PLTW Human Body Systems Glossary
Cardiovascular System and Cardiology
ABO system: A system of four types (, , , and ) which human blood is classified into, based on the presence or absence of certain antigens.
Agglutination: The clumping of particles.
Albumin: A protein made by your liver that plays an essential role in keeping the fluid in your blood from leaking into your tissues.
Angiogram: A medical imaging technique, using an imaging dye, to visualize blood vessels.
Angioplasty: A surgical method to restore the flow of blood through an artery.
Aorta: The largest artery in the body. It carries oxygenated blood from the left ventricle of the heart to the rest of the body.
Aortic valve: One of four valves in the heart. It separates the left ventricle and the aorta, and functions to prevent blood from flowing back into the left ventricle.
Arrhythmia: A problem with the rate or rhythm of your heartbeat.
Artery: A type of vessel that carries blood from the heart through the body. Arteries are part of the circulatory system.
Atherosclerosis: The deposition of fats and/or cholesterol on artery walls, which negatively impacts blood flow.
Atrioventricular node (AV node): Part of the heart’s conduction system that is responsible for controlling the impulse delivered by the sinoatrial node (SA).
Atrium: An upper chamber of the heart where blood enters. The heart has two atria: the left atrium connects to the lungs and the right atrium connects to the veins.
Blood plasma: The pale yellow, liquid portion of blood that consists of water and dissolved substances, including sugars, lipids, metabolic waste products, amino acids, hormones, and vitamins.
Blood pressure: The pressure that blood exerts upon the walls of blood vessels, especially arteries, usually measured with a sphygmomanometer and expressed in .
Cardiac muscle: Striated muscle fibers (cells) that form the wall of the heart. They are stimulated by the intrinsic conduction system and autonomic motor neurons.
Cardiac output: A measure of how much blood is pumped by both ventricles in one minute.
Cardiology: The field of study focused on the function and diseases of the heart.
Cardiovascular system: The transport system of the body responsible for carrying oxygen and nutrients to the body and carrying away carbon dioxide and other wastes. It is composed of the heart, blood vessels, and blood.
Cholesterol: A lipid that is an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
Coronary arteries: The arteries that supply blood to the heart.
Coronary artery disease: The narrowing or blockage of the coronary arteries, usually caused by atherosclerosis.
Coronary bypass: A surgical bypass procedure to reroute blood around an obstruction in a coronary artery. The procedure involves grafting one end of a segment of vein removed from another part of the body onto the aorta and the other end onto the coronary artery beyond the obstructed area to allow for increased blood flow.
Diastole: The stage in a heartbeat when the heart is relaxed and the heart chambers fill with blood.
Diastolic pressure: The pressure in arteries between heartbeats, when the heart is relaxed.
Electrocardiogram (EKG): A measurement of heart electrical activity.
Erythrocyte (red blood cell): Hemoglobin-rich red blood cells that transport oxygen through the body. Erythrocytes give the red color to vertebrate blood and do not have nuclei.
Heart attack: An acute episode of heart disease that leads to damage or death of heart muscle due to insufficient blood supply to the muscle.
Heart disease: An abnormal organic condition of the heart or circulation.
Heart rate: A measure of cardiac activity usually expressed in number of beats per minute.
Hematocrit: The proportion, by volume, of blood that is made up of red blood cells.
Hemoglobin: A protein found in red blood cells that transports oxygen.
High-density lipoprotein (HDL): The “good” cholesterol that helps remove the less beneficial forms of cholesterol from blood.
Inferior vena cava: The largest vein in the human body, which returns blood to the right atrium of the heart from body parts below the diaphragm.
Low-density lipoprotein (LDL): The “bad” cholesterol that can build up in the arteries and help form plaques, which can cause coronary artery disease.
Mitral valve: A valve in the heart that guards the opening between the left atrium and the left ventricle. It prevents the blood in the ventricle from returning to the atrium. It is also called the bicuspid valve.
Pacemaker: A device implanted under a person’s skin that works to correct irregular heart rhythm.
Pulmonary circulation: Part of the circulatory system in which deoxygenated blood moves from the right ventricle of the heart to the lungs (through arteries) to become oxygenated and then returns to the left side of the heart (through veins).
