A vessel that conveys blood between an artery and a capillary bed
A vessel that carries blood away from the heart to organs throughout the body
A chamber of the vertebrate heart that receives blood from the veins and transfers blood to a ventricle
A heart valve located between each atrium and ventricle that prevents a backflow of blood when the ventricle contracts
Force exerted by blood against vessel walls
A microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid.
The alternating contractions and relaxations of the heart
Closed circulatory system
A circulatory system in which blood is confined to vessels and is kept separate from the interstitial fluid
The stage of the cardiac cycle in which a heart chamber is relaxed and fills with blood
A blood cell that contains hemoglobin, which transports oxygen, also called a red blood cell
In invertebrates with an open circulatory system, the body fluid that bathes tissues
A blood cell that funtions in fighting infections, also called a white blood cell.
The colorless fluid, derived from interstitial fluid, in the lymphatic system of vertebrates
Open circulatory system
A circulatory system in which fluid called hemolymph bathes the tissues and organs directly and there is no distinction between circulatory fluid and the interstitial fluid
The liquid matrix of blood in which the cells are suspended
A pinched-off cytoplasmic fragment of a specialized bone marrow cell. Platelets circulate in the blood and are important in blood clotting
The branch of the circulatory system that supplies the lungs
A valve located at each exit of the heart, where the aorta leaves the left ventricle and the pulmonary artery leaves the right ventricle
The branch of the circulatory system that supplies all body organs except those involved in gas exchange
A heart chamber that pumps blood out of the heart
In animals, a vessel that carries blood toward the heart
A vessel that conveys blood between a capillary bed and a vein
One of the dead-end, multilobed air sacs where gas exchange occurs in a mammalian lung
One of a pair of breathing tubes that branch from the trachea into the lungs
A fine branch of the bronchi that transports air to the alveoli
The exchange of a eubstance or heat between two fluids flowing in opposite directions
An iron-containing protein in red blood cells that reversibly binds oxygen
An oxygen-storing, pigmented protein in muscle cells
The pressure exerted by a particular gas in a mixture of gases
The volume of air a mammal inhales and exhales with each breath
In insects, a system of branched, air-filled tubes that extends throughout the body and carries oxygen directly to cells
The flow of air or water over a respiratory surface
A lowering of the affinity of hemoglobin for oxygen, caused bya drop in pH. It facilitatkes the release of oxygen from hemoglobin in the vicinity of active tissues
Acquired (adaptive) immunity
A vertebrate-specific defense that is mediated by B lumphocytes and T lymphocytes. It exhibits specificity, memory, and self-nonself recognition.
A form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encounterred previously
A protien secreted by plasma cells that binds to a particular antigen. All antibody molecules have the same Y-shaped structures and in their monomer form consist of two identical heavy chains of two identical light chains
An enzyme that destroys bacterial cell walls' in mammals, found in sweat, tears, and saliva
A type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certian immune cells of animals. In mammals mainly macrophages, neutrophils, and dendritic cells.
A phagocytic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as an antigen-presenting cell
A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagoocytosis, or idrectly lyse extracellular pathogens
A protin that has antiviral or immune regulatory functions. Interferon-a and interferon-b, secreted by virus-infected cells, help nearby cells resist vireal infection; interferon-y, secreted by T cells, helps activate microphages
An innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the infiltration of white blood cells, and aid in tissue repair and destruction of invading pathogens
Natural killer (NK) cell
A type of white blood cell that can kill tumor cells and virus infected cells as part of innate immunity
Any of a group of protines secreted by a number of cell types, including macrophages and helper T cells, that regulate the function of lymphocytes and other cells of the immune system
A macromolecule that elicits an immune response by binding to receptors of B cells or T cells
A small, accessible region of an antigen to which an antigen receptor or antibody binds, also called an antigenic determinant
The antigen receptor on B cells, a Y-shaped, membrane-bound molecule consisting of two identical heavy chains and two identical light chains linked by disulfide bridges and containing two antigen-binding sites
B lymphocyte (B cell)
The lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response
The antigen receptor on T cells; a membrane-bound molecule consisting of one alpha chain and one beta chain linked by a disfulfide bridge and containing one antigen bidning site
Major histocompatibility complexy (MHC)
A family of genes that encode a large set of cell-surface protiens that function in antigen presentation. Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead to rejection of the transplant
A lymphcyte that has undergone clonal selection and is capable of mediating an acquired immune response
One of a clone of long-lived lymphocytes, formed during the primary immune response, that remains in a lymphoid organ until activiated by exposure to the same antigen that triggered its formation. Activated memory cells mount the secondary immune response.
The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen
Humoral immune response
The branch of acquired immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids
Cell-mediated immune response
The branch of acquired immunity that involved the activation of cytotoxic T cells, which defend against infected cells
The most abundant type of white blood cell. Neutrophils are phaocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days.
T helper cells
A type of T cell that , when activated, secretes cytokines that promote the response of b cells (humoral response) and cytotoxic T cells (cell-mediated response) to antigens
The process by which an MHC molecule binds to a fragment of an intracellular protien antigen and carries it to the cell surface, which it is displayed and can be recognized by a T cell.
Toll-like receptor. a membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to set of pathogens
Primary immune response
The initial acquired immune resonse to an antigen, which appears after a lag of about 10 to 17 days.
Secondary immune response
The acquired immune response elicited on second or subsequent exposures to a particular antigen, The secondary immune response is more rapid, of greater magnitued, and of longer duration thatn the primary immune response.
An antigen-presenting cell, located mainly in lymphatic tissues and skin, that is particulalry efficeitn in presenting antigens to helper T cells, thereby initiating a primary immune resposne
Long-lasting immunity conferred by the action of B cells and T cells and the resulting B and T memory cells specific for a pathogen. Active immunity can develop as a result of natural infection of immunization
Short-term immunity conferred by the transfer of antibodies, as occurs in the transfer of maternal antibodies to a fetus or nursing infant.
A disorder in which the ability of an immune system to protect against pathogens is defective or absent.
In homeostasis, a fluctuation in a variable that triggers a return to a set point
The conversion of stimulus energy to a change in the membrane potential of a sensory receptor cell
An initial response of a receptor cell to a stimulus, consisting of a change in voltage across the receptor membrane proportional to the stiumuls strength. The intensity of the receptor potential determines the frequency of action potentials traveling to the nervous system
The interpretation of sensory system input by the brain
Inherited characteristic of an organism that enhances its survival and reproduction in specific enviroments
A fibril collectively arranged in longitudinal bundles in muscle cells (fibers); composed of thin filaments of actin and regulatory protien and thick filaments of myosin
The fundamental, repeating unit of striated muscle, delimited by the Z lines
A single motor neuron and all the muscle fibers it controls
The maximal, sustained contraction of a skeletal muscle, caused by a very high frequency of action potentials elicited by continual stimulation
A hard skeleton buried within the soft tissues of an animal
A hard encasement on the surface of an animal that provides protection and points of attachment for muscles
A skeletal sysstem complosed of fluid held under pressure in a closed body compartment
A type of movement on land produced by rhythmic waves of muscle contractions passing from front to back, as in many annelids
A type of protien filament that acts as a motor protien with actin filaments to cause cell contraction
the regulatory protein that blocks the moysin-binding sites on actin molecules