The circulatory system is one of the primary systems of the body. Massage students and therapists need to have a good understanding of the circulatory system anatomy and physiology before taking the MBLEx. It is also important to have a good understanding of the circulatory system because improving circulation is one of the most common claims of why massage therapy is beneficial. So it is useful to be able to explain why this is to potential clients.
Sometimes called the cardiovascular system, the circulatory system is responsible for circulating blood throughout the body. It works together with other body systems to support their functions.
The circulatory system can be divided into two major components: the cardiovascular system and the lymphatic system. The MBLEx massage exam content outline lists the lymphatic system separately. So that will be discussed in a different blog post. This post focuses primarily on the cardiovascular component of the circulatory system.
The purpose of this post is to help massage students and therapists preparing for their massage exam to understand the most important features and functions of the circulatory system.
Primary functions of the circulatory system
The primary function of the circulatory system is to circulate blood throughout the body. As the blood circulates, it transports various substances to enable the rest of the body to functions properly. This circulation of blood helps to maintain homeostasis.
Functions that the circulatory system performs include:
- Picking up oxygen from the lungs and delivering it to the cells of the body.
- Removing carbon dioxide that is produced by cellular metabolism, and delivering it to the lungs to be removed.
- Transporting nutrients that are absorbed through the gastrointestinal system (GI) to the body cells to produce energy.
- Transporting blood through the filtering organs to remove or recycle waste products. These filtering organs are the kidneys, liver, and spleen.
- Circulating hormones that act like messengers to communicate with other organs and tissues.
- Transport other substances like antibodies, electrolytes and platelets.
- Transfer heat from the core to help warm the extremities when cold, and dissipate heat when hot.
There are two main types of circulation: pulmonary circulation and systemic circulation.
Blood circulates to and from the lungs in a process called pulmonary circulation. The blood is pumped out through the right ventricle to the lungs, and returned to the left atrium of the heart. This process works with the respiratory system to get rid of carbon dioxide (CO2) and pick up oxygen (O2) at the alveoli.
Systemic circulation covers the rest of the body, from the brain to the toes. In systemic circulation, CO2 and waste products are picked up from the cells of the bodies and later removed or recycled. The transfer of these substances occurs at the capillaries.
The core components of the circulatory system that performs these functions are the heart, vessels, and blood.
The heart muscle, or myocardium, is the engine that runs the circulatory system. An adult heart weighs about 8-10 ounces and is about the size of two adult hands clasped together. It is positioned between, and in front of the 2 lungs, slightly to the left side. It beats about 100,000 times per day, based on an average heart rate of 70 beats per minute.
The human heart consists of 4 chambers. The superior two chambers are called atria, and the inferior two chambers are called ventricles. Ventricles have thicker and stronger walls because they need to be able to pump the blood farther than the atria.
Atria contract together while the ventricles are relaxed. And the ventricles contract together while the atria are relaxed. Valves separate each chamber of the heart to prevent the backflow of blood.
The heart muscle gets its own blood supply from a division of systemic circulation called coronary circulation. You may need to know the names of these arteries for tests in massage school but it is very unlikely that you will see any questions about this on the MBLEx. Find out more about the MBLEx.
Heart rate is regulated by the medulla oblongata, located in the brainstem. However the heart also has its own internal pacemaker. Blood pressure and respiration rate are also regulated by the medulla.
The part of the circulatory system that specifically refers to the blood vessels is sometimes called the vascular system, which is made up of nearly 60,000 miles of blood vessels. There are three main types of blood vessels: arteries, veins and capillaries.
Arteries carry blood away from the heart, to the rest of the body. The blood in arteries is usually oxygenated, except in the arteries that carry blood to the lungs in pulmonary circulation.
The walls of the arteries are thicker in order to withstand the higher blood pressure in arteries. Arteries also have a muscular layer, which allows them to adjust the pressure in the circulatory system. Normal blood pressure is 120/80 mmHg. Large arteries divide into smaller arterioles, which eventually connect with the capillaries.
Veins carry blood towards the heart. They usually carry blood that has already delivered the oxygen to the body cells, and has picked up carbon dioxide (CO2) to be taken to the lungs for removal. An exception to this are the pulmonary veins which carry oxygenated blood back from the lungs to the heart.