Pulmonary valve: A one-way valve by which blood leaves the heart through arteries. The valve prevents blood from returning into the right ventricle.
Pulse: The rhythmic expansion and recoil of arteries resulting from heart contraction.
Sinoatrial node (SA node): Part of the heart’s conduction system that is responsible for heart rate.
Sphygmomanometer: An instrument for measuring blood pressure, especially arterial blood pressure.
Stenting: A surgical procedure to insert a stent into a patient. A stent is a hollow structure designed to keep a passageway open, such as a vessel or ureter.
Superior vena cava: The second largest vein in the human body. The superior vena cava returns blood to the right atrium of the heart from the upper half of the body.
Systemic circulation: The series of vessels that bring oxygenated blood from the heart to tissues and return deoxygenated blood from the tissues back to the heart.
Systole: The stage in a heartbeat when contraction of the heart pushes blood out of the chambers and into the aorta and pulmonary artery.
Systolic pressure: The pressure generated by the heart’s left ventricle during systole.
Thrombocyte (platelet): A minute, colorless, anucleate disk-like body of mammalian blood that assists in blood clotting by adhering to other platelets and damaged epithelium.
Tricuspid valve: The valve situated at the opening of the right atrium of the heart into the right ventricle. It consists of three triangular membranous flaps and resembles the mitral valve in structure.
Valve: A body structure that temporarily closes a passage or orifice, or permits movement of fluid in only one direction.
Vasodilation: The widening of blood vessels as a result of the relaxation of the blood vessel’s muscular walls, which decreases blood pressure.
Vein: A vessel that returns blood (typically deoxygenated) to the heart.
Ventricle: A lower chamber of the heart where blood exits. The left ventricle connects to the aorta, and the right ventricle connects to the main pulmonary artery (or pulmonary trunk).
Nervous System and Sensory Organs
Action potential: A brief electrical impulse that travels along the axon of a neuron.
Aqueous humor: The fluid that fills the space between the lens and the cornea.
Axon: A long nerve cell process that usually conducts impulses away from the cell body.
Axon terminals: The endings of axons; the location where axons make contact with other nerve or effector cells.
Blind spot: The small circular area in the retina where the optic nerve enters the eye that is devoid of rods and cones and is insensitive to light.
Brain stem: The part of the brain that is composed of the midbrain, pons, and medulla oblongata and connects the spinal cord with the forebrain and cerebrum.
Cell body: The central part of a neuron that contains the nucleus and is the main structural component of gray matter.
Central nervous system (CNS): The part of the nervous system which, in vertebrates, consists of the brain and spinal cord, to which sensory impulses are transmitted and from which motor impulses pass out, and which supervises and coordinates the activity of the entire nervous system.
Cerebellum: A large dorsally projecting part of the brain concerned especially with the coordination of muscles and the maintenance of bodily equilibrium, situated between the brain stem and the back of the cerebrum.
Cerebrum: The dorsal portion, composed of right and left hemispheres, of the vertebrate forebrain. It is the integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system.
Chronic traumatic encephalopathy (CTE): A progressive degeneration and/or death of nerve cells caused by repeated head injuries.
Concussion: An injury to the head that causes the brain to quickly move back and forth, hitting the inside of the skull.
Cone: Any of the conical photosensitive receptor cells of the vertebrate retina that function in color vision.
Cornea: The transparent part of the coat of the eyeball that covers the iris and pupil and admits light to the interior.
Dendrites: Any of the usually branching protoplasmic processes that conduct impulses toward the cell body of a neuron.
Gyrus: A convoluted ridge between anatomical grooves.
Iris: The opaque muscular contractile diaphragm suspended in the aqueous humor in front of the lens. It is perforated by the pupil, has a pigmented posterior surface, and a colored anterior surface determining eye color.
Lens: A transparent structure of the eye that works with the cornea to refract light to be focused on the retina.
Myelin sheath: In a neuron, an insulating coat of cell membrane from Schwann cells that is interrupted by nodes of Ranvier.
Nervous system: The body system in vertebrates made of the brain, spinal cord, nerves, ganglia, and receptor organs. It receives/interprets stimuli and transmits impulses to muscles/glands.
Neurotransmitter: A substance (as norepinephrine or acetylcholine) that transmits nerve impulses across a synapse.
