Heart development Flashcards
The heart tube remains attached to the dorsal side of the pericardial cavity by
the dorsal
mesocardium
• Later, dorsal mesocardium disappears forming————————- which connects both sides of the pericardial cavity
the transverse sinus of the pericardium
Development of heart & embryonic blood vessels begin —————-
week of gestation.
during the 3rd
Cardiac progenitor cells lies in
These cells lie in the epiblast
They migrate through the
primitive streak
Cells reside within the
splanchnic (visceral) layer of lateral plate mesoderm (Cardiogenic field).
• The cells lie——-the buccopharyngeal membrane and
neural plate
anterior to (rostral)
The heart primordium arises predominantly from
splanchnic layer of lateral plate
mesoderm
The progenitor cells are transformed into
the cardiac myoblasts
The cardiac myoblasts will later form the
myocardium of the heart
Vasculogenesis : Blood islands appear in the splanchnic layer of mesoderm
to form the blood cells and
blood vessels
• The blood islands unite and form a
horseshoe-shaped endothelial-lined heart tube
surrounded by myoblasts
The horseshoe-shaped cardiogenic cords is s surrounded
myoblasts
The intraembryonic cavity over the cardiogenic field develops into the
pericardial
cavity
The horseshoe-shaped cardiogenic cords later develop into
2 endothelial –lined
tubes
Effect of cephalic and lateral folding After cephalic folding, the cardiogenic area becomes———
buccopharyngeal membrane
ventral & caudal
• After the lateral folding, the 2 endocardial tubes except at most —— end
fuse ———— caudal
• Most caudal regions
receive the venous drainage (inflow tract).
Most cranial region
expand and join to the 2 dorsal aortae (outflow
tract)
The developing heart bulges more into the
pericardial cavity
The heart tube remains attached to the dorsal side of the pericardial cavity by
the dorsal
mesocardium
Later, dorsal mesocardium disappears forming ————————–which connects both sides of the pericardial cavity
the transverse sinus of the pericardium
Formation of the Primitive 4 Chambered Heart: Single heart tube——
elongates.
It has 2 ends
caudal & cranial ends
• Bulges (dilatations) appear forming
4 chambers
Sinus venosus (RT & LT horns):
receives blood from veins
4 chambers are:
a) Sinus venosus (RT & LT horns) veins.
b) Primitive single atrium.
c) Primitive single ventricle.
d) Bulbus cordis
Bulbus cordis: it leads into
2 dorsal aortae.
Layers forming wall of heart :
- Endocardium
- Myocardium
- Epicardium
Endocardium develops from
the vascular endothelium
Myocardium develops from
the myoblasts
Epicardium develops from
the mesothelial cells migrating from
the sinus venosus
—————-separates the endocardium from the myocardium
Layer of extracellular matrix ( Cardiac jelly)
Causes: continuous elongation
cell shape
different rates of growth in the
of the heart tube
changes
heart tube
The cephalic portion of heart tube bends
ventrally, caudally and to right
The caudal part
shifts dorso-cranially and to the left
When Cardiac looping star to form ?
starts by day 23 & ends by day 28
—– shaped then ——shaped tube is formed
u then s
Narrow atrioventricular canal connects the primitive
atrium & ventricle
Bulboventricular sulcus (between
the bulbus cordis & the ventricle
Proximal 1/3 of bulbus cordis give
trabeculated part (Rough part) of right ventricle.
middle part of bulbus cordis is called
Conus cordis
Middle 1/3 of bulbus cordis (conus cordis ) give
outflow tracts of both ventricles (aortic vestibule &pulmonary infundibulum
Distal 1/3 of bulbus cordis is called
truncus arteriosuis
Distal 1/3 truncus arteriosus of bulbus cordis give
the roots and the proximal part of the aorta and
pulmonary trunk.
junction between the
ventricle and bulbous cordis give
primitive interventricular foramen internally and sulcus
externally
Trabeculated Primitive ventricle will give
Primitive left ventricle
Trabeculea are formed ——– & ———– to the primary interventricular
foramen
proximal - distal
Trabeculated proximal 1/3 of bulbus
cordis
Primitive right ventricle
The sinus venosus is cavity receiving venous
blood from RT & LT horns, each horn receives
3 main veins:
- Common cardinal vein (CCV) from body of
the embryo. - Umbilical vein (UV) from the placenta.
- Vitelline vein (VIT) from the yolk sac.