The walls of veins are thinner because there is very little pressure. Because of this low pressure, veins have valves to prevent backflow of blood.
Capillaries are tiny blood vessels that extend from the arterioles to allow the blood vessels to reach all the body cells and tissues. Substances like nutrients, waste products and gasses are exchanged here.
The vascular system is a closed system except at the capillaries. Here, certain substances are permitted to either leak through tiny holes or diffuse through the very thin capillary walls. Capillaries also exchange blood gasses with the alveoli of the lungs.
Blood is made up of plasma and formed elements. The plasma is the fluid component of blood, which makes up about 55% of the total blood volume. Gases, hormones and dissolved substances like glucose, electrolytes, and proteins are located in the plasma.
Formed elements makes up the remaining 45% of blood volume. This refers to red blood cells (RBC), white blood cells (WBC), and platelets. Adults have an average of 4.7 to 5.6 liters of blood in the body, about 5-6 quarts.
Red blood cells contain protein molecules called hemoglobin, which bind with oxygen molecules. White blood cells are usually larger than RBCs and primarily function to fight off infection. The primary function of platelets is to stop bleeding.
According to the FSMTB, it is not necessary for massage therapists taking the MBLEx to know the details about the 5 different types of WBCs and their functions. Just know that they primarily work to support the body’s immune response.
The flow of blood through the body is as follows: heart, arteries, arterioles, capillaries, venules, veins, and heart.
How the circulatory system interacts with other body systems
The circulatory system helps all other systems of the body to perform their functions. Here is a brief list of the primary ways that the circulatory system supports and interacts with other body systems:
The circulatory system provides the muscular system the fuel it needs for the muscles to contract and move the body. It provides muscle cells oxygen, glucose and other nutrients. The circulatory system also transports the waste products from cellular metabolism away from the muscles to be filtered, recycled, or eliminated from the body.
The respiratory system and circulatory system work very closely together. Sometimes they are referred to as the cardiopulmonary system. The pulmonary capillaries in the lungs trade carbon dioxide for oxygen at the alveoli.
The urinary system includes the kidneys, which are primary filtering organs for blood. Renal arteries carry blood to the kidneys where it is filtered during renal circulation. The kidneys filter about 150 to 200 quarts of blood every day.
The digestive system digests food into usable components that are picked up by the capillaries around the intestines. Nutrients are then transported to their destination. Blood is supplied to all the organs of the digestive system including the liver, stomach, gall bladder, and pancreas.
Hormones are chemical messengers that are produced by the endocrine system and transported by the circulatory system.
The lymphatic system actually a component of the circulatory system and shares many of the same primary functions including transporting fluids and metabolic waste products in lymph. The heart does not pump lymph as it does blood. Instead, body movement is what causes the lymph movement. Like the veins of the vascular system, lymph vessels have valves to prevent backflow in these low-pressure vessels.
The circulatory system provides the brain its own blood supply through cerebral circulation. This system includes the internal carotid arteries and the vertebral arteries that transport blood to the brain.
The organs of the reproductive system require a constant supply of oxygen and nutrients like every other system of the body.
The circulatory system provides bones the nutrients and oxygen they need to grow and repair. Bone marrow produces blood cells in a process called hematopoiesis.
The integumentary system and circulatory system work closely together to accomplish several functions. Capillaries in the skin can dilate to release heat and cool the body down. They can also constrict to conserve heat. The capillaries of the skin can also absorb certain medications from patches, such as pain medication, nicotine, and nitroglycerine.
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How massage therapy effects the circulatory system
Massage therapy influences the flow of both blood and lymph. Massage techniques that appear to have the greatest mechanical effect on circulation are compression and gliding strokes. These techniques are integral components of systems like Swedish massage and sports massage.
There are other massage techniques that can increase blood flow through mechanical effects. Trigger point massage uses static pressure that increases local capillary flow once the pressure is relieved. Friction and tapotement (percussion) will also increase local blood flow, which is easily observed through the increased heat and redness that occurs.
Massage therapy can also increase blood flow through the physiological effect. Increased relaxation triggers the parasympathetic nervous system to relax peripheral blood vessels, which decreases resistance to blood flow.
For more information on getting ready to pass the massage exam, check out our Ultimate Guide to Passing The MBLEx.