Nodes of Ranvier: The gaps in the myelin sheath of nerve cells found between neighboring Schwann cells.
Optic nerve: Either of the pair of sensory nerves comprising the second pair of cranial nerves, conducting visual stimuli to the brain.
Peripheral nervous system (PNS): The part of the nervous system outside the central nervous system comprising cranial nerves (excluding the optic nerve), spinal nerves, and the autonomic nervous system.
Proprioception: The body’s ability to sense movement, action, and location, such as walking without looking at your feet.
Pupil: The opening in the iris that admits light into the interior of the eye; muscles in the iris regulate its size.
Reflex: An automatic and often inborn response to a stimulus involving a nerve impulse passing from a receptor to the spinal cord and then to an effector without reaching consciousness.
Retina: The light-sensitive layers of nerve tissue lining the most posterior chamber of the eye that receive images and send electric signals through the optic nerve to the brain.
Rod: Any of the long rod-shaped photosensitive receptors in the retina responsive to faint light.
Schwann cell: The cell that produces the myelin sheath.
Sulcus: A shallow furrow on the surface of the brain separating adjacent gyri.
Synapse: The place at which a nervous impulse passes from one neuron to another.
Traumatic brain injury (TBI): A brain dysfunction caused by an outside force to the head.
Vitreous humor: The clear viscous substance that fills the eyeball behind the lens.
Genetics and Molecular Biology
Adenine: A purine base and component of nucleic acids in DNA and RNA and in the energy-carrying molecule ATP.
Allele: Any of the alternative forms of a gene that could occur at the same place on a chromosome, such as genes for blood type found on chromosome .
Anticodon: A sequence of three nucleotides in a transfer RNA (tRNA) molecule complementary to a codon on messenger RNA (mRNA).
Autosome: A chromosome that is not directly involved in determining sex (e.g., chromosomes ).
Centromere: The central region joining two sister chromatids.
Chromatid: One half of a chromosome.
Chromosome: Tightly coiled DNA found in the nuclei of cells.
Codon: A sequence of three nucleotides found in DNA or mRNA coding for a specific amino acid or stop signal.
Cytosine: A component of nucleic acids (DNA and RNA); a pyrimidine base.
Dehydration synthesis: A chemical reaction that results in the loss of a water molecule.
Deoxyribonucleic acid (DNA): A nucleic acid consisting of nucleotide monomers with a deoxyribose sugar and nitrogenous bases adenine (), cytosine (), guanine (), and thymine ().
Dominant trait: A genetic trait where the phenotype is seen in an individual with only one copy of the associated gene.
Familial hypercholesterolemia: An autosomal dominant genetic disorder disrupting the body’s ability to eliminate low-density lipoprotein (LDL) from the blood.
Gel electrophoresis: The separation of nucleic acids or proteins on the basis of their size and electrical charge.
Gene: A sequence of nucleotides that codes for a protein, resulting in a specific phenotype.
Genetic material: Nucleic acids (DNA and RNA) responsible for phenotypic traits and variation.
Genetics: A branch of biology dealing with heredity and variation of organisms.
Genome: A complete set of the genes in one organism.
Genotype: All or part of the genetic constitution of an individual or group.
Guanine: A component of nucleic acids; a purine base.
Heredity: The transmission of traits from parent to offspring.
Heterozygous: Having two different alleles at one location on two homologous chromosomes.
Histone: A protein that DNA winds around to condense into a chromosome.
Homologous chromosomes: Chromosome pairs, one from each parent, having similar gene composition, size, and structure.
Homozygous: Having two identical alleles at one location on two homologous chromosomes.
Hydrolysis: A chemical reaction that uses water to split bonds between molecules.
Karyotype: An image of the chromosome pairs of a cell arranged by size and shape.
Meiosis: Cellular process reducing the number of chromosomes in gamete-producing cells by half.
Messenger RNA (mRNA): RNA transcribed from DNA and translated by ribosomes to produce proteins.
Mitosis: The doubling and separation of genetic material resulting in two new nuclei with the same number of chromosomes as the parent.
Mutation: A rare change in genetic material creating genetic diversity.
Nondisjunction: An error during mitosis or meiosis where homologous chromosomes or sister chromatids fail to move apart properly.
