Circulatory System

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Circulatory System

v  The circulatory system can be compared to a system of interconnected, one-way roads that range from superhighways to back alleys.

v  Like a Network of roads, the job of the circulatory system is to allow the transport of materials from one place to another.

v  As described in Figure below, the materials carried by the circulatory system include HORMONES, Oxygen, cellular wastes, and nutrients from digested food.

v  Transport of all these materials is necessary to maintain homeostasis of the body. The main components of the circulatory system are the heart, blood vessels, and blood. Each of these components is described in detail below

The Heart

v  The heart is a muscular organ in the chest. It consists mainly of cardiac muscle tissue and pumps blood through blood vessels by repeated, rhythmic contractions.

v  The heart has four chambers, as shown in Figure below: two upper atria (singular, atrium) and two lower ventricles. Valves between chambers keep blood flowing through the heart in just one direction

 

 

Blood Flow through the Heart

Blood flows through the heart in two separate loops, which are indicated by the arrows in Figure above.

1.      Blood from the body enters the right atrium of the heart. The right atrium pumps the blood to the right ventricle, which pumps it to the lungs. This loop is represented by the blue arrows in Figure above.

2.      Blood from the lungs enters the left atrium of the heart. The left atrium pumps the blood to the left ventricle, which pumps it to the body. This loop is represented by the red arrows in Figure above.

 

Heartbeat

v  Unlike skeletal muscle, cardiac muscle contracts without stimulation by the nervous system. Instead, specialized cardiac muscle cells send out electrical impulses that stimulate the contractions.

v  As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart

 


Blood Vessels

v  Blood vessels form a network throughout the body to transport blood to all the body cells.

v  There are three major types of blood vessels: arteries, veins, and capillaries. All three are shown in Figure below and described below

 

v  Arteries are muscular blood vessels that carry blood away from the heart. They have thick walls that can withstand the pressure of blood being pumped by the heart. Arteries generally carry oxygen-rich blood. The largest artery is the aorta, which receives blood directly from the heart.

v  Veins are blood vessels that carry blood toward the heart. This blood is no longer under much pressure, so many veins have valves that prevent backflow of blood. Veins generally carry deoxygenated blood. The largest vein is the inferior vena cava, which carries blood from the lower body to the heart.

v  Capillaries are the smallest type of blood vessels. They connect very small arteries and veins. The exchange of gases and other substances between cells and the blood takes place across the extremely thin walls of capillaries

 

Blood Vessels and Homeostasis

v  Blood vessels help regulate body processes by either constricting (becoming narrower) or dilating (becoming wider).

v  These actions occur in response to signals from the autonomic nervous system or the Endocrine System.

v  Constriction occurs when the muscular walls of blood vessels contract. This reduces the amount of blood that can flow through the vessels. Dilation occurs when the walls relax.

v  This increases blood flows through the vessels. Constriction and dilation allow the circulatory system to change the amount of blood flowing to different organs.

v  For example, during a fight-or-flight response, dilation and constriction of blood vessels allow more blood to flow to skeletal muscles and less to flow to digestive organs.

v  Dilation of blood vessels in the skin allows more blood to flow to the body surface so the body can lose heat. Constriction of these blood vessels has the opposite effect and helps conserve body heat.

 

Blood Vessels and Blood Pressure

v  The force exerted by circulating blood on the walls of blood vessels is called blood pressure. Blood pressure is highest in arteries and lowest in veins.

v  When you have your blood pressure checked, it is the blood pressure in arteries that is measured. High blood pressure, or hypertension, is a serious Health risk but can often be controlled with lifestyle changes or medication

 

Pulmonary Circulation

v  Pulmonary circulation is the part of the circulatory system that carries blood between the heart and lungs (the term pulmonary means “of the lungs”).

v  It is illustrated in Figure below. Deoxygenated blood leaves the right ventricle through pulmonary arteries, which transport it to the lungs.

v  In the lungs, the blood gives up carbon dioxide and picks up oxygen. The oxygenated blood then returns to the left atrium of the heart through pulmonary veins

