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30 Cards in this Set
- Front
- Back
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Protozoans
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Movement of gases and nutrients is accomplished by simple diffusion within the cell.
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Cnidarians
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Have body walls that are two cells thick. All cells are in direct contact with either the internal or external environments so there is no need for a specialized circulatory system.
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Arthropods
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Have open circulatory systems in which blood (interstitial fluid) is in direct contact with the body tissues. The blood is circulated primarily by body movements. Blood flows through a dorsal vessel and into spaces called sinuses where exchange occurs.
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Annelids
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The earthworm (annelida) uses a closed circulatory system to deliver materials to cells that are not in direct contact with the external environment. In a closed circulatory system, blood is confined to blood vessels. Blood moves towards the head in the dorsal vessel which functions as the main heart by coordinated contractions. Five pairs of vessels called aortic loops connect the dorsal vessel to the ventral vessel and function as additional pumps. Earthworm blood lacks any red blood cells. There is a hemoglobin-like pigment that is dissolved in the aqueous solution.
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Circulation in Humans
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Composed of a muscular four-chambered heart, a network of blood vessels, and the blood itself. Blood is pumped into the aorta, which branches into a series of arteries. The arteries branch into arterioles, and then into microscopic capillaries. Exchange of gases, nutrients, and cellular waste products occurs via diffusion across capillary walls. The capillaries then converge into venules, and eventually into veins, leading deoxygenated blood back towards the heart.
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The Heart
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The driving force of the circulatory system. The right and left halves can be viewed as two separate pumps: the right side of the heart pumps deoxygenated blood into pulmonary circulation (towards the lungs), while the left side pumps oxygenated blood into systemic circulation (throughout the body). The two upper chambers are called atria and the two lower chambers are called ventricles. The atria are thin-walled, while the ventricles are extremely muscular.
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Blood Vessels
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Three types: arteries, veins, and capillaries. Arteries are thick-walled, muscular, elastic vessels that transport oxygenated blood away from the heart – except for the pulmonary arteries, which transport deoxygenated blood from the heart to the lungs. Veins are thin-walled, inelastic vessels that conduct deoxygenated blood towards the heart – except for pulmonary veins, which carry oxygenated blood from the lungs to the heart. Venous circulation is often at odds with gravity; thus larger veins, especially those in the legs, have valves that prevent backflow. Capillaries have very thin walls composed of a single layer of endothelial cells across which respiratory gases, nutrients, enzymes, hormones, and wastes can readily diffuse. Capillaries have the smallest diameter of all three types; red blood cells must often travel through them single file.
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Lymph Vessels
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The lymphatic system is a secondary circulation system distinct from the cardiovascular circulation. Its vessels transport excess interstitial fluid (lymph), to the cardiovascular system, thereby keeping fluid levels in the body constant. Lymph nodes are swellings along lymph vessels containing phagocytic cells (leukocytes) that filter the lymph, removing and destroying foreign particles and pathogens.
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Blood
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The human body contains 4-6 liters of blood. It is composed of liquid (55%) and cellular components (45%). Plasma is the liquid portion of blood. It is an aqueous mixture of nutrients, salts, respiratory gases, wastes, hormones, and blood proteins (e.g. immunoglobulins, albumin, and fibrinogen). The cellular components include erythrocytes, leukocytes, and platelets. Blood transports nutrients and O2 to tissue, and wastes and CO2 from tissue. Platelets are involved in injury repair and leukocytes are the main component of the immune system.
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Erythrocytes
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Red blood cells that are oxygen-carrying components of blood. An erythrocyte contains around 250 million molecules of hemoglobin, each of which can bind up to four molecules of oxygen. When hemoglobin binds to oxygen, it is called oxyhemoglobin. This is the primary form of oxygen transport in the blood. They have a distinct biconcave, disk-like shape, which gives them both increased surface area for gas exchange and greater flexibility for movement through tiny capillaries. They are formed from stem cells in the bone marrow, where they lose their nuclei, mitochondria, and membranous organelles. Once mature, RBCs circulate in the blood for about 120 days, after which they are phagocytized by special cells in the spleen and liver.
