Chapter 11
The Cardiovascular System
Be Able To:
•Describe the location of the heart and list its major anatomical areas.
•Trace the pathway of blood through the body.
•Compare the pulmonary and systemic circuits.
•Explain how the heart valves operate.
•Describe the nerve impulse pathways of heart tissue.
•Explain the differences between systole and diastole and between stroke volume and cardiac cycle.
Anatomy of the Heart
• The human fist-sized heart weighs less than a pound within the mediastinum of the thorax.
• The pointed apex rests on the diaphragm at the fifth intercostal space.
• The base of the heart points toward the right shoulder and lies beneath the second rib.
• The pericardium is a double serous membrane that encloses the heart.
• The visceral layer or epicardium covers the
external surface and the parietal layer covers the arteries.
• A fibrous connective tissue layer or fibrous pericardium:
1) Protects the heart 2) Anchors the heart
3) Prevents it from overfilling
• Serous fluid is produced by the serous pericardial membranes to allow the heart to beat in a
relatively frictionless environment.
Anterior View Posterior View
Anatomy of the Heart
• The heart wall is comprised of three layers:
1) Superficial epicardium or visceral layer of the serous pericardium often infiltrated with fat.
2) The middle myocardium made of cardiac muscle that does the contracting.
3) The deepest thinnest layer or endocardium made of
squamous epithelium lines the heart chambers.
Chambers and Associated Vessels
• The heart is comprised of 4 hollow chambers lined with endocardium
1) 2 superior atria 2) 2 inferior ventricles
• The atria are receiving chambers whereas the ventricles are discharging chambers.
• Oxygen poor blood enters the right atrium through the superior and inferior venae cavae.
• The right ventricle pumps this blood out through the right and left pulmonary arteries to the lungs where CO2 is unloaded.
• Oxygen rich blood drains from the lungs to the left atrium of the heart through 4 pulmonary veins.
• This oxygen rich blood is pumped out of the left
ventricle through the aorta which branches to form the systemic circuit.
• The pulmonary circuit carries blood to the lungs for gas exchange and back so that the systemic circuit can supply oxygen and nutrients to all body organs.
• Why is the left ventricle’s body wall the thickest of the 4 chambers?
Valves
• Blood flows through the heart in only one direction that is enforced by the four heart valves:
1) Paired atrioventricular valves (AV) 2) Paired semilunar valves
• The valves open and close in response to
differences in blood pressure on the two sides.
• The AV valves prevent backflow into the atria when the ventricles contract.
• The left AV known as bicuspid or mitral valve has 2 flaps of epicardium whereas the right AV valve known as tricuspid valve has three flaps.
• Tiny tendons called the chordae tendineae anchor the cusps to the ventricle walls.
• The semilunar valves known as the pulmonary and aortic semilunar valves each have 3
cusps that prevent arterial blood from reentering the heart.
Mitral Valve
Physiology of the Heart
• The right and left coronary arteries supply the myocardial tissue with
oxygen and nutrients.
• The myocardium drains this blood into the coronary sinus which empties in the right atrium.
• The heart pumps about 6,000 quarts of blood in a single day!
• The autonomic nervous system acts to speed up or slow down heart rate.
• The intrinsic conduction system or nodal system enforces a continuous heart rate.
• The sinoatrial node or SA is tissue of the right atrium that starts each heartbeat also called the
pacemaker.
Physiology of the Heart
• Systole and diastole mean heart contraction and relaxation, usually of the ventricles.
• The cardiac cycle is the events of one complete heartbeat in three periods:
1) Mid-to-late diastole 2) Ventricular systole 3) Early diastole
• Stroke volume is the volume of blood pumped out by a ventricle with each heartbeat.
• Cardiac output is the product of heart rate and stroke volume.
• A healthy heart pumps 70 ml of blood with each heartbeat.
• The parasympathetic nerves steady heart rate.
• Epinephrine and thyroxine are hormones that increase heart rate.
• At what age is resting heart rate the highest?
Chapter 11
The Cardiovascular System
Be Able To:
•Compare and contrast the structure and function of arteries, veins, and capillaries.
•Identify the major arteries and veins and the regions of the body they supply.
•Define blood pressure and pulse.
•Explain various factors that affect blood pressure.
•Define hypertension and hypotension and the health consequences of atherosclerosis.
The Anatomy of Blood Vessels
• Blood vessels form a closed transport system.
• Blood leaves the heart through arteries and then moves into
successively smaller arteries and into arterioles.
• Capillary beds are fed by the
arterioles which then drain venules that finally empty into veins.
• Capillaries branch through tissues to directly serve needy cells.
• The walls of blood vessels have 3 coats called tunics:
1) Tunica interna is a thin layer of endothelium on connective tissue.
2) Tunica media is smooth muscle and elastic tissue.
3) Tunica externa is fibrous connective tissue
Gross Anatomy of Blood Vessels
• The aorta is the largest artery of the body.
• The aorta snakes upward from the left
ventricle in the ascending aorta, arches to the left as the aortic arch and plunges
downward into the descending aorta.
• Most veins are more superficial than arteries.
• Major systemic veins converge at the venae cavae.
• The head and arms drain into the superior vena cava whereas lower body drains into the inferior vena cava.
• The brain is supplied by two pairs of internal carotid arteries and vertebral arteries that branch to different regions of the brain.
• The digestive organs drain blood into the hepatic portal vein that delivers blood to the liver.
Physiology of Circulation
• What make up vital signs?
• A pulse is a pressure wave created by the left ventricle through the arterial system.
• Pulse rate normally equals heart rate.
• Blood pressure is the pressure that blood exerts against the inner walls of the blood vessels.
• Systolic pressure is the pressure in the arteries at the peak of ventricular
contraction.
• Diastolic pressure is the pressure when ventricles are relaxed.
• Systolic pressure is recorded over diastolic, e.g. 120 mm Hg/ 80 mm Hg.
• Arterial pressure is related to cardiac
output and peripheral resistance which is the amount of friction encountered by the blood as it flows through blood vessels.
• Age, weight, time of day are just a few factors that can alter blood pressure.
• The sympathetic division of the autonomic nervous system raises blood pressure by constricting the blood pressure.
• The kidneys alter blood pressure by allowing more water to leave the blood which helps lower blood pressure.
• Cold causes vasoconstriction whereas heat dilates blood vessels.
• Chemicals have various effects on heart rate and blood pressure.
• Hypertension can be related to diet.