Cardiovascular System Flashcards
Which germ layer is the cardiovascualr system derived from?
Mesoderm
The cardiovascualr system is the _____major system in the embryo to become functional
First
What is the job of the cardiovascualr system in an embryo?
Reuqired to supply embryo with nutrients and dispose of wastes
The cardiovascualr system is derived mainly from which 3 things?
- Splanchnic mesoderm forms the primordium of the heart
- praxial and lateral mesoderm (near the otic placodes from which the internal ears develop)
- neural crest cells (from the regions between the otic vesicles and the caudal limits of the third pair of somites
Development of intraembryonic coelom
Spaces appear in the lateral mesoderm and coalesce to form the intraembryonic coelom
-this divided the intraembryonic meaoderm into a somatic layer and a splanchnic layer
What forms tbe body wall and what forms the gut wall?
Intraembryonic somatic mesoderm and ectoderm=somatopleure (body wall)
Intraembryonic splanchnic mesoderm and endoderm=splanchnipleure (gut wall)
Intrembryonic coleom will give rise to….
Pericardial, pleural and peritoneal cavities
The cardiogenetic field is established ______ to the ____
Cranial
Neural pate (brain)
Why does the cardiovascualr sysfem develop in the embryo when it does?
By day 16-18 embryo grows rapidly and needs more nutrients than diffusion can offer
How does the cardiogenic field form and when?
Epiblast cells by day 16-18 migrate to form cardiogenic field
Primary Heart Field (PHF) forms what
Development of Atria, left ventricle and most of the right ventrical
Secondary Heart Field (SHF) forms what
Rest of the right ventricle and outflow ducts
When do the primary and secondary heart fields develop?
Day 16-18
Day 18-20
What induces the formation of myoblasts and blood islands?
Underlying pharyngeal endoderm induces overlying mesoderm and cardiogenic region to form these
Formation of blood and vessels using signalling?
- FGF2 binds to FGFR to form mesoderm cells
- VEGF binds to VEGF-R2 to form hemangioblasts
- VEGF binds to VEGF-R1 to create tube formation (hemangioblasts on outside become angioblasts)
- VEGF binds to VEGFR1,2 to form arteries and veins
Vasculogenesis
Angiogenesis
The formation of new vascular channels by assembly of individual precursor cells called hemangioblasts
Formation of new vessels by budding and branching from preexisting vessels
The umbilical vein carries what to where
The umbilical arteries carries what to where
Well-oxygenated blood and nutrients from the chorion sac to the embryo
Poorly oxygenated blood and waste products from the embryo to the chorion
How mang veins drain into the tubular heart of a 4-week embryo?
3
3 paired veins that darin into the tubular hesrt of a 4-week emrbyo are:
- Vitelline veins: return poorly oxygenated blood from the umbilical vesicle to heart
- umbilical veins: carry well oxygenated blood from the chorion to heart
- common cardinal veins return poorly oxygenated blood from the body of the embryo to heart
The vitelline veins follow the ______ (yolk stalk) into the embryo
Omphaloenteric duct
-narrow tube connecting the umbilical vesicle (yolk sac) with the midgut
Where do the vitelline veins enter
Enter the venous end of the heart-sinus venosus
The _____ Vitelline vein regresses while the ______ vitelline vein…..
Left
Right forma most of the hepatic portal system
Umbilical veins run on each side of the ______ and go from where to where?
Liver
Carry well oxygenated blood from the placenta to the sinus venosus
What parts of the umbilical vein degenerate?
Right umbilical vein abd the cranial part of the left umbilical vein between the liver and the sinus venosus
The persistent caudal part of the __________ becomes the _______, which careies all the blood from the placenta to the embryo.
Left umbilical cord
Umbilical vein
Ductus venosus (DV)
A large venous shunt that develops within the liver and connects the umbilical vein with the inferior vena cava (IVC)
Which veins constitute the main venous drainage system of the embryo?
Cardinal veins
The anterior cardinal veins drain_____ part of the embryo
The posterior cardinal veins drain_____ parts of the embryo
Cranial
Caudal
Both the Cardinal Veins join the _________, which enter the_____
Common cardinal veins
Sinus venosus
During the 8th week, what happens to the cardinal veins?
