Medical Jargon - What it really means

Glossary (An explanation of scientific and medical terms in this website):

There is a lot of jargon in biology.  I listed aphabetically scientific terms that need explantion.  Please contact heuckerothr [at] email.chop.edu (subject: Website%20Glossary) (Dr. Heuckeroth) if you find additional words in our website that should be included. 
Adhesion molecule: A molecule on the surface of a cell that helps it attach to other cells or other components of the cell's environment.
Aganglionosis: The absence of ganglion cells.  In the bowel, aganglionosis means that a region of the bowel is completely missing neurons (ganglion cells).  People with aganglionosis at the end of the bowel have Hirschsprung disease.
Allele: A DNA coding sequence that is found at a specific position on a specific chromosome.  Usually alleles code for a gene.  Because human cells have pairs of homologous chromosomes, we typically have two alleles for each gene.
Bowel: Intestine or colon.
Cell: The most basic unit of life.  Humans and other complex organisms are made up of many millions of cells, each of which has the ability to perform specialized functions.
Cell cycle: An organized series of steps that a cell goes through to divide.  Differentiated cells do not progress through the cell cycle but instead stay in a single phase of the cycle.
Chromosome: A single long piece of DNA with associated proteins.  Human cells in healthy individuals have 46 chromosomes of different lengths.  Chromosomes differ in size even more dramatically between species.  DNA molecules may vary from 10,000 to 1,000,000,000 nucleotides in length. The information encoded in the DNA of chromosomes provides instructions for making living cells.
Colon: Same as "large intestine".
Covalent: A type of strong chemical bond that connects atoms.  These bonds can be broken when molecules undergo chemical reactions.
CNV:  "Copy Number Variant".  Duplications or deletions in DNA that result in more or less than 2 copies of the affected region.  Individual CNVs may range in size from on kilobase (1000 nucleotide bases) to several megabases (million bases").  Approximately 0.4% of the genome of unrelated people differ in copy number.  This is part of what makes each of us unique.  CNVs may or may not cause disease.  Some CNVs may reduce the risk of specific types of disease. 
Culture: In this case we mean "cell culture".  This is a method for growing cells in a dish to study their properties.
Development:  In this context we are referring to the steps required for a baby to develop from a single fertilized egg.  The fertilized egg divides to generate two cells.  Each of those cells divides again to generate 4 cells.  This process continues to generate enough cells to form a bably.  Individual cells then become specialized to perform unique functions (e.g. muscle cells, nerve cells, etc.).
Differentiation: The process by which a pluripotent cell becomes a more specialized cell.
Distal: "Far away from".  When used to refer to the bowel, this means the end farthest from the mouth.  When used to refer to the arm, this term refers to the fingers.
DNA: Deoxyribonucleic acid.  This is the molecule that provides instructions for making living organisms.  DNA is made up of 4 building blocks ("bases" (or nucleotides) called adenine "A", guanine "G", cytosine "C" and thymidine "T") that are linked together via covalent bonds in a specific sequence.  The order in which the A, G, C, and T bases are linked together tells the cell in what order to link together amino acids to form proteins.  Two DNA strands link together to form a double helix via base pairing.  Each human cells has approximately 3 billion base pairs of DNA contained in 46 individual chromosomes.
Duodenum: The first part of the small bowel.  This region is connected to the stomach proximally and to the jejunum distally.
E9, E12.5 or E14:  "E" means "Embryonic day" in the mouse.  While human pregnancy is 9 months long, mouse pregnancy lasts only about 19 days. E14 therefore means 14 days after fertilization of the mouse egg.
Enteric: Related to the intestines.
ENS: Abbreviation for "Enteric Nervous System".
Enteric nervous system: A complex nervous system in the bowel that controls most aspects of intestinal function.  In humans there are approximately 500 million neurons and 20 different types of neuron that must work together for the bowel to function properly.
Enzymes: Proteins that make chemical reactions go much faster than normal.
Environmental:  Here we mean primarily the environment of the developing baby.  Because babies form inside the mother's uterus, the babys environment is influenced by the mother's health, medicines taken, nutrition, and a variety of other maternal exposures (toxins, drugs, alcohol, etc.).
Esophagus: The first part of the bowel. A tube in the chest that transports food from the back of the mouth to the stomach.
