Chapter 5 Cardiovascular System: Heart and Blood Vessels Mader, Sylvia S. Human Biology. 13th Edition. McGraw-Hill, 2014.

Points to Ponder What are the functions of the cardiovascular system? What is the anatomy of the heart and blood vessels (veins and arteries)? How is the heart beat regulated? What is blood pressure? What are common cardiovascular diseases and how might you prevent them?

Cardiovascular system Includes heart and blood vessels Brings nutrients to cells that are bathed by tissue fluid and helps get rid of wastes Exchanges with tissue fluid and not directly with cells Blood is refreshed in Lungs: gas exchange Kidneys: water and salt retained, waste excreted Intestine: nutrient intake Liver: amino acid uptake and remove toxin Lymphatic vessels help this system by collecting excess fluid surrounding tissues and return it to the cardiovascular system

What are the function of the cardiovascular system? 5.1 Overview of the cardiovascular system What are the function of the cardiovascular system? Generate blood pressure via heart contractions Transport blood via blood vessels Exchange of nutrients and wastes at the capillaries refreshes blood and tissue fluid Regulate blood flow as needed

What is the main pathway of blood in the body? 5.2 The types of blood vessels What is the main pathway of blood in the body? Heart – arteries – arterioles – capillaries - venules – veins – back to the heart…

Arteries and arterioles: 5.2 The types of blood vessels Arteries and arterioles: Carry blood away from the heart Their walls have 3 layers: Thin inner epithelium Thick smooth muscle layer Outer connective tissue elastic tissue to absorb pressure Strong walls support vessel when blood enters under pressure Arterioles are small arteries that regulate blood pressure Muscle fibers contract  vessel constricts Muscle fibers relax  vessel dilates Regulate blood pressure

Capillaries: Microscopic vessels between arterioles and venules Made of one layer of epithelial tissue only Form beds of vessels where exchange with body cells occurs Combined large surface area Only certain capillaries are open at any given time After eating, capillaries serve the digestive system are open Those that serve the muscles are closed Precapillary sphincters contract, and blood moves from arteriole to venule by way of an arteriovenous shunt

Blood Vessels

Exchange at the capillary beds is primarily a result of osmotic and blood pressure Causes water to move from capillary to tissue fluid Osmotic Pressure created by presence of salts and plasma proteins Causes water to move in the opposite direction At arterial end of capillaries Blood pressure is higher than osmotic pressure of blood Water exits a capillary at this end Midway along the capillaries Two forces are equal and cancel each other out No net movement of water Solutes diffuse according to their concentration gradient Oxygen and nutrients out and CO2 and waste into capillary Venule end of capillaries Blood pressure decreased, osmotic pressure is greater in blood Water tends to move into the capillary

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

Lymphatic Capillaries Collects excess tissue fluid once collected in lymphatic capillaries  lymph Lymph is returned to the systemic venous blood at the subclavian veins of the shoulder

5.2 The types of blood vessels Veins and venules: Venules are small veins that receive blood from the capillaries Venule and vein walls have 3 layers: Thin inner epithelium Thick smooth muscle layer Outer connective tissue Wall is thinner and can expand to a greater extent 70% of blood in veins  blood reservoir If blood lose occurs veins constrict to provide more blood to body Veins carry blood toward the heart Veins that carry blood against gravity have valves to keep blood flowing toward the heart

How can you tell the difference between an artery and vein? 5.2 The types of blood vessels How can you tell the difference between an artery and vein?

5.3 The heart is a double pump Anatomy of the Heart A large, muscular organ consisting of mostly cardiac tissue called the myocardium Serviced by the coronary artery and cardiac vein Muscle fibers branched and joined at intercalated disks Allow atrium and ventricles to contract simultaneously It is surrounded by a sac called the pericardium Supports and protects the heart Consists of two sides, right and left, separated by a septum Consists of 4 chambers: 2 atria (thin walled) and 2 ventricles (thick walled)

