Circulation The Heart and Blood Vessels What

Circulation The Heart and Blood Vessels

What is the function of the circulatory system? » » » » consists of a muscular pump and two circulatory loops one loop delivers blood to the body, one delivers blood to the lungs

Functions of the blood: • transports oxygen to the body cells • transports nutrients from the digestive system to body cells • transports hormones to body cells • transports wastes from the body cells to excretory organs • distributes body heat • helps to maintain a constant p. H in tissue fluids • prevents infections

Blood is supplied to three separate sections of the body. They are the systemic system, the pulmonary system and the coronary system.

Systemic system • carries blood throughout the body (except the heart and lungs) • brings nutrients and oxygen to the body tissues • removes carbon dioxide and other wastes

Pulmonary System • carries blood from the right side of the heart to the lungs where carbon dioxide is eliminated and oxygen is picked up • blood returns to the left side of the heart where it is distributed via the systemic system

Coronary system • provides blood to the heart • http: //www. youtube. com/watch? v=Lqhv m. UEd. OYY&feature=related • http: //www. youtube. com/watch? v=nx-XRC_1 n. Q&p=426 FEBCEBDD 42 DD 1&playnext=1&inde x=12 • http: //www. youtube. com/watch? v=o. Hg 5 Zvr. I 4 N Y

The Blood Vessels • there are three major divisions of blood vessels:

The arteries (carry blood away from the heart to body tissues) • thick muscular walls with three distinct layers of tissue • stretch to accommodate blood rushing in • blood flows due to the elasticity of the artery walls • arteries of various sizes (large to medium to small) branch the entire body • the largest artery is the aorta, found in the heart • smaller sized arteries are called arterioles whose diameter is regulated by nerves • arterioles branch into capillaries

Capillaries (form an extensive exchange system) • have thin walls through which nutrients and wastes can pass • provide a site of exchange between the blood and the tissue fluid surrounding the cells of the body • permeable to many substances: O 2, CO 2, water soluble ions, vitamins and some proteins • oxygen diffuses from the blood through the capillary walls to the surrounding tissue, and carbon dioxide and other wastes move in the opposite direction • work through the processes of endocytosis, exocytosis, osmosis and diffusion • one cell layer thick – easy to destroy (high blood pressure can burst a capillary, even a bruise is evidence of ruptured capillaries)

Remember the alveoli?

Veins (carry blood back to the heart) • capillaries merge and form venules, which then merge into veins • walls are thinner and weaker than the walls of arteries • the pressure of blood is less than it is in the arteries so veins need valves to move the blood back to the heart • contractions of the skeletal muscles surrounding the veins also aid in the pushing of blood back to the heart • veins start off small and converge with other veins, forming larger and larger vessels • the largest veins are the superior and inferior vena cava found in the heart

http: //defiant. corban. edu/jjohnson/Pages/Bio. II/42/Circulation. Notes. html

All blood vessels are capable of changing in diameter depending on a situation: • vasoconstriction is the narrowing of blood vessels due to the contraction of smooth muscle fibres in the arterioles. – for example, when we turn white in fright, skin blood vessels constrict so that more blood is supplied to the muscles • vasodilation is the widening of blood vessels resulting in more blood entering the tissue area, caused by a relaxation of the muscle fibres in the blood vessels – for example, blushing is a vasodilation of skin blood vessels

Dissection • http: //www. zerobio. com/videos/sheep_he art_anatomy. html • http: //www. zerobio. com/videos/dissect_s heepheart 1. html

The Heart • the heart is a muscular pump in the chest cavity • it is the workhorse of the circulatory system propelling blood through 80, 000 km of blood vessels • each day the heart beats 100, 000 times, adjusting its rate to meet the needs of the body

Human hearts have four chambers – Composed of two thin walled atria and two thick walled ventricles – The atria act as holding chambers for blood entering the heart from the systemic or pulmonary circulatory systems – Ventricles are stronger and more muscular, they pump blood to the tissues in the body http: //www. wvhsta. org/summer_2003/biomed/teachers/Anatomy 1/anatomy 2/index_anat omy. htm

Layers of Heart tissue

Layers of Heart Tissue • • • Pericardium – a thin closed sac surrounding the heart and the bases of the vessels that enter and leave the heart. It is filled with a clear slippery fluid that reduces friction caused by heart contractions Myocardium – the middle layer, it is the thickest part of the wall and is composed mostly of cardiac muscle cells Endocardium – inner layer that forms the lining of the heart chambers

The flow of blood • each side of the heart is a separate pump with the right side pumping blood to the lungs (pulmonary circulation), and the left side pumping blood to the body (systemic circulation). http: //www. pbs. org/wgbh/nova/heartmap. html

Orientation of the heart • Drawings of the heart will show the left side of the heart on the right side of the diagram, and the right side on the left. WHY IS THIS? – This is what your heart would look like if you were looking directly at your own heart. It is like a photograph of your heart

