front 1 Abductor | back 1 A muscle that moves a limb away from the center of the body. |
front 2 Absorption | back 2 The process by which substances are taken up into or across tissues. |
front 3 Acetylcholine | back 3 A neurotransmitter found throughout the nervous system (somatic motor neurons, preganglionic parasympathetic and sympathetic nerves, and postganglionic parasympathetic neurons); metabolized by acetylcholinesterase. |
front 4 Acrosome | back 4 The large vesicle at the head of a sperm cell containing enzymes that degrade the ovum cell membrane to allow fertilization. |
front 5 Actin | back 5 A protein found in the cytoskeleton and muscle cells; it is the principle constituent of the thin filaments and microfilaments. |
front 6 Action Potential | back 6 An abrupt change in the membrane potential of a nerve or muscle caused by changes in membrane ionic permeability; results in conduction of an impulse in nerves or contraction in muscle. |
front 7 Active Immunity | back 7 An immune response (antibody production or cellular immunity) acquired in response to exposure to an antigen. |
front 8 Active Site | back 8 Substrate-binding region of an enzyme. |
front 9 Adaptation | back 9 The development of characteristics that enable an organism to survive and reproduce in its habitat. |
front 10 Adaptive Immunity | back 10 Highly specific form of immunity that retains chemical memory of each invader encountered and is able to tailor the immune response to the specific pathogen. |
front 11 Adaptive Radiation | back 11 The evolutionary process by which one species gives rise to several species, each specialized for different niches. |
front 12 Adductor | back 12 A muscle that moves a limb toward the center of the body. |
front 13 Adenine | back 13 A purine base present in DNA and RNA; it forms hydrogen bonds with thymine and uracil. |
front 14 Adenosine Triphosphate (ATP) | back 14 A nucleotide molecule consisting of adenine, ribose, and three phosphate moieties; the outer two phosphates are bound by high energy bonds. |
front 15 Adipose | back 15 Refers to fatty tissue, fat-storing tissue, or fat within cells. |
front 16 Aerobic | back 16 Refers to a biological process that occurs in the presence of molecular oxygen (O2) or to organisms that cannot live without molecular oxygen. |
front 17 Afferent (sensory) neuron | back 17 A neuron that picks up impulses from sensory receptors and transmits them toward the CNS. |
front 18 Agranulocyte | back 18 Type of leukocyte that does not contain cytoplasmic granules, including lymphocytes and monocytes. |
front 19 Albumin | back 19 Protein synthesized in the liber that maintains the oncotic pressure of the blood and serves as a carrier for many drugs and hormones. |
front 20 Allantois | back 20 One of four embryonic membranes; it contains the growing embryo's waste products. |
front 21 Allele | back 21 Alternative forms of the same gene coding for a particular trait; they segregate during meiosis. |
front 22 Allergy | back 22 A type of autoimmunity in which a person's immune system becomes over-activated by common substances in the environment. |
front 23 Alveolus | back 23 Basic functional unit of the lung; a tiny-sac specialized for passive gas exchange between the lungs and the blood. |
front 24 Amino Acids | back 24 The building blocks of proteins, each containing an amino group, a carboxylic acid group, and a side chain (or R group) attached to the alpha-carbon. |
front 25 Amnion | back 25 The innermost fluid filled embryonic membrane; it forms a protective sac surrounding the embryos of birds, reptiles, and mammals. |
front 26 Amplification | back 26 Characteristic of signaling cascade, in which the binding of a single peptide hormone to a membrane bound receptor results in a signal that increases in strength through the signaling cascade. |
front 27 Ananerobic | back 27 Refers to a biological process that can occur without oxygen or to organisms that can live without molecular oxygen. |
front 28 Anaphase | back 28 The stage of mitosis or meiosis characterized by the migration o chromatids or homologous chromosomes to opposite poles of the dividing cells. |
front 29 Androgen | back 29 Any male sex hormone, such as testosterone. |
front 30 Antibiotic | back 30 Substance that kills or inhibits the growth of bacteria or fungi (usually by disrupting cell wall assembly or by binding ribosomes, thus inhibiting protein synthesis.) |
