The vascular system, also called the circulatory system, is made up of the vessels that carry blood and lymph through the body. The arteries and veins carry blood throughout the body, delivering oxygen and nutrients to the body tissues and taking away tissue waste matter. The lymph vessels carry lymphatic fluid a clear, colorless fluid containing water and blood cells.
The lymphatic system helps protect and maintain the fluid environment of the body by filtering and draining lymph away from each region of the body. Tiny blood vessels between arteries and veins that distribute oxygen-rich blood to the body.
Blood moves through the circulatory system as a result of being pumped out by the heart. Blood leaving the heart through the arteries is saturated with oxygen. The arteries break down into smaller and smaller branches to bring oxygen and other nutrients to the cells of the body's tissues and organs. As blood moves through the capillaries, the oxygen and other nutrients move out into the cells, and waste matter from the cells moves into the capillaries. As the blood leaves the capillaries, it moves through the veins, which become larger and larger to carry the blood back to the heart.
In addition to circulating blood and lymph throughout the body, the vascular system functions as an important component of other body systems. Examples include:. Respiratory system. As blood flows through the capillaries in the lungs, carbon dioxide is given up and oxygen is picked up. The carbon dioxide is expelled from the body through the lungs, and the oxygen is taken to the body tissues by the blood.
Digestive system. As food is digested, blood flows through the intestinal capillaries and picks up nutrients, such as glucose sugar , vitamins, and minerals. These nutrients are delivered to the body tissues by the blood. Kidneys and urinary system. Waste materials from the body tissues are filtered out from the blood as it flows through the kidneys. Arrows indicate that pyruvate, fatty acids, and amino acids are transported into the mitochondrion where they are oxidized to CO 2.
In general, the energy to synthesize ATP molecules must be obtained from rather complex fuel molecules. The human body uses three types of molecules to yield the necessary energy to drive ATP synthesis: fats, proteins, and carbohydrates. Lipids are broken down into fatty acids, proteins into amino acids, and carbohydrates into glucose.
Via a series of oxidation-reduction reactions, mitochondria degrade fatty acids, amino acids, and pyruvate the end product of glucose degradation in the cytoplasm into several intermediate compounds, as well as into the reduced electron carrier coenzymes NADH and FADH 2 Figure 1.
These reduced electron carriers are themselves oxidized via the electron transport chain, with concomitant consumption of oxygen and ATP synthesis Figure 1. This process is called oxidative phosphorylation. Over a hundred ATP molecules are synthesized from the complete oxidation of one molecule of fatty acid, and almost forty ATP molecules result from amino acid and pyruvate oxidation.
Two ATP molecules are synthesized in the cytoplasm via the conversion of glucose molecules to pyruvate. Both the apparatus enzymes and the physical environment necessary for the oxidation of these molecules are contained in the mitochondria. The brain uses glucose and ketone bodies for energy. Adipose tissue uses fatty acids and glucose for energy. The liver primarily uses fatty acid oxidation for energy.
Muscle cells use fatty acids, glucose, and amino acids as energy sources. Most cells use glucose for ATP synthesis, but there are other fuel molecules equally important for maintaining the body's equilibrium or homeostasis. Indeed, although the oxidation pathways of fatty acids, amino acids, and glucose begin differently, these mechanisms ultimately converge onto a common pathway, the TCA cycle, occurring within the mitochondria Figure 1.
As mentioned earlier, the ATP yield obtained from lipid oxidation is over twice the amount obtained from carbohydrates and amino acids. So why don't all cells simply use lipids as fuel? In fact, many different cells do oxidize fatty acids for ATP production Figure 2. Skeletal muscle cells also oxidize lipids. Indeed, fatty acids are the main source of energy in skeletal muscle during rest and mild-intensity exercise. As exercise intensity increases, glucose oxidation surpasses fatty acid oxidation.
Other secondary factors that influence the substrate of choice for muscle include exercise duration, gender, and training status. Another tissue that utilizes fatty acids in high amount is adipose tissue. Since adipose tissue is the storehouse of body fat, one might conclude that, during fasting, the source of fatty acids for adipose tissue cells is their own stock. Skeletal muscle and adipose tissue cells also utilize glucose in significant proportions, but only at the absorptive stage - that is, right after a regular meal.
Other organs that use primarily fatty acid oxidation are the kidney and the liver. The cortex cells of the kidneys need a constant supply of energy for continual blood filtration, and so does the liver to accomplish its important biosynthetic functions.
