Cells Come in all Shapes and Sizes Cells come in all shapes and sizes. In this diagram we have examples of the different types of cells in your arm. Notice that the cells are shaped differently, packed differently and carry out different functions. How did this variety of cells arise since you started as a single cell? It’s in the genes. Different genes are turned on and off in different types of cells. All cells have certain genes that are active – like the ones that code for the enzymes in cellular respiration and the ones that build the enzyme responsible for making membrane phospholipids. But the different cell types seen here also have different combinations of proteins.

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Differentiation Go Undifferentiated Cell aka “Stem Cell”

How do Cells Differentiate aka Specialize? Cells get signals from: their own genes chemical signals from neighbors neighbor contact chemicals in their microenvironment Cells become specialize in a series of steps

Tissues, and Their Cell Types The four types of tissues are found in all organ

Epithelium Stratified Squamous Sweat Gland – stratified cuboidal These are the general shapes that epithelial cells take on . Our skin is an organ made up of layers of epithelium. The outermost layer is squamous and our inner most layer is columnar. Sweat Gland – stratified cuboidal Uterine Gland - Simple Columnar

Muscle (skeletal) Bar = 30 Microns

Nervous Tissue Types Nerve cells are divided into three regions: the cell body, the dendrite and the axon. The nerve cell receives signals through its dendrites and then sends the signal along the cell membrane to the axon where secretory granules release the neurotransmitters into the gap or between its axon and the neighboring cell’s dendrites.

Cell Potency Early Embryonic Cells Stem Cells Later Embryonic cells All cells in an individual contain the same DNA. In the early embryo, all the cells are “totipotent” i.e. every cell can make all the cell types in the adult form. As the embryo continues to grow and develop, its cells lose their totipotency but still retain the ability to make a variety of related cell types. i.e. they can make any kind of muscle or any kind of epithelium or any kind of nerve cell. These cells are called pluripotent i.e. they can make a limited variety of different cell types. Specialized Cells

Growing Tissues and Organs

Breast Cancer Cells Dividing

Are Stem Cells and Cancer Related?