front 31 Antibody | back 31 Immune or protective protein whose synthesis is induced by the presence of foreign substances (antigens) in the body; each antibody binds to a specific antigen in an immune response; also called immunoglobulin. |
front 32 Antigen | back 32 A substance that binds to an antibody; may be foreign or a self antigen. |
front 33 Antigen-Binding Region | back 33 Portion of an antibody that is specific for a particular antigen the area of the antibody to which the antigen binds. |
front 34 Aortic-Valve | back 34 One of the semilunar valves, separating the left ventricle from the aorta. |
front 35 Apoptosis | back 35 Process by which a cell undergoes programmed cell death in a highly organized manner in response to either external or internal signals. |
front 36 Appendicular Skeleton | back 36 Peripheral portion of the skeleton consisting of arms, legs, and pelvic and pectoral girdles. |
front 37 Archenteron | back 37 The central cavity in the gastrula stage of embryological development; it is lined by endoderm and ultimately gives rise to the adult digestive tract. |
front 38 Arterioles | back 38 Small arterial structures that link the arteries to the capillaries. |
front 39 Artery | back 39 Thick-walled, muscular blood vessels that generally carries blood away from the heart. |
front 40 Articular Cartilage | back 40 Cartilaginous coating at the ends of bones that provides a smooth surface for articulation of bones with a joint. |
front 41 Asexual Reproduction | back 41 Any reproductive process that does not involve the fusion of gametes (such as budding). |
front 42 Asters | back 42 Star-shaped structures that form around the centrosome during mitosis. |
front 43 Atrium | back 43 One of two paired structures on either side of the heart, into which blood returning from either the body (right atrium) or the lungs (left atrium) flows. |
front 44 Autocrine | back 44 Form of cell-cell communication in which a cell releases a substance that then binds to the membrane of the releasing cell to either inhibit or activate a cellular activity. |
front 45 Autoimmunity | back 45 Inappropriate immune response that targets self-antigens. |
front 46 Autonomic Nervous System | back 46 Subdivision of the PNS responsible for involuntary activities, which is further subdivided into the parasympathetic and sympathetic nervous systems. |
front 47 Autosome | back 47 Any chromosome other than a sex chromosome. |
front 48 Axial Skeleton | back 48 Midline structures of the skeleton including the skull, vertebral column, and rib-cage; provides the central framework of the body. |
front 49 Axon | back 49 The longer fiber of a neuron; it conducts impulses away from the cell body toward the synapse. |
front 50 Axon Hillock | back 50 Transition point between the cell body (soma) and the axon of a neuron; the site of action potential initiation. |
front 51 Bacillus | back 51 Red-shaped bacterium. |
front 52 Bacteriophage | back 52 A virus that invades bacteria and sometimes uses bacterial RNA and ribosomes to self replicate. |
front 53 Basophil | back 53 Type of granulocytic leukocyte that largely participates in allergic reactions and local inflammation. |
front 54 Bile | back 54 A solution of salts, pigments, and cholesterol produced by the liver and stored in the gallbladder; it emulsifies large fat droplets when secreted into the small intestine via the bile duct. |
front 55 Bilirubin | back 55 Product of the breakdown of hemoglobin that is modified to a more soluble form in the liver. |
front 56 Binary Fission | back 56 A type of asexual reproduction characteristic of prokaryotes in which there is equal nuclear and cytoplasmic division. |
front 57 Blastocoel | back 57 The fluid filled central cavity of the blastula. |
front 58 Blastocyst | back 58 A mammalian blastula, consisting of the trophoblastic cells and an inner cell mass. |
front 59 Blastopore | back 59 Opening of the archenteron to the external environment in the gastrula stage of embryonic development. |
front 60 Blastula | back 60 The early embryonic stage during which the embryo is a hollow fluid filled sphere of undifferentiated cells. |
front 61 Blastulation | back 61 Process by which a solid mass of early embryonic cells, known as the morula, becomes the blastula, a hollow fluid filled sphere of undifferentiated cells. |
front 62 Bohr Effect | back 62 Changes in the affinity of hemoglobin for oxygen caused by changes in the environment; when pH is low (increased concentration of hydrogen ions), the oxyhemoglobin dissociation curve shifts right, indicating a decreased affinity of hemoglobin for oxygen and more efficient off-loading of oxygen from hemoglobin. |