5.3 The heart is a double pump

Anatomy of the Heart 2 sets of valves keep blood flowing in the right direction: atrioventricular valves (AV valves)  between atria and ventricle Supported by chordae tendineae attached to papillary muscles Prevent valve from inverting when the heart contracts Right = tricuspid, Left = bicuspid (mitral valve) semilunar valves  between ventricle and attached vessels Pulmonary semilunar valve and aortic semilunar valve The valves give the resulting “lub” and “dup” sound of the heart

5.3 The heart is a double pump

Two cardiovascular pathways in the body Pulmonary circuit: the right side of the body that brings blood from the body to the heart and the lungs Systemic circuit: the left side of the heart that brings blood to the entire body to deliver nutrients and rid it of wastes

Blood flow through the heart 1. Inferior and superior vena cava (1) dump oxygen poor blood into the right atrium (2) 2. Right atrium sends oxygen poor blood through AV valve (tricuspid) 3. Right ventricle (3) oxygen poor blood through the pulmonary semilunar valve 4. 2 pulmonary arteries (4) that lead to the lungs (5) where blood becomes oxygenated 5. Pulmonary veins (6) bring oxygen rich blood from the lungs back the left atrium (7) 6. Left atrium sends blood through AV valve (bicuspid/mitral) 7. Left ventricle (8) is large and muscular to pump blood through aortic semilunar valve Aorta (9) and to the rest of the body (10) Arterioles from the artery branch into capillaries, where exchange takes place, and then venules join into the vein Eventually blood will be pumped back to each vena cava(1)

Visualizing blood flow through the heart 5.3 The heart is a double pump Visualizing blood flow through the heart

How do the structure of the vessels and heart match their functions? 5.3 The heart is a double pump How do the structure of the vessels and heart match their functions? The left ventricle is much more muscular than the right ventricle (pumps to the lungs) because the left ventricle must pump blood to the entire body Heart sends blood out under pressure into the arteries 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 does the heartbeat occur? 5.3 The heart is a double pump How does the heartbeat occur? Heartbeat = cardiac cycle During systole the atria contract together followed by the ventricles contracting together This is followed by diastole a rest phase, when the chambers relax This cardiac cycle, heartbeat, on average occurs 70 times/minute Lub: increased pressure of blood inside ventricle forces the cusps of the AV valve to shut Dub: Pressure of blood inside a ventricle causes the semilunar valves (pulmonary and aortic) to open Ventricle relaxes and blood in the arteries pushes back, causing the semilunar valves to close

Cardiac Cycle

How is the heartbeat controlled? 5.3 The heart is a double pump How is the heartbeat controlled? 1. Internal control: Node tissue in two locations of the heart The sinoatrial (SA) node in the right atrium initiates the heartbeat and causes the atria to contract Also known as pacemaker, keeps heartbeat regular This impulse reaches the atrioventricular (AV) node, in the right atrium send a signal down the AV bundle and Purkinje fibers that causes ventricular contraction These impulses travel between gap junctions at intercalated disks Allow electrical current to flow from cell to cell

How is the heartbeat controlled? 2. External control: heartbeat is also controlled by cardiac center in the medulla oblongata of the brain Parasympathetic (resting) and sympathetic (fight or flight) portions of the nervous system Hormones released by adrenal medulla, such as epinephrine and norepinephrine, stimulate the heart

Visualizing the heartbeat

Visualizing the gap junctions at the intercalated disks 5.3 The heart is a double pump Visualizing the gap junctions at the intercalated disks

What is an electrocardiogram (ECG)? 5.3 The heart is a double pump What is an electrocardiogram (ECG)? A record of the electrical changes in the heart muscle during a cardiac cycle The atria produce an electrical current when stimulated by the SA node called the P wave The contraction of the ventricles is the QRS complex The recovery of the ventricles is called the T wave Looking at these electrical changes allows doctors to detect abnormalities

How does a “normal” and abnormal ECG compare?

