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Main Structures of the Circulatory System 1. The heart 2. Blood vessels 3. Blood Blood vessels found in glands. Functions of the Circulatory System Transport gases- oxygen from the lungs to cells around the body and carbon dioxide from the cells to the lungs. Transport nutrients (sugars, calcium). Transport wastes from cells to organs that are capable of breaking wastes down (liver, kidneys) Blood contains white blood cells that fight infection. Maintains the pH levels and ionic concentration of fluids in the body. Helps maintain body temperature The Heart The heart is a hollow organ about the size of a clenched fist. It is made almost entirely of muscle. As the heart pumps blood, it creates a pressurized system that forces blood to travel through the blood vessels throughout your body, and back to the heart again, thus circulation! Your heart pumps more than 6,000 Liters a day! (Equivalent to 1600 gallons of blood a day). The Heart The heart has two layers: 1. The outer layer of the heart is a protective film called pericardium. (peri means outer) 2. The inner layer of the heart is known as myocardium. (myo means muscle) Heart Chambers The Human heart has 4 chambers, as follows: the right ventricle the left ventricle the right atrium the left atrium. Atria pump blood into the heart. Ventricles pump blood out of the heart. *Notice the sides of the heart are reversed. Think of yourself as the doctor, and the heart you are looking at as the patient’s. Your rights and lefts would be switched. Heart Valves Blood is pumped through the chambers, aided by four heart valves. The valves open and close to allow the blood to flow in only one direction. The function of the heart valves is to act as a oneway door to prevent the backflow of blood. Heart Valves The tricuspid valve is between the right atrium and right ventricle. The pulmonary valve is between the right ventricle and the pulmonary artery. The mitral valve is between the left atrium and left ventricle. The aortic valve is between the left ventricle and the aorta. Each valve has a set of flaps (also called leaflets or cusps). When working properly, the heart valves open and close fully. The average person’s heart beats about 70 times per minute- the more “fit” you are, the less your heart beats. The heart’s pacemaker is an electrical signal called an SA node (sinoatrial node). It is located in the right atrium. The SA node is a bundle of nerve cells that control the hearts muscle contractions in an orderly manner by triggering electricity! The Heart Aorta Superior Vena Cava Pulmonary Artery Pulmonary Veins Pulmonary Veins Left atrium Right atrium Mitral Valve Tricuspid valve Right ventricle Inferior vena cava Left ventricle Label the remaining parts of the heart! BLOOD VESSELS There are 3 types of blood vessels: 1. Arteries 2. Capillaries 3. Veins Arteries Arteries are blood vessels made of smooth muscle that carry blood away from the heart. This definition suggests that all arteries carry oxygenated blood- which is true for all except the pulmonary arteries. Arteries con’t Some major arteries you may have heard of before: Femoral artery Carotid artery Abdominal artery Coronary artery Major arteries the biggest ones of all, but still very thin (less than 1 mm in diameter). Arteries get smaller as they approach the tiniest blood vessels, the capillaries. These smaller versions of arteries are known as arterioles. Veins Veins are blood vessels made of smooth muscle that carry blood towards the heart. All veins in your body, except the pulmonary veins carry deoxygenated blood. Veins have valves to ensure that there is no backflow of blood as the blood works its way up to the heart. Valve Varicose veins are veins that have faulty valves. They are common in older people, when valves may not work as well. This causes the veins to swell. Capillaries Capillaries are the tiniest blood vessels. Capillaries deliver oxygen and nutrients to cells as well as take waste from cells. Therefore, they can carry oxygenated or deoxygenated blood. They are found between arteries and veins. Blood Vessel Network Direction of Blood Flow The direction of blood flow is very specific. Deoxygenated blood (blood that contains carbon dioxide) travels differently from oxygenated blood as there are different destinations. The lungs work very closely with the circulatory system to release CO2 and gain oxygen. Direction of Blood Flow: Oxygenated blood The following sequence is the path that oxygenated blood will travel through the different parts of the body: a. Capillaries within the lungs b. Pulmonary vein The ONLY vein that carries oxygenated blood! c. Left atrium d. Left ventricle e. Aorta f. Arteries Blood becomes oxygenated when oxygen diffuses across the alveolar membrane into the capillaries of the lungs. h. Cells (ALL cells need O2 to survive!) g. Capillaries in the body tissues Direction of Blood Flow: Deoxygenated Blood Once blood reaches the cells, red blood cells drop off oxygen, and pick up carbon dioxide, becoming deoxygenated. The following sequence is