lec 4 Flashcards
Cardiac Skeleton is
Dense fibrous CT framework lies
at the junction of the atria with the ventricles.
Cardiac Skeleton is in the form of
4 rings:
4 rings of Cardiac Skeleton
- Right fibrous ring (of tricuspid valve)
- Left fibrous ring (of Mitral valve)
- Fibrous ring of pulmonary valve
- Fibrous ring of aortic valve
Functions of Cardiac Skeleton
1- Supports the valves.
2- Electrically separating atria from ventricles.
Operation of the atrioventricular (AV) valves of the heart
- B returning to the atria puts pressure against AV valve > AV valve opens
- As the ventricular fill , the AV cusps
hang limply into ventricles - atria contract , forcing ++++ B into ventricles
- ventricles contract forcing b against AV valve cusps
- AV valve close
- chordae tendineae tighten preventing
valve cusps from everting into artria
Operation of the semilunar
of the heart
- as a ventricles contract and intraventricular P ↑ > B is pushed up against semilunar valve forcing them to open
- as a ventricles relaxed and intraventricular P ↓ B flows back from arteries → filling the cusps of semilunar valves close
The “lub” is produced by the
the closing of the AV valves at the start of
ventricular systole
The “dup” is produced by the
closing of the semilunar valves at the
end of ventricular systole
Nerve supply of the heart By
cardiac plexus
cardiac plexus branches from
sympathetic & parasympathetic fibers
Cardiac plexus lies superficially
inferior to aortic arch
Cardiac plexus lies deeply
between aortic arch and trachea
The parasympathetic fibers arise from
the vagus nerves.
The sympathetic fibers arise from
the cervical & upper thoracic ganglia of
sympathetic trunks.
Sympathetic Fibers function
increases heart rate & force of contraction.
Parasympathetic Fs
decreases heart rate, decreases force of contraction, & constricts the coronary arteries.
The beating of the heart is regulated by
the intrinsic conduction (nodal) system
intrinsic conduction (nodal) system function
to ensure that the chambers of the heart
contract in the proper rhythm and sequence
The cardiac pacemaker is
sinuatrial (SA) node.
SA node is located at
superior end of the crista terminalis at the junction of the SVC and the right atrium.
SA node is called
the pacemaker of the heart, because it generates the impulse
The atrioventricular (AV) node is located at
the junction of the atria and the ventricles, near the opening of the coronary sinus.
atrioventricular (AV) bundle (bundle of His) is located in the
interventricular septum
atrioventricular (AV) bundle (bundle of His) Divided into
right and left bundles to the right and left ventricles
atrioventricular (AV) bundle (bundle of His) terminates with
purkinje fibers
The heart contraction begins with
an electrical impulse in the SA node.
The impulse spreads
the two atria and triggers their contraction → it reaches the AV node → AV bundle → Purkinje fibers
Purkinje fibers
triggers ventricles contraction