Nucleotide: Building block of DNA consisting of a five-carbon sugar, nitrogenous base, and phosphate group.
Nucleus: The organelle in eukaryotic cells containing all chromosomal DNA.
Phenotype: The physical and physiological traits of an organism determined by genetic makeup.
Polymerase chain reaction (PCR): A laboratory technique for amplifying DNA in vitro using a thermocycler, primers, DNA polymerase, and nucleotides.
Protein synthesis: The creation of a protein from a DNA template.
Punnett square: A graphical way to discover potential combinations of offspring genotypes given the parents' genotypes.
Purine: An aromatic, heterocyclic organic compound (Adenine and Guanine).
Pyrimidine: An aromatic, heterocyclic organic compound (Thymine, Cytosine, and Uracil).
Recessive trait: A trait evident only when an organism inherits two copies of a recessive allele.
Recognition sites: A sequence of DNA where a restriction enzyme cuts.
Restriction digestion: The process of cutting DNA molecules into smaller pieces using restriction enzymes.
Restriction enzyme: A degradative enzyme that recognizes specific nucleotide sequences and cuts DNA; also known as a restriction endonuclease.
Restriction fragment length polymorphisms (RFLPs): Variations in DNA fragment sizes produced when DNA is cut with restriction enzymes.
Ribonucleic acid (RNA): A nucleic acid with ribose sugar and bases adenine (), cytosine (), guanine (), and uracil ().
Ribosome: Cell organelle functioning as the site of protein synthesis.
Sex chromosome: One of the pair of chromosomes (X and Y) determining the sex of an individual.
Thymine: A component of DNA; a pyrimidine base.
Transcription: The synthesis of RNA from a DNA template.
Transfer RNA (tRNA): An RNA molecule that transfers specific amino acids onto a growing protein chain.
Translation: The synthesis of protein using the genetic information encoded in mRNA.
Uracil: A component of RNA; a pyrimidine base.
Digestive and Urinary Systems
Accessory organs: Organs that aid digestion but are not part of the GI tube: teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
Bile duct: A tube carrying bile from the liver and gallbladder into the small intestine.
Crypts: Moat-like pockets in the epithelium around villi involved in secretion.
Digestion: Mechanically and enzymatically breaking down food in the alimentary canal.
Digestive system: Organ system that extracts energy and nutrients from food and evacuates waste.
Enterocytes: Simple, columnar epithelial cells lining the intestines that aid in absorption.
Filtering (Filtration): Extraction of water and small solutes from the blood by nephrons in the kidney.
Fundic glands: Tubes in the stomach stomach fundus secreting hydrochloric acid () and gastric intrinsic factor for Vitamin absorption.
Gastric pits: Inward folds on stomach epithelium connected to glands that secrete gastric acid.
Gastrointestinal tract (GI tract): The stomach and intestine as a functional unit.
Glomerular filtration rate (GFR): Fluid and dissolved substances filtered by both kidneys per minute.
Glucagon: Hormone from pancreatic endocrine cells that raises blood glucose levels.
Glucose: A monosaccharide sugar () made primarily by plants.
Glucose tolerance test: A test used to detect diabetes by measuring blood glucose levels at intervals after administering a dose of glucose.
Gut microbiome: The community of microorganisms living within the digestive tract.
Islets of Langerhans: Pancreatic endocrine cell clusters producing insulin and glucagon.
Kidney: Vertebrate organ ( or long in humans) that excretes metabolic waste and secretes urine via nephrons.
Lobules: Hexagonal collections of liver cells (hepatocytes) with a central vein.
Nephron: The tubular excretory unit of the vertebrate kidney.
Portal vein: The vessel carrying blood from the GI tract, gallbladder, pancreas, and spleen to the liver.
Pyloric glands: Glands in the pylorus secreting gastrin, which stimulates secretion.
Urethra: A tube that releases urine from the body; in males, it also serves as the reproductive exit.
Urinalysis: Macroscopic, chemical, and microscopic analysis of urine.
Urine: Waste material secreted by the kidney, rich in end products of protein metabolism like urea, uric acid, and creatinine.
Villi: Fingerlike projections in the digestive system that increase surface area for nutrient absorption.
Skeletal and Muscular Systems
Actin: Contractile protein forming thin filaments in muscle fibers.
