Heart internal feature

1. Internal structure of the heart
Dr. Mohammed Mahmoud Mosaed

2. THE HEART
• The heart is divided by
vertical septa into four
chambers:
1. the right and left atria
2. the right and left
ventricles.
• The right atrium lies
anterior to the left atrium,
and the right ventricle lies
anterior to the left ventricle

3. Internal structure of the right atrium
• The right atrium consists of cavity and small
auricle
• The cavity of the right atrium is divided by
cresta terminalis into;
• 1. Posterior smooth part is derived
embryologically from the sinus venosus
• 2. Anterior rough part is roughened or
trabeculated by bundles of muscle fibers, the
musculi pectinati, which run from the crista
terminalis to the auricle.
• This anterior part is derived embryologically
from the primitive atrium.

4. Openings into the Right Atrium
• 1.The superior vena cava opens into the upper part
of the right atrium; it has no valve.
• 2.The inferior vena cava opens into the lower part of
the right atrium; it is guarded by a rudimentary,
nonfunctioning valve.
• 3. The coronary sinus, which drains most of the
blood from the heart wall. opens into the right atrium
between the inferior vena cava and the atrioventricular
orifice. It is guarded by a rudimentary, nonfunctioning
valve.
• 4. The right atrioventricular orifice lies anterior to
the inferior vena caval opening and is guarded by the
tricuspid valve.
• 5. Many small orifices of small veins also drain the
wall of the heart and open directly into the right atrium

7. Fetal Remnants in the right atrium
• 1. The rudimentary valve of the inferior vena cava.
• 2. The fossa ovalis and anulus ovalis. These
structures lie on the atrial septum, which separates
the right atrium from the left atrium.
• The fossa ovalis is a shallow depression, which is
the site of the foramen ovale in the fetus.
• The anulus ovalis forms the upper margin of the
fossa.
• The floor of the fossa represents the persistent
septum primum of the heart of the embryo, and the
anulus is formed from the lower edge of the septum
secundum.

8. Internal structures of the right ventricle
• The walls of the right ventricle show several internal projecting
ridges formed of muscle bundles known as trabeculae
carneae.
• The trabeculae carneae are composed of three types.
• The first type; the papillary muscles, which project inward,
being attached by their bases to the ventricular wall; their
apices are connected by fibrous chords (the chordae
tendineae) to the cusps of the tricuspid valve.
• The second type is attached at the ends to the ventricular wall,
being free in the middle. One of these, the moderator band,
crosses the ventricular cavity from the septal to the anterior
wall. It conveys the right branch of the atrioventricular bundle,
which is part of the conducting system of the heart.
• The third type is simply composed of prominent ridges

11. The tricuspid valve
• The tricuspid valve guards the atrioventricular
orifice and consists of three cusps: anterior,
septal, and inferior (posterior) cusps.
• The bases of the cusps are attached to the
fibrous ring of the skeleton of the heart,
whereas their free edges and ventricular
surfaces are attached to the chordae
tendineae.
• The chordae tendineae connect the cusps to
the papillary muscles. The chordae tendineae
of one papillary muscle are connected to the
adjacent parts of two cusps.

14. The pulmonary valve
• The pulmonary valve guards the pulmonary orifice
and consists of three semilunar cusps; one
posterior (left cusp) and two anterior (anterior and
right cusps).
• The curved lower margins and sides of each cusp
are attached to the arterial wall this attachment
prevent the cusps from prolapsing into the ventricle.
• No chordae or papillary muscles are associated
with these valve cusps;
• At the root of the pulmonary trunk are three
dilatations called the sinuses, and one is situated
external to each cusp

17. The internal structure of the left atrium
• The interior of the left atrium is smooth, but the
left auricle possesses muscular ridges as in the
right auricle
• Openings into the Left Atrium
• 1. The four pulmonary veins, two from each
lung, open through the posterior wall and have
no valves.
• 2. The left atrioventricular orifice is guarded by
the mitral valve

20. Left Ventricle
The walls of the ventricle show internal
projecting ridges formed of muscle bundles
known as trabeculae carneae.
The trabeculae carneae are composed of two
large papillary muscles, which project inward,
being attached by their bases to the ventricular
wall and their apices are connected by the
chordae tendineae to the cusps of the mitral
valve.
There is no moderator band.