front 63 Bolus | back 63 An initial dose of medication; in the digestive system, chewed food leaving the moth, traveling through the esophagus, and entering the stomach. |
front 64 Bone Marrow | back 64 Central portion of bones, especially long bones, that contains fat and developing blood cells, including erythrocytes, leukocytes, and megakaryocytes. |
front 65 Bone Matrix | back 65 Organic and inorganic minerals that provide strength to compact bone; organic components include collagen, glycoproteins, and other peptides; inorganic components include calcium, phosphate, hydroxide ions (in hydroxyapatite). |
front 66 Bowman's Capsule | back 66 The cup-like structure of the nephron; it collects the glomerular filtrate and channels it into the proximal convoluted tubule. |
front 67 Bronchi | back 67 Tube-like passages for air that connect the trachea to the bronchioles. |
front 68 Bronchioles | back 68 Passageways for air that start at the bronchi, dividing into continuously smaller passageways that eventually lead to the alveoli, where gas exchange occurs. |
front 69 Brush-Border Enzymes | back 69 Group of enzymes present on the luminal surface of cells lining the duodenum that break down larger biomolecules into monomers that are able to be absorbed. |
front 70 Bundle of His | back 70 Part of the conduction system of the heart; it carries impulses from the AV node to the ventricles. |
front 71 Callus | back 71 Area of excessive deposition of keratin in response to repeated strain due to friction. |
front 72 Canaliculi | back 72 Small canals connecting lacunae within the bone matrix with Haversian canals, allowing for the flow of nutrients and wastes. |
front 73 Capillary | back 73 Small, thin-walled blood vessel where gas, nutrients, and waste exchange occurs between blood and tissues. |
front 74 Capsid | back 74 Protein coat surrounding a virus. |
front 75 Cardiac Output | back 75 Total blood volume pumped by the left ventricle in one minute, found by multiplying the heart rate by the stroke volume. |
front 76 Cartilage | back 76 A firm, elastic, translucent connective tissue produced by cells called chondrocytes. |
front 77 Catabolism | back 77 The chemical breakdown of complex substances (macromolecules) to yield simpler substances and energy. |
front 78 Cecum | back 78 The first part of the large intestine, accepts material flowing through the ileocecal valve and is the point of attatchment of the appendix. |
front 79 Cell Body | back 79 Portion of a neuron where the nucleus, endoplasmic reticulum, and ribosomes are located; also known as the soma. |
front 80 Cell Theory | back 80 A foundational belief in modern biology that all living things are composed of cells, that the cell is the basic functional unit of life, that all cells arise from preexisting cells, and that DNA is the genetic material. |
front 81 Cell-Mediated Immunity | back 81 Type of immunity that uses cytotoxic chemicals released from cells to cause death of cells that have been infected by viruses. |
front 82 Central Nervous System (CNS) | back 82 The brain and spinal cord. |
front 83 Centriole | back 83 A small organelle in the cytoplasm of animal cells; it organizes the spindle apparatus during mitosis and meiosis. |
front 84 Centromere | back 84 The area of a chromosome where sister chromatids are joined; it is also the point of attachment to the spindle fiber during mitosis and meiosis. |
front 85 Centrosomes | back 85 Paired cylindrical organelles, located in the cytoplasm, that contain the centrioles. |
front 86 Cerebellum | back 86 The section of the mammalian hindbrain that controls muscle coordination and equilibrium. |
front 87 Cerebral Cortex | back 87 The outer layer of the forebrain, consisting of grey matter; it is the site of higher cognitive functions in humans. |
front 88 Cervix | back 88 Lower end of the uterus that marks the transition between the vagina and the uterus. |
front 89 Chemical Digestion | back 89 Enzymatic cleavage of chemical bonds within foodstuffs, resulting in smaller molecules. |
front 90 Chemotaxis | back 90 Movement of cells toward or away from a chemical within the environment. |
front 91 Chiasmata | back 91 Sites where crossing over occurs between homologous chromosomes during meiosis. |
front 92 Chief Cells | back 92 Cells within the stomach that secrete pepsinogen, a zymogen that is converted to its active form, pepsin, by the acidic environment of the stomach. |