The Course that Blood Takes • blood that is low in O 2 enters the right side of the heart through the superior and inferior vena cavae (plural of cava) – these veins empty directly into the right atrium, the top chamber on the right side of the heart • blood is pumped from the right atrium into the right ventricle which is the lower chamber on the right side of the heart • when the right ventricle is full, the muscles in its wall contract forcing blood into the pulmonary arteries which lead to the lungs

• blood whose oxygen supply has been restored (from the lungs) flows back to the heart via the pulmonary veins • the pulmonary veins empty directly into the left atrium, the upper chamber on the left side of the heart • the blood is pumped from the left atrium to the left ventricle • when the left ventricle is full, its thick muscular walls contract, propelling blood into the aorta • the aorta carries oxygenated blood away from the heart delivering it to the cells and tissues of the body

• both atria fill simultaneously, then contract, bringing blood to the ventricles. • Both ventricles fill simultaneously pumping blood to the pulmonary and systemic systems • Flow of blood animation: • https: //www. youtube. com/watch? v=TMd. Kp 2 z. Hgog

The Valves of the Heart http: //www. lifeisnow. com/My. Heart/Anatomy. aspx

Atrioventricular Valves (A-V valves) • the valves between the atria and ventricles on the left and right sides of the heart • consists of two or there flaps of tissue that are anchored to the inner walls of the ventricles by the chordae tendinae • the A-V valve on the right side of the heart, between the right ventricle and atrium is called the tricuspid valve (has three flaps of tissue) • the A-V valve on the left side of the heart is called the bicuspid valve (has two flaps of tissue)

Semilunar Valves • found at the areas in which blood vessels attach to the ventricles (at the pulmonary artery and aorta) • consists of three semicircular flaps of tissue (resemble half moons)

• both types of valves are one way valves which open when blood pressure builds on one side and close when blood pressure increases on the other – when the ventricles contract, blood forces the semilunar valves to open forcing the blood to rush out of the ventricles into the arteries (aorta and pulmonary artery) – the semilunar valves then close, preventing blood from flowing back to the ventricles – the A-V valves function in the same way

Nervous Control of the Heart • cardiac muscle is able to contract without nervous stimulation • called myogenic muscle • a heart that is removed from the body will continue to beat over a short period of time • http: //www. youtube. com/watch? v=i. Kntqy nko. FICouple Married 72 Years Dies Holding Hands

The SA node (sino-atrial node) • the hearts tempo is set by a bundle of specialized nerve and muscle fibres located where the vena cava enters the right atrium • acts as a pacemaker setting the rate of the heart at about 70 beats per minute • nerve impulses go from the SA node to the other muscle cells by modified muscle tissue – contractions originate in the atria and travel to a second node, the atrioventricular node (A-V node)

The A-V node • passes nerve impulses along special tracts through the dividing septum – the muscle that divides the left and right sides of the heart http: //hrspatients. org/patients/the_normal_heart/electrical_system. asp

The Bundle of His and Perkinje Fibres • splits into two trunks part way down the septum • at the lower portion of the venticle, one bundle turns up along the outside wall of the left ventricle and branches out • the other bundle turns up the outside wall of the right ventricle • these bundles branch out into Perkinje Fibres – Perkinje Fibres pass into muscle cells and cause contraction of the ventricles – Electrical System animation: http: //www. nhlbi. nih. gov/healthtopics/hhw/electrical. html

Autonomic Nerves • nerves that we cannot control • two autonomic nerves from the brain affect heart rate – Vagus Nerve – an inhibitory nerve that causes the heart rate to decreases • this is a parasympathetic nerve that operates in times of relaxation – Augmentor Nerve – an excitatory nerve that causes the heart rate to increase • this is a sympathetic nerve that operates in times of stress (eg. An adrenaline rush)

Heart Sounds • the sound that we hear when listening to the heart is caused by the closing of the valves • the lubb sound is caused by the closing of the AV valves • the dub sound is caused by the closing of the semilunar valves • the left and right AV valves and the two semilunar valves do not close at the same time • Heart in action: http: //www. nhlbi. nih. gov/healthtopics/hhw/electrical. html http: //www. bostonscientific. com/templatedata/imports/HTML/CRM/heart_signals. html

• a heart murmur is caused by faulty heart valves which permit the backflow of blood into the heart – the AV valves must withstand much pressure and are susceptible to defects – heart murmur patients will compensate for the increased blood in the ventricle by increasing the heart rate and strength of each contraction

Heart Beat Impairments • tachycardia – heart beats more that 100 times per minute due to increased exercise, some drugs or severe angina • brachycardia – the heart beats slower than normal

The Electrocardiogram • measures the electrical activity of the heart – changes in the electrical activity of the heart can reveal normal or abnormal occurrences of the cardiac system – see figure 8. 8 on page 275

• the electrocardiograph can be interpreted on the basis of three waves – P wave – measures atrial contraction – QRS wave – measures ventricular contraction – T wave – signals that the ventricles have recovered from their contraction. • A stress test is an electrocardiograph of a persons response to exercise – Indicates the heart working in a stressful situation

Cardiac Output • is the total volume of blood pumped by the ventricle per minute • product of heart rate (HR) and stroke volume (SV) • The stroke volume at rest in the standing position averages between 60 and 80 ml of blood in most adults. • Thus at a resting heart rate of 80 beats per minute the resting cardiac output will vary between 4. 8 and 6. 4 L per min. • The cardiac output of Olympic medal winners in cross country skiing increased 8 times above resting cardiac output to approximately 40 liters for one minute of maximal work with an accompanied stroke volume of 210 ml per beat.

