LEC 19: Heart Flashcards
What are the 4 chambers of the heart
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
What are the 4 valves of the heart and what do they separate
Tricuspid Valve (separates RA/RV)
Pulmonic Valve (separates RV/pulmonary artery)
Mitral (Bicuspid) Valve (separates LA/LV)
Aortic Valve (separates LV/aorta)
What are the primitive tissues that form the heart
- Heart primordium (cardiac mesoderm)
- Forms cranial to neural plate
Cross Section
- Intra/extra embryonic coelom communicate
- along entire region of the fetus pairs of blood vessels are forming from angioblastic cords–paired aorta that will fuse to eventually form the AORTA
Lateral Section
- Cardiac mesoderm
- Pericardial coelom will eventually engulf the heart
- Septum transversum
- Head fold will bring heart into chest
Angioblastic cords
Angioblastic cords form paired heart tubes, and eventually fuse to form a single tube
Blood islands form primitavely on the surface of the yolk sac, coallesce to form a network of arteries and veins
- arteries and veins communicate with embryonic circulation via vitelline veins/arteries (empty into caudal end of heart tube)
- heart tube forms from fusion of 2 endocardial tubes, then folds upon itself (heart)
- blood vessels coming from placenta
- 2 umbilical arteries
- 2 umbilical veins (1 disappears)
- these also empty into caudal heart tube
Common cardinal vein
- anterior cardinal vein
- posterior cardinal vein
- drain upper and lower portions of embryonic body
Components of Primitive Embryonic Heart Tube (cranial to caudal)
- Aortic sac
- Truncus arteriosis
- Bulbus cordis
- Primitive ventricle
- Primitive atrium
- Sinus venosus (veins entering into here from placenta)
Single Heart Tube
- genes telling heart to fold, more cells proliferating on one side of heart type
- cranial folding assists with fold
- sinous venous, primitive atrium, primitive ventricle, bulbous cordis, truncus arteriosus, aortic sac
What separates primitive atrium from primitive ventricle
- endocardial cushions that grow toward each other
- divides AV canal into (2) AV canals
- partition primitive atrium from primitive ventricle
- play role in formation of mitral and tricuspid valve
Ventricular Septal Defect (VSD)
- common congenital heart defect
- opening in ventricular septum that allows oxygen rich and oxygen deficient blood to mix
How to Right and Left Ventricle get separated (interventricular septum)
- Interventricular septum (muscular growth of thick cardiac mesoderm inward toward endocardial cushion)
- Membranous tissue (thin layer of tissue that grows inward medially, meets up with interventricular septum)
Papillary muscles
- whisps of tissue attached to endocardial tissue of the fused endocardial cushions are valves
- valves held in place by papillary muscles
- prevent valves from prolapsing into atrium
Mitral Valve Prolapse: leaflets of mitral valve (between LA/LV) bulge (prolapse) upward or back into left atrium as heart contracts; blood may leak backward into left atrium (mitral valve regurgitation)
Division of primitive atrium (overview)
- Septum primum
* foramen secundum - Septum secundum
* foramen ovale
Septum primum
- primary division of atrium
- starts from posterior wall of primitive atrium
- grows toward endocardial cushions
- fenestrations form in septum primum during development of septum secundum
- these fenestrations will give rise to foramen primum and foramen secundum
foramen primum
- foramen primum eventually grown over/obliterated
- only opening left in septum primum is the formen secundum
Patent Foramen Ovale (PFO)
- congenital atrial septal defect
- if young person has a stroke, should suspect PFO
Septum secundum
- forms after septum primum
- faces right atrium (while septum primum faces left atrium)
- foramen ovale forms in septum secundum
foramen ovale
- forms in septum secundum
- Right to Left Atrial shunt
- allows blood to bypass the fetal lungs
- close after birth when
- pulmonary vascular resistance decreases
- left atrial pressure increases
Great Vessels
- aorta (left ventricular outflow tract)
- pulmonary artery (right ventricular outflow tract)
Formation of great vessels
- conotruncal ridges (aka: bulbar and truncal ridges) form in the truncus arteriorsis and part of the bulbus cordis)
- cranial most part of the cardiac tube
- aorticopulmonary septum (dividing aorta from pulmonary trunk)
- 180 degree spiraling results in separation of aorta and pulmonary artery, but they are hugging still
- Formation
- aorta (left ventricular outflow tract)
- pulmonary artery (right ventricular outflow tract)
Which is more dorsal/ventral, aorta or pulmonary trunk
AORTA = more dorsal
PULMONARY TRUNK = more ventral
Formation of aortic and pulmonic valves
- semilunar valves
- aortic
- pulmonic
- conotruncal ridges meet interventricular septum (IVS)
- three subendocardial swellings for each valve
- remodeled to form three (3) thin-walled cusps
Formation of atrioventricular valves
- Tricuspid (RA/RV)
- Mitral (LA/LV) (also called bicuspid)
- develop from proliferation of tissue around endocardial cushions/AV canals
Dorsal Aorta
- initially a pair of tubes
- first fuse to form cardiac tube —> primitive heart
- next, fuse to form single dorsal aorta
- connect with aortic arches (cranial region)
- aortic arches connect to the aortic sac in the primitive heart tube
Paired dorsal aorta
- each paired arch of the dorsal aorta is associated with a pharyngeal arch
- these arches connect to the aortic sac
- 6 pairs of arches develop, but not all at same time
Fate of the 4th and 6th Left Aortic Arches
- 4th Left Aortic Arch
- part of aortic arch
- 6th Left Aortic Arch
- left pulmonary artery and ductus arteriosis
ductus arteriosis
- shunts blood away from lungs in the fetus
primitive cardiac veins
- 3 pairs of primitive veins
- vitelline veins
- umbilical veins from placenta
- common cardinal veins from the body of the embryo
- all three pairs of veins empty into the sinus venosus
What are the oxygen contents of the three (3) primitive veins
- vitelline veins drain the yolk sac (low O2)
2. umbilical veins from placenta (high O2)
- common cardinal veins from the body of the embryo (low O2)
What do vitelline veins do
drain the yolk sac (low O2)
What do umbilical veins do
Bring oxygen rich blood to fetus
What do common cardinal veins do
carry oxygen poor blood from the body of the embryo
What is the fate of the primitive veins
- very complex
- high degree of variability between individuals
What are the important derivatives of the veins
- right umbilical vein
* disappears - left umbilical vein
- umbilical vein within umbilical cord
- ductus venosus
- superior vena cava
- right anterior cardinal vein
- right common cardinal vein
ductus venosus
shunts blood away from fetal liver
What is the derivative of the right umbilicial vein
NOTHING; it disappears
What does the left umbilical vein derive from
- umbilical vein within the umbilical cord
- ductus venosus
What does the superior vena cava derive from
- right anterior cardinal vein
- right common cardinal vein
Tetralogy of Fallot (TOF)
(aka: most common cause of blue baby syndrome)
- congenital heart defect, 4 abnormalities of heart
1. pulmonary stenosis (narrowing)
2. ventricular septal defect
3. overriding aorta
4. right ventricular hypertrophy (enlargment of muscles of right ventricle) - unequal partitioning of the truncus arteriosis