Systemic Circulation

v  Systemic circulation is the part of the circulatory system that carries blood between the heart and body. It is illustrated in Figure below.

v  Oxygenated blood leaves the left ventricle through the aorta.

v  The aorta and other arteries transport the blood throughout the body, where it gives up oxygen and picks up carbon dioxide.

v  The deoxygenated blood then returns to the right atrium through veins

 


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The circulatory system is an organ system that permits blood to circulate and transport nutrients (such as amino acids, electrolytes, glucose, hormones, and oxygen) and wastes (such as carbon dioxide) to and from cells in the body to nourish it and help to fight diseases, stabilize body temperature and pH, and to maintain homeostasis.

The circulatory system is composed of the heart, blood vessels, and blood. The heart is a muscular organ that pumps blood throughout the body. The blood vessels are a network of tubes that carry blood to and from the heart. The blood is a fluid that contains red blood cells, white blood cells, and platelets.

The heart is located in the chest cavity, between the lungs. It is about the size of a fist and weighs about 10 ounces in adults. The heart is made up of four chambers: two atria and two ventricles. The atria are the upper chambers of the heart, and the ventricles are the lower chambers of the heart.

The heart muscle is made up of special cells that contract and relax to pump blood. The heart muscle cells are controlled by electrical signals that originate in the sinoatrial node (SA node), also known as the pacemaker of the heart. The SA node sends out electrical signals that cause the atria to contract. The contraction of the atria causes blood to flow into the ventricles.

The ventricles are then filled with blood. The electrical signals from the SA node then travel to the atrioventricular node (AV node), which is located between the atria and the ventricles. The AV node delays the electrical signals for a short period of time, which allows the ventricles to fill with blood.

After the ventricles are filled with blood, the electrical signals travel to the bundle of His, which is located in the lower right chamber of the heart. The bundle of His divides into the right and left bundle branches, which carry the electrical signals to the right and left ventricles. The electrical signals cause the ventricles to contract, which pumps blood out of the heart.

The blood vessels are a network of tubes that carry blood to and from the heart. The blood vessels are divided into three types: arteries, veins, and capillaries.

The arteries are the blood vessels that carry blood away from the heart. The arteries are thick and muscular, and they have a lot of elastic tissue. The elastic tissue allows the arteries to stretch and recoil, which helps to maintain blood pressure.

The veins are the blood vessels that carry blood back to the heart. The veins are thin and have a lot of valves. The valves help to prevent blood from flowing backwards.

The capillaries are the smallest blood vessels. The capillaries are very thin, and they allow nutrients and oxygen to pass from the blood to the cells, and wastes to pass from the cells to the blood.

Blood is a fluid that contains red blood cells, white blood cells, and platelets. Red blood cells are the most common type of blood cell. They carry oxygen from the lungs to the cells. White blood cells fight infection. Platelets help to form blood clots.

The lymphatic system is a network of vessels that carry lymph throughout the body. Lymph is a fluid that contains white blood cells. The lymphatic system helps to fight infection and remove waste products from the body.

The lymph nodes are small, bean-shaped organs that are located throughout the body. The lymph nodes filter lymph and produce white blood cells.

The spleen is a large, flat organ that is located in the upper left abdomen. The spleen filters blood and removes old red blood cells. The spleen also produces white blood cells and platelets.

The thymus is a small, glandular organ that is located in the upper chest. The thymus produces white blood cells that help to fight infection.

The circulatory system is a complex system that is essential for life. The heart pumps blood throughout the body, and the blood vessels carry blood to and from the heart. The blood contains red blood cells, white blood cells, and platelets. The lymphatic system helps to fight infection and remove waste products from the body. The lymph nodes, spleen, and thymus are all organs that are part of the lymphatic system.

