List+of+Helpful+Terms


 * Adduct**: This is any chemical/DNA covalent bond. In this case when we refer to DNA adducts we are talking about any place where DMBA has bound to the DNA


 * Alveolar Bud (AB)**: This is the most //terminally// differentiated structure of the breast tissue. These cells group together in what is known as a bud and then aggregate to form the functional lactation unit (lobules) that produces milk after the first full term pregnancy. These cells proliferate at the slowest rate in comparison to the other types of cells we discussed.


 * Differentiation**: this term is indicative of a change in cell type or morphology. As the breast tissue differentiates from almost all terminal end bud cells to alveolar bud cells we mean that the cell's function becomes different and therefore it starts to take on characteristics that are different that its "mother" cell type. The new cell will start to express and make proteins that the cell type before it will never make. For example the TEB cells do not create milk.


 * G0 Phase**: This is the quiescent state that cells revert to when they are not stimulated to grow. Most cells live in this state until they are prompted by extracellular cues to either differentiate (depending on what type of cell it is) or to grow and divide.


 * G1 Phase**: This is the phase of the cell cycle in which those extracellular cues are very important in stimulating a new cycle of growth and division. Hormones and growth factors will essentially tell the cell that the time is right to divide! (estrogen acts as a growth factor). It is in this phase that the cell assesses its DNA for any damage that may be present due to environmental DNA damaging agents (such as UV rays or carcinogens such as DMBA). The damage MUST BE REPAIRED before entering S phase or else the cell can pick up deleterious mutations.


 * G2 Phase**: This is the phase just after the DNA replication phase. Here the cell assesses the overall cell size (to make sure it is large enough to divide) and the extent of DNA damage that needs to be repaired as a result of replication.


 * Lobules**: this is a cluster of ABs in the terminally differentiated breast structure responsible for milk secretion.


 * Lobular Tissue Types 1–4**: There are many ways of describing and categorizing breast tissue. In this paper we have chosen to primarily focus of the functional structures (TEBs, TDs, ABs). But these structures are all made of different proportion of these 4 cell types, each with slightly different properties. Lob1 tissues are the most undifferentiated and they make up a majority of the TEBs because they have the potential to differentiate into any of the 3 remaining types. Lob2 tissue is more differentiated than Lob1 and therefore it makes up a majority of the semi-differentiated/developed TDs and ABs. Lob3 and Lob4 are very similar in the fact that they are the more complex of the cell types, but some people do not feel that they are actually different. For our purposes, when a cell reaches the Lob4 state it is capable of producing milk whereas the Lob3 cells cannot.


 * Mammary Gland**: This is the functional unit of the breast including the lobules that actually make the milk.


 * M Phase**: This is mitosis! In order to pass through this and end up with two daughter cells the chromosomes must all be aligned and properly replicated. This is not a crucial step in terms of our discussion about pregnancy and breast cancer, but it is important to see that DNA damage is constantly being searched for throughout the cell cycle!


 * Nuliparity**: This is what we call a woman who has never had a child


 * Parity**: This is a term for women who have had a child.


 * Proliferation**: This is a term for when cells grow and divide mitotically, often in response to extracellular cues


 * S** **Phase**: This is the phase in which the DNA is replicated in preparation for mitotic cell division!


 * Terminal Duct (TD)**: These are the "duct" structures that will eventually connect the lobules (or milk producing compartments) to the nipple so that the milk can be delivered to newborns. While //terminal// is in the title, simply having terminal ducts does not mean that the breast is fully differentiated. Often if a woman is nulliparous you can see terminal duct regression structures where the fully developed ABs are missing.


 * Terminal End Bud (TEB)**: These are the most undifferentiated structures at the tips of the growing and branching functional breast unit. The cells in this region divide rapidly in order to form TDs that are highly branched and clusters of ABs so that the breast can eventually provide milk for the newborn child.