Despite their massive use as fuels, fatty acids are oxidized only in the mitochondria. But not all human cells possess mitochondria! Although that may sound strange, human red blood cells are the most common cells lacking mitochondria.
Other examples include tissues of the eyes, such as the lens, which is almost totally devoid of mitochondria; and the outer segment of the retina, which contains the photosensitive pigment. You may have already guessed that these cells and tissues then must produce ATP by metabolizing glucose only.
In these situations, glucose is degraded to pyruvate, which is then promptly converted to lactate Figure 2. This process is called lactic acid fermentation. Although not highly metabolically active, red blood cells are abundant, resulting in the continual uptake of glucose molecules from the bloodstream. Additionally, there are cells that, despite having mitochondria, rely almost exclusively on lactic acid fermentation for ATP production.
This is the case for renal medulla cells, whose oxygenated blood supply is not adequate to accomplish oxidative phosphorylation. Finally, what if the availability of fatty acids to cells changes? The blood-brain barrier provides a good example. In most physiological situations, the blood-brain barrier prevents the access of lipids to the cells of the central nervous system CNS.
Therefore, CNS cells also rely solely on glucose as fuel molecules Figure 2. In prolonged fasting, however, ketone bodies released in the blood by liver cells as part of the continual metabolization of fatty acids are used as fuels for ATP production by CNS cells. In both situations and unlike red blood cells, however, CNS cells are extremely metabolically active and do have mitochondria. Thus, they are able to fully oxidize glucose, generating greater amounts of ATP. Indeed, the daily consumption of nerve cells is about g of glucose equivalent, which corresponds to an input of about kilocalories 1, kilojoules.
However, most remaining cell types in the human body have mitochondria, adequate oxygen supply, and access to all three fuel molecules. Which fuel, then, is preferentially used by each of these cells? Virtually all cells are able to take up and utilize glucose.
What regulates the rate of glucose uptake is primarily the concentration of glucose in the blood. Glucose enters cells via specific transporters GLUTs located in the cell membrane. There are several types of GLUTs, varying in their location tissue specificity and in their affinity for glucose.
Summary Read the full fact sheet. On this page. All cells in the body need to have oxygen and nutrients, and they need their wastes removed. These are the main roles of the circulatory system. The heart, blood and blood vessels work together to service the cells of the body. Using the network of arteries, veins and capillaries, blood carries carbon dioxide to the lungs for exhalation and picks up oxygen.
From the small intestine, the blood gathers food nutrients and delivers them to every cell. Blood Blood consists of: Red blood cells — to carry oxygen White blood cells — that make up part of the immune system Platelets — needed for clotting Plasma — blood cells, nutrients and wastes float in this liquid.
The heart The heart pumps blood around the body. It sits inside the chest, in front of the lungs and slightly to the left side. The heart is actually a double pump made up of four chambers, with the flow of blood going in one direction due to the presence of the heart valves.
The contractions of the chambers make the sound of heartbeats. The right side of the heart The right upper chamber atrium takes in deoxygenated blood that is loaded with carbon dioxide. The blood is squeezed down into the right lower chamber ventricle and taken by an artery to the lungs where the carbon dioxide is replaced with oxygen.
Blood clots. A blood vessel may be blocked by an embolus. This is a tiny mass of debris that moves through the bloodstream. Or it may be blocked by a thrombus. This is a blood clot. In general, inflammation of blood vessels is referred to as vasculitis. This includes a range of disorders. Inflammation may lead to narrowing and blockage of blood vessels. Injury of the blood vessels may lead to inflammation or infection. This can damage the blood vessels and lead to narrowing and blockage.
The functions of the blood vessels include supplying all organs and tissues of the body with oxygen and nutrients. They include removing waste products, fluid balance, and other functions. Because of all these functions, conditions that affect the vascular system may affect the part s of the body supplied by a certain vascular network.
Coronary artery disease. This can cause heart attack or angina chest pain. Cerebrovascular disease. This can cause stroke or transient ischemic attack TIA. TIA is a short-term loss of blood flow to an area of the brain. It usually last less than 5 minutes but not longer than 24 hours, with complete recovery. Peripheral arterial disease. This may cause claudication. This is pain in the thigh, calf, or buttocks that occurs when walking.
It can also cause critical limb ischemia. This is lack of blood supply and oxygen to the limb or leg at rest. Vascular disease of the great vessels. This can cause an aortic aneurysm. This is a bulging, weakened area in the wall of a blood vessel due to an abnormal widening or ballooning.
It can also cause coarctation of the aorta. This is narrowing of the aorta, the largest artery in the body.
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