Articular cartilage: Hyaline cartilage attached to articulating bone structures.
Appendicular: Relating to appendages, particularly the limbs.
Axial: Relating to the central part of the body (head and trunk), such as the axial skeleton.
Calcified: Build-up of calcium in tissue, adding strength and rigidity.
Callus: Fibrous tissues and cartilage replacing the blood clot at a fracture site.
Cartilage: Flexible connective tissue providing shape, support, and cushioning for movement.
Compact bone: Hard, solid outer layer of bones and shafts of long bones.
Condyle: Smooth rounded protuberance at the end of a bone articulating with another.
Contraction: Process leading to shortening or development of tension in muscle tissue.
Endomysium: Connective tissue surrounding individual muscular fibers.
Epimysium: External connective tissue sheath of a muscle.
Fascicle: A small bundle of nerve or muscle fibers.
Fibrocartilage: Strongest type of cartilage providing support and cushioning.
Fracture: A crack or break in a bone.
Joint: Location where two or more bones meet.
Joint capsule: Dense fibrous tissue forming a sleeve around a joint, producing synovial fluid.
Muscle: Fibrous tissue (skeletal, cardiac, or smooth) specialized for contraction.
Muscle fatigue: Decrease in the force or power output of muscle.
Myofibril: Threadlike structure in muscle fiber consisting of thick (myosin) and thin (actin) filaments.
Myosin: Contractile protein making up thick filaments.
Osteoblast: A bone-forming cell.
Osteoclast: Large cell associated with bone resorption/healing.
Perimysium: Connective-tissue sheath surrounding bundles of muscle fibers.
Sarcomere: Repeating structural units of striated muscle fibrils.
Skeletal muscle: Striated muscle tissue attached to bone by tendons, stimulated oleh somatic motor neurons.
Sliding filament theory: Explanation of how filaments slide relative to one another during contraction.
Smooth muscle: Non-striated tissue in the walls of hollow internal organs innervated by autonomic motor neurons.
Spongy bone: Porous bone containing red bone marrow.
Synovial fluid: Secretion that lubricates joints and nourishes articular cartilage.
Synovial joint: A moveable joint containing synovial fluid.
Tendon: Flexible but inelastic cord of collagen tissue attaching muscle to bone.
Tropomyosin: Protein regulating the interaction of actin and myosin.
Troponin: Protein complex that, when combined with calcium, permits muscular contraction.
Immune System and Microbiology
Acquired immunity: Specific defense mechanisms acquired over a lifetime ( via infection/vaccine or via mother).
Antibody: Protein produced by B cells to impair pathogens; also called an immunoglobulin.
Antigen: Anything that stimulates an immune response.
B lymphocyte (B cell): White blood cell that matures in bone marrow and produces antibodies.
Bacillus: A rod-shaped (cylindrical) bacterium.
Bacteria: Single-celled, prokaryotic microorganisms.
Coccus: A spherical or round bacterium.
Immunity: Ability to defend against a pathogen by preventing entry or neutralizing products.
Innate immunity: Non-specific immune defense mechanisms we are born with.
Lymph: Clear fluid passing from intercellular spaces into lymphatic vessels.
Lymph node: Masses of lymphoid tissue filtering the flow of lymph and housing lymphocytes.
Lymphatic system: Organs, ducts, and nodes transporting lymph; interacts with the circulatory system.
Macrophage: Specialized white blood cell involved in detection and phagocytosis of pathogens.
Phagocyte: A cell that consumes and digests foreign material like microorganisms and debris.
Sepsis: Life-threatening condition where a pathogen causes an extreme systemic response.
T lymphocyte (T cell): White blood cell that attacks infected or cancerous cells.
Tissue typing: Testing surface antigens (HLA) to determine donor-recipient compatibility.
Vaccine: Substance used to stimulate antibody production and provide specific immunity.
Virulent: An infectious agent likely to cause disease.
Virus: Nonliving, submicroscopic agents with an RNA or DNA core requiring a host to replicate.
Biochemistry, Metabolism, and Nutrition
Adenosine triphosphate (ATP): Compound composed of adenosine and three phosphate groups supplying energy for cellular processes.
Amino acid: Compounds that link in chains to form proteins.