Umbilical vein (UV) from the placenta carry ——–blood
oxygenated
Blood shunt from—— to —— resulting in
left to right
Most of the veins of the Lt Horn are
obliterated
The—– horn of sinus venosus becomes very small after obliteration
left
The right sinus horn ——–after obliteration of left horn
enlarges
The sino-atrial opening shifts to the—— and opens
into the future ——- atrium
right - right
The veins of the LT horn obliterates except for —–
part of the ——–vein that persists to carry
oxygenated blood from the placenta to the fetus
distal - left umbilical
remains of the left sinus
horn give
1.the oblique vein of left
atrium
2.the coronary sinus.
body & right sinus horn
smooth part of Rt. atrium
right common cardinal vein give
SVC
right vitelline vein
IVC
The entrance of sinus venosus is guarded by —–
valves (right & left)
valves fuse cranially to form the
septum spurium
• Left venous valve + the septum spurium fuse with the
inter-atrial septum
Right venous valve the superior part ———inferior part gives ———
disappears - inferior part gives the valves of IVC and coronary sinus
a line demarcating the smooth and the rough parts of the right atrium.
The crista terminalis
body & right sinus horn give
smooth part of the right atrium
absorbed parts of pulmonary veins give
smooth posterior part of left atrium
common atrium gives ——————-and————
trabeculated part of the Rt. Atrium
trabeculated part of the Lt. Atrium( Left auricle )
Formation of Cardiac septa
In… 4 things
- Atrio ventricular canal
- Common atria
- Common ventricle
- Truncus arteriorsus
- Bulbus cordis
The septa of the heart are formed at end of the ——– week
the 4th week of development.
• There are two main methods of cardiac septa formation :
- Growth of two active growing opposing masses until they fuse and divide the lumen.
- Narrow strip of the wall fail to grow while areas on each side of it expand rapidly.
Two superior and inferior A-V endocardial cushions appear at
t the borders of the A-V
canal.
Two right and left A-V endocardial cushions appear
on borders of the canal
The superior and inferior cushions project into the——— and ——resulting in a
complete division of the canal into right and left orifices
lumen - fuse
a sickle shaped crest grows from the roof of the common
atrium into the lumen
Formation of septum primum
The —– limbs of this septum extend into the direction of the ——— in the A-V
canal.
2 - endocardial cushions
The opening between the lower limbs of the septum primum and the
endocardial cushions.
Ostium primum
Before complete closure, perforations appear in the septum primum and the ————- is form when perforations fuse together.
Ostuim secundum
This ensures free blood flow from —– to —– primitive atrium
right - left
: A new crescent-shaped fold
from above down on the right side of the septum
primum
Septum secundum
When the left venous valve and septum spurium
fuse with the right side of septum secundum, the
free concave edge of the septum secundum begin
to overlap the ostium secundum.
is The opening left by the septum
secundum
oval foramen
the remaining part of
septum primum after it mostly disappears.
valve of oval foramen
———— is formed by edge of the
septum secundum
limbus fossa ovalis
——–is formed by septum
primum
floor of fossa ovale
After birth…4 things
-Pulmonary circulation starts
-The pressure in the left atrium increases
-It presses the valve of foramen oval against
-the septum secundum leading to closure of
foramen oval.
-fossa ovalis is formed
The interventricular (IV)septum has two main parts———————–and———–
muscular & membranous.
the medial walls of the expanding ventricles are apposed, merge and , this is the formation of —————
the muscular IV septum
The space between the free rim of the muscular ventricular septum
and the fused endocardial cushions.
• Interventricular foramen
Develops from the fusion between:
..inferior endocardial cushion
..conus septum.
..muscular IV septum
Membranous part of IV septum
Two opposing ridges appear in the ————–
Rt. Superior truncus swelling and Lt. inferior truncus swellings.
truncus arteriosus
on right dorsal and left ventral walls. Grow towards each other distally and fuse
with truncus septum
Neural crest cells migrate into truncal and conal swellings
• The swelling merge, fuse, twist around each other spirally.
Two swellings appear in the conus cordis
Division of the Truncus arteriosus results in
An aortic and pulmonary channels are formed.
Division of the conus results in
anterolateral outflow tract of right ventricle
(Infundibulum of pulmonary trunk)
postero-medial outflow tract of left ventricle (Aortic
Vestibule).
Fusion of the endocardial cushions forms the ———-
Atrio-ventricular Valves
•in av valve formation Each A-V orifice is surrounded by
local mesenchymal proliferations
• Blood stream thins & hollows out that from ——
But remain attached to the ventricular wall by
their ventricular surface-muscular cords
The muscular tissue in the cords degenerates and is replaced———–They are connected by the trabeculae in the wall of the ventricle————- by
means of
dense connective tissue- papillary muscles-chordae tendinae
bicuspid (mitral) valve have——leaflet
2
the tricuspid valve has——- leaflets.
3
The ——- appear as small tubercles of mesenchyme at the root of ———————————
semilunar valves-ascending aorta & pulmonary trunk.
• The —— surface is hollowed to form the valves (cusps).
upper
• Each valve (cusp) is formed of layer of ——– covered on both
surfaces by ——————–
connective tissue-endocardium (endothelial cells).
Smooth part of ventricles comes from
Middle 1/3 of bulbus cords