front 93 Chondrin | back 93 Elastic cartilage matrix substance secreted by chondrocytes. |
front 94 Chondrocyte | back 94 A differentiated cartilage cell that synthesizes the cartilaginous matrix. |
front 95 Chromatid | back 95 Each of the two chromosomal strands formed by DNA replication in the S phase of the cell cycle; held together by the centromere. |
front 96 Chromosome | back 96 A filamentous body found within the nucleus of a eukaryotic cell or nucleoid region of a prokaryotic cell, composed of DNA. |
front 97 Chylomicron | back 97 Soluble lipid molecule that consists of triglycerides and esterified cholesterol molecules; absorbed into lacteals from the digestive tract. |
front 98 Chyme | back 98 Aqueous mixture of food and secretions that leaves the stomach to enter the duodenum. |
front 99 Cilia | back 99 Projection from a cell involved in movement of materials on the outside of the cell. |
front 100 Circadian Rhythm | back 100 A behavioral pattern based on a 24-hour cycle, related to cycling of hormones such as cortisol and melatonin. |
front 101 Cleavage | back 101 A series of mitotic divisions of the zygote immediately following fertilization, resulting in progressively smaller cells with increased nucleus to cytoplasmic ratios. |
front 102 Clonal Selection | back 102 Phenomenon in which only B- or T- cells specific to a particular pathogen are activated. |
front 103 Coccus | back 103 Spherically shaped bacterium. |
front 104 Codominance | back 104 A genetic effect in which the phenotype of a heterozygote is a distinct reflection of both alleles at a particular locus. |
front 105 Competent | back 105 Describes a cell capable of responding to induction signals. |
front 106 Conjugation | back 106 The temporary joining of two organisms via a tube called a pilus, through which genetic material is exchanged; a form of sexual reproduction used by bacteria. |
front 107 Connective Tissue | back 107 Animal tissue composed of cells lying in an extracellular proteinaceous network that supports, connects, and surrounds the organs and structures of the body. |
front 108 Constant Region | back 108 Portion of an antibody molecule that is not variable and participates in the binding other other immune modulators. |
front 109 Convergent Evolution | back 109 The process by which unrelated organisms living in a similar environment develop analogous structures. |
front 110 Corona Radiata | back 110 Layer of cells surrounding an oocyte that aids in the development of the ovum. |
front 111 Corpus Luteum | back 111 The remnant of the ovarian follicle, which after ovulation continues to secrete progesterone. It degeneration leads to menstruation; it also maintains the uterine lining during pregnancy. |
front 112 Cortex | back 112 The external layer found in many organs of the body, including the brain, adrenal glands, and kidney. |
front 113 Cortical Reaction | back 113 Release of calcium ions by the ovum after fertilization, resulting in the creation of a fertilization membrane, a structure that prevents fertilization of an ovum by multiple sperm cells. |
front 114 Corticosteroids | back 114 Steroid hormones produced in the adrenal cortex, including glucocorticoids (cortisol), mineralocorticoids (aldosterone), and cortical sex hormones. |
front 115 Crossing Over | back 115 The exchange of genetic material between homologous chromosomes during meiosis. |
front 116 Cyclin Adenosine Monophosphate (cAMP) | back 116 An intracellular second messenger in the signaling cascade initiated by a peptide hormone; synthesized from ATP by adenylate cyclase. |
front 117 Cytokine | back 117 Chemical substance that stimulates inflammation and recruits additional immune cells to a specific area. |
front 118 Cytokinesis | back 118 The division and distribution of parent cell cytoplasm to the two daughter cells during mitotic and meiotic cell division. |
front 119 Cytoplasm | back 119 The fluid and solutes within a cell membrane, external to the nucleus and cellular organelles. |
front 120 Cytotoxic T-Cell | back 120 T-cell that seeks out infected cells and induces apoptosis in these cells to prevent spread of the pathogen. |
front 121 Deletion | back 121 A type of genetic mutation in which some variable amount of DNA is removed. |
front 122 Dendrite | back 122 The portion of a neuron that receives stimuli and conveys them toward the cell body. |
front 123 Dermis | back 123 The layer of skin cells under the epidermis. Contains sweat glands, hair follicles, fat, and blood vessels. |
