The circulatory system - heart
scientific study of the heart and treatment of its disorders—the science we now call cardiology.The
cardiovascular system consists of the heart and the blood vessels.
Pulmonary and systemic circuits:
Cardiovascular system has 2 major division. a pulmonary circuit, which carries blood to the lungs
for gas exchange and returns it to the heart, and a systemic circuit, which supplies blood to every
organ of the body, including other parts of the lungs and the wall of the heart itself.
The right half of the heart supplies the pulmonary circuit. It receives blood that has circulated
through the body, unloaded its oxygen and nutrients, and picked up a load of carbon dioxide and
other wastes. It pumps this oxygen-poor blood into a large artery, the pulmonary trunk, which
immediately divides into right and left pulmonary arteries. These transport blood to the air sacs
(alveoli) of the lungs, where carbon dioxide is unloaded and oxygen is picked up. The oxygen-
pulmonary veins to the left side of the heart.
The left side supplies the systemic circuit. Blood leaves it by way of another large artery, the
aorta. The aorta turns like an inverted U, the aortic arch, and passes downward posterior to the
heart. The arch gives off arteries that supply the head, neck, and upper limbs. The aorta then travels
through the thoracic and abdominal cavities and issues smaller arteries to the other organs before
branching into the lower limbs. After circulating through the body, the now deoxygenated systemic
blood returns to the right side of the heart mainly by way of two large veins: the superior vena cava
and inferior vena cava. The major arteries and veins entering and leaving the heart are called the
great vessels because of their relatively large diameters.
position, size and shape of heart:
the heart lies within a thick partition called mediastinum between 2
lungs. It extends from a broad base at upper end and apex at lower
end just above the diaphragm. Normally, the adult heart is about 9
cm wide and 13 cm from base to apex. The heart is enclosed in a
double walled sac pericardium. the outer wall is called pericardial
sac. A tough and superficial fibrous layer of dense connective
tissue is serous layer. This layer turns inward at the base of heart
and form visceral pericardium. The pericardium isolates the
heart from other thoracic organs and allows it room to expand.
between the parietal and visceral membranes is a space called the
pericardial cavity. The pericardial cavity contains 5 to 30 ml of
pericardial fluid. The fluid lubricates the membranes and allows
heart to beat with minimal friction.
, Gross anatomy of heart
The heart wall Consist of 3 layers
Epicardium: also called visceral pericardium.
It’s a serous membrane of external heart
surface. It consists of simple squamous
epithelium overlying a thin layer of areolar
tissue. The largest branches of the coronary
blood vessels travel through the epicardium.
Endocardium: simple squamous epithelium
overlying a thin areolar tissue layer . it has no
adipose tissue. covers the valve surface and is
continuous with the endothelium of the blood vessel.
Myocardium: these 2 layers are composed of cardiac muscle. This is the thickest layer and
performs the work of the heart. Its thickness is proportional to the workload on the individual
chambers.
The heart also has a framework of collagenous and elastic fibers that make up fibrous skeleton.it
has multiple function:
1.provides structural supports for heart. 2. It anchores the cardiomyocytes and gives them some
thing to pull against. 3. Serves as electrical insulation between the atria and the ventricles. 4. Elastic
recoil of the fibrous skeleton may aid refilling the heart blood after each beat.
Heart has 4 chambers. 2 superior chambers are the right and left atria. They are receiving chambers
for blood returning to the heart.each atrium has an earlike flap called an auricle that slightly increases
its volume. all they do is pump blood into the ventricles immediately below. They are separated from
each other by a wall called the interatrial septum. The right atrium and both auricles exhibit internal
ridges of myocardium called pectinate9 muscles.
The two inferior chambers, the right and left ventricles are the pumps that eject blood into the arteries
and keep it flowing around the body. The right ventricle constitutes most of the anterior aspect of
the heart, whereas the left ventricle forms the apex and inferoposterior aspect. he ventricles are
separated by a thick muscular wall, the interventricular septum. The right ventricle pumps blood only
to the lungs and back to the left atrium.the wall of left ventricle is 2 to 4 times thick as it takes more
workload for all chambers pumping blood through the entire body.both ventricles exhibit internal
ridges called trabeculae carneae that allows the chambers to expand more easily when they refill.
