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Cell Cycle and Cancer

Investigation 1 – Concept Day

 

 

 

 

 

 

 

Cell Cycle and Cancer: Investigation 1

Concept Day

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In this Investigation, we wish to return your thinking to cells and tissues. In the lab, you will examine normal skin, lung, and breast tissue. In Investigation 3, they will compare two of these normal tissues (lung and breast tissue) to biopsies that display cancer of these organs.

In addition to introducing you to normal human tissue, we will take some time to discuss the extreme value of using human tissue in medical research so that you can begin contemplating the ethical and moral aspects of the study of human