The Circulatory System
The human circulatory system is made up of the blood, the heart, and the blood vessels. Th e function of the circulatory system is to transport
substances around the body. It moves nutrients absorbed from the intestine to all of the body’s cells. Blood flows through the lungs (part of the
respiratory system) to pick up oxygen and then flows through the body to deliver it to active cells. Blood also carries wastes from the body tissues
for disposal. It carries carbon dioxide to the lungs, where it is released into the air. Other waste substances are carried to the kidneys (an organ of the
urinary system), where the substances are filtered out and excreted. Among the circulatory system’s other vital functions are the regulation of
body temperature and the transport of disease-fighting white blood cells to areas of the body where there are viruses or bacteria.
The human circulatory system is made up of the blood, the heart, and the blood vessels. Th e function of the circulatory system is to transport
substances around the body. It moves nutrients absorbed from the intestine to all of the body’s cells. Blood flows through the lungs (part of the
respiratory system) to pick up oxygen and then flows through the body to deliver it to active cells. Blood also carries wastes from the body tissues
for disposal. It carries carbon dioxide to the lungs, where it is released into the air. Other waste substances are carried to the kidneys (an organ of the
urinary system), where the substances are filtered out and excreted. Among the circulatory system’s other vital functions are the regulation of
body temperature and the transport of disease-fighting white blood cells to areas of the body where there are viruses or bacteria.
Parts of the Circulatory System
The three main parts of the circulatory system are the blood, the heart, and the blood vessels. The heart pumps the blood through large blood vessels, called arteries, which branch into smaller and smaller blood vessels. The smallest blood vessels are called capillaries. In the capillaries, blood exchanges many substances with the surrounding tissues. After this exchange, blood flows into larger blood vessels called veins and eventually returns to the heart. Let’s now look at these parts in detail.
The three main parts of the circulatory system are the blood, the heart, and the blood vessels. The heart pumps the blood through large blood vessels, called arteries, which branch into smaller and smaller blood vessels. The smallest blood vessels are called capillaries. In the capillaries, blood exchanges many substances with the surrounding tissues. After this exchange, blood flows into larger blood vessels called veins and eventually returns to the heart. Let’s now look at these parts in detail.
Blood
Blood is a type of connective tissue that circulates throughout all
parts of your body. The blood consists of four components:
• Red blood cells are the most plentiful of the body’s blood
cells. These cells make up almost half of the blood’s volume.
Red blood cells contain a protein called hemoglobin, which
allows them to transport oxygen throughout the body.
Hemoglobin makes the cells appear red.
• White blood cells are infection-fighting cells in the blood.
They recognize and destroy invading bacteria and viruses.
White blood cells make up less than 1 % of the volume
of blood. They are the only blood cells to have a nucleus.
• Platelets are tiny cells that help in blood clotting. They also
comprise less than 1 % of the blood.
• Plasma is a protein-rich liquid that carries the blood cells along.
It makes up over half of blood’s volume.
Blood is a type of connective tissue that circulates throughout all
parts of your body. The blood consists of four components:
• Red blood cells are the most plentiful of the body’s blood
cells. These cells make up almost half of the blood’s volume.
Red blood cells contain a protein called hemoglobin, which
allows them to transport oxygen throughout the body.
Hemoglobin makes the cells appear red.
• White blood cells are infection-fighting cells in the blood.
They recognize and destroy invading bacteria and viruses.
White blood cells make up less than 1 % of the volume
of blood. They are the only blood cells to have a nucleus.
• Platelets are tiny cells that help in blood clotting. They also
comprise less than 1 % of the blood.
• Plasma is a protein-rich liquid that carries the blood cells along.
It makes up over half of blood’s volume.
The Heart
The heart is made up of three different types of tissue: cardiac muscle tissue, nerve tissue, and connective tissue. Cardiac muscle tissue is a special type of muscle found only in the heart. All of the cardiac muscle tissue in each part of the heart contracts at the same time. Th is makes the heart
contract and moves the blood around the body. Your heart pumps with a regular beat. The frequency of the beat (the heart rate) changes depending on your physical activity and other factors, such as stress, temperature, and your general health. The muscles and nerves are covered by a smooth layer of epithelial tissues. This covering reduces friction and protects the heart from damage when the lungs expand and contract. The inner surface of the heart, where the blood flows, is also lined with smooth epithelial tissue to allow the blood to flow freely. Any hardening or roughening of this inner lining can lead to health problems.
Blood Vessels
Three types of blood vessels form a network of tubes throughout the body to transport the blood. These three types of blood vessels are arteries, veins, and capillaries. Arteries carry blood away from the heart. Because the blood in the arteries is being pumped away from the heart, it is under greater pressure than the blood in other blood vessels. Th e walls of arteries are thicker than the walls of other blood vessels to withstand this pressure. Veins carry blood toward the heart. This blood is at lower pressure, so the walls of the veins are not as thick. Both arteries and veins can vary considerably in size. The largest are nearest the heart, where just a few blood vessels carry large volumes of blood. Further from the heart, the blood vessels are much smaller, and there are more of them, like twigs on a tree. Arteries and veins are linked together by the capillaries. Capillaries are tiny blood vessels with very thin walls that allow substances to diffuse between the blood and other body fluids and tissues. Oxygen and nutrients diffuse from the blood into the surrounding tissues. Carbon dioxide and other wastes pass from the body tissues into the blood to be carried away for disposal. Every part of the body is supplied with blood by a network of capillaries.
