The Heart The heart or cardiac muscle is

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The Heart The heart or cardiac muscle is a hollow cone shaped muscular organ

The Heart The heart or cardiac muscle is a hollow cone shaped muscular organ that is divided into four chambers. The heart straddles the midline within the thoracic cavity just dorsal to the sternum

The base of the heart is located craniodorsally and the apex points ventrally and

The base of the heart is located craniodorsally and the apex points ventrally and to the left. The apex is free within the pericardium. The heart is a pump that circulates blood throughout the body to nourish and remove waste

The Structure of the Heart The heart is covered by a saclike membrane which

The Structure of the Heart The heart is covered by a saclike membrane which has 3 layers *pericardium tough external layer *parietal the lining of the pericardium *visceral covers the surface of the heart

The space between the inner layers is the pericardial space which contain pericardial fluid

The space between the inner layers is the pericardial space which contain pericardial fluid The heart is composed of three layers The outer layer (epicardium) The middle layer (myocardium, the muscle itself) The inner most layer (endocardium, lines the chambers and covers the valves)

The Chambers of the Heart The heart is divided into a right and left

The Chambers of the Heart The heart is divided into a right and left side. The hollow of the heart is divided into four chambers. The cranial chambers are called the atrium and the ventral chamber is called the ventricle

A wall (interatrial septum) divides the atria into right and left sides. A wall

A wall (interatrial septum) divides the atria into right and left sides. A wall (the interventricular septum) divides the ventricles into right and left sides. There is no communication between the two sides.

The atrium have thin walls and are receiving chambers. The ventricles do the pumping

The atrium have thin walls and are receiving chambers. The ventricles do the pumping and have thick walls

The right side of the heart receives blood from the body and sends it

The right side of the heart receives blood from the body and sends it to the lungs to be oxygenated.

The left side of the heart receives oxygenated blood from the lungs and sends

The left side of the heart receives oxygenated blood from the lungs and sends it to all tissues. Because the left ventricle pumps the blood to all of the body the walls are much thicker.

Valves Between the atria and ventricles are valves that ensures that blood flows in

Valves Between the atria and ventricles are valves that ensures that blood flows in only one direction. The right atrium and ventricle are separated by the tricuspid valve and the left atrium and ventricle is separated by the mitral or bicuspid valve.

The semilunar valves prevent backflow from the arteries into the ventricles and are located

The semilunar valves prevent backflow from the arteries into the ventricles and are located at the base of the pulmonary and aortic arteries.

Conduction System The heart begins pumping in utero. This action consists of: sinoatrial node

Conduction System The heart begins pumping in utero. This action consists of: sinoatrial node (SA node): called the pacemaker. This impulse contracts the atrium and forces blood into the ventricles

The atrioventricular node (AV node) This consists of cells that conduct the electrical impulses

The atrioventricular node (AV node) This consists of cells that conduct the electrical impulses down to:

The atrioventricular bundle (bundle of his) This continues down as the Purkinje fibers which

The atrioventricular bundle (bundle of his) This continues down as the Purkinje fibers which stimulate ventricular contraction

Purkinje fibers

Purkinje fibers

Nerve Function: The autonomic nervous system has two divisions with opposite actions within the

Nerve Function: The autonomic nervous system has two divisions with opposite actions within the heart.

The parasympathetic division: Mainly supplies the SA and AV nodes. This slows the heart

The parasympathetic division: Mainly supplies the SA and AV nodes. This slows the heart rate, reduces impulse conduction and constricts the coronary arteries

The sympathetic division: Through cardiac nerves and also acts on the SA and AV

The sympathetic division: Through cardiac nerves and also acts on the SA and AV nodes to increase heart rate and impulse conduction and dilate the coronary arteries

Cardiac Cycle: The cycle includes the contraction (sysole) and relaxation (diastole) of the atria

Cardiac Cycle: The cycle includes the contraction (sysole) and relaxation (diastole) of the atria and ventricles. The heart chambers do not contract all at once. The two atria contract in unison and as they relax the two ventricles contract, as the ventricles relax the atria contract.

When the atria contract they force blood through the bicuspid and tricuspid valves into

When the atria contract they force blood through the bicuspid and tricuspid valves into the ventricles, the semilunar valves close to prevent blood from entering the arteries

When the atria relax blood enters the atrial chambers from the pulmonary veins (left)

When the atria relax blood enters the atrial chambers from the pulmonary veins (left) and the vena cava (right) and the ventricles contract. When the ventricles contract the bicuspid and tricuspid valves close to prevent backflow of blood into the atria

Blood vessels: arteries capillaries veins

Blood vessels: arteries capillaries veins

Arteries: Arteries carry oxygenated blood to all structures of the body. Ateries are elastic

Arteries: Arteries carry oxygenated blood to all structures of the body. Ateries are elastic tubes with thick walls composed of three layers: *tunica intima (inner) *tunica media (middle) tunica adventitia (outer)

Arterioles, capillaries and venules Ateries become smaller and smaller becoming arterioles. The arterioles feed

Arterioles, capillaries and venules Ateries become smaller and smaller becoming arterioles. The arterioles feed the blood into the capillaries. The capillaries distribute blood to all tissue and return to the venules which pass the blood into the veins which return blood to the heart

Veins: These are tubes similar to arteries but have thinner and less elastic walls.

Veins: These are tubes similar to arteries but have thinner and less elastic walls. These transport blood back to the heart. The smallest veins (venules) collect the blood from the capillaries and connect to larger veins and finally join the vena cava that returns the blood to the heart