The heart and great vessels Flashcards
What is the base of the heart?
Its posterior surface where it is attached to the great vessels
Where are the surface markings on the right border of the heart?
Right 3rd to 6th costal cartilages
Where are the surface markings on the left border of the heart?
Left 2nd costal cartilage to 5th intercostal space
Where is the auscultation point for the pulmonary valve?
2nd and 3rd left intercostal spaces
Where is the auscultation point for the aortic valve?
2nd right intercostal space radiating up to the neck
Where is the auscultation point for the mitral valve?
Apex, 5th intercostal space, mid-clavicular line
Where is the auscultation point for the tricuspid valve?
Lower left sternal edge, may also be heard on the right
How are the chambers of the heart separated?
The heart is divided longitudinally into right and left halves by a vertical septum lying almost in the coronal plane. Atria are divided from ventricles by the coronary (atrioventricular) groove lying almost in the sagittal plane
What forms the right border of the heart?
The right atrium with its auricle as a triangular, muscular structure pointing to the left
What forms the anterior surface of the heart?
Mostly the right ventricle
What forms the left border of the heart?
Left atrium
What forms the apex of the heart?
Left atrium
Where is the left atrium located within the heart?
At the base of the heart posteriorly but sends its auricle around the left upper aspect of the left ventricle
What proportion of the anterior surface of the heart is formed by the right ventricle?
2 thirds (1 third LV)
What proportion of the inferior (diaphragmatic) surface of the heart is formed by the left ventricle?
2 thirds (1 third RV)
Where do the coronary arteries arise from?
They arise as the first branches of the aorta, from the aortic sinuses above the right and left cusps of the aortic valve
Describe the path taken by the right coronary artery
Arises from the right aortic sinus and passes between the pulmonary trunk and the right auricle.
It runs downwards and backwards in the coronary (atrioventricular) groove
What are the branches from the right coronary artery?
Right marginal
Posterior interventricular
Nodal branches
Where does the right marginal artery run?
Along the inferior border of the heart
What does the posterior interventricular artery supply?
The ventricles and septum
What percentage of the population are right cardiac dominant?
90%
In what proportion of people does the nodal branch from the RIGHT coronary artery supply the SAN?
60%
In what proportion of people does the nodal branch from the LEFT coronary artery supply the SAN?
40%
In what proportion of people does the nodal branch from the RIGHT coronary artery supply the AVN?
90%
In what proportion of people does the nodal branch from the LEFT coronary artery supply the AVN?
10%
Describe the path of the left coronary artery?
Arises from the left aortic sinus and passes between the pulmonary trunk and the left auricle
What are the branches from the left coronary artery?
Anterior interventricular
Circumflex
Nodal branches
Describe the path taken by the anterior interventricular artery
Descends into the anterior interventricular groove, then turning backwards into the posterior interventricular groove
What is another name for the anterior interventricular artery?
Left anterior descending artery
Where does the circumflex artery travel?
Passes around the left edge of the heart in the coronary (atrioventricular) groove between the left atrium and left ventricle
In left cardiac dominance where does the posterior interventricular artery come from?
How common is this?
Branch from the circumflex artery
10%
What is the function of the cardiac veins?
Return blood from the muscular wall of the heart
Where do the coronary arise from?
From the coronary sinus which runs in the posterior atrioventricular groove. It enters the lower aspect of the right atrium, just to the left of the inferior vena caval opening
What are the cardiac veins?
- The great cardiac vein
- Middle cardiac vein
- Small cardiac vein
- Anterior cardiac veins
- Venae cordis minimae
Where does the great cardiac vein run?
In the anterior interventricular groove and follows the route of the circumflex artery in the atrioventricular groove
Where does the middle cardiac vein run?
In the posterior interventricular groove
Where does the small cardiac vein run?
With the right marginal artery
Where does the anterior cardiac vein drain?
Directly into the right atrium
What are the venae cordis minimae
Very small veins opening into all the chambers, especially the right atrium, and which account for 20-30% of all drainage
How do the vagus nerves supply the heart?
From their cervical and thoracic branches, provide parasympathetic innervation via the superficial and deep cardiac plexuses
Where does the cervical sympathetic chain sends branches from?
Each ganglion and local branches from T1-5 thoracic ganglia
What are the 2 autonomic contributors to the heart?
Where do they converge?