front 124 Determinate Cleavage | back 124 Rapid mitotic divisions ocurring in an embryo that result in cells with predetermined fates; these cells are only capable of differentiating into certain kinds of tissues within an organism. |
front 125 Determination | back 125 Designation of a cell within an embryo as having a particular future function. |
front 126 Diaphragm | back 126 Thin, muscular structure that divides the thorax from the abdomen and provides the driving force for inhalation. |
front 127 Diaphysis | back 127 Cylindrical shaft of a long bone. |
front 128 Diastole | back 128 The period of relaxation of cardiac muscle during which the atrioventricular valves open and the ventricles fill with blood. |
front 129 Differentiation | back 129 The process by which unspecialized cells become specialized. Involves selective transcription of the genome. |
front 130 Digestion | back 130 The breakdown of macromolecular nutrient material via mechanical and chemical means to simple molecular building blocks; this facilitates absorption. |
front 131 Diploid | back 131 Having two chromosomes of each type per cell; symbolized by 2n. |
front 132 Direct Hormone | back 132 Substance secreted into the bloodstream that causes a change in the physiological activity of cells without requiring an intermediary. |
front 133 Directional selection | back 133 Selective pressures favor the development of an extreme phenotype that provides a selective advantage; this phenotype emerges as the primary phenotype over time. |
front 134 Disruptive Selection | back 134 Type of selection in which selective pressures favor extreme phenotypes over the norm.. |
front 135 Divergent Evolution | back 135 A process of change whereby organisms with a common ancestor evolve dissimilar structures (such as dolphin flippers and human arms). |
front 136 Dominant | back 136 Refers to an allele that requires only one copy for expression. |
front 137 Ductus Arteriosus | back 137 Fetal structure that shunts blood from the pulmonary artery to the aorta to bypass the developing lungs. |
front 138 Ductus Venosus | back 138 Shunt from the umbilical vein to the inferior vena cava, allowing oxygenated blood returning from the placenta to bypass the liver and enter the systemic circulation. |
front 139 Duodenum | back 139 First segment of the small intestine; the contents of the stomach and the pancreatic and bile ducts empty into it; side of digestion and some absorption. |
front 140 Ectoderm | back 140 Outermost embryonic germ layer; it gives rise to the skin, nervous system, inner ear, lens of the eye, and other structures. |
front 141 Effector | back 141 An organ, muscle, or gland used by an organism to respond to a stimulus. |
front 142 Efferent (motor) Neuron | back 142 A neuron that transmits nervous impulses from the central nervous system to an effector. |
front 143 Embryo | back 143 An organism at the early developmental stage; in humans, the erm refers to the first eight weeks after fertilization. |
front 144 Endocrine | back 144 A form of cell-cell communication that involves the secretion of hormones into the bloodstream by ductless glands; these hormones then travel to distant locations within the organism to cause a change in cellular activity. |
front 145 Endoderm | back 145 Innermost embryonic germ layer; it later gives rise to the linings of the alimentary canal and of the digestive and respiratory organs. |
front 146 Endometrium | back 146 Uterine lining that is regenerated each month in preparation for implantation of an embryo; absence of an embryo results in sloughing off of the endometrium in a process known as menstruation. |
front 147 Endoplasmic Reticulum | back 147 Membrane bound channels in the cytoplasm that transport proteins and lipids to various parts of the cell. |
front 148 Endothelium | back 148 Lining of blood vessels consisting of endothelial cells. |
front 149 Enteric Nervous System | back 149 Collection of neurons within the gastrointestinal tract that governs peristalsis. |
front 150 Eosinophil | back 150 Type of granulocytic leukocyte that largely participates in the immune response against parasites; also involved in the pathogenesis of allergies. |
front 151 Epidermis | back 151 The outermost layer of the skin. |
front 152 Epididymis | back 152 The coiled tube in which sperm gain motility and are stored after production in the testes. |