Respiration

Digestion

Excretion

Nervous System

Endocrine System

  1. The heart is a muscular organ that pumps blood throughout the body. It is located in the chest, between the lungs. The heart has four chambers: two atria and two ventricles. The atria are the upper chambers, and the ventricles are the lower chambers. The heart contracts and relaxes in a rhythmic pattern called the cardiac cycle. The cardiac cycle is divided into two phases: systole and diastole. Systole is the contraction phase, and diastole is the relaxation phase.

  2. The blood vessels are a network of tubes that carry blood throughout the body. There are three types of blood vessels: arteries, veins, and capillaries. Arteries carry blood away from the heart. Veins carry blood back to the heart. Capillaries are tiny blood vessels that connect arteries and veins.

  3. The blood is a fluid that carries oxygen and nutrients to the cells and removes waste products from the cells. Blood is made up of plasma, red blood cells, white blood cells, and platelets. Plasma is the liquid part of blood. Red blood cells carry oxygen. White blood cells fight infection. Platelets help the blood to clot.

  4. The lymphatic system is a network of vessels that helps to remove waste products from the body. The lymphatic system also helps to fight infection. The lymphatic system is made up of lymph nodes, lymph vessels, and the spleen. Lymph nodes are small, bean-shaped organs that filter lymph. Lymph vessels are tubes that carry lymph. The spleen is an organ that helps to filter blood and fight infection.

  5. The Respiratory System is a system of organs that takes in oxygen and releases carbon dioxide. The respiratory system is made up of the lungs, trachea, bronchi, and alveoli. The lungs are two spongy organs that take in oxygen and release carbon dioxide. The trachea is a tube that carries air from the nose and mouth to the lungs. The bronchi are two tubes that branch off from the trachea and lead to the lungs. The alveoli are tiny air sacs in the lungs where oxygen is exchanged for carbon dioxide.

  6. The Digestive System is a system of organs that breaks down food into nutrients that the body can use. The digestive system is made up of the mouth, esophagus, stomach, small intestine, large intestine, and rectum. The mouth is where food is chewed and mixed with saliva. The esophagus is a tube that carries food from the mouth to the stomach. The stomach is a muscular sac that churns food and mixes it with digestive juices. The small intestine is a long, coiled tube that absorbs nutrients from food. The large intestine is a shorter, wider tube that absorbs water from food and stores waste products. The rectum is the last part of the large intestine, and it stores waste products until they are eliminated from the body.

  7. The Excretory System is a system of organs that removes waste products from the body. The excretory system is made up of the kidneys, ureters, bladder, and urethra. The kidneys are two bean-shaped organs that filter blood and produce urine. The ureters are two tubes that carry urine from the kidneys to the bladder. The bladder is a muscular sac that stores urine. The urethra is a tube that carries urine from the bladder to the outside of the body.

  8. The endocrine system is a system of glands that produce hormones. Hormones are chemicals that regulate body functions. The endocrine system is made up of the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, and testes. The pituitary gland is a small gland at the base of the brain that produces hormones that control growth, reproduction, and other body functions. The thyroid gland is a butterfly-shaped gland in the neck that produces hormones that regulate metabolism. The parathyroid glands are four small glands in the neck that produce hormones that regulate calcium levels in the blood. The adrenal glands are two small glands on top of the kidneys that produce hormones that regulate Stress, blood pressure, and other body functions. The pancreas is a gland behind the stomach that produces hormones that regulate blood sugar levels. The ovaries are two female reproductive organs that produce hormones that regulate the menstrual cycle and female sexual characteristics. The testes are two male reproductive organs that produce hormones that regulate sperm production and male sexual characteristics.

  9. The immune system is a system of organs and cells that protects the body from infection and disease. The immune system is made up of the skin, white blood cells, antibodies, and the lymphatic system. The skin is the body’s largest organ, and it helps to protect the body from infection. White blood cells are cells that fight infection. Antibodies are proteins that help the body to fight infection. The lymphatic system is a network of vessels that helps to remove waste products from the body and fight infection.

  10. The nervous system is a system of organs and cells that controls the body’s functions. The nervous system is made up of the brain, spinal cord, and nerves

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