Internal features of
Heart
Dr. Sama ul Haque
Dr Rania Gabr
Objectives
 List the chambers of the heart.
 Describe the internal features of right atrium.
 Describe the internal features of the right ventricle.
 Discuss internal features of the left atrium.
 Discuss the internal features of the left ventricle.
 Differentiate between right and left ventricles.
 Define conducting system of the heart.
Chambers of Heart
1.Right Atrium
2.Right Ventricle
3.Left Atrium
4.Left Ventricle
Internal Structure of Heart
Right Atrium
The right atrium consists
of a main cavity and a
small out pouching, the
auricle.
On the outside of heart
at the junction between
the right atrium and the
right auricle is a vertical
groove.
 This is called the sulcus
terminalis, which on the
inside forms a ridge, the
crista terminalis.
Right Atrium
1. Rough
anterior part.
Crista Terminalis
2. Smooth
posterior
part.
1
2
Musculi pectinati
(Pectinate muscles)
Cavity of Right Atrium
Crista terminalis divides right
atrium into:
1- Anterior part: rough and
trabeculated by bundles of
muscle fibres (musculi pectinati).
2- Posterior part (sinus venarum):
is smooth.
The interatrial septum carries
an oval depression called Fossa
ovalis.
The margin of this depression
is called Anulus ovalis.
The blood leaves right atrium to
right ventricle via tricuspid valve.
Right Ventricle
Right ventricle
Infundibulum
•The right ventricle
communicates with the
right atrium through
right atrioventricular
orifice.
•It also communicates
with the pulmonary
trunk through the
pulmonary orifice.
Cavity of right ventricle
Its wall is thinner than that of
left ventricle.
Its wall contains rough muscular
projections called trabeculae
carneae.
Tricuspid valve has three cusps:
anterior, septal, and posterior
S
Large projections arise from the
walls called papillary muscles :
P
• Anterior papillary muscle
•Posterior papillary muscle
A
trabeculae carnae.
•Septal papillary muscle
Cavity of right ventricle
Infundibulum
Each papillary muscle is
attached to the cusps of
tricuspid valve by tendinous
threads called chordae
tendinae (Tendinous cords).
Infundibulum
The wall of infundibulum
is smooth and contains no
trabeculae.
Interventricular septum is
connected to anterior
papillary muscle by a
muscular band called
moderator band ( the
septomarginal trabecula )
Right Ventricle
Infundibulum
• The conus arteriosus (infundibulum): is the cone-shaped portion
of the right ventricle inferior to the opening of the pulmonary trunk.
• The pulmonary valve: consists of three semilunar cusps: anterior,
right, and left.
Right atrio-ventricular (tricuspid) orifice
It is surrounded by a fibrous ring
which gives attachment to the
tricuspid valve.
It has 3-cusps (anteriorposterior-septal or medial).
The atrial surface of the cusps
are smooth, while their ventricular
surfaces give attachment to the
chordae tendinae.
P
A
M
Pulmonary orifice
Surrounded by a fibrous
ring which gives attachment to
the cusps of the pulmonary
valve.
The valve is formed of
3 semilunar cusps :
one anterior only.
P P
A
No chordae tendineae or
papillary muscles are attached to
these cusps
Right Ventricle
Left atrium of the heart
Left
atrium
It communicates with the left
ventricle through left
atrioventricular orifice.
It forms the greater part of base
of heart.
Its wall is smooth except for
small musculi pectinati in the left
auricle.
Recieves 4 pulmonary veins
which have no valves.
Sends blood to left ventricle
through the left atrioventricular
orifice which is guarded by mitral
valve.
• Bicuspid valve:
blood passes
through it into left
ventricle (mitral
valve has two
cusps).
Left Atrium
Left ventricle of the heart
Its wall is thicker than that
of right ventricle.
It receives blood from left
atrium through left atrioventricular orifice which is
guarded by mitral valve.
Its wall contains trabeculae
carnae.
Its wall contains 2 large
papillary muscles (anterior &
posterior). They are attached
by chordae tendinae to cusps
of mitral valve.
Left ventricle of the heart
Aortic
vestibule
The blood leaves
the left ventricle to
the ascending aorta
through the aortic
orifice.
The part of left
ventricle leading to
ascending aorta is
called aortic
vestibule. The wall of
this part is fibrous
and smooth.
Left Ventricle have thick muscular wall
Left atrio-ventricular (mitral) orifice
P
A
• Smaller than the right, admitting
only tips of 2 fingers.
•Guarded by a mitral valve.
•Surrounded by a fibrous ring
which gives attachment to the
cusps of mitral valve.
• Mitral valve is composed of 2
cusps:
• Anterior cusp : lies anteriorly
and to right.
• Posterior cusp : lies posteriorly
and to left.
• The atrial surfaces of the cusps
are smooth, while ventricular
surfaces give attachment to
chordae tendinae.
Aortic orifice
P
A
A
• Surrounded by a fibrous
ring which gives
attachment to the cusps
of aortic valve.
• Aortic valve is formed
of 3 semilunar cusps
which are similar to those
of pulmonary valve, but
the position of the cusps
differs being one
posterior only.
Valves of the Heart
1. Right Atrioventricular
(Tricuspid)
2. Left Atrioventricular
(Bicuspid or Mitral)
3. Pulmonary
3
4. Aortic
1
4
2
Fibrous Skeleton of the Heart
Dense collagenous fibrous tissue framework lies
at the junction of the atria with the ventricles.
Includes:
1-Tricuspid fibrous annulus: 2-Mitral fibrous annulus
3-Pulmonary fibrous annulus: 4-Aortic fibrous annulus
Functions:
1-Supports the valves. 2-Electrically separetes atria from ventricles.
Valves of the Heart
Valves of Heart in Diastole
(Viewed from base with atria
removed)
Valves of Heart in Systole
(Viewed from base with atria removed)
Direction of blood flow
Conducting system of Heart
Sinu-Atrial Node (S-A Node)
Atrio-ventricular Node (A-V Node)
Atrio-ventricular Bundle
Right and left Bundle branch
Purkinje Fibers
Conducting system of Heart
S-A Node
A-V Node
Conducting system of Heart
PF
Conducting system of Heart