Circulatory System Development I Flashcards
Percentage of congenital defects that are heart defects
20%
Most common heart defect
Ventricular septal defect
Percentage of congenital heart defects w/ unknown cause
85%
Percentage of heart defects have genetic basis
10%
Down syndrome is assoc. w/ congenital heart defects in ___ percentage of cases
50%
Percentage of congenital heart defects caused by teratogens
5% of cases
What kind of drug is assoc. w/ heart defects
Lithium
Maternal diseases that affect heart formation
Diabetes and German measles
How long does embryo obtain nourishment via simple diffusion
Through 2nd week
First organ system to develop
Cardiovascular system formed primarily by extraembryonic and intraembryonic mesoderm
Mesenchymal cells
. Primary CT cells in extraembryonic and intraembryonic mesoderm form clumps
Blood islands
. Clumps in mesoderm
. Coalesce to form primitive blood vessels lined w/ endothelial cells and filled w/ primitive blood cells
. smooth muscle and CT of blood. Vessels form later from same mesoderm
Primitive blood vessels connect the embryo to vessels in the ____
Yolk sac (Vitelline vessels) and the placenta (umbilical vessels)
Blood flows out to embryo proper in ____ that fuse caudally to form ___
. Paired dorsal aortae
. Single dorsal aorta
Cardinal veins
. Carries blood back from embryo proper
Heart development begins as paired ______
Cardiogenic cords in the intraembryonic splanchnic mesoderm in the cardiogenic area
Cardiogenic area
. Originally lies cranial to oropharyngeal membrane
. Comes to lie in area of future thoracic cavity when embryo undergoes folding
Cardiogenic cords develop lumens and become ____
Paired R and L endothelial heart tubes
Heart tubes
. Formed only of endothelium, but cardiac muscle and CT layer develop later from surrounding mesoderm
. Non-cellular layer of cardiac jelly lies immediately external to the endothelium
. Mucopolysaccharide-rich layer is later invaded by endothelial cells forming endocardium cushion tissue that helped form heart valves
. Tubes fuse together to form a single heart tube
Single heart tube
. Connected to embryonic vessels and vessels in the umbilical cord and yolk sac
. Heart tube elongates and develops various dilutions and constrictions
Sinus venous (SV)
. Received blood from Vitelline, cardinal and umbilical veins via sinus horns
Common atrium (A)
Single chamber
SV and A constitute the ____
Venous (caudal) region
Primitive ventricle (V)
. Single chamber
. Called primitive L ventricle when it develops trabeculae Carneae
Constriction btw primitie atrium and primitive ventricle becomes ___
Coronary (AV) sulcus
Atrioventricular canal
Channel btw common atrium and primitive ventricle
Bulbus cordis (B)
. Prox. Portion develops trabeculae carneae and becomes primitive R ventricle
. Distal portion adjacent to truncus arteriosus (TA) is called conus cordis
truncus arteriosus (TA) leads into ___
. Right and left aortic arches that connect to dorsal aortae
Arterial (cranial) region
V, B, and TA
Day primitive heart starts to beat and how
22 by peristaltic contractions that begin at sinus venosus and push blood through heart
T/F primitive heart contractions DO NOT require innervation or development of conducting system
T
Looping process of heart
. Heart grows and forms S-shaped loop that projects anteriorly
. Venous end of heart moves cranially by moving dorsal to arterial end
Formation of visceral and parietal pericardium
. After embryo folds, developing heart lies dorsal to portion of intraembryonic celom that will form pericardial sac
. Sac grows ant. And it pushes into the intraembryonic celom forming this
Because of heart looping, venous portions of the heart form _____ and primitive ventricle projects ____ and the truncus arteriosus exits pericardial sac ____
. Form base of heart
. Projects ant.
. Superiorly
What weeks does partitioning of the heart into 4 chambers begin?
