TOPIC 1 CLASSIFICATION KINGDOM FUNGI
The wall of the heart is made up of
the cardiac muscles. Cardiac muscle is never fatigued (tired). It works
continuously as long as a person is alive. This type of muscle is found only in
the heart.
The wall of the heart has three
layers:
The epicardium is
the outer protective layer.
The myocardium is
the middle layer.
The endocardiumis
the inner most layer. This layer is continuous with the lining of the blood
vessels attached to the heart.
The coronary artery supplies the
heart with oxygenated blood. The coronary vein carries blood containing waste
materials away from the heart.
The vena cava and pulmonary vein
bring blood from the rest of the body to the heart. The aorta and pulmonary
artery transport blood from the heart to the rest of the body.
The internal structure of the
mammalianheart
Figure shows a longitudinal section
of the mammalian heart
The heart has four chamber right
auricle, right ventricle, left auricle and left ventricle. The auricles are
also called atria (singular: atrium). The walls of the ventricles are thicker
than those of the auricles. This is because the ventricles pump blood to a
greater distance than the auricles. Auricles pump blood to the ventricles.
Ventricles pump blood to all other parts of the body. The left ventricle is
thicker than the right ventricle because the right ventricle pumps
blood to the lungs while the left ventricle pumps blood to the rest of the
body.
The heart has several valves. Valves
have flaps that ensure that blood flows in one direction only. The tricuspidvalve
is found between the right auricle and right ventricle. The bicuspid valve
is found between the left auricle and left ventricle. Semi lunar valves are
located at the bases of the pulmonary artery and aorta to prevent blood from
flowing back into the ventricles.
Valves close when blood tries to
flow back.
The left and right sides of the
heart are separated by the septum. The septum is a thick muscular wall
that prevents mixing of oxygenated and deoxygenated blood.
The flow of blood through the heart;
The vena cava brings deoxygenated
blood to the heart. Deoxygenated blood contains low amounts of oxygen.
The vena cava has two branches:
The superior vena cava which
transports deoxygenated blood from the upper parts of the body such as head,
neck and upper limbs.
