Cell Specialization Lesson 7 January 27th, 2011

The Process of Cell Specialization All cells in an organism contain the same DNA but are not all alike. Cells develop in different ways to perform particular functions in a process called cell specialization.

lung cells, skin cells, or brain cells. Examples Animal cell examples: lung cells, skin cells, or brain cells. Plant cell examples: xylem or phloem in the root, stem, or leaf.

Stem Cells Every cell in your body originally came from a small group of stem cells. A stem cell is an unspecialized cell that can form specialized cells when exposed to the proper environmental conditions, or they can remain unspecialized and actively dividing for long periods.

Stem cells may be used to treat injuries, diseases and regenerate organs. Stem cells are capable of becoming any cell, including: nerve cells, blood cells, or muscle cells in the human body.

Embryonic and Adult Stem Cells There are two types of stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells are found in embryos.

Embryonic stem cells are able to undergo differentiation Embryonic stem cells are able to undergo differentiation. – The ability to specialize Specialized cells look different from one another and perform different functions. As these cells divide, further specialization occurs, leaving cells with a limited ability to create a variety of cell types. These cells are called adult stem cells.

Cell Differentiation and Stem cells

Potency definitions: Totipotent (a.k.a omnipotent) stem cells can differentiate into embryonic and extraembryonic cell types. Such cells can construct a complete, viable, organism. These cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent.

Potency definitions: Pluripotent embryonic stem cells originate as inner mass cells within a blastocyst. The stem cells can become any tissue in the body, excluding a placenta. Only the morula's cells are totipotent, able to become all tissues and a placenta. Potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.

Potency definitions: Pluripotent stem cells are the descendants of totipotent cells and can differentiate into nearly all cells, i.e. cells derived from any of the three germ layers.

Most stem cells used for research are taken from embryos created by in vitro fertilization. The egg is fertilized 5 days later there is around 40 cells which are then transferred to a Petri dish After many months, the original stem cells have grown into millions of healthy cells without beginning to differentiate into specialized cells.

Example : found in skin, blood, and neural tissue. Most adult stem cells are involved in the replacement of damaged tissue. Example : found in skin, blood, and neural tissue. Satellite Cells – Found in the muscle Very exciting topic

Recent studies have found that adult stem cells from the tissue of one organ can regenerate tissue in another organ. Example: adult blood stem cells have regenerated liver, kidney, and brain cells.

Stem cell Research Scientists from University of Montreal found that skin contains stem cells. They located Fibroblasts (unspecialized skin cells) that they have been able to grow into bone, and cartilage. From this they have been able to grow new cartilage for patients without the risk of the cartilage being rejected because it contains the patients DNA

Current research involves the use of stem cells in the treatment of such diseases as cancer, Parkinson’s disease, Alzheimer’s disease, stroke, heart disease, diabetes, and rheumatoid arthritis.

There is much public debate about the use of embryonic stem cells There is much public debate about the use of embryonic stem cells. It is possible to harvest a few embryonic stem cells from the umbilical cord or placenta, but to collect larger amounts of embryonic stem cells, it is necessary to destroy the embryo.

Meristematic Cells Plant stem cells are called meristematic cells. They are found in the growing tips of roots and stems and also in a layer in the stem known as the cambium. Plant meristematic cells are active throughout the life of a plant, which means that they continually produce new cells of various types.

Stem cell Video if time permits

Examples of Specialized cells A nerve cell or neuron is a specialized cell that uses electrical signals to communicate with other cells of the body. The electrical signal called an impulse, moves through a neuron at a very fast rate, allowing for quick responses. A bundle of neurons is called a nerve.

Neurons Must be linked to each other in order to transmit signals. The connection between two neurons is a synapse.

Specialized cells - Blood cells – Connective Tissue Plasma Transports blood cells, nutrients, waste, and gases Contains several proteins which have specialized purposes Blood clotting Antibodies IT IS NOT A CELL ITSELF

Specialized cells - Blood cells – Connective Tissue Erythrocytes (red blood cells) Contain Haemoglobin (transports Oxygen) Do not contain a nucleus in mature stage

Specialized cells - Blood cells – Connective Tissue Platelets Initiate clogging

Specialized cells - Blood cells – Connective Tissue Leukocytes (white blood cells) Protect the body against invaders Part of the immune system – create pus

Elongated cells that are able to contract (shorten) Two main components that cause the contraction Actin Myosin Generate mechanical force

Specialized cells - Muscle Fibers – Muscle tissue Elongated cells that are able to contract (shorten) Two main components that cause the contraction Actin Myosin Generate mechanical force

Specialized cells – Skin cells – Epidermal Tissue Epidermal skin – Epithelial tissue The skin protects the inner cells from damage, acts as a defence against disease organisms, insulates, releases heat, and excretes bodily wastes. The skin is made up of two different layers of tissues: the epidermis and the dermis.

The epidermis is the outer protective layer that is made up of epithelial tissue. Prevents bacteria and viruses from entering the body Produces vitamin D when the skin is exposed to ultraviolet radiation from the Sun. Vitamin D is essential for bone development

RULES FOR SCIENTIFIC DRAWINGS Scientific drawings can be made using several methods, depending on a particular laboratory investigation. For a microscopy lab, the drawings are made in circles that represent the viewing field of a microscope. For other labs such as dissection labs, the drawings are representative of the entire organism or parts of the organism. These drawings show the relative size, shape, and location of anatomical structures. Most scientific drawings are labelled.

RULES FOR SCIENTIFIC DRAWINGS Use the following guidelines to help make your scientific drawing as clear as possible: Draw in PENCIL ALWAYS! Title your drawing Drawings should be about ¼ - ½ page in size or kept in the circular field of view frame that was provided in lab. Use a ruler to draw label lines Do not use arrows for label lines Label lines should point to the center of the structure being labelled

RULES FOR SCIENTIFIC DRAWINGS Print all labels horizontally Print, do not write in cursive Label the right-hand side of the drawing, if possible Do not cross label lines Include magnification (if a microscopic drawing) or a scale (if a macroscopic drawing) Draw what you see Shading should be done by stippling.

Microviewer Set 58 Complete and hand in. Also complete and hand in questions

Questions – Hand In K (5) 1. Define the term “stem cell.” 2. Explain how stem cells can become specialized. 3. What are meristematic cells? 4. How are nerve cells vastly different from other cells in the body? 5. What makes muscle tissue so unique?