, Valves:
To pump blood effectively, the heart needs valves that ensure a one way flow. Each valve consists
of two or three fibrous flaps of tissue called cusps or leaflets, covered with endocardium. The
atrioventricular (AV) valves regulate the openings between the atria and ventricles. The right AV
(tricuspid) valve has three cusps and the left AV valve has two AV valve is also known as the mitral
valve also formerly gone by the name of bicuspid valve.connect the valve cusps to conical papillary
muscles on the floor of the ventricle. They prevent the AV valves from flipping inside out or bulging
into the atria when the ventricles contract.
The seminular valves regulate the flow of blood from the ventricles into the great arteries. The
pulmonary valve controls the opening from the right ventricle into the pulmonary trunk, and the aortic
valve controls the opening from the left ventricle into the aorta. When blood is ejected from the
ventricles, it pushes through these valves from below and presses their cusps against the arterial
walls. When the ventricles relax, arterial blood flows backward toward the ventricles, but quickly fills
the cusps.
The valves do not open and close by any muscular effort of their own. The cusps are simply pushed
open and closed by changes in blood pressure that occur as the heart chambers contract and relax
When the right ventricle contracts, it ejects blood through the pulmonary valve into the pulmonary
trunk, on its way to the lungs to exchange carbon dioxide for oxygen.Blood returns from the lungs
by way of two pulmonary veins on the left and two on the right; all four of these empty into the left
atrium. Blood flows through the left AV (mitral) valve into the left ventricle. Contraction of the left
ventricle ejects this blood through the aortic valve into the ascending aorta, on its way to another
trip around the systemic circuit.
The blood vessels of the heart wall constitute the coronary circulation. the coronary blood vessels
supply the myocardium with about 250 mL of blood per minute. This constitutes about 5% of the
circulating blood going to meet the metabolic needs of the heart,
Arterial supply:
Immediately after the aorta leaves the left ventricle, it gives off a right and left coronary artery. The
left coronary artery (LCA) travels through the coronary sulcus divides into 2 branches.
1. anterior interventricular branch travels down the anterior interventricular sulcus to the apex,
rounds the bend, and travels a short distance up the posterior side of the heart. it is also called the
left anterior descending (LAD) branch. 2. The circumflex branch continues around the left side of
the heart in the coronary sulcus. It gives off a left marginal branch that passes down the left margin
of the heart and furnishes blood to the left ventricle.
scientific study of the heart and treatment of its disorders—the science we now call cardiology.The
cardiovascular system consists of the heart and the blood vessels.
Pulmonary and systemic circuits:
Cardiovascular system has 2 major division. a pulmonary circuit, which carries blood to the lungs
for gas exchange and returns it to the heart, and a systemic circuit, which supplies blood to every
organ of the body, including other parts of the lungs and the wall of the heart itself.
The right half of the heart supplies the pulmonary circuit. It receives blood that has circulated
through the body, unloaded its oxygen and nutrients, and picked up a load of carbon dioxide and
other wastes. It pumps this oxygen-poor blood into a large artery, the pulmonary trunk, which
immediately divides into right and left pulmonary arteries. These transport blood to the air sacs
(alveoli) of the lungs, where carbon dioxide is unloaded and oxygen is picked up. The oxygen-
pulmonary veins to the left side of the heart.
The left side supplies the systemic circuit. Blood leaves it by way of another large artery, the
aorta. The aorta turns like an inverted U, the aortic arch, and passes downward posterior to the
heart. The arch gives off arteries that supply the head, neck, and upper limbs. The aorta then travels
through the thoracic and abdominal cavities and issues smaller arteries to the other organs before
branching into the lower limbs. After circulating through the body, the now deoxygenated systemic
blood returns to the right side of the heart mainly by way of two large veins: the superior vena cava
and inferior vena cava. The major arteries and veins entering and leaving the heart are called the
great vessels because of their relatively large diameters.
position, size and shape of heart:
the heart lies within a thick partition called mediastinum between 2
lungs. It extends from a broad base at upper end and apex at lower
end just above the diaphragm. Normally, the adult heart is about 9
cm wide and 13 cm from base to apex. The heart is enclosed in a
double walled sac pericardium. the outer wall is called pericardial
sac. A tough and superficial fibrous layer of dense connective
tissue is serous layer. This layer turns inward at the base of heart
and form visceral pericardium. The pericardium isolates the
heart from other thoracic organs and allows it room to expand.
between the parietal and visceral membranes is a space called the
pericardial cavity. The pericardial cavity contains 5 to 30 ml of
pericardial fluid. The fluid lubricates the membranes and allows
heart to beat with minimal friction.