Week 4
Initial separation of the primitive atrium
. After heart tube, the truncus arteriosus located anteriorly presses on the common atrium (post. To the truncus arteriosus)
. Protrusion of truncus arteriosus into the common atrium divides the chamber into primitive R and L atria (no septum formed)
. Opening of sinus venosus shifts from midline to right so sinus venosus only opens into R atrium
Path of blood flow through developing heart at time of initial separation of primitive atrium
.sinus venosus primitive R atrium . Primitive L atrium . Atrioventricular canal . Primitive left ventricle . Primitive R ventricle (caudal part of bulbus cordis) . Conus cordis (cranial part of bulbus cordis) . Truncus arteriosus . Aortic arches
Atrioventricular canal shift
. Originally lies btw primitive left atrium and primitive L ventricle then shifts from left side to midline
. Blood passes from primitive atria into both of the primitive ventricles
Valve formation
. Endocardial cushions derived from cardiac jelly project into undivided AV canal
. Cushions fuse and divide the canal into R and L AV openings
. Tri/bicuspid valves will eventually form tissue of endocardial cushions and control blood flow through the R and L AV canals
Formation of the definitive R atrium
. Opening btw R atrium and sinus venosus enlarges so right horn of sinus venosus becomes incorporated into wall of R atrium
. Primitive R atrium represents by portion of R atrium and auricle lined w/ musculi pectinati
. Sinus venosus becomes smooth post. Wall in adult R atrium
. Left horn of sinus venosus becomes coronary sinus
Formation of definitive L atrium
. As lungs form, the primitive L atrium send vein buds out to each lung
. These buds branch out and enlarge
. Initial portion of pulmonary veins becomes incorporated into developing L atrium forming its wall
. The L auricle is the only remnant of primitive L atrium
Foramen (ostium) primum
. Opening btw R and L atrium
. Originally very large
Septum primum
. Membrane that grow inf. From the roof of the common atrium
. Separates R and L atria and closes the foramen primum as it grows toward endocardial cushions and then fuses w/ cushion
Foramen (ostium) secundum
. Before primum disappears the sup. Portion degenerates and this a opening appears
. Degeneration of septum primum involves apoptosis
. Blood flows from R atrium into L atrium through this
Septum secundum
. Second membrane that grows down from atrial roof directly adjacent to septum primum
. More rigid than septum primum
. Grows until it covered foramen secundum but doesn’t form completely wall btw atria
. Oval opening present at inf. End (foramen ovale)
T/F septum primum overlaps foramen ovale so there is not a direct line btw foramen secundum and foramen ovale
T, look moves obliquely through interatrial septum prenatally
How blood passes from R to L atrium
. Goes through foramen ovale and then through foramen secundum by pushing down portion of septum primum that covers foramen ovale
What occurs to septum primum a and secundum after birth?
. Fuse due to shifting in pressure dynamics of the heart from beginning of respiration in newborn
. L atrium has high pressure than R atrium
. Pressure difference forces septum primum against secundum so that they fuse into solid structure closing the openings btw atria
Atrial septal defect (patent foramen ovale)
. Common
. Ostium primum type: foramen primum remains open from inadequate septum primum or endocardial cushions growth, located inf. On interatrial septum close to cushions
. Foramen secundum: excessive resorption of septum primum during development resulting in large foramen secundum OR inadequate septum secundum development resulting in large foramen ovale, or combo of both
Atrial septal defects allow ____
Shunting of blood btw R and L atria mixing oxygenated and deoxygenated blood
What happens immediately after birth with atrial septal defects?
. Blood shunts from high pressure L atrium to R atrium
. Reactive pulmonary vasoconstriction from volume loading on R side
. Inc. resistance o right side causes secondary inc. in pressure in R atrium
. Shunt will change direction from left-to-right to right-to-left forcing more deoxygenated blood into L atrium and ventricle
. Eventually causes death due to ischemia in organs like kidney and liver
