the septum primum and the septum secundum, grow to separate the right and left atria.
→ These septa are perforated by a staggered pair of foramina that allow right-to-left shunting of blood throughout gestation.
→ What are the 2 foramina
– foramen primum
– foramen secundum
Formation of the interatrial septum
In the 5th and 6th weeks, a pair of septa, the septum primum and the septum secundum, grow to separate the right and left atria.
→ These septa are perforated by a staggered pair of foramina that allow right-to-left shunting of blood throughout gestation.
→ What happen to foramina when the septum primum goes down?
– foramen primum, finally disappears
– foramen secundum (opens by apoptosis)
Formation of the interatrial septum
In the 5th and 6th weeks, a pair of septa, the septum primum and the septum secundum, grow to separate the right and left atria.
→ Septum secundum will become ____
foramen ovale
Formation of the interatrial septum
Two non-overlapping openings, valve-like septum primum: blood can only flow in ______ (direction?), according to the pressure gradient.
After birth, the pressure in the left atrium increases, the plates merge
the left-right direction
Formation of the interatrial septum
Two non-overlapping openings, valve-like ____: blood can only flow in the left-right direction (direction?), according to the pressure gradient.
After birth, the pressure in the left atrium increases, the plates merge
septum primum
The bulbus cordis expands to form _____, and during the 6th week a muscular ventricular septum partially separates the ventricles
the right ventricle
____ expands to form the right ventricle, and during the 6th week a muscular ventricular septum partially separates the ventricles
The bulbus cordis
The bulbus cordis expands to form the right ventricle, and during the 6th week a muscular ventricular septum partially separates the ventricles
→ What are the 2 parts of septum interventriculare?
- Muscular part
- pars membranacea
The bulbus cordis expands to form the right ventricle, and during the 6th week a muscular ventricular septum partially separates the ventricles
2 parts of septum interventriculare
→ describe the muscular part?
a muscular septum growing from below that never reaches the AV orifice
The bulbus cordis expands to form the right ventricle, and during the 6th week a muscular ventricular septum partially separates the ventricles
2 parts of septum interventriculare
→ describe the membranous part?
a septum separating the truncus arteriosus, which grows downwards and fuses with the pars muscularis.
Septum aorticopulmonale
During the 7th and 8th week, the outflow tract of the heart has completed the process of ___ (2)
septation and division
Septum aorticopulmonale
During the 7th and 8th week, the outflow tract of the heart has completed the process of septation and division
→ converting it into the separate, helically arranged outflow regions of____ (4)
both ventricles and ascending aorta and pulmonary trunk.
Development of AV valves
The bicuspid (mitral) and tricuspid atrioventricular valves also develop from _____ tissue during the 5th and 6th weeks.
atrioventricular cushion
Development of AV valves
____ and _____ (valves?) also develop from atrioventricular cushion tissue during the 5th and 6th weeks.
The bicuspid (mitral) and tricuspid atrioventricular valves
Development of AV valves
The bicuspid (mitral) and tricuspid atrioventricular valves also develop from atrioventricular cushion tissue during the 5th and 6th weeks.
→ Meanwhile, the heart undergoes ___
remodeling
(that brings the future atria and ventricles into correct alignment with each other and also aligns both ventricles with their respective outflow vessels.)
Development of semilunar valves
During formation of _____, two smaller and shorter intercalated cushion tissues form in the opposite quadrants.
conotruncal septum
Development of semilunar valves
During formation of conotruncal septum, two smaller and shorter ____ form in the opposite quadrants.
intercalated cushion tissues
Development of semilunar valves
During formation of conotruncal septum, two smaller and shorter intercalated cushion tissues form in the opposite quadrants.
In the most distal most conal segment, this new cushion tissue is exacavated and remodeled within _____ to form 2 cavities
the wall of each new vessel
Development of semilunar valves
During formation of conotruncal septum, two smaller and shorter intercalated cushion tissues form in the opposite quadrants.
In the most distal most conal segment, this new cushion tissue is exacavated and remodeled within the wall of each new vessel to form 2 cavities
→ a similar cavity forms in both ___ and ____
the aortic and pulmonary sides of conotruncal septum.
Development of semilunar valves
During formation of conotruncal septum, two smaller and shorter intercalated cushion tissues form in the opposite quadrants.
In the most distal most conal segment, this new cushion tissue is exacavated and remodeled within the wall of each new vessel to form 2 cavities
→ a similar cavity forms in both the aortic and pulmonary sides of conotruncal septum.
→ These cavities and the intervening tissue are subsequently remodeled to form ____ and ____
the valvular sinuses and semilunar valves