the path of deoxygenated blood throughout the body: a. Cells b. Capillaries c. Veins d. Vena cava Blood becomes deoxygenated when the oxygen diffuses from your blood to your cells, and carbon dioxide (celluar waste) diffused to the blood. e. Right atrium f. Right ventricle g. Pulmonary artery The ONLY artery that carries deoxygenated blood! h. Capillaries within the Lungs. … And the cycle repeats (circulates) when oxygen diffuses into the capillaries at the lungs! The heart is a double pump! This is because one half of the heart (the right ventricle) sends blood through the lungs; and the other half of the heart (the left ventricle) sends blood through the body. The right ventricle contains deoxygenated blood and the left ventricle contains oxygenated blood. Diffusion of Oxygen and Carbon Dioxide across the Alveoli The lungs contain tiny structures called alveoli (singular: alveolus). Diffusion of O2 Alveoli is where gas exchange occurs. Oxygen enters the alveolus and then diffuses into the blood stream. Carbon dioxide takes the opposite route. Diffusion of CO2 The Heart Song Blood Pressure (BP) When you go to the doctor they take your BP. You’ve probably heard something like “120 over 80! Excellent!” And you’ve probably just smiled and nodded Sphygmomanometer What do those numbers mean? When your heart is beating, it is contracting and relaxing. This creates two different pressures, one will be higher than the other. Systolic pressure- the pressure measured on your blood vessels during heartbeats (contractions). Diastolic pressure- the pressure measured on your blood vessels between heartbeats (relaxed). Systolic BP is measured in milimeters of mercury mm/Hg Diastolic (mmHg), the SI unit for fluid pressure. Common Term Scientific Term Red Blood Cell Erythrocyte White Blood Cell Leukocyte Platelets Thrombocytes Functions of Blood: 1) Transportation: o oxygen & carbon dioxide o nutrients o waste products (metabolic wastes, excessive water, & ions) 2) Regulation - hormones & heat (to regulate body temperature) 3) Protection - clotting mechanism protects against blood loss & leukocytes provide immunity against many disease-causing agents What is blood made of? Components of Blood - average adult has about 5 liters 1) Formed Elements o Red blood cells (or erythrocytes) o White blood cells (or leucocytes) o Platelets (or thrombocytes) Formed elements account for 45% of the total volume of blood, most of which is erythrocytes. Components of Blood 2) Plasma= water + dissolved solutes , accounts for 55% of the total volume of blood. Red blood cell, platelet, white blood cell. Red Blood Cells (or erythrocytes) 1 - biconcave discs 2 - lack a nucleus & cannot reproduce (average lifespan = about 120 days) 3 - transport hemoglobin (each RBC has about 280 million hemoglobin molecules) 4 - Typical concentration is 4-6 million per cubic mm 5 - contain carbonic anhydrase (critical for transport of carbon dioxide) How do we know percentages? A centrifuge is a device that rotates materials at a very high speed to separate solids and liquids. Hemoglobin composed of globin (made up of 4 highly folded polypeptide chains) + 4 heme groups (with iron) each molecule can carry 4 molecules of oxygen • called oxyhemoglobin when carrying oxygen & called reduced hemoglobin when not carrying oxygen • can also combine with carbon dioxide & helps transport carbon dioxide from the tissues to the lungs White blood cells (or leucocytes or leukocytes): have nuclei & do not contain hemoglobin typical concentration is 5,000 - 9,000 per cubic millimeter Types of WBCs: o Granular white blood cells include: neutrophils (50 - 70% of WBCs) eosinophils (1 - 4%) basophils (less than 1%) o Agranular (or non-granular) white blood cells include: lymphocytes (25 - 40%) monocytes (2 - 8%) White Blood Cells Platelets (or thrombocytes) 1 - formed in the bone marrow (from cells called megakaryocytes) 2 - have no nucleus, but can secrete a variety of substances & can also contract (because they contain actin & myosin) 3 - normal concentration in the blood is about 250,000 per cubic millimeter 4 - remain functional for about 7 - 10 days (after which they are removed from the blood 5- play an important role in hemostasis (preventing blood loss) Plasma Components: 1 - Water - serves as transport medium; carries heat 2 - Proteins Albumins Globulins Fibrinogen o important in clotting Recall that your blood is mostly plasma (55%). Plasma is mostly water. Plasma continued 3 - Inorganic constituents (1% of plasma) - e.g., sodium, chloride, potassium, & calcium 4 - Nutrients - glucose, amino acids, lipids & vitamins 5 - Waste products - e.g., nitrogenous wastes like urea 6 - Dissolved gases - oxygen & carbon dioxide 7 - Hormones Hemostasis - prevention of blood loss from broken vessel. Hemostasis results in a clot- formed primarily of fibrin threads but also including blood cells & platelets. Fibrin is a protein that your body builds in response to blood loss. Blood clots in the right places prevent the loss of blood from ruptured vessels, but in the wrong place can cause problems such as a stroke.