front 153 Epiglottis | back 153 The small flap of cartilage that covers the glottis during swallowing, preventing food from entering the larynx. |
front 154 Epinephrine | back 154 A hormone synthesized by the adrenal medulla; it stimulates the fight or flight response; also a neurotransmitter in the sympathetic nervous system. |
front 155 Epiphyseal Plate | back 155 Cartilaginous structure in the epiphysis where growth occurs. |
front 156 Epiphysis | back 156 Dilated end of a long bone. |
front 157 Episomes | back 157 A specialized subset of plasmids capable of integrating into the genome bacteria under specific circumstances. |
front 158 Epithelium | back 158 The cellular layer that covers internal and external surfaces of body structures and cavities. |
front 159 Erythrocyte | back 159 Red blood cells; a biconcave, dic-shaped cell that contains hemoglobin and has no nucleus. |
front 160 Esophagus | back 160 Portion of the alimentary canal connecting the pharynx and the stomach. |
front 161 Eukaryote | back 161 A unicellular or multicellular organism composed of cells that contain a membrane bound nucleus and other membrane bound organelles. |
front 162 Evolution | back 162 The changes in the gene pool from one generation to the next caused by mutation, nonrandom mating, natural selection, and genetic drift. |
front 163 Exocrine Glands | back 163 Glands that release their secretions into ducts (such as the parts of the liver and sweat glands). |
front 164 Expressivity | back 164 Varying expression of disease symptoms despite identical genotypes. |
front 165 Extensor | back 165 A muscle used in the straightening of a limb. |
front 166 Facultative Anaerobes | back 166 Prokaryotes that can exist with or without oxygen. |
front 167 Fertilization | back 167 Fusion of two gametes. |
front 168 Fertilization Membrane | back 168 Structure created by the cortical reaction after fertilization of an ovum by a sperm cell; prevents fertilization of an ovum by multiple sperm cells. |
front 169 Fetus | back 169 A developing organism that has passed the early developmental stages. In humans, the term refers to an embryo from the ninth week after fertilization until birth. |
front 170 Fibrin | back 170 The insoluble protein that forms the bulk of a blood clot. |
front 171 Filial Generation | back 171 Offspring in a genetic cross; may be supplemented with a subscript to show how many generations out from the parents. |
front 172 Filtration | back 172 In the nephron, the process by which blood plasma is forced (under high pressure) out of the glomerulus into Bowman's capsule. |
front 173 Fitness | back 173 Reproductive success of an individual, measured in increased number and survival of offspring. |
front 174 Flagellum | back 174 A microscopic, whip-like filament that functions in the locomotion of sperm cells and some unicellular organisms; composed of microtubules. |
front 175 Flexor | back 175 A muscle used in the bending of a limb. |
front 176 Follicle | back 176 The set of cells surrounding a developing or mature ovum. Secretes nutrients and estrogen and atrophies into the corpus luteum after ovulation. |
front 177 Foramen Ovale | back 177 Shunt within the fetal heart between the right and left atria that allows the circulation to largely bypass the developing lungs. |
front 178 Gallbladder | back 178 Organ below the liver that stores bile; contracts in response to stimulation by cholecystokinin, resulting in release of bile into the biliary system and eventually into the duodenum. |
front 179 Gamete | back 179 Sperm or ovum; a cell that has half the number of chromosomes of a somatic cell (haploid) and can fuse with another gamete to form a zygote. |
front 180 Ganglion | back 180 A mass of neuron cell bodies outside the central nervous system. |
front 181 Gastrula | back 181 The embryonic stage characterized by the presence of ectoderm, mesoderm, and endoderm. |
front 182 Gene | back 182 The basic unit of heredity; a region on a chromosome that codes for a specific product. |
front 183 Gene Pool | back 183 All of the alleles for every gene in every individual in a given population. |
front 184 Genetic Drift | back 184 Variations in the gene pool caused by chance. |
front 185 Genetic Map | back 185 A diagrammatic representation of a chromosome indicating distance between two genes on a chromosome as determined by recombination frequencies. |
front 186 Genome | back 186 An organism's complete set of chromosomes. |
front 187 Genotype | back 187 The genetic composition of an entire organism or in reference to a particular trait. |