The anterior cardinal veins become connected by an anastomosis which shunts blood from the left to the right anterior cardinal vein and become left brachiocephalic vein when the caudal part of the left anterior cardinal vein degenerates
Why does the liver grow rapidly?
Gots lots of nutrients and oxygen from umbilical vein so bypasses are needed
Umbilical vein looses connection with the hesrt and empty into the liver
When does the Inferior Vena Cava develop (not a date)
During a series of changes in the primordial veins of the trunk that occur as blood, returning from the caudal part of the emrbyo, is shifted from the left to the right side of the body.
The IVC is composed of what 4 segments?
- Hepatic segment (derived from the hepatic vein (proximal part of the right vitelline vein) and hepatic sinusoids)
- prerenal segment (derived from the right subcardinal vein)
- renal segment derived from the subcardinal-supracardinal anastomosis
- postrenal segment (dereived from the right supracaedinal vein)
What stops the liver from taking all the nutrients?
Venous shunt-ductus venosus develops in the liver and connects umbilical vein with the IVC. This created a bypass through the liver enabling more palcental blood to go to the heart
Phayngeal arches form during the _____
Fourth and fifth weeks
Pharyngeal arch arteries supply _____ to _____
Blood
Pharyngeal arches
Pharyngeal aech arteries arise from
The aortic sac and terminate in the dorsal aortae
Dorsal aortae
- initally, the paired dorsal aortas run through the entire length of the embryo
- later, the caudal portions of the dorsal aortae fuse to form a single lower thoracic/ abdominal aorta
- of the remianing paired dorsal aortae the right aorta regresses and the left becomes the primordial aorta
Intersegmental arteries
- are branches of the dorsal aorta
- 30 or so intersegmental arteies, pass between and carey blood to the somites and their derivaties
- intersegmental arteries in the neck join to form vertebral artery
- in the thorax, it persists as intercostal arteries
Most of the intersegmental arteries in the abdomen become ________ but the 5th pair _______. In sacral region form ______
Lumbar arteries, but the 5th pair of lumbar intersegmental arteries remain as the common iliac arteries
Lateral sacral arteries
Fate of the Vitelline arteries
Which 3 remain?
Vitwlline arteries Pass to the vesicle and later the primoridal gut, which forms from the incorporated part of tbe umbilical vesicle.
Only 3 remain:
- celiac arterial trunk to foregut
- superior mesenteric artery to midgut
- inferior mesenteric artery to hindgut
Fate of the umbilical arteries
Proximal part of the umbilical arteries become the internal iliac arteries and superior vesicle arteries whereas distal part become medial umbilical ligament
Development of the heart
- heart formation begins toward the end of the 3rd week with a condensation of mesoderm ventral to the intraembryonic coelom-called the cardiogenic area
- forms 2 angioblastic cords that canalize to become heart tubes
- as lateral body folding occurs, heart tubes fuse to become single heart tube
Genetic induction of the cardiogenic field
Endoderm expresses BMP 2,4 to increase expression of NKX-2.5 in mesoderm which is a master regulator transcription factor for development of cardiovascualr system.