Ganglion cell: Neuron
Gene: A region of DNA on a chromosome that codes for a specific protein.
Genetic: Related to information contained in a person's DNA.
Glia: A specialized cell of the nervous system.  Glia are required for neurons to work properly.
Hirschsprung disease: A birth defect where the enteric nervous system is missing from the end of the bowel.  This disease is described in more detail in our website.
Homologous chromosomes: Pairs of chromosomes that are the same length, have the same staining patterns and same sets of genes.
Ileum:  The third and final part of the small bowel.  This part is connected to the jejunum proximally and the colon distally.
Irritable bowel syndrome:  A problem affecting about 10% of all adults caused by increased pain sensitivity in the bowel and abnormal intestinal motility.
Jejunum: The second part of the small bowel.  This part is connected to the duodenum proximally and the ileum distally.
Large Intestine: The last part of the bowel and is sometimes called the colon.  The colon's main function is to reabsorb water from the stool into the blood stream.  The longer stool stays in the colon, the less water it contains.  
Maternal: Related to the mother.
Mendelian: This term refers to classical genetic rules first described by Gregor Mendel in 1865 and 1866. Non-Mendelian diseases do not appear to follow Mendel's rules in a simple way usually as a result of gene-gene or gene-environment interactions that impact disease occurrence.
Migrate: During development individual cells move relative to neighboring cells to form complex structures.  ENS precursor cells, for example move all the way through the bowel during the first trimester of human pregnancy.  The movement of individual cells or groups of cells is called "migration".
Molecular: Related to molecules. A molecule is composed of a group of atoms that are covalently bonded to each other.  Each cell is composed of millions of molecules.
Morphogen: A molecule whose primary function is to direct cells to form complex structures during development.  Morphogens may influence cell migration, differentiation, or survival, but they are distinguished because they influence the shape of developing organs.
Morphogenesis: The process of forming specific shapes and structures during development.
Motility: The intestine moves in complex ways to move the food you eat through the bowel, help to digest the food, enhance absorption and control the elimination of waste.  All of these types of movement are called "motility".  Motility is controlled by the ENS, but also by other signals.
Mucosal: This term refers to the single layer of cells that lines the inner surface of the intestine.
Mutation: A change in DNA.  There are many different types of changes that can occur in DNA including SNPs, CNVs, translocations, trisomy, partial trisomy, and chromosome loss.
Mutant: A living organism whose DNA differs from most healthy organisms of the same species.  This term is usually used to refer to organisms with DNA changes expected to increase risk of disease.
Myenteric plexus: Part of the enteric nervous system.  These cells primarily control intestinal motility.
Neural crest:  A small population of cells that originate in the neural tube, but migrate out of the neural tube during development.  The neural crest-derived cells give rise to many structures in developing babies including the ENS, great vessels of the heart, pigment cells in the skin, bones of the face, other parts of the peripheral nervous system, and other derivatives.
Neural tube:  The part of the developing fetus that becomes the spinal cord and brain in the baby.
Neurite: A thin process that extends from the cell body of a neuron.  Refers to both axons and dendrites.
Neuron: A cell that conducts electrical impulses to transmit information.  There are many different types of neuron in the body and each type has a specific function.  Neurons communicate with each other at synapses (specialized junctions) by the release of specific chemicals called neurotransmitters.
Neuronal lineage: During development, cells can be committed to a specific fate.  Neuronal lineage refers to all cells that are destined to become neurons or are already neurons.
Ostomy: An abnormal opening or connection.  This term is often applied in a modified form that describes the part of the body with the ostomy (e.g., colostomy refers to an ostomy that connect the colon to the skin surface of the abdomen; ileostomy is the same type of opening but connects the end of the small bowel to the skin surface).
Pathogenesis: "Cause of disease".
Pluripotent:  A cell that is able to become many different types of differentiated cells is called "pluripotent".  The final fate for the pluripotent cells is directed by factors in their environment that are often made by other nearby cells.
Polymorphism: A DNA sequence that differs between different individuals of the same species.  Polymorphisms may or may not affect gene function or influence risk of disease. 
Prenatal: Before birth.
Pseudo-obstruction syndrome:  A medical problem where the enteric nervous system is present, but motility of the bowel is severely abnormal.  This problem may cause vomiting, abdominal distension, abdominal pain, and severe constipation.  Problems may be bad enough to prevent people from obtaining adequate calories by eating to survive.