Vagus nerves and sympathetic chain
On the two cardiac plexuses which function as one unit and are found around the tracheal bifurcation and ligamentum arteriosum
Where does the right atrium receive deoxygenated blood from?
The two venae cavae, the coronary sinus, and the anterior cardiac veins
Where is the smooth walled part of the right atrium derived from?
The sinus venosus
What is the non-smooth portion of the right atrium?
The auricle ridged by musculi pectinati
How is the musculi pectinati delineated from the sinus venosus?
The crista terminalis
What is the counterpart of the crista terminalis?
Sulcus terminalis
Where is the fossa ovalis?
On the septum forming the posterior wall
this was the site of the foramen ovale
Where is the opening of the coronary sinus in relation to the foramen ovale?
Inferior
Where is the SAN located within the right atrium?
The upper end of the crista terminalis, to the left of the superior vena cava, where auricle meets atrium
Where is the AVN located within the right atrium?
On the septum just above the tricuspid valve
How is random propagation of conduction to the ventricles prevented?
A figure-of-eight fibrous skeleton which supports the atria on one side, the ventricles on the other, and the valves in between
Where does the bundle of His run?
Through the fibrous skeleton into the interventricular septum where it divides into left and right bundles to supply each ventricle.
The right bundle also sends a branch across the moderator band (or septomarginal trabecula) to the anterior wall of the right ventricle
What is another term for the moderator band?
Septomarginal trabecula
Where are the cusps of the tricuspid valve located?
Anteriorly, posteriorly, and on the septum
What is the purpose of the chordae tendinae?
Prevent the valve cusps from everting back to the atria
How do the chordae tendinae act on the cusps?
Each papillary muscle sends chordae to two cusps, drawing them together on contraction
Describe the appearance of ventricular muscle
Ridged by trabeculae carneae, and the moderator band may be seen.
The inner surface is smooth towards its outflow at the infundibulum
Why is the inner surface of the ventricle smooth towards its outflow at the infundibulum?
To create laminar blood flow into the pulmonary trunk
Which valves have chordae tendinae and papillary muscles?
AV valves
How do the trabeculae carneae on the left ventricle compare with those on the right ventricle?
They are finer and more numerous on the left
How many cusps does the mitral valve have?
2 (anterior and posterior)
How many cusps does the aortic valve have?
3
How many cusps does the pulmonary valve have?
3
Where is the anterior cusp of the mitral valve?
Between the mitral and aortic orifices
How much thicker is the wall on the LV than on the RV?
3 times
How does the left ventricle appear in cross section?
Circular with the right ventricle wrapped round it as a crescent
In the fetus, how is de-oxygenated blood returned to the placenta?
Via two umbilical arteries from the superior vesical or internal iliac arteries
How is oxygenated blood returned to the fetus?
Via the left umbilical vein that joins the left branch of the portal vein in the region of the porta hepatis.
Some of the blood passes into the liver, but the majority bypasses it via the ductus venosus onto the inferior vena cava and right atrium
Is there a low or high resistance in fetal pulmonary vasculature?
Why is this?
High
The high resistance of the pulmonary vasculature leads to a high pulmonary arterial pressure which exceeds the systemic arterial pressure, so the blood flows via the ductus arteriosus into the aortic arch beyond its main branches
What does the blood passing through the foramen ovale supply?
The coronary arteries, and the head and upper limbs via the main branches of the aortic arch.
Thus the brain and the heart get the benefit of this well-oxygenated blood.
Where does deoxygenated blood travel in the fetus?
Returns to the right atrium via the superior vena cava.
It passes directly into the right ventricle and out into the pulmonary trunk
What happens to the lungs as a baby takes its first breath
The lungs expand, decreasing the pressure in the pulmonary vasculature so that the output of the right ventricle now passes to the lungs. This leads to an increased return of oxygenated venous blood to the left atrium
What causes the closure of the foramen ovale?
As left atrial pressure rises, the septum primum is pressed against the septum secundum
What happens to the ductus arteriosus after birth?
As the ductus arteriosus is not needed for shunting blood from right to left sides of the heart, functional closure occurs over several hours due to decreasing maternal prostaglandin levels and release of bradykinin from the lungs.
It becomes the ligamentum arteriosum
What causes the closure of the umbilical vein?
Clamping of the umbilical cord
What happens to the ductus venosus as it closes?
Closes over hours or days and becomes the ligamentum venosum.
