Structure of Heart Wall
| Home |Chapter: HAP - Cardiovascular System
The structure of the heart wall consists of three distinct layers epicardium, myocardium, and endocardium-each playing a vital role in protection, contraction, and smooth blood flow within the heart.
STRUCTURE OF HEART WALL
The
heart wall consists of three layers:
- Pericardium
- Myocardium
- Endocardium
Pericardium
The
pericardium is a fibro-serous sac that surrounds the heart.
Functions
of pericardium:
- Protects
the heart
- Prevents
overstretching
- Reduces
friction during heart movements
- Keeps
the heart in proper position
The
pericardium has two main parts:
Fibrous
Pericardium
- Outer
tough layer
- Made
of dense connective tissue
- Prevents
excessive expansion of the heart
- Anchors
the heart in the thoracic cavity
Serous
Pericardium
- Thin,
delicate membrane
- Forms
a double layer around the heart
It
has:
- Parietal
layer (lines the fibrous pericardium)
- Visceral
layer (Epicardium) (covers the heart)
Between
these layers is the pericardial cavity, which contains pericardial
fluid that lubricates the heart.
LAYERS
OF THE HEART WALL
Epicardium
- Outermost
layer
- Also
called the visceral layer of pericardium
- Protects
and lubricates the heart surface
Myocardium
- Thick
muscular middle layer
- Composed
of cardiac muscle fibers
- Responsible
for pumping action of the heart
- Thickest
in the left ventricle
Endocardium
- Innermost
layer
- Made
of simple squamous epithelium
- Lines
heart chambers and valves
- Continuous
with the lining of blood vessels
CHAMBER OF THE HEART
The
heart is divided into right and left sides by a septum and consists of four
chambers.
Chambers
of the Heart:
|
UPPER CHAMBERS (ATRIA) |
LOWER CHAMBERS (VENTRICLES) |
|
Right atrium |
Right ventricle |
|
Left atrium |
Left ventricle |
- Atria
are receiving chambers with thinner walls
- Ventricles
are pumping chambers with thicker muscular walls
- Right
side pumps blood to lungs (pulmonary circulation)
- Left
side pumps blood to the whole body (systemic circulation)
VALVE OF THE HEART
Heart
valves ensure that blood flows in one direction only.
There
are four heart valves, divided into two groups:
1.
Atrioventricular Valves
Located
between atria and ventricles.
|
VALVE |
LOCATION |
CUSPS |
|
Tricuspid valve |
Right atrium → Right ventricle |
3 cusps |
|
Mitral (Bicuspid) valve |
Left atrium → Left ventricle |
2 cusps |
- These
valves close during ventricular contraction
- Closure
produces the first heart sound (Lub)
2.
Semilunar Valves
Located
between ventricles and arteries.
|
VALVE |
LOCATION |
|
Pulmonary valve |
Right ventricle → Pulmonary artery |
|
Aortic valve |
Left ventricle → Aorta |
- Each
has three cusps
- Close
during ventricular relaxation
- Closure
produces the second heart sound (Dub)
