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68 Cards in this Set

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When does partitioning occur?
Weeks 5-8
4 Cardiac tissues used for partitioning:
-Cardiac muscle
-Cardiac mesenchyme
-Extracardiac Mesenchyme
-Neural crest
What does partitioning of the heart accomplish?
It separates the R/L sides
What exact Cardiac mesenchyme contributes to partitioning?
Endocardial Cushion Tissue
What is the origin of the Extracardiac mesenchyme that contributes to the heart forming?
Mesoderm (splanchnic, but outside the forming heart)
What doesthe Definitive Right Atrium develop from?
-Primitive Right Atrium
-Sinus Venosus
How does the opening of the Sinus Venosus change as the early right atrium develops?
Each horn contributes to form a COMMON opening into the Right atrium
What happens to the Left horn of the sinus venosus?
It atrophies - develops 2 tributaries:
-Left brachiocephalic vein
-Inferior vena cava
What is the common sinus opening into the atrium called?
Sinoatrial Opening
What does the Sinus Venosus ultimately become?
Smooth portion of the right atrium
What does the Coronary Sinus develop from?
Left horn of SV
What develops from the Rt valve of the SV?
-Crista terminalis
-Valve of IVC
-Valve of CS
What does the smooth portion of the RA develop from?
Sinus venosus
What does the IVC (minus the valve) develop from?
Rt vitelline vein
What does the valve of the IVC develop from again?
Rt valve of the SV
What does the Smooth portion of the LA develop from?
Resorbed pulmonary veins
What does the trabeculated portion (auricle) of LA develop from?
Primitive left atrium
What is the initial connection from atria to ventricles like?
Common - called the Common AV canal
Where exactly is the common AV canal situated initially?
Between the LEFT atrium/ventricle.
What is the result of the AV canal only being on the left initially?
There is no inflow to the RIGHT VENTRICLE initially - it must be established.
What is the site where remodeling opens the right atrium/ventricle passageway.
Inner Curvature
What cellular process accomplishes formation of a right AV canal?
MYOCARDIALIZATION
What is myocardialization?
Transformation of Endocardial Cushion tissue into Cardiac Muscle.
What cells form the partitioning of the heart?
Cardiac mesenchyme
How does Cardiac mesenchyme form?
By signals for the endocardial lining of the heart to bud off and form Endocardial Cushion tissue
Where does Cardiac mesenchyme form?
2 REGIONS:
-Common AV canal
-Outflow region
Where are the Endocardial Cushions and Bulbar ridges?
Endocardial cushions: AV canal
Bulbar ridges: Conus/Truncus
What ARE the endocardial cushions and bulbar ridges?
Expanded areas of Cardiac Jelly
What are the 2 endocardial cushions that form?
-Ventral (inferior)
-Dorsal (superior
What happens to the Superior and inferior cushions?
They fuse to form the Septum Intermedium
What is accomplished by formation of the Septum Intermedium?
Separate Right and Left AV canals
What important relationship remains constant as the heart grows?
Distance between the septum intermedium and Muscular Interventricular septum.
What 3 structures are derived from Endocardial cushion tissue?
-Valve leaflets
-Chordae tendinae
-Fibrous cardiac skeleton
2 portions of Interventricular septum that develops:
-Muscular
-Membranous
What makes up most of the IVS? What is it made of?
Muscular portion - Cardiac muscle
What type of tissue is the Membranous portion of IVS made from?
Fibrous Connective tissue (ECT)
What does the Muscular portion of the IVS develop from?
Trabeculae - a buildup of cardiac muscle
Where does the Muscular IVS form?
Between the Left primitive ventricle and Right ventricle portion of the bulbus cordis.
What is the Membranous IVS formed from? (tissue/area)
Endocardial Cushion tissue
-Bulbar region
-Septum intermedium (AV canal)
What happens in order for the membranous IVS to form?
The endocardial cushions FUSE together, and with the top part of the muscular portion of IVS.
What hole remains in the membranous IVS?
Primary Interventricular Foramen
So what's important to remember about formation of the Membranous IVS?
IT NEVER CLOSES ALL THE WAY - it leaves the small PIF
What are the upper/lower borders of the IVF?
Upper: septum intermedium
Lower: Top of muscular IVS
Why is the Primary IVF never closed?
Because it is the AORTIC OUTFLOW from the left ventricle - opens into the aortic vestibule.
What other hole is in the Aortic vestibule?
Secondary IVF
What does the Secondary IVF connect?
Aortic Vestibule (outflow) to the Right Ventricle
What will happen to the 2dary IVF?
This one will get closed by ECT.
What is the area of cushion tissue that closes off the 2ndary IVF called?
MEMBRANOUS IVS
When does the 2ndary IVF close?
LAST - this is the last section of the heart to partition.
How does the Interatrial septum form?
By developing Two Septa and 2 ostiums
What does the septum primum become?
The valve that closes Foramen ovale
What does the first ostium become?
It gets closed off by endocardial cushion
What does the 2nd septum (septum secundum) form?
The superior border that leaves an inferior opening called Foramen ovale
What is the function of the interatrial septum in utero?
It acts as a one-way valve that allows blood to flow from RA to LA and bypass pulmonary circuln.
What is the adult derivative of the Conus Cordis?
The L/R Ventricle outflow regions - SMOOTH PARTS
What is the adult derivative of the Truncus Arteriosus?
Aortic and Pulmonary Semilunar valves
What is the adult derivative of the Aortic Sac?
Aortic and Pulmonary Trunks
What allows the division of the cardiac outflow area into a Pulmonary trunk & Aortic trunk?
The presence of Bulbar Ridges of endocardial cushion tissue.
What are the Bulbar ridges and where are they?
Swellings of cushion tissue
-2 in Conus (ventral/dorsal)
-2 in Truncus (superior/inf)
What happens to the Bulbar ridges?
They fuse all together to form the Conotruncal septum.
How are the ridges in the conus oriented w/ respect to truncus?
At right angles - so the formation of the septum has a spiral to it.
What is the wall of the Aortic Sac made of?
Smooth muscle
What allows partitioning of the Aortic Sac into an Aortic outflow and Pulmonary outflow?
Invasion of Neural Crest - forms a new septum
What septum develops from Neural Crest in the Aortic Sac?
Aorticopulmonary Septum
What does the Aorticopulmonary Septum divide the Aortic Sac into?
2 compartments:
-Aortic root is dorsal
-Pulmonary root is ventral
What happens to the aorticopulmonary septum after it develops?
It fuses with the Conotruncal septum so the roots are combined with trunks.
What 3 structures make up the Membranous IVS?
-Inf border of Dorsal Conotruncal Septum
-Inf edge of Septum intermedium
-Sup edge of muscular IVS
What does formation of the Membranous IVS do?
Closes off the secondary IVF