22. The mitral valve
• The mitral valve guards the atrioventricular
orifice.
• It consists of two cusps, one anterior and one
posterior.
• The anterior cusp is the larger and intervenes
between the atrioventricular and the aortic
orifices.
• The attachment of the chordae tendineae to the
cusps and the papillary muscles is similar to
that of the tricuspid valve.

24. The aortic valve
• The aortic valve guards the aortic orifice.
• It has 3 cusps: One cusp is situated on the
anterior wall (right cusp) and two are located
on the posterior wall (left and posterior cusps).
• Behind each cusp the aortic wall bulges to
form an aortic sinus.
• The anterior aortic sinus gives origin to the
right coronary artery, and the left posterior
sinus gives origin to the left coronary artery

26. Conducting System of the Heart
• The pumping action of the heart (heart beat) is
controlled by the heart’s electrical system or the
cardiac conduction system. This is a group of
specialised cells located in the wall of the heart
which send electrical impulses to the cardiac
muscle causing it to contract.
• The rhythmic contractile process originates
spontaneously in the conducting system and the
impulse travels to different regions of the heart, so
the atria contract first and together, to be followed
later by the contractions of both ventricles together.

27. The conducting system of the heart
The conducting system of the heart consists of:
the sinuatrial node,
the atrioventricular node,
the atrioventricular bundle and its right and left
terminal branches
the subendocardial plexus of Purkinje fibers
(specialized cardiac muscle fibers that form
the conducting system of the heart).

29. Sinuatrial Node
• Site: located in the wall of the right atrium in
the upper part of the sulcus terminalis just
to the right of the opening of the superior
vena cava.
• The node spontaneously gives origin to
rhythmic electrical impulses that spread in
all directions through the cardiac muscle of
the atria and cause the muscle to contract.

30. Atrioventricular Node
• Site: on the lower part of the atrial septum
just above the attachment of the septal cusp
of the tricuspid valve.
• From it, the cardiac impulse is conducted to
the ventricles by the atrioventricular bundle.
• The atrioventricular node is stimulated by the
excitation wave as it passes through the atrial
myocardium.

31. Atrioventricular Bundle
• The atrioventricular bundle (bundle of His) is the only
pathway of cardiac muscle that connects the
myocardium of the atria and the myocardium of the
ventricles
• At the upper border of the muscular part of the
ventricular septum it divides into two branches, one for
each ventricle.
• The right bundle branch (RBB) reach the moderator
band, where it crosses to the anterior wall of the right
ventricle. Here it becomes continuous with the fibers
of the Purkinje plexus
• The left bundle branch (LBB) pierces the septum
and passes down on its left side beneath the
endocardium. It usually divides into two branches
(anterior and posterior), which eventually become
continuous with the fibers of the Purkinje plexus of the
left ventricle.

32. Arterial Supply to the Conducting System
• The sinuatrial node is usually supplied by the
right but sometimes by the left coronary
artery.
• The atrioventricular node and the
atrioventricular bundle are supplied by the
right coronary artery.
• The RBB of the atrioventricular bundle is
supplied by the left coronary artery;
• The LBB is supplied by the right and left
coronary arteries

33. Nerve Supply of the Heart
• The heart is innervated by sympathetic and parasympathetic fibers of the
autonomic nervous system via the cardiac plexuses situated below the
arch of the aorta.
• The sympathetic supply arises from the cervical and upper
thoracic portions of the sympathetic trunks
• The postganglionic sympathetic fibers terminate on the sinuatrial and
atrioventricular nodes, on cardiac muscle fibers, and on the coronary
arteries. Activation of these nerves results in cardiac acceleration,
increased force of contraction of the cardiac muscle, and dilatation of the
coronary arteries.
• the parasympathetic supply comes from the vagus nerves.
• The postganglionic parasympathetic fibers terminate on the sinuatrial and
atrioventricular nodes and on the coronary arteries. Activation of the
parasympathetic nerves results in a reduction in the rate and force of
contraction of the heart and a constriction of the coronary arteries.
• Afferent fibers running with the sympathetic nerves carry nervous
impulses that normally do not reach consciousness. However, should the
blood supply to the myocardium become impaired, pain impulses reach
consciousness via this pathway. Afferent fibers running with the vagus
nerves take part in cardiovascular reflexes