Precursor: Used to refer to an "immature" cell during development that will eventually become another type of more mature cell by differentiating.
Proliferation: This is another word for "cell division", the process of generating two cells from one precursor cell.
Protein: A chain of amino acids connected to each other by covalent bonds.  Proteins perform many different functions required for cells to work properly.  The human genome provides instructions to make about 23,000 different proteins.  Mutations in DNA that cause disease may inactivate or increase the activity of one or more proteins and this change in protein activity makes the cells function abnormally.
Proximal: "Near".  When used in reference to the bowel, it refers to the part closest to the mouth.
Ret: A protein on the surface of enteric neuron precursors, some mature enteric neurons and many other cells throughout the body.  Ret is a growth factor receptor that is required for the survival, proliferation, migration, and differentiation of enteric neurons.  It also has other roles.
Sacral: A region near the lower end of the spinal cord.  A small percentage of enteric neurons in the distal bowel are derived from the sacral neural crest.
Sensory: Refers to the ability of cells in the body to detect specific signals in the environment.  Sensory neurons in the bowel, for example, can detect stretching of the bowel and bending of villi, among other signals.
Signaling molecule: Cells respond to their environment when one molecule within the cell interacts with another molecule in the environment.  The cells response often involves the activation or inhibition of many other molecules to change cellular function.  "Signaling molecule" refers to all the different molecules that cells use to respond to their environment.

Small intestine: The part of the bowel between the stomach and colon.  This is the primary area where food is broken down and where nutrients are absorbed.  This area is sometimes called the small bowel.

SNP: "Single Nucleotide Polymorphism".  A change in a single DNA base pair within the genome.  SNPs may cause disease, reduce disease risk or not affect disease risk depending on the SNP.  There are many known SNPs in the genome of most species including humans.  This is one way that people differ from each other.  SNPs are part of what make us unique. 
Sporadic:  In the context of Hirschsprung disease, "sporadic" refers to children with Hirschsprung disease who do not have known affected family members.
Stem cell: A cell that can divide extensively to form many more cells.  The "daughter" cells that come from stem cells can become many other types of cells, but at least some of the daughter cells must also be stem cells for the original cell to be considered a stem cell.
Submucosal plexus: Part of the enteric nervous system.  These cells control epithelial secretion and respond to sensory stimuli from the bowel.
Thoracic: Related to the chest region.
Transcription: The process of converting the information encoded in DNA into RNA.
Transcription factor: A protein that controls which DNA regions undergo transcription. 
Transition zone: In people with Hirschsprung disease, the end of the bowel is missing all enteric neurons.  The region without neurons does not "relax" well to allow the passage of stool.  The more proximal bowel with nerve cells will relax, but becomes full of stool.  The end of the bowel without nerve cells is therefore usually more narrow than the more proximal bowel.  The region where the bowel transitions from narrow aganglionic bowel to more dilated bowel that contains enteric neurons is called the "transition zone".
Translation: The process of converting information encoded in RNA into protein.
Translational research:  Studies intended to "translate" discoveries in model systems (e.g. animal models, test tubes, or culture dishes) into new methods to treat, diagnose, prevent or cure human disease.
Trimester:  Human pregnancy normally lasts about 38 weeks (9 months) after conception.  Pregnancy can be divided into 3 month intervals called "trimesters".  Most of the major organs in human infants form during the first trimester (i.e., the first 3 months of pregnancy).  During the second and third trimester, the organs become larger and more complex in ways that allow them to function well in full term babies (i.e. babies born at 37-42 weeks after the last normal menstrual period)
Trisomy: This means that the cell has an entire extra chromosome.  Human cells in healthy individuals have 46 chromosomes (22 pairs of autosomes and one pair of sex chromosomes).  Individuals with a trisomy have 47 chromosomes.  Down syndrome is caused by a common trisomy (an extra copy of chromosome 21). 
Trophic factor: A molecule outside of a cell that makes the cell "bigger, stronger and more active".  Trophic factors under some circumstances may also be required for cell survival.
Vagal: A region of the neural tube near the neck. The vagal neural crest is the site of origin of most enteric neurons.
Villi: Small finger-like projections along the inside of the small bowel that increase surface area of the bowel to increase food absorption.