CARDIOVASCULAR SYSTEM

CIRCULATORY SYSTEM, HEART VESSEL SYSTEM

Prof. Dr. Sevim AYDIN

 CIRCULATORY SYSTEM
• Transport system • The cardiovascular system
• Consists of liquid carries blood between
intermediates and cells tissue and heart
• Carries nutrients, • The lymphatic system
hormones, antibodies and carries excess
metabolites extracellular fluid through
• Circulation from center to the lymphatic vessels to
periphery with pressure the heart
• Lymph circulation is • Therefore, while the
linked to blood circulation lymphatic system is one-
way, the cardiovascular
system is two-way
Cardiovascular system features

• Pump Heart
• Circulation Heart and Vessels
• Pressure Systole and Diastole
• Viscosity Blood Cells
 Once a heart beats, it sends 80 ml of
blood to the pulmonary artery and aorta

6 liters of blood are excreted throughout

the heart per minute.
• CVC consists of the
heart, blood vessels and
lymphatic vessels

• There are 2 types of

circulation in the body
– Pulmonary circulation
– Systemic circulation
 HEART
LEARNING OBJECTIVES
•Layers of the heart
• Histological properties of layers
•Functions of the heart muscle cells
•Histological features of the impulse forming
and transmitting system
•Histological features of the heart valves and
fibrous skeleton
 HEART

It is a muscular organ
It contains four chambers :

– Two atria
– Two ventricles
 Systemic blood
VCS ve VCI
right atrium
right atrioventricular
(tricuspid) valve
right ventricle
semilunar (pulmonary) valves

pulmonary turuncus and right pulmonary artery /

left pulmonary vein (Pulmoner circulation)

left atrium
left atrioventricular
(Bicuspid / mitral) valve
left ventricle
semilunar (aortic) valves

Aorta
 HEART HISTOLOGY
• It is a sac that pumps blood
through rhythmic
contractions.

• It consists of three layers:

* Endocardium
* Myocardium
* Epicardium
 ENDOCARDIUM
From inside out;
1. Endothelial layer; A simple squamous
epithelium
2. Subendotelial connective tissue layer;
contains elastic and collagen fibers and few
smooth muscle cells
3. Musculoelastic layer; consists of elastic fibers
and smooth muscle bundles.
4. Subendocardial layer; is in the structure of
loose connective tissue containing small blood
vessels, nerves and Purkinje fibers.
 MYOCARDIUM

It is equivalent to T. Media and is the thickest of tunica

It consists mostly of cardiac muscle fibers.
Includes impulse-transmitting system and parts of the heart
skeleton.
Each muscle fiber is surrounded by an endomisyum and
each fascicle surrounded by perimisyum
 MYOCARDIUM

• It is the thickest layer of the heart Wall.

• It consists of heart muscle cells.
1. Contractile cardiocytes, which contract to pump blood through the
circulation.
2. Myoendocrine cardiocytes, producting atrial natriuretic factor.
3. Nodal cardiocytes, specialized to control the rhythmic contraction of
the heart. These cells are located in sinoatrial node (SA) and
atrioventricular node (AV).
CARDIOCYTES
*85-100 µm in length,
1.5 µm in diameter.
A single centrally located nucleus
Branched cylinders
(Atrium myocardiocytes are smaller than ventricular
myocardiocytes.)
*Glycogen, lipofuskin, pigment granules are common
in cytoplasm.
 CARDIOCYTES
1- Contractile Cardiocytes:
✓ Cardiac (heart) muscles have striated, branched fibers.
✓ Contractile proteins are the same as skeletal muscle.

✓ Cytomembranes exhibit some differences:

1. T tubules are found at the level of Z disk.
2. Sarcoplasmic reticulum is not as extensive as that of skeletal muscle.
3. Diads are typical in cardiocytes.
4. Mytochondria are not abundant in cardiac muscle than in skeletal
muscle.
Cardiac muscle cells are joined end - to - end by the intercalated discs (junctional
complex of the two cell membranes of two adjacent cardiac muscle cells)

The intercalated disks provide direct electrical coupling between cells to

coordinate contraction of the heart

The transvers component consist of:

1. Desmosomes, which mechanically link cardiac cells.
2. Zonula adherens contains α-actinin and vinculin .
Longitudinal component
1. Gap junctions; This structure provides ionic communications.
 MYOCARDIUM
Atrial Cardiac Muscles
• The heart muscle is thin in the atria and thick in
the ventricles.
• The muscles in the outer part of the atrium are
transverse and oblique.
• Between the muscle cells are collagen and
elastic fibers
 According to the ventricular muscles;
Atrial muscles
1- They are smaller,
2- They contain many secretion granules such as
atrial natriuretic factor,
3- It has fewer T tubule systems,
4- There are many more gap junctions,
5- Impulse transmission is fast
6- They contract more rhythmically.
2- Nodal cardiocytes:
- It controls the rhythmic contractions of the heart.
These cells are located in
the sinoatrial node, at the superior vena cava-right
atrium junction;
the atrioventricular node, present under the
endocardium of the interatrial and interventricular
septa.
The action potential responsible for cardiac contraction
is generated primarily from the sinoatrial node, located
near the orifice of the superior vena cava. The impulse
is transmitted across the atria and to the
atrioventricular node, where it then depolarizes the
ventricles via the bundle of His and associated Purkinje
fibres.
• SA and AV node cells are
structurally similar.
• These cells are smaller and
paler than the surrounding
cardiac muscle cells.
• The cells are spread out
within a mesh of
connective tissue,
containing nerves, blood
vessels, collagen and fat.
The bundle of His is characterized by
longitudinal collagen partitioning histology,
distinguishing it from the AV node

https://healthiack.com/encyclopedia/pictures-of-bundle-of-his?ref=driverlayer.com
 Purkinje fibres
• The purkinje fibres are found in the sub-
endocardium.

• They are larger than cardiac muscle cells, but

have fewer myofibrils, lots of glycogen and
mitochondria, and no T-tubules. These cells
are connected together by desmosomes and
gap junctions, but not by intercalated discs.

• They are specialised conducting fibres, which

extend from the interventricular septum, to
the papillary muscles, and up the lateral walls
of the ventricles.
 PERİCARDİUM
• The pericardium is a double-walled sac enclosing the heart.
• Fibrous Layer (pericardium fibrosum)
• Serous Layer(pericardium serosum)
• Parietal Layer (outer serous layer)
• Visceral Layer (inner serous layer)(epikardiyum)

• The fibrous pericardium is strong fibrous sac which supports the delicate
parietal layer of the serous pericardium with which it is firmly adherent.

https://quedeus.com/uploads/2017-11-04/heart_2.jpg
SEROUS PERICARDIUM
• Enclosed within the
fibrous pericardium,
the serous
pericardium is itself
divided into two
layers:
–The outer parietal layer
that lines the internal
surface of the fibrous
pericardium.
–The internal visceral
layer that forms the Each layer is made up of a single sheet of
outer layer of the heart epithelial cells, known as mesothelium.
(also known as the
epicardium).
Epikardiyum;
• The Epicardium (Visceral
Pericardium) is a serous
membrane covered externally by a
single layer of mesothelial cells
• Beneath the mesothelium, there is
a relatively thick layer of areolar or
adipose tissue.
• The subepicardial layer lies
between, and joins, the
myocardium and the epicardium.
• The subepicardial layer contains
the coranary blood vessels and
nerves.
 CARDIAC SKELETON
• It provides structural support
for the heart.
• The fibrous rings are composed
of dense irregular connective
tissue.

• It creates areas of attachment

to the heart muscles and
valves.
• Skeleton of heart forms basis of
electrical discontinuity
between atria and ventricles.
A fibrous skeleton that consists of four
fibrous rings surrounding the valve
orifices, two fibrous trigones connecting
the rings, and the membranous part of
the interventricular and interatrial septa.
 CARDIAC SKELETON

• Major elements;
– Anuli fibrozi ; in the aorta,
pulmonary artery bases and
at the base of the openings of
the atrioventricular valves,
– Trigonum fibrozum ; The
triangle between annuli
fibrosa and ostium
atrioventricularis
– Septum membranaseum ;
membranous parts of the
septum between the atrium
and ventricles
 HEART VALVES
• The heart valves attach to the complex
framework of dense irregular connective
tissue that forms the fibrous rings and
surrounds the orifices containing the
valves.

• Valve cusps are normally avascular.

• In the AV valves, the ventricularis

continues into the chordae tendineae,
which are fibrous, thread-like cords
also covered with endothelium.
Each valve is composed of three layers:

• The fibrosa forms the core of the valve

and contains fibrous extensions from the
dense irregular connective tissue of the
skeletal rings of the heart.
• The spongiosa is loose connective tissue
located on the atrial or blood vessel side of
each valve.
• The ventricularis is immediately adjacent
to the ventricular or atrial surface of each
valve and is covered with endothelium.
 VESSELS OF THE HEART
• The heart vessels occur anastomosis
through the subepicardial layer.
• Coronary arteries are muscular type
arteries.
• Lymph capillaries are located;
– in the subendothelial layer in the
endocardium,
– around the muscle cells in the
myocardium
– in the epicardium.
 NERVES OF THE HEART

• The parasympathetic and sympathetic system

nerve fibers form neural network in the
subepicardial layer.
• This neural network enters the myocardium
and ends on muscle cells.
• Motor end plates are not observed.
http://www.histology.leeds.ac.uk/circulatory/heart.php
Thank you
https://en.wikipedia.org/wiki/Cardiac_muscle

Human Anatomy, McKinley & O'Loughlin, Third edition