Chapter 5 Cardiovascular System: Heart and Blood Vessels

What is the cardiovascular system? Includes the heart and blood vessels. Brings nutrients to cells and helps get rid of wastes. Blood is refreshed in the lung, kidneys, intestine and liver.

Circulation Performs Exchanges Blood circulates to serve cells. Cells are served through tissue fluid. Exchanges oxygen and nutrients; removes waste products.

Blood and Organs LUNGS: Carbon dioxide (waste) leaves blood; oxygen enters. KIDNEYS: Purifies blood of wastes; water and salts retained as needed. INTESTINES: Blood absorbs nutrients. LIVER: Takes up amino acids from blood; returns proteins back to blood; removes poisons from blood; destroys bacteria and pathogens using white blood cells.

Functions of the Cardiovascular System Generate blood pressure. Transport blood. Exchange of nutrients and wastes at the capillaries. Regulate blood flow as needed.

Roles of the Lymphatic System Collects excess tissue fluid and returns it to the cardiovascular system. Fluid enters lymphatic vessels in the tissues and end in cardiovascular veins in the shoulder.

Main Pathway of Blood in the Body? Heart – Arteries – Arterioles – Capillaries – Venules – Veins – Back to the heart…

Artery Structure and Function CARRY BLOOD AWAY FROM THE HEART. Arterial walls have 3 layers: Thin innermost endothelium. Thick smooth muscle layer and elastic tissue. Outermost connective tissue.

Artery Structure and Function Strong walls withstand blood entering under pressure. Elastic tissue allows for expansion and contraction.

Arterioles ARTERIOLES: Small arteries that regulate blood pressure. Composed mostly of smooth muscle. Muscles contract, vessel constricts; blood pressure rises. Muscles relax, vessel dilates; blood pressure falls. Branch into capillaries.

Capillaries Microscopic vessels between arterioles and venules. Composed of endothelial tissue. Single layer of epithelium connected to a basement membrane.

Capillaries CAPILLARY BED: Network of many capillaries where exchange with body cells occurs. Cover nearly every square inch of the body. PRECAPILLARY SPHINCTER: Control blood flow through capillary beds.

Exchange at the capillary beds is primarily a result of osmotic and blood pressure.

Veins and Venules VEINS CARRY BLOOD TOWARD THE HEART. Veins that carry blood against gravity have valves to keep blood flowing toward the heart; no backwards movement. At any given time, 70% of blood is in veins.

Veins and Venules VENULES: Small veins that receive blood from the capillaries. Venule and vein walls have 3 layers: Thin inner endothelium. Thin smooth muscle layer. Thin outer connective tissue. ** Thinner than artery walls! Allows for greater expansion.

How can you tell the difference between an artery and vein?

Anatomy of the Heart Large, muscular organ consisting of mostly of the myocardium region. Surrounded by the pericardium. Consists of two sides, right and left, separated by the septum. Consists of 4 chambers: 2 upper, thin-walled atria 2 lower, thick-walled ventricles

Anatomy of the Heart 2 sets of valves: Semilunar valves between ventricles and attached vessels. Atrioventricular valves (AV valves) between atria and ventricles. The valves give the resulting “lub” and “dup” sound of the heart. Heart muscle itself is served by the coronary arteries.

External Anatomy of the Heart

Internal Anatomy of the Heart

Two cardiovascular Pathways of the Body PULMONARY CIRCUIT: The right side of the heart that brings blood from the body to the heart and the lungs

Two cardiovascular Pathways of the Body SYSTEMIC CIRCUIT: Left side of the heart that brings blood to the entire body to deliver nutrients and rid it of wastes

Pathway of Blood Through the Heart Inferior and superior vena cava dump O₂-poor blood into the right atrium. Passes through triscupid atrioventricular valve to the right ventricle. Passes through pulmonary semilunar valve into two pulmonary arteries; lead to the lungs. Blood becomes oxygenated in the lungs; carbon dioxide is released from blood.

Pathway of Blood Through the Heart Four pulmonary arteries bring oxygen-rich blood to the left atrium. Moves through biscupid atrioventricular valve to left ventricle. Enters into the aorta to then be pumped to the rest of the body. Eventually returns to each vena cava.

How do the structure of the vessels and heart match their functions? The left ventricle is much more muscular than the right ventricle because it must pump blood to the entire body. The arteries are more muscular than veins to withstand the higher pressure exerted on them. The veins have a thinner wall and a larger center to store blood.

How the Heart Beats 1 heart beat = 1cardiac cycle SYSTOL: Working phase; Atria contract simultaneously, then ventricles contract simultaneously. DIASTOL: Rest phase; chambers relax. Ave. hearts beat 70x/min; each heartbeat lasts 0.85sec.

What is the Cardiac Cycle?

How is the heartbeat controlled? NODAL TISSUE: Unique cardiac muscle tissue with both muscular and nervous characteristics. Two types: SA (SINOATRIAL) NODE: Upper dorsal wall of right atrium. “Pacemaker” of the heart. AV (ATRIOVENTRICULAR) NODE: Base of right atrium, near septum.

