Download The Circulatory System

The Circulatory System
“The Heart and Blood Vessels”
Location of the Heart
• The heart is a 4 chambered muscle
that pumps blood
through a closed
circulatory system
• 2/3 of the heart lies to
the left of the midline
of the body
• The apex lies on the
diaphragm and the
upper border (base)
just below the second
rib
Anterior View
Posterior View
Coverings of the Heart
Pericardium is the tough sac
that surrounds the heart.
• Fibrous pericardium- tough
inelastic sac around the
heart.
• Serous pericardium-consists
of parietal layer (outside)
and visceral layer (touches
the heart).
• Pericardial space is filled
with lubricating (pericardial)
fluid.
3 Layers of the Heart
• Epicardium- same as the
visceral layer of the
pericardium
• Myocardium- thick contractile
cardiac muscle cells. The cells
are tightly joined together to
form a syncytium which
transmits action potentials
seamlessly.
• Endocardium- thin layer that
covers muscular projections
called trabeculae. This
tissue’s folds make up the
valves. It is also continuous
with lining of blood vessels.
Chambers of the Heart
Septum separates the chambers
Atria- two upper chambers
of heart - “receiving
chambers” Veins carry
blood into the atria
Ventricles- two lower
chambers which have
very thick myocardial
“pumping chambers”
Valves of the Heart
Valves permit blood flow in only
one direction.
Atrioventricular (cuspid valves)
are anchored to papillary
muscles through chordae
tendineae
– Tricuspid valve has three
flaps of endothelium and
connects right atrium and
ventricle
– Bicuspid valve (mitral
valve) has two flaps and
connects left atrium and
ventricle
Semilunar Valves have half-moon
shaped flaps growing out of
lining of blood vessels.
– Pulmonary semilunar valve
– Aortic semilunar valve
Blood Flow Through the Heart
Arteries always carry blood away
from heart
Veins always carry blood toward the
heart
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Superior and inferior vena
cavae
Right atrium
Tricuspid valve
Right ventricle
Semilunar pulmonary valve
Pulmonary arteries
Lungs
Pulmonary veins
Left atrium
Mitral valve
Left ventricle
Aortic semilunar valve
Aorta to the rest of the body
Blood Supply to the Heart
Coronary Arteries branch off
directly from the aorta. They
can form anastomoses to
ensure blood flow.
Coronary Veins drain blood into
the right atrium through the
coronary sinus.
Heart Disorders
Myocardial infarction (heart attack) – when
coronary arteries are clogged (by a clot or
plaque) and cardiac cells are starved of
oxygen (ischemia).
Mitral valve prolapse – mitral valve
(bicuspid) flaps extend into atrium causing
leaking