Development of the Heart Flashcards
when does the CV system begin to appear?
mid week 3, heart functions during week 4
establishing and patterning of primary heart
-progenitor cells (once in epiblasts) migrate thru primitive streak into splanchnic layer of lat plate mesoderm
what is the first sign of heart
solid horseshoe shape = primary heart field (PHF) (cells will form atria, LV and part of RV)
- underlying endoderm induces PHF to form cardiac myoblasts
- blood islands and vessels via vasculogenesis)
- vasculogenesis: BVs arise from blood islands
- angiogenesis: BVs sprout from existing vessels
when does heart tube formation and positioning occur
18-22 days
heart tube formation and positioning
- blood islands unite in jorseshoe shaped endotheliam lined tube in cardiogenic region (endocardial tubes)
- other islands appear at midline to form dorsal aortae
- lat body folding creates primordial heart tube (lat sides forl ventrally and medially and fuse at midline)
- cranial caudal folding occurs and repositions developing heart and pericardial cavities
what is the hinge for ventral swinging during body folding?
oropharyngeal mem
position of heart prior to folding
rostral to oropharyngeal mem and ventral to pericardial cavity
what initially attaches heart tube to dorsal side of pericardial sac
dorsal mesocardium
*middle part disappears to form transverse pericardial sinus (present in adults)
what gives rise to SA and AV nodes
SA canal
sinus venoses
- receive blood from 3 paired vv
1. viteline vv
2. umbilical vv
3. common cardinal vv
what happens when blood flow in heart shifts R
R horn becomes larger than L
-L sinus horn becomes 1. oblique vv of LA 2. coronary sinus
what does R sinus horn become incorporated into
R atrium (smooth walled part, sinus venarum), resulting in 1. L valve and septum spurium fuse with atrial septum
- sup portion of R valve disappears
- inf part of R valve becomes valve of IVC and coronary sinus
what is the ridge separating smooth and rough wall of RA
crista terminalis
when does partitioning of heart occus
30 days
partitioning of heart
- atrial partitioning beginning
- primary IV foramen undivided
- outflow tracts undivided
- prox part bulbus cordis becomes trabeculated = R vent
- AV canal undivided
what are the two ways to form septa
- endocardial cushions
2. growth/expansion (meeting and fusing)
septum primum
-extends toward end cushions in AV canal (opening below = ostium primum, foramen primum), it closes perforations in septum primum coalesce to form ostium/foramen secundum
septum secundum
develops from roof of primordial atrium, to the R of the septum primum, grows inferiorly and develops opening (foramen ovale)
formation of fossa ovalis
after birth, prressure forces septums primum and secundum together
partitioning of outflow tracts
- neural crest cells migrate into truncus arteriosus and bulbus cordis
- form truncal ridges and bulbar ridges (helps create septum in outflow tract)
- ridges spiral 180 resulting in spiral aorticopulmonary septum when ridges fuse
definitive structure of truncus arteriosus
roots and prox portions of aorta and pulm tr
definitive structure of conus cordis
outflow tracts of ventricles
definitive structure of prox segment of bulbus cordis
R vent
definitive structure of primordial vent
L vent
definitive structure of primordial atrium
L and R auricles and trabeculated portions of aorta
definitive structure of R horn of sinus venosus
sinus venarum (smooth walled part of RA)
definitive structure of L horn of sinus venosus
coronary sinus
definitive structure of primordial pulm v and brs
smooth walled portions of LA
