Understanding the Circulatory System and Its Functions

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All cells in your body are surrounded by a liquid environment. They depend on it to stay alive. The internal environment is made up of the interstitial fluid and the circulating fluids. Lymph is the fluid that flows through the lymphatic vessels. It is formed from the remaining interstitial fluid. Blood is the fluid in charge of transporting substances through the inside of blood vessels. Interstitial fluid is the fluid that surrounds every cell. Cells extract nutrients, oxygen and release into the waste and carbon dioxide produced in cell metabolism. The circulatory system connects the system involved in the nutrition function with the interstitial fluid that surrounds the cells in the body. It has 2 systems: the cardiovascular system through which blood flows, and the lymphatic system through which lymph flows. It is responsible for transporting nutrients and oxygen to the cells in your body, and transports them to the excretory organs. It is made up of blood vessels and the heart, the organ that pumps blood. Arteries carry blood from the heart to the body. Capillaries go from arterioles to venules, and the exchange of substances provokes a change of color. Veins carry blood from the organs to the heart. Arteries have a muscular and elastic wall to resist the pressure pumped by the heart. Walls of capillaries are made up of a single layer of cells that allow the exchange of nutrients, oxygen, carbon dioxide, and waste with cells. Veins have thin walls that are formed by the union of venules. The more important function of the blood is transport: Nutrients, metabolic waste, oxygen, carbon dioxide, and hormones. Defence blood transports the cells that defend the body. Thermal regulation regulates the temperature of the body by conducting heat. Components of human blood: liquid part, blood plasma that contains different cells. Blood plasma is a yellowish liquid, is 90% water and substances that are dissolved like protein, nutrients, gases, mineral salts, and hormones. Blood cells are created in red bone marrow that is inside the bone of the skeleton. There are 3 types of cells: Red blood cells that are small, have no nucleus, they have hemoglobin, carry oxygen, and give the red color. White blood cells are large, with a nucleus and have defensive functions. Platelets are cellular fragments, have no nucleus, and are involved in blood clotting processes. The heart is at the central part of the thorax, between the lungs. It is in charge of pumping blood through the vessels, is made up of cardiac muscle tissue, myocardium which contracts and relaxes autonomously, and is divided into two halves, each half has an upper chamber and lower chamber. The ventricles have thick muscular.

Parts of the heart: sigmoid valves prevent blood from flowing back to the ventricle. Atrioventricular valves connect the atrium with the ventricles. Aorta's function is to carry oxygenated blood from the heart to all our organs. Pulmonary arteries are arteries in the pulmonary circulation that carry deoxygenated blood from the right side of the heart to the lungs. Pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart. Venae cavae receive blood from the upper half of the body, and a lower half that collects blood from the organs below the diaphragm. If you press your fingertips in your chest you can notice your heartbeat, it has 2 types of movements: contraction (systole) and relaxation (diastole). Cardiac cycle:

Atrial diastole: as these contract, all the blood they contain is expelled into the ventricles. Atrial systole: The left and right atria contract at the same time and push blood into the left and right ventricle, respectively. Ventricular diastole: the heart relaxes after a contraction, in preparation for filling with blood. Ventricular systole: the ventricles contract and vigorously pulse separate blood supplies to the heart, one to the lungs and one to all other organs and systems in the body. Double circulation: blood flows twice through the heart, in this type of circulation, the pulmonary circulation is separated from the systemic circulation.

Pulmonary or first-order circuit: carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium and ventricle of the heart.

Systemic or Second-order circuit: blood is pumped to the lungs, at the same time releasing carbon dioxide, goes to the brain and body.

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