The heart is made up of three different types of tissue: cardiac muscle tissue, nerve tissue, and connective tissue. Cardiac muscle tissue is a special type of muscle found only in the heart. All of the cardiac muscle tissue in each part of the heart contracts at the same time. Th is makes the heart
contract and moves the blood around the body. Your heart pumps with a regular beat. The frequency of the beat (the heart rate) changes depending on your physical activity and other factors, such as stress, temperature, and your general health. The muscles and nerves are covered by a smooth layer of epithelial tissues. This covering reduces friction and protects the heart from damage when the lungs expand and contract. The inner surface of the heart, where the blood flows, is also lined with smooth epithelial tissue to allow the blood to flow freely. Any hardening or roughening of this inner lining can lead to health problems.
Blood Vessels
Three types of blood vessels form a network of tubes throughout the body to transport the blood. These three types of blood vessels are arteries, veins, and capillaries. Arteries carry blood away from the heart. Because the blood in the arteries is being pumped away from the heart, it is under greater pressure than the blood in other blood vessels. Th e walls of arteries are thicker than the walls of other blood vessels to withstand this pressure. Veins carry blood toward the heart. This blood is at lower pressure, so the walls of the veins are not as thick. Both arteries and veins can vary considerably in size. The largest are nearest the heart, where just a few blood vessels carry large volumes of blood. Further from the heart, the blood vessels are much smaller, and there are more of them, like twigs on a tree. Arteries and veins are linked together by the capillaries. Capillaries are tiny blood vessels with very thin walls that allow substances to diffuse between the blood and other body fluids and tissues. Oxygen and nutrients diffuse from the blood into the surrounding tissues. Carbon dioxide and other wastes pass from the body tissues into the blood to be carried away for disposal. Every part of the body is supplied with blood by a network of capillaries.
Diseases and Disorders of the Circulatory System
There are many conditions that affect the function of the circulatory system.
There are over a dozen types of heart disease alone that can affect people
of all ages and all levels of fitness. The most common heart problems is
coronary artery disease, which can lead to heart attack.
Coronary Artery Disease
Your heart is a hard-working organ, and the cardiac muscle tissue needs a steady supply of oxygen and nutrients. Coronary arteries are the blood vessels that provide blood to the heart muscle tissue itself. These arteries can become partially blocked with plaque--a deposit made of fat, cholesterol, calcium, and other substances that normally circulate in the blood. This plaque buildup can be caused by inherited genetic information or by poor lifestyle choices, such as a high-fat diet, smoking, and lack of exercise.
Symptoms of coronary artery disease include tiredness, dizziness, and pain or a burning sensation in the chest or arms. The problem can be diagnosed with the aid of a special X-ray called an angiogram, in which a fluorescent dye is injected into the bloodstream. This dye shows up on the X-ray image.
There are many conditions that affect the function of the circulatory system.
There are over a dozen types of heart disease alone that can affect people
of all ages and all levels of fitness. The most common heart problems is
coronary artery disease, which can lead to heart attack.
Coronary Artery Disease
Your heart is a hard-working organ, and the cardiac muscle tissue needs a steady supply of oxygen and nutrients. Coronary arteries are the blood vessels that provide blood to the heart muscle tissue itself. These arteries can become partially blocked with plaque--a deposit made of fat, cholesterol, calcium, and other substances that normally circulate in the blood. This plaque buildup can be caused by inherited genetic information or by poor lifestyle choices, such as a high-fat diet, smoking, and lack of exercise.
Symptoms of coronary artery disease include tiredness, dizziness, and pain or a burning sensation in the chest or arms. The problem can be diagnosed with the aid of a special X-ray called an angiogram, in which a fluorescent dye is injected into the bloodstream. This dye shows up on the X-ray image.
Heart Attack
Coronary arteries can become completely blocked, either with plaque or with a blood clot. When this happens, the heart muscle cells no longer
receive the oxygen and nutrients they need to function. The heart stops pumping, and the heart tissue starts to die.General symptoms of a possible heart attack include:
• chest pain or pressure
• shortness of breath
• nausea
• anxiety
• upper body pain
• abdominal orstomach pain
• sweating
• dizziness
• unusual fatigue
Coronary arteries can become completely blocked, either with plaque or with a blood clot. When this happens, the heart muscle cells no longer
receive the oxygen and nutrients they need to function. The heart stops pumping, and the heart tissue starts to die.General symptoms of a possible heart attack include:
• chest pain or pressure
• shortness of breath
• nausea
• anxiety
• upper body pain
• abdominal orstomach pain
• sweating
• dizziness
• unusual fatigue