1. Cell Differentiation & Organization of the Human Body Ch 10.4 & 30.1 (M)

2. One Cell to Many Cells Each of us started just as a single cell, a zygote The question of how a zygote becomes an animal  Has been asked for centuries As recently as the 18th century  The prevailing theory was a notion called preformation

3. The Theory of Homunculus A preformed miniature infant, or “homunculus,” that simply becomes larger during development Small individual

4. Cell Differentiation & Morphogenesis Cell differentiation  specialization of cells in their structure and function During development cell differentiate into many type of cells Differentiated cells carry out the jobs that multicellular organisms need to stay alive Morphogenesis  Is the process by which an animal takes shape

5. Cell Differentiation During development, an organism’s cells become more differentiated and specialized for particular functions. For example, a plant has specialized cells in its roots, stems, and leaves

6. Mapping Differentiation  In some organisms, a cell’s role is determined at a specific point in development.  In the worm C. elegans, daughter cells from each cell division follow a specific path toward a role as a particular kind of cell.

7. Differentiation in Mammals Cell differentiation in mammals is controlled by a number of interacting factors in the embryo. Adult cells generally reach a point at which their differentiation is complete and they can no longer become other types of cells.

8. Stem Cells and Development The unspecialized cells from which differentiated cells develop are known as stem cells How all cell types in the body are formed from just a single cell. This cell is totipotent  able to do everything, to form all the tissues of the body. Only the fertilized egg and the cells produced by the first few cell divisions of embryonic development are truly totipotent.

9. Human Development After about four days of development, a human embryo forms into a blastocyst, a hollow ball of cells with a cluster of cells inside known as the inner cell mass. The cells of the inner cell mass are said to be pluripotent, which means that they are capable of developing into many, but not all, of the body's cell types

10. Stem Cells Stem cells are unspecialized cells from which differentiated cells develop. There are two types of stem cells: embryonic and adult stem cells

11. Embryonic Stem Cells Embryonic stem cells are found in the inner cells mass of the early embryo.  Embryonic stem cells are pluripotent.  Researchers have grown stem cells isolated from human embryos in culture. Their experiments confirmed that embryonic stem cells have the capacity to produce most cell types in the human body.

12. Adult Stem Cells Adult organisms contain some types of stem cells. Adult stem cells are multipotent  can produce many types of differentiated cells. Adult stem cells of a given organ or tissue typically produce only the types of cells that are unique to that tissue.

13. Stem Cell Research Possible benefits and issues associated with stem cell research  Stem cells offer the potential benefit of using undifferentiated cells to repair or replace badly damaged cells and tissues  Human embryonic stem cell research is controversial because the arguments for it and against it both involve ethical issues of life and death.

14. Potential Benefits Stem cell research may lead to new ways to repair the cellular damage that results from heart attack, stroke, and spinal cord injuries One example is the approach to reversing heart attack damage illustrated below.

15. Ethical Issues Most techniques for harvesting, or gathering, embryonic stem cells cause destruction of the embryo Government funding of embryonic stem cell research is an important political issue Groups seeking to protect embryos oppose such research as unethical Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.

16. Organization of the Body The levels of organization in the body include cells, tissues, organs, and organ systems At each level of organization, these parts of the body work together to carry out the major body functions

17. Cells & Tissues A cell is the basic unit of structure and function in living things. Specialized cells, such as bone cells, blood cells, and muscle cells, are uniquely suited to perform a particular function

18. Epithelial Tissue The tissue that lines the interior and exterior body

19. Connective Tissue Tissue that provides support for the body and connects its parts Includes fat cells, bone cells, and even blood cells. Many connective tissue cells produce collagen, a long, tough fiber-like protein that is the most common protein in the body

20. Nervous Tissue Nerve impulses are transmitted throughout the body by nervous tissue. Neurons, the cells that carry these impulses, and glial cells, which surround and protect neurons, are both examples of nervous tissue.

21. Muscle Tissue Makes movements of the body possible Voluntary  movements you control, such as the muscles that move your arms and legs. Involuntary  movements you cannot control  the tiny muscles that control the size of the pupil in the eye

22. Organs & Organ Systems A group of different types of tissues that work together to perform a single or several related functions is called an organ An organ system is a group of organs that perform closely related functions The organ systems interact to maintain homeostasis in the body as a whole

23. Human Body Systems

25. Homeostasis The relatively constant internal physical and chemical conditions that organisms maintain despite changes in internal and external environments.

26. Feedback Inhibition The systems of the body work to keep internal conditions within a certain range, never allowing them to go too far one way or the other

27. Examples Non Living Systems Living Systems

28. The Liver and Homeostasis The liver plays an important role. When proteins are broken down for energy, ammonia, a toxic byproduct, is produced. The liver quickly converts ammonia to urea, which is much less toxic. The kidneys then remove urea from the blood and excrete it from the body. The liver also converts many dangerous substances, including some drugs, into compounds that can be removed from the body safely

29. The Liver and Homeostasis Most important roles  regulating the level of glucose in the blood. Right after a meal, the level of glucose in the blood begins to rise. The liver takes glucose out of the blood to keep the level of glucose from rising too much. As the body uses glucose for energy, the liver releases stored glucose to keep the level of the sugar from dropping too low. The liver’s role in keeping blood glucose levels within a certain range is critical.

30. The Liver and Homeostasis Too little glucose, and the cells of the nervous system will slow down to the point that you may lose consciousness and pass out. Too much glucose gradually damages cells in the eyes, kidneys, heart, and even the immune system

31. The Liver and Homeostasis Abnormally high levels of glucose are associated with a disease called diabetes. In diabetes, changes occur in either the pancreas or body cells that affect the cells’ ability to absorb glucose. Diabetes is the unfortunate result of failure of homeostasis with respect to blood sugar levels