How is the heartbeat controlled? Internal control: SA node initiates the heartbeat. Automatic every 0.85 sec. Causes the atria to contract. Impulse reaches AV node. Sends signal down the AV bundle and Purkinje fibers Causes ventricular contraction. Impulses travel between gap junctions at intercalated disks.

How is the heartbeat controlled? External control: Cardiac control center in brain regulates heartbeat via parasympatheic and sympathetic nervous system. Epinephrine and norepinephrine also stimulate heart.

Visualizing the Heartbeat

Gap Junctions at the Intercalated Disks

What is an electrocardiogram (ECG)? A record of the electrical changes in the heart muscle during a cardiac cycle. P WAVE: Electrical current produced by the atria when stimulated by the SA node. Indicate atria are about to contract. QRS COMPLEX: Contraction of the ventricles. T WAVE: Recovery of ventricles. Looking at these electrical changes allows doctors to detect abnormalities

Normal ECG

Pulse Rate Rhythmic expansion and recoil of arteries. Pulse rate = heart rate Felt in the radial artery or carotid artery in the neck.

What is blood pressure? The pressure against a blood vessel wall, measured in the brachial artery of the arm. Measured with a sphygmomanometer. SYSTOLIC PRESSURE: Highest pressure during blood ejection from the heart. DIASTOLIC PRESSURE: Lowest when the ventricles relax. Average blood pressure is recorded at about 120/80 mmHg (systolic/diastolic). **Blood pressure is controlled by the arterioles!

Blood Pressure

How is blood pressure categorized?

What is important about blood flow? Blood flow is under highest pressure in the arteries to reach all of the body. Blood flow is slower in the capillaries which allows time for exchange between cells. Blood pressure is minimal in the veins and venules, but does increase after it leaves the capillaries.

If blood pressure is so low in the veins how does the blood flow increase to get back to the heart? Skeletal muscle pump Dependent on muscle contraction Respiratory pump Dependent on breathing Valves in the veins

Hepatic Portal System Brings blood from the digestive tract rich in amino acids, glucose and other nutrients to the liver. The liver synthesizes blood proteins and stores the glucose as glycogen. Liver purifies blood of toxins and pathogens before entering the hepatic vein, returning to the inferior vena cava.

Why should we care about cardiovascular disease? Cardiovascular disease (CVD) is the most common cause of death in the western world.

Disorders of the Blood Vessels: Hypertension/high blood pressure Atherosclerosis Stroke Heart attack Aneurysm

Hypertension HIGH BLOOD PRESSURE Results when blood moves through vessels at a rate higher than normal. Often due to arterial plaque. 140/90 mmHg is considered hypertensive. “Silent killer”; few symptoms. Can lead to a heart attack, stroke or kidney failure. Treated by prescription drugs and healthy lifestyles.

Atherosclerosis BUILD UP OF PLAQUE IN BLOOD VESSELS. Narrows passageway for blood and to travel the blood vessels; starves tissues. Often begins in early adulthood; symptoms usually appear after 50. Associated with a stroke, heart attack and aneurysm. Caused by smoking and fat/cholesterol-rich diets.

Atherosclerosis THROMBUS: Stationary clots on plaque. EMBOLUS: Detached clot traveling with the blood. THROMBOEMBOLISM: Clot that is first carried by blood and then stationary when lodged in small blood vessels.

Stroke Aka. Cerebrovascular accident (CVA) Usually occurs when a cranial artery bursts or is blocked by an embolism. Part of the brain dies dues to lack of oxygen. Symptoms may occur, include: Numbness of hands or face Difficulty speaking Temporary blindness in one eye.

Heart attack Aka. Myocardial infarction (MI) Portion of heart muscle dies due to lack of oxygen. If coronary becomes blocked, causes ANGINA PECTORIS: Pressure, squeezing or pain in the chest that can extend to left arm, neck, jaw, shoulder or back. Nausea, vomiting, anxiety, dizziness and shortness of breath may also occur. Nitroglycerin treatment dilates blood vessels.

Aneurysm A ballooning of a blood vessel. Atherosclerosis and hypertension can weaken a vessel and cause ballooning May eventually burst. Most commonly affect the abdominal artery or the arteries leading to the brain. Treated with surgery to replace weak portion with plastic tubing.

How are disorders of the blood vessels treated? Dissolving blood clots: t-PA is a drug that dissolves clots Aspirin thins blood

How are disorders of the blood vessels treated? Treating clogged arteries: BYPASS SURGERY: A vein from the leg is taken and used to bypass a clogged artery. STENTS: Metal mesh cylinder inserted into a clogged artery to hold it open ANGIOPLASTY: Tube with a balloon is inserted into the clogged area and the balloon is then inflated to open the vessel. A stent and angioplasty may be used in combination.

Disorders of the Heart and Treatments HEART FAILURE: Heart no longer pumps properly. Treatments: Abnormal heart rhythm; Carioverter-defibrillator (ICD). Left ventricular assist device (LVAD). Heart transplant Either natural or artificial (TAH)

Do’s and Don’ts for Prevention of Cardiovascular Disease Do not smoke. Do not abuse drugs. Keep your weight down to decrease chances of hypertension and Type II diabetes. Eat a healthy diet. Low in saturated and trans fats Low in cholesterol Know your blood cholesterol . Exercise.