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Leukocytes
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White blood cells. They are larger than erythrocytes and serve protective functions. Some of these cells phagocytize foreign matter and organisms such as bacteria. Others migrate from the blood to tissue, where they mature into stationary cells called macrophages. Other WBCs, called lymphocytes, are involved in immune response and the production of antibodies (B cells) or cytolysis of infected cells (T cells).
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Platelets
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The cell fragments that lack nuclei and are involved in clot formation.
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Transport of Gases
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Erythrocytes transport O2 throughout the circulatory system. It is the hemoglobin molecules in erythrocytes that actually bind to O2. Each hemoglobin molecule is capable of binding to four molecules of O2. Hemoglobin also binds to CO2.
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Transport of Nutrients/Wastes
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Amino acids and simple sugars are absorbed into the bloodstream at the intestinal capillaries and are transported throughout the body. Throughout the body, metabolic waste products (e.g. water, urea, and CO2) diffuse into capillaries from surrounding cells; these wastes are then delivered to the appropriate excretory organs.
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Clotting
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When platelets come into contact with the exposed collagen of a damaged vessel, they release a chemical that causes neighboring platelets to adhere to one another, forming a platelet plug. Both the platelets and the damaged tissue release the clotting factor thromboplastin. Thromboplastin, with the aid of its cofactors calcium and vitamin K, converts the inactive plasma protein prothrombin to its active form, thrombin. Thrombin then converts fibrinogen (another plasma protein) into fibrin. Threads of fibrin coat the damaged area and trap blood cells to form a clot. Clots prevent extensive blood loss while the damaged vessel heals itself. The fluid remaining after clotting is called serum.
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Immunological Rxns
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The body has an ability to distinguish between self and nonself, and to remember nonself entities (antigens) that it has previously encountered. These defense mechanisms are an integral part of the immune system. The immune system is composed of two defense mechanisms: humoral immunity, which involves the production of antibodies, and cell-mediated immunity, while involves cells that combat fungal and viral infection. Lymphocytes are responsible for both mechanisms.
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Humoral Immunity
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This immunity is responsible for the proliferation of antibodies following exposure to antigens. Antibodies (immunoglobulins or lgs) are complex proteins that recognize and bind to specific antigens and trigger the immune system to remove them. Antibodies either attract other cells (like leukocytes) to phagocytize the antigen, or cause the antigens to clump together (agglutinate) and form large insoluble complexes, facilitating their removal by phagocytic cells.
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Active Immunity
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Refers to the production of antibodies during an immune response. It can be conferred by vaccination; an individual is injected with a weakened, inactive, or related form of a particular antigen, which stimulates the immune system to produce specific antibodies against it. It may require weeks to build up.
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Passive Immunity
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Involves the transfer of antibodies produced by another individual or organism. It is acquired either passively or by injection. During pregnancy, some maternal antibodies cross the placenta and enter fetal circulation, conferring this immunity upon the fetus. Although it is acquired immediately, it’s very short-lived, lasting only as long as the antibodies circulate in the blood system. It is usually not very specific. Gamma globulin, the fraction of the blood containing a wide variety of antibodies, can be used to confer temporary protection against hepatitis and other diseases by this immunity.
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Nonspecific Defense Mechanism
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Skin is a physical barrier against bacterial invasion. Pores on the skin’s surface secrete sweat, which contains an enzyme that attacks bacterial cell walls. Passages (e.g. the respiratory tract) are lined with ciliated mucous-coated epithelia, which filter and trap foreign particles. Macrophages engulf and destroy foreign particles. The inflammatory response is initiated by the body in response to physical damage: injured cells release histamine, which causes blood vessels to dilate, thereby increasing blood flow to the damaged region. Granulocytes attracted to the injury site phagocytize antigenic material. An inflammatory response is often accompanied by a fever. Proteins called interferons are produced by cells under viral attack. Interferons diffuse to other cells, where they help prevent the spread of the virus. Inappropriate response to certain foods and pollen can cause the body to form antibodies and release histamine – inducing allergic reactions.