• As a result of increased training, the crosscountry skier exhibits a greater stroke volume (240) compared to untrained (110), trained (150), and highly trained (210) individuals during exercise. • Why do athletes typically have lower heart rates and cardiac output? • If I have a low heart rate, does that necessarily mean that I am physically fit?

Blood Pressure • blood pressure of the brachial artery (major artery of the arm) is measured with a device called a sphygmomanometer – shuts off the flow of blood to the brachial artery by increasing air in the cuff around the arm – two readings are given when reading blood pressure: • systolic pressure – read at the point where a heart beat sound is heard after the cuff is slowly drained of air as the blood flows back into the brachial artery during ventricular contraction • diastolic pressure – measured when the sound disappears as blood is flowing into the brachial artery and the ventricles relax

• blood pressure is read systolic/diastolic • normal pressure is 120 mm Hg systolic/ 80 mm Hg diastolic • blood pressure is not the same in all arteries, the further away from the heart you are, the lower the blood pressure • Factors that affect blood pressure: – Cardiac output – the greater the cardiac output, the greater the blood pressure – Arteriolar resistance – vasoconstriction increases blood pressure, vasodilation decreases blood pressure

The Lymphatic System • Lymph is a fluid that is found outside the capillaries – most often lymph contains some small proteins that have leaked out of the capillary walls • The lymphatic system is a network of vessels that operate in an open ended system (similar to the circulatory system) – it returns excess proteins of the ECF to the circulatory system – it is key in maintaining osmotic pressure in the tissues and surroundings, and preventing tissue swelling

• Lymph nodes are enlarged areas on the lymph vessels that contain white blood cells to filter bacteria from the lymph – they filter damaged cells and debris from the lymph – found throughout the body – mononucleosis infects the lymph nodes in your neck region

• edema (tissue swelling) occurs if the lymphatic system fails to remove excess fluids from the tissues Examples of edema: Obstructed veins (varicose veins) Localized edema – occurs around injuries Malnutrition (starvation) Kidney Damage Elephantiasis – filaria worm block the lymph nodes that usually drain the leg and the leg swells literally to the size of an elephant’s leg. (Can also affect the scrotum of males causing it to enlarge so much in some cases that a man must carry his scrotum in a wheelbarrow to move it about).

Diseases and Disorders of the Circulatory System Angina • pain that is felt when oxygen supply to the myocardium is reduced • pains appear in the center of the chest and spread to the neck, upper back and left arm • caused by stress or CO exposure • a symptom of a heart attack http: //www. supplementnews. org/angina/

Diseases and Disorders of the Circulatory System Myocardial Infarction (heart attack) • caused by thrombosis (blockage of a coronary artery or blood clot) • blood flow is restricted to the heart cutting off the supply of oxygen and nutrients • usually occur when the arteries are already narrowed • severity depends on the amount of damage to the heart

Treatment for Heart Attack: • proper diet and exercise • doses of aspirin can reduce the chances of having a heart attack • blood clot dissolving agents reduce damage to heart tissue (streptokinase, TPA tissue plasminogen activator) • coronary bypass surgery • cleaning clogged blood vessels with a catheter (balloon angioplasty) • lasers to burn away plaque in artery walls http: //heart. health. ivillage. com/bypasssurgery 7. cfm

Diseases and Disorders of the Circulatory System Atherosclerosis • a buildup of fat covered by mineral plaque deposits on the arteries • blood clots can build up around these deposits

Diseases and Disorders of the Circulatory System Varicose Veins • occur when the valves in the veins are not functioning properly and gravity carries the blood down the legs where pooling occurs • surface veins bulge and become larger • caused by genetics and lifestyle http: //www. vintage 3. com/servces. Surgery. htm

Diseases and Disorders of the Circulatory System Hypertension • also called high blood pressure • caused by heredity, stress, poor diet, high salt intake and by disorders of other organ systems • more common in men than in women

Diseases and Disorders of the Circulatory System Heart Murmur • caused by faulty heart valves Stroke • caused by the blood being restricted from a certain part of the brain, or a blood vessel bursting in the brain Heart Problems: http: //www. bostonscientific. com/te mplatedata/imports/HTML/CRM/h eart/cardiovascular. html http: //www. heartzine. com/heart-disease/188 -Stroke. html