Respiration and Circulation lood Functions of lood Have your ever had an injury that caused bleeding? lood is a red liquid that is a little thicker than water. You learned that your circulatory system works closely with all your other body systems to maintain homeostasis. lood is the link that connects the circulatory system with all the other body systems. lood transports substances around your body. It helps protect your body from infection. lood also helps keep your body s temperature steady. Transportation lood transports many substances through your body. You have read that blood carries oxygen to and carbon dioxide from your lungs. lood also picks up nutrients in the small intestine and carries them to all body cells. It transports hormones that are produced by the endocrine system. lood carries waste products to the excretory system. Most of the substances are dissolved in the liquid part of blood. Protection Some blood cells fight infection. They help protect you from harmful organisms, such as bacteria, viruses, fungi, and parasites. lood also contains materials that help repair torn blood vessels and heal wounds. When you get a cut or a scrape, materials in your blood help protect your body from losing too much blood.
Temperature Regulation lood helps your body stay at a temperature of about 37 C. When your body temperature is too high, blood vessels near the surface of your skin widen. This increases blood flow to your skin s surface and releases more thermal energy into the air. Your body cools down. When your body temperature lowers, blood vessels at your skin s surface get narrower. This decreases blood flow to your skin s surface and reduces the amount of thermal energy that is lost to the air. Your body warms up. Parts of lood lood is a tissue because it is made up of different kinds of cells that work together. The figure shows blood s four main parts: red blood cells, white blood cells, platelets, and plasma. Most adults have about 70 ml of blood per kilogram of body weight. n average adult has about five to six liters of blood. Platelets Red blood cells White blood cells Plasma Red lood Cells Every cubic milliliter of your blood contains four to six million red blood cells, or erythrocytes (ih RITH ruh sites). Red blood cells are made mostly of iron-rich protein molecules called hemoglobin (HEE muh gloh bun). In the alveoli of the lungs, oxygen attaches to the hemoglobin. The hemoglobin releases the oxygen when red blood cells enter the capillaries and get close to body cells. Look at the red blood cells in the figure above. How would you describe their shape? You might say that they look like doughnuts without holes. This flattened disk shape gives red blood cells more surface area. They can carry more oxygen than they could if they were round like a ball. Red blood cells wear out after a few months, so your body produces new red blood cells all the time.
White lood Cells Your blood contains several kinds of white blood cells, or leukocytes (LEW kuh sites). White blood cells protect your body from illness and infection. Some attack viruses, bacteria, fungi, and parasites that might invade your body. Most white blood cells last only a few days. Your body is always replacing them. You have fewer white blood cells 5,000 to 10,000 per cubic millimeter than red blood cells. Pl atelets What happens if you get a cut? The cut, or wound, bleeds for a short time. Then the blood clots, as shown below. Platelets are small, irregularly shaped pieces of cells in the blood that plug wounds and stop bleeding. Platelets produce proteins that help make the plug stronger. Without platelets, blood would not stop flowing through the wound. Your blood contains 150,000 to 440,000 platelets per cubic millimeter. Red blood cells ctivated platelets White blood cell Step 1 Platelets rush to the tear and form a plug to stop the bleeding. Step 2 web of fibrin forms around the platelets to hold them in place. Step 3 More platelets and red blood cells are caught in the fibrin web, forming a blood clot. Plasma The yellowish, liquid part of blood, called plasma, transports blood cells. Plasma is 90 percent water. It helps thin the blood. lood has to be thin to move through small blood vessels. Plasma contains many dissolved molecules that travel along in the blood. They include salts, vitamins, sugars, minerals, proteins, and cellular wastes. Plasma also helps control the activities of cells in your body. Plasma carries chemical messengers that control the amounts of salts and glucose that enter cells.
lood Types Do you know someone who has donated blood? Doctors use donated blood to help people who have lost too much blood from an injury or surgery. blood transfusion is the transfer of one person s blood to another person. ll human blood has the same four parts red blood cells, white blood cells, platelets, and plasma. ut you cannot receive a blood transfusion from just anyone. Different people have different blood types. The O System You inherited your blood type from your parents. lood type refers to the type of proteins, or antigens, on red blood cells. The table below shows the four human blood types:,,, and O. s you can see, type blood cells have the antigen. Type blood cells have the antigen. Type blood cells have both and antigens. Type O blood cells have no antigens. lood Type Type Type Type Type O ntigens on red blood cells If different antigens are introduced through a blood transfusion, the red blood cells will clump together and no longer function. Clumps form because of clumping proteins in blood plasma, shown in the table above. The type of clumping proteins in your blood determines what blood type you could safely get in a transfusion.,, and O blood types have clumping proteins in their plasma. person with type blood has anti- clumping proteins that attack type antigens and cause type red blood cells to clump together. Type blood has no clumping proteins. People with type blood can receive any blood type because it has no clumping proteins. Type O blood has anti- and anti- proteins. People with type O blood can donate blood to anyone. Percentage of US population with this blood type 42 10 4 44 Clumping proteins in plasma nti- nti- None nti- and anti- lood type(s) that can be RECEIVED in a transfusion or O or O or or or O O only This blood type can DONTE TO these blood types or or only or or or O
The Rh Factor nother protein found on red blood cells is a chemical marker called the Rh factor. Some people have this protein on their red blood cells. People who have this protein are Rh positive. People without this protein are Rh negative. If Rh positive blood mixes with Rh negative blood, clumping can result. lood types usually have a plus (+) or a negative ( ) sign to show whether the person is Rh positive or negative. For example, a person with an + blood type has red blood cells with antigens and the Rh factor. Someone with O blood has no antigens and no Rh factor. lood Disorders Sometimes a person s blood does not function as it should. People with hemophilia do not have a protein needed to clot blood. They bleed at the same rate as other people. However, their bleeding does not stop as quickly as it does for other people. People with anemia have low numbers of red blood cells or have red blood cells that do not contain enough hemoglobin. Their blood might not carry as much oxygen as their bodies need. one marrow is the soft tissue in the center of bones. It produces red blood cells. Cancer of the bone marrow is called leukemia. Leukemia can slow or prevent blood cell formation. Leukemia can lead to anemia and a damaged immune system. People who inherit sickle-cell disease have red blood cells shaped like crescents, or sickles (old-fashioned farm tools with curved blades). s shown in the figure below, sickleshaped cells do not move through blood vessels as easily as normal, disk-shaped cells do. They form clumps that can block blood vessels. Sickle cells can keep oxygen from reaching tissues and cause sickle-cell anemia. Normal red blood cells Sickle cells