Pulse Pulse = rhythmic expansion and recoil of an arterial wall Arterial walls pulse whenever the left ventricle contracts Can be felt in any artery that runs close to the body’s surface Commonly used Radial Artery: palm side of wrist Carotid Artery: either side of the trachea in the neck

5.4 Features of the cardiovascular system What is blood pressure? The pressure against a blood vessel wall, usually measured in a brachial artery in the arm The highest pressure is during blood ejection from the heart called the systolic pressure The lowest pressure is the diastolic pressure when the ventricles relax Average blood pressure is recorded at about 120/80 mmHg (systolic/diastolic) Reminder: this is controlled by the arterioles Systolic and diastolic blood pressure decrease with distance from the left ventricle

Blood Pressure

How is blood pressure categorized? 5.4 Features of the cardiovascular system How is blood pressure categorized?

What is important about blood flow? 5.4 Features of the cardiovascular system What is important about blood flow? Blood flow is under the highest pressure in the arteries but remember the thick, muscular walls Blood flow is slower in the capillaries which is important to allow time for exchange between cells Blood pressure is minimal in the veins and venules but blood flow increases

If blood pressure is so low in the veins why does the blood flow increase? Venous Return Depends on: Skeletal muscle contraction Compression forces blood past valves Breathing - inhale, chest expand and decrease pressure in thoracic cavity. Blood flows from higher pressure (abdominal cavity) to lower pressure (thoracic cavity) - exhale, reverse but valves prevent back wash Valves

The heart’s blood supply: Coronary circulation 5.5 Two cardiovascular pathways The heart’s blood supply: Coronary circulation There are small coronary arteries that supply the heart with oxygen rich blood that are separate from the systemic and pulmonary pathways of the body First branch off of the aorta, just above the aortic semilunar valve Aorta  coronary artery  arterioles  coronary capillary bed  venules  converge at cardiac veins  right atrium

What is the hepatic portal system? 5.5 Two cardiovascular pathways What is the hepatic portal system? A system that brings blood from the digestive tract rich in amino acids and glucose to the liver The liver synthesizes blood proteins and stores the glucose as glycogen The liver also plays a role in purifying blood from the digestive tract Finally, the blood exit the liver via the hepatic vein and blood will return to the heart via the inferior vena cava

Why should we care about cardiovascular disease? 5.7 Cardiovascular disorders 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: 5.7 Cardiovascular disorders Disorders of the blood vessels: Hypertension/high blood pressure Atherosclerosis Stroke Heart attack Aneurysm

5.7 Cardiovascular disorders 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 hypertension A silent killer because there are few symptoms Can lead to a heart attack, stroke or kidney failure

Atherosclerosis A build up of plaque in blood vessels 5.7 Cardiovascular disorders Atherosclerosis A build up of plaque in blood vessels Plaque that is stationary is called a thrombus and an embolus when it detaches and can move to distant sites Associated with a stroke, heart attack and aneurysm

Stroke Also known as a cerebrovascular accident (CVA) 5.7 Cardiovascular disorders Stroke Also known as a cerebrovascular accident (CVA) Usually occurs when a cranial artery is blocked or bursts Part of the brain dies dues to lack of oxygen Symptoms may occur including numbness of hands or face, difficulty speaking and inability to see in one eye

Heart attack Also known as a myocardial infarction (MI) 5.7 Cardiovascular disorders Heart attack Also known as a myocardial infarction (MI) Part of the heart dies due to lack of oxygen Can begin with angina pectoris, a pain that radiates down the left arm due to a blockage of a coronary artery

Aneurysm A ballooning of a blood vessel 5.7 Cardiovascular disorders Aneurysm A ballooning of a blood vessel Atherosclerosis and hypertension can weaken a vessel and cause ballooning The most commonly affected is the abdominal artery or the arteries leading to the brain

How are disorders of the blood vessels treated? 5.7 Cardiovascular disorders How are disorders of the blood vessels treated? Dissolving blood clots: t-PA is a drug that dissolves clots Treating clogged arteries: Bypass surgery: usually a vein from the leg is taken and used to bypass a clogged artery Stents: wire mesh cylinder inserted into a clogged artery to hold it open Angioplasty: a 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 its treatment 5.7 Cardiovascular disorders Disorders of the heart and its treatment Disorders: Heart failure is when the heart no longer pumps properly Treatments: Left ventricular assist device(LVAD) Heart transplant either natural or artificial

5.7 Cardiovascular disorders Health Focus: The 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