Bioactive compounds: Substances with biological effects (e.g., anticancer, antifungal).
Biomolecule: Large macromolecules produced by organisms: nucleic acids, carbohydrates, proteins, and lipids.
Calorie: Heat energy required to raise of water by .
Carbohydrate: Compounds like sugar, starch, and cellulose used for energy.
Insulin: Protein hormone secreted by the pancreas essential for carbohydrate metabolism and blood glucose regulation.
Lipid: Compounds (fats, phospholipids, steroids) insoluble in water.
Metabolic syndrome: Concurrent diseases (high BP, high sugar, obesity, high cholesterol) leading to heart disease and stroke.
Metabolism: Processes of breaking down molecules for energy and building complex molecules for repair.
Nucleotide: Building block of nucleic acids.
Nutrient: Substances needed to maintain life (proteins, lipids, vitamins, minerals).
Protein: Three-dimensional polymer made of amino acid monomers.
Medical Research and Scientific Process
Bioassay: Experiment using living materials to detect substances or determine toxicity; example: "canary in the coal mine."
Biomarker: Measurable signal of disease or injury (e.g., hormone levels).
Clinical research: Determining safety and effectiveness of medications or devices for human use.
Clinical trial: Scientifically controlled study involving human subjects for therapeutic evaluation.
Control group: Group in an experiment where the independent variable is not applied.
Dependent variable: Variable being measured and influenced by another variable.
Design brief: Written plan identifying a problem, criteria, and constraints.
Experiment: Study determining the effect of one variable on another.
Hypothesis: Statement predicting anticipated results.
Independent variable: Variable intentionally changed by the researcher.
Negative control: Group expected to produce a negative outcome to identify outside influences.
Positive control: Group expected to show a positive result to confirm the setup works.
Standard curve: Graph plotting known values allowing determination of unknown samples by interpolation.
Testable hypothesis: Proposed explanation that can be affirmed or disproved via testing.
General Medical and Procedural Terms
Anemia: Deficiency in red blood cells leading to reduced oxygen levels.
Aseptic technique: Practice of preventing contamination.
Diagnosis: Determining which condition explains a person’s symptoms.
Dialysis: Purifying blood when kidneys are not working correctly.
Edema: Swelling caused by excess fluid building up in tissues.
Endoscopy: Procedure using an endoscope to look inside a hollow organ or cavity.
HIPAA: U.S. national standards protecting privacy rights related to personal medical information.
Homeostasis: Maintenance of stable internal physiological conditions (e.g., temperature/pH).
Hypertension: Abnormally high blood pressure.
Metastasis: Spread of cancerous cells to other tissues.
Personal protective equipment (PPE): Specialized clothing/equipment worn for protection against hazards.
Prognosis: Likely course a disease will take over a lifetime.
Radiology: Branch of medicine using imaging technology (X-ray, MRI, ultrasound).
Symptom: Subjective evidence of disease perceived by the patient.
Triage: Sorting and prioritization of patients based on urgency.
Vital signs: Measurements (pulse, temperature, respiration, blood pressure) of essential body functions.
X-ray: Electromagnetic wave radiation used for imaging. "X-ray" is the noun; "to x-ray" is the verb.
Anatomy and Integumentary System
Anatomical planes: Hypothetical planes used to intersect the body to describe location or direction.
Body cavities: Spaces in the body containing internal organs (viscera).
Dermis: Middle layer of skin containing collagen, blood vessels, and nerves.
Epidermis: Top layer of skin providing a barrier and color.
Histology: Study of the microscopic anatomy of tissues (microanatomy).
Organ system: Group of organs working together for specific functions.
Subcutaneous fatty tissue: Bottom layer of skin providing cushioning and temperature regulation.
Tissue: Integrated group of cells with a common function or structure.
Forensic Science and Mortality
Algor mortis: Change in body temperature after death.
Autopsy: Postmortem evaluation to determine cause of death.
Livor mortis (lividity): Pooling of blood following death causing skin discoloration.
Medical examiner: Physician performing autopsies in accidental or intentional deaths.
Morgue: Place where bodies are kept pending identification or release.
Rigor mortis: Stiffening of joints and muscles after death.
Trace evidence: Tiny fragments of physical evidence (hair, fibers, glass).