Heart Development Flashcards
Where do the first blood cells arise? Are these different from hematopoeitic stem cells?
First blood cells arise in blood islands on the wall of the yolk sac (mesoderm)- this population is transitory
Definitive hematopoeitic stem cells are derived from mesoderm surrounding the aorta in a site near the developing mesonephric kidney called the AGM
What is the major hematopoietic organ in the fetus from month 2-7?
Liver
Yolk sac mesoderm forms the first blood cells at day 17 and finishes by day 60. The liver primordia is colonized beginning at day _____ and continues until birth. The AGM begins hematopoietic processes at day _____ prior to contributing to liver colonization
23; 27-40
[bone marrow also hematopoietic at 10.5 weeks]
Process by which cells of the primary heart field are induced by the underlying pharyngeal endoderm to form cardiac myoblasts and blood islands that will form blood cells and vessels
Vasculogenesis
Blood cells may only belong to what lineage prior to colonization of the liver?
Myeloid
____________ = common precursor for vessel and blood cell formation that are formed in blood islands of yolk sac
Hemangioblasts
What is the difference in fate of hemangioblasts at the center of blood islands vs at the periphery?
Central hemangioblasts form hematopoietic stem cells (precursors of all blood cells)
Peripheral hemangioblasts differentiate into angioblasts (precursors to blood vessels)
______ = formation of blood vessels by sprouting from existing vessels
Angiogenesis
_____ = existing blood vessel splits into 2
Intussusception
What is the AGM region?
Aortic-gonadal-mesonephric region
Where definitive hematopoietic stem cells are programmed from hemogenic endothelial precursor cells
[hematopoietic stem cells appear at day 27 and disappear from AGM by day 40]
What is the major difference between intraembryonic vasculogenesis and extraembryonic vasculogenesis?
Intraembryonic vasculogenesis involves coupling with hematopoiesis (because it all starts with the blood islands)
All other de novo blood vessel formation occurs SEPARATE from hematopoeisis
Extraembryonic vasculogenesis begins around day 17 when extraembryonic ______ and _______ mesoderm differentiate into either hematopoietic progenitors or ___________ precursor cells. The primary function is to meet immediate need for blood cells
Splanchnic; chorionic
Endothelial
What are the 2 major mechanisms of vascular plexus expansion
Angiogenesis
Intussusception
______ are characterized by abnormal blood vessel and lymphatic capillary growth
Angiomas
What type of angioma is characterized by excessive growth of capillaries?
Capillary hemangioma
What type of angioma is characterized by excessive growth of venous sinuses?
Cavernous hemangioma
Generation of ______ _______ forms 2 bilateral primary heart fields which eventually fuse, thereby creating linear primary heart tube
Precardiac mesoderm
By day 18 of heart development, the lateral mesoderm of the primary heart tube has ______ and _______ components, and the latter will give rise to almost all heart components
Somatopleure; splanchnopleure
Early endocardial cells separate from the mesoderm to create paired heart tubes; what process occurs to bring the paired heart tubes together into a single tube?
Lateral embryonic folding
What structures eventually unite to form a horseshoe shaped endothelial lined tube surrounded by myoblasts, forming the cardiogenic region?
Blood islands
The intraembryonic cavity over the cardiogenic region of the primitive heart will later develop into what structure?
Pericardial cavity
What structures form from blood islands that appear bilaterally and close to midline of the embryonic shield?
Dorsal aortae
All heart structures come from embryonic _______ _______, except for neural crest cells which are ________
Splanchnic mesoderm; ectoderm
When does the primary heart field form
Around day 19 (range of 16-18)
Where is the primary heart field located?
Splanchnic layer of lateral plate mesoderm, cranial to neural folds (these are progenitor heart cells which migrated from the epiblast - aka the area just cranial to the primitive streak)
As progenitor cells migrate from the epiblast to form the primary heart field, they are specified on both sides from lateral to medial to become what heart structures?
Atria
Left ventricle
Most of right ventricle
The primary heart field appears around day 19. When does the secondary heart field appear?
Day 20-21
What structures are formed from the secondary heart field?
Remainder of right ventricle Outflow tract (conus cordis, truncus arteriosus)
Where is the secondary heart field found?
Splanchnic mesoderm ventral to posterior pharynx
What regulates formation of secondary heart field
Neural crest cells - which control concentrations of FGFs in the area and pass the SHF in the pharyngeal arches as they migrate from the hindbrain to septate the outflow tract
What gives rise to the epicardium, interstitial cells and vasculature smooth muscle, and coronary vasculature?
Pro-epicardium
What are the 3 layers of the simple single heart tube?
Primordial myocardium (external layer)
Epicardium (visceral pericardium)
Endocardium (internal endothelial lining of the heart)
What forms the external layer (primordial myocardium) of the simple single heart tube
Splanchnic mesoderm surrounding the pericardial cavity (cardiac precursors of anterior/secondary heart field)
Which layer of the heart tube is derived from mesothelial cells that arise from external surface of sinus venosus and spread over myocardium?
Epicardium - often referred to as cardiac jelly
When is cardiac looping complete and what are the results?
Complete by day 28
Result is an S-shaped heart with atrium located dorsal to outflow part of heart
Outflow part of heart (bulbus cordis) leads to the aortic sac and aortic arch system
Internal septum begins to divide ventricle and later an internal septum will begin to divide the atria
__________ = broader proximal part of bulbus cordis
____________ = narrower distal part of bulbus cordis
[bulbus cordis is the outflow part of the heart]
Conus arteriosus
Truncus arteriosus
How is the transverse pericardial sinus formed during heart looping?
The central part of the dorsal mesentery degenerates (which was suspending the heart tube), forming TPS between the right and left sides of the pericardial cavity
What is the role of the secondary heart field in cardiac looping?
Cells from the secondary heart field are added to cranial end of the heart tube as it continues to elongate
This lengthening process is essential for normal formation of part of RV, outflow tract, and looping
What do the bulbus cordis and conus cordis become?
Bulbus cordis becomes trabeculated part of RV
Conus cordis forms outflow tracts of both ventricles
At first, circulation through the primordial heart is an ebb-and-flow type, but by the end of the 4th week coordinated contractions of the heart result in unidirectional flow.
Initially, the ______ acts as an interim pacemaker of the heart, the ______ _______ then takes over this function.
The SA node develops in the ______ week, located in the right wall of the RA.
Atrium; sinus venosus