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Rejection of Transplants
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Transplanted tissues or organs are detected as foreign bodies by the recipients immune system. Resulting immune response can cause the transplant to be rejected. Immuno-suppressing drugs can be used to lower the immune response to transplants and decrease the likelihood of rejection.
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ABO Blood Types
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Erythrocytes have characteristic cell-surface proteins (antigens). Antigens are macromolecules that are foreign to the host organism and trigger an immune response. The two major groups of RBC antigens are the ABO group and the Rh factor. Type A blood has the A antigen present. Type A individuals will recognize type A antigen as self and will not respond to it. During blood transfusions, donor and recipient blood types must be matched. The rule of matching: If the donor’s antigens are already in the recipient’s blood, no clumping occurs. Type AB blood is termed the “universal recipient” as it has neither anti-A nor anti-B antibodies. Type O blood is considered to be the universal donor; it will not elicit a response from the recipient’s immune system since it does not possess any surface antigens.
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Rh Factor
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Another antigen that may be present on the surface of RBCs. Individuals may be Rh+, possessing the Rh antigen, or Rh-, lacking the Rh antigen. This is important during pregnancy. An Rh- woman can be sensitized by an Rh+ fetus if fetal RBCs enter maternal circulation during birth. If this woman carries another Rh+ fetus, the anti-Rh antibodies she produced when sensitized by the first birth may cross the placenta and destroy fetal RBCs. This results in a severe anemia for the fetus, known as erythroblastosis fetalis. This is not caused by ABO blood-type mismatches between mother and fetus, since anti-A and anti-B antibodies cannot cross the placenta.
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Transport Systems in Plants
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Transport in plants must supply plant cells with nutrients and remove waste products. In plants, circulation is called translocation. The plant stem is the primary organ of transport in the plant. Vascular bundles run up and down the stem. The vascular bundle at the center of the stem contains xylem, phloem and cambium cells.
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Xylem
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Thick-walled cells, often hollow, and located on the inside of the vascular bundle. They carry water and minerals up the plant and their thick walls give the plant its rigid support. Older xylem cells die and form the heartwood used for lumber. The outer layer of xylem is alive and is called the sapwood. Two types of xylem cells have been differentiated: vessel cells and tracheids. The rise of water in the xylem is explained: Transpiration pull – as water evaporates from the leaves of the plant, a vacuum is created which pulls water up the stem. Capillary action – any liquid in a thin tube will rise due to the surface tension of the liquid and interactions between the liquid and the tube. Root pressure – water entering the root hairs exerts a pressure which pushes water up the stem.
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Phloem
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Thin-walled cells on the outside of the vascular bundle. They usually transport nutrients (carbohydrates produced in the leaves) down the stem. These cells are living and include sieve tube cells, and companion cells. If a tree is girdled by removing a strip of bark around the trunk, the phloem connections are severed and the tree will die.
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Cambium
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Two layers thick and are actively dividing, undifferentiated cells that give rise to xylem and phloem. They are located between the xylem and phloem cell layers; as they divide, the cells near the phloem differentiate into phloem cells and the cells near the xylem differentiate into xylem cells.
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Gross Structure of Woody Stem
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From the outside inwards: epidermis (outer-bark), cortex, phloem, cambium, xylem, and pith (tissue involved in storage of nutrients and plant support). The phloem, cambium, and xylem layers are known as the fibrovascular bundle.
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Root
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It functions to absorb materials through the root hairs and anchor the plant. Some provide storage for energy reserves (turnips and carrots). Root hairs are specialized cells of the root epidermis with thin-walled projections. They increase the surface area for absorption of water and minerals from the soil. Like the stem, the root has the following layers: epidermis, cortex, phloem, xylem, and cambium. The epidermis contains the root hair cells.
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Regions of Growth in Plants
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Meristem refers to the actively dividing, undifferentiated cells of a plant. Cambium, lying between the phloem and xylem, is a type of meristem called lateral meristem. It provides for lateral growth of the stem by adding to the phloem or xylem (growth in diameter). Apical meristem is also located at the tips of roots and stems where division leads to increase in length. After actively dividing, the new cells elongate and finally differentiate into one of the many specialized cells of the plants.
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