Ectoderm (neural tube) increases WNT inhibitors like crescent and cerebus to inhibit wnt 3a,8 to inhibit cardiogenic field
The fusion of the heart tubes begins at the ____ end and extends ______ until it is a singular tube
Cranial
Caudally
The epitheliem of the heart tube develops from the
Endocardium of the heart
Wall of ghe heart tube (and heart) consists of:
- endothelium (becomes endocardium)
- cardiac jelly (becomes subendocardial CT)
- myocardium (thick layer of carduac muscle)
- epicardium (or visceral later of oericardium forms from mesothelial cells on surface)
Heart tube elingates and 5 dialations appear
- Truncuc arteriosus
- bulbus cordis
- ventricle
- atrium
- sinus venosus
The heart is initally suspended from the ___________ by _______, called the _________, but the central part of this mesentery soon degenerates, forming a communication ________
Dorsal wall
Mesentery
Mesocardium
The transcere pericardial sinus between the right and left sides of the pericardial
Arterial and venous ends of the heart tube are _____
Fixed in position
As bulbud cordis and ventricle grow, the heart tube bends upon itself becomes a
This causes the atrium and sinus venosus to move
This causes the bulbus cordis, ventrical and truncus arteriosis to move
U shaped bulboventricular loop
Dorsally and cranially and to the left
Ventrally and caudally and to the right (slightly)
Contraction of the heart begins at ____
Blood circulation begins in _____
Day 22-myogenic origin
4th week
Blood returns to the sinus venosus via…
- cardinal veins from embryo
- umbilical bein from placenta
- vitelline veins from yolk sac
Primitive citculation pathway in heart
Blood flows through the sinus venosus, atrium, ventricle, bulbus cordis, truncus arteriosis, aortic sac, aortic arches and into the dorsal aorta
From the dorsal aorta blood flow to
The embryo via intersegmental arteries
The placenta via the umbilical arteries
The yolk sac via the vitelline arteries
Partitioning of the heart begins when and is complete when
4th week
End of 8th week
Partitioning processes occur simultaneoulsy
Division of the Atrioventricular (AV) Canal
- seperates the atria from the ventricles and the left from the right side of the heart
- endocardial cushions form on the ventral and dorsal walls. Grow ans fuse which divides the AV canal into left and right AV canals
- after inductive signals from the myocaardium of the AV canal, a segment of the in er endocardial cells undergoes epithelial mesenchymal transformation (EMT), which then invaded the extracellular matrix
Factors for EMT
- TGF-Beta1 and beta2
- BMP-2A and -4
- Sinc finger protein slug
- activin-receptor-like kinase (chALK2)
Reproted to be involved in the epithelial-mesenchymal transformation and formation of the endocardial cushions
Division of the Primitive Artrium
- need to divide the primitive atrium into the RA and LA
- occurs via the formation of 2 septa-septum primum and septum secundum
- septun primum grows down from the roof of the primitice atrium
- opening between the bottom of the septum primum and the endocardinal cushions is the foramen primum
- foramen primum disappears as the septum lrimin fuses with the endocardial cushions
- perforations appear in the upper part of the septhm primun and join to form the foramen secundum
- septum secundum grows downward from thr roof to the right of the septum primum
- septum secundum does not fuse with the endocardial cushions but leaves an oval opening called the foramen ovale
Before birth, well oxygenated blood is shunted from the right atrium through the ______ when the pressure increases
When the pressure decreases in the right atrium, the flaplike valve of the oval foramen is _____
Oval foramen into the left atrium
Pressed against the relatively rigid septum secundum which closes the oval foramen
After birth, the pressure in the _______ increases as the blood returnes from the lungs.
Eventually the septum primum is ____
Left atrium
Pressed against the septum secundum and adheres to it permenantly closing the oval foramen and forming the oval fossa
Rapid growth of heart tube is by
SHF proliferating rapidly and adding cells to the top (tube elongation)
Cardiac jelly becomes
Connective tissue and then epithelail lining
The primitive heart (tubular structure) is hanging where?
Pericardial cavity
Division of the primitive ventricle
- need to divide the primitive ventricle into a LV and RV
- muscular ridge grows upward from the floor of the ventricle to form the interventricular septum
- stops short of the endocardial cushions leaving the interventricular (IV) foramen
- by end of 7th week, membrane grows downward to compelte the IV septum
Closure of the IV foramen and formation of the membranous part of the IV septum result from the fusion of tissues from which sources:
- right bulbar ridge
- left bulbar ridge
- Endocardial cushion
After the closure of the IV foramen and formation of the membranous part of the IV seltum, the ________ is in communication with the ______ and the _____ commhnicates with the ______
Pulmonary trunk
Right ventricle
Aorta
Left ventricle
Changes to the sinus venosus
- initially, the sonus venosus has L and R horns that open into the atrium
- R horn increases and L horn decreases
- orifice moves to the R and opens into the RA
- R horn of sinus venosus is incorporated into the wall of the RA
- L horn of sinus venosus becomes the coronary sinus
Most of the wall of the left atrium is ______ because it is formed by incorporation of the ______
Smooth
Primoridal pulmonary vein
As the atrium expands, the primordial pulmonary vein and its main branches are incorporated into the wall of the _______as a result _____ are formed
Left atrium
4 pulmonary
Partitioning of the bulbus cordis and trunchs arteriosus
Is a spiral partition, not a straight wall as they undergo a 180° spiraling.
- divides the BC and TA into 2 channels
- pulmonary trunk from the RV
- Aorta from the LV
Muscular bulbar and truncal ridges form and fuse to form the
Aorticopulmonary septum
Bulbar and truncal ridges are derived largely from _________
Neural crest mesenchyme
Neural crest cells migrate through the primordial pharynx and pharyngeal arches to reach the ridges
Fate of bulbus cordis
Bulbus cordis is incorporates into the walls of the definitive ventricle
- in right ventircle, BC is represented by the conus arteriosus (infundibulum), which gives origin to the pulmonary trunk
- in left ventricle, the bulbus cordis forms the walls of the aprtic vestibjle, the part of the ventriclar cavity just inferior to the aortic valve
Structural anomalies of the cardiovascualr system occurance
Common
0.7% of live births and 2.7% of still births
One of the Most common congential heart defects
Atrial septal defects (ASD) m
- result from excessive resorption of the septum primim and or defective development of the septum secundum
- can result in patent foramen ovale or patent foramen primum
Ventricular septal defects (VSD)
Most common congenital heart defects
- usually involve the membranous part of the septum
- results in a patent interventricular foramen
TGA
Transposition of the great arteries
Results when the aorticopulmonary septum doesn’t spiral and origin of great arteries is reversed
Prental circulation differs from postnstal because
- The lungs are nonfunctional
- the placenta serves in gas exchange, obtaining nutrients and elminating wastes
Blokd returns to the fetus from the placenta via the ______
Umbilical vein (90% O2 saturated)
Half of the blood retunring from placenta goes through the __________ to the________ and half goes trhough the ________ to the ______
Liver
IVC
Ductus venosus
IVC (67% 02 saturated)
From IVC, blood goes to the ______ then either
Right atrium
Through the foramen ovale into the Left atrjym (90%) or
To the Right ventricle and pulmonary circuit (10%)
Blood that leaves the Right ventricle into the ________ can go directly into the _____ via the ______
Pulmonary trunk
Aorta
Ductus arteriosus
From the left ventricle, blood leaves the heart via the _______
Aorta (58% O2 saturated in descending aorta)
Umbilical arteries arise as branches of the ______and carry blood to the ______
Internal iliac arteries
Placenta
At the time of birth, must close fetal shints and replace palcental circulation with
Pulmonary circulation
At birth, there is a decrease in pressure in the ______ and ______ of the heart because of
IVC
Rifht side
Loss of blood flow from the placenta
Inflation of the lungs which decrease pulmonary vascular resistance
Pressure on the left sude of the heart increases because of the increase in ___
Pulmonary flow
There is a breif period when blood flows from the aorta backward through ghe ductus venosus into the ___
Pulmonary trunk
-wall of ductus arteriosus constructs and closes
Because pressure in the Left atrium is now greater then the Right atrium, fhe septum primum is______
Pressed against thr septum secundum and the foramen ovale closes
Adult derivitates of fetal structures
- umbilical vein
- ductus venosus
- umbilical arteries
- foramen ovale
- ductus arteriosus
Ligamentum teres
Ligamentun venosun
Medial umbilical ligaments and vesicular arteries
Fossa ovalis
Ligamentum arteriosum
Patent Ductus Arteriosus (PDA)
Occurs commonly in premature babies
Patent foramen ovale results from
Blood flowing from LA into RA and deceeae cardiac output
3 bypasses
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
Ductus arteriosus
Sends medium oxygenated blood to descending aorta instead of pulmonary trunk (non functional lungs)
What creates the muscular ridge
Myoblast proliferation