, Gross anatomy of heart
The heart wall Consist of 3 layers
Epicardium: also called visceral pericardium.
It’s a serous membrane of external heart
surface. It consists of simple squamous
epithelium overlying a thin layer of areolar
tissue. The largest branches of the coronary
blood vessels travel through the epicardium.
Endocardium: simple squamous epithelium
overlying a thin areolar tissue layer . it has no
adipose tissue. covers the valve surface and is
continuous with the endothelium of the blood vessel.
Myocardium: these 2 layers are composed of cardiac muscle. This is the thickest layer and
performs the work of the heart. Its thickness is proportional to the workload on the individual
chambers.
The heart also has a framework of collagenous and elastic fibers that make up fibrous skeleton.it
has multiple function:
1.provides structural supports for heart. 2. It anchores the cardiomyocytes and gives them some
thing to pull against. 3. Serves as electrical insulation between the atria and the ventricles. 4. Elastic
recoil of the fibrous skeleton may aid refilling the heart blood after each beat.
Heart has 4 chambers. 2 superior chambers are the right and left atria. They are receiving chambers
for blood returning to the heart.each atrium has an earlike flap called an auricle that slightly increases
its volume. all they do is pump blood into the ventricles immediately below. They are separated from
each other by a wall called the interatrial septum. The right atrium and both auricles exhibit internal
ridges of myocardium called pectinate9 muscles.
The two inferior chambers, the right and left ventricles are the pumps that eject blood into the arteries
and keep it flowing around the body. The right ventricle constitutes most of the anterior aspect of
the heart, whereas the left ventricle forms the apex and inferoposterior aspect. he ventricles are
separated by a thick muscular wall, the interventricular septum. The right ventricle pumps blood only
to the lungs and back to the left atrium.the wall of left ventricle is 2 to 4 times thick as it takes more
workload for all chambers pumping blood through the entire body.both ventricles exhibit internal
ridges called trabeculae carneae that allows the chambers to expand more easily when they refill.
, Valves:
To pump blood effectively, the heart needs valves that ensure a one way flow. Each valve consists
of two or three fibrous flaps of tissue called cusps or leaflets, covered with endocardium. The
atrioventricular (AV) valves regulate the openings between the atria and ventricles. The right AV
(tricuspid) valve has three cusps and the left AV valve has two AV valve is also known as the mitral
valve also formerly gone by the name of bicuspid valve.connect the valve cusps to conical papillary
muscles on the floor of the ventricle. They prevent the AV valves from flipping inside out or bulging
into the atria when the ventricles contract.
The seminular valves regulate the flow of blood from the ventricles into the great arteries. The
pulmonary valve controls the opening from the right ventricle into the pulmonary trunk, and the aortic
valve controls the opening from the left ventricle into the aorta. When blood is ejected from the
ventricles, it pushes through these valves from below and presses their cusps against the arterial
walls. When the ventricles relax, arterial blood flows backward toward the ventricles, but quickly fills
the cusps.
The valves do not open and close by any muscular effort of their own. The cusps are simply pushed
open and closed by changes in blood pressure that occur as the heart chambers contract and relax
When the right ventricle contracts, it ejects blood through the pulmonary valve into the pulmonary
trunk, on its way to the lungs to exchange carbon dioxide for oxygen.Blood returns from the lungs
by way of two pulmonary veins on the left and two on the right; all four of these empty into the left
atrium. Blood flows through the left AV (mitral) valve into the left ventricle. Contraction of the left
ventricle ejects this blood through the aortic valve into the ascending aorta, on its way to another
trip around the systemic circuit.
The blood vessels of the heart wall constitute the coronary circulation. the coronary blood vessels
supply the myocardium with about 250 mL of blood per minute. This constitutes about 5% of the
circulating blood going to meet the metabolic needs of the heart,
Arterial supply:
Immediately after the aorta leaves the left ventricle, it gives off a right and left coronary artery. The
left coronary artery (LCA) travels through the coronary sulcus divides into 2 branches.
1. anterior interventricular branch travels down the anterior interventricular sulcus to the apex,
rounds the bend, and travels a short distance up the posterior side of the heart. it is also called the
left anterior descending (LAD) branch. 2. The circumflex branch continues around the left side of
the heart in the coronary sulcus. It gives off a left marginal branch that passes down the left margin
of the heart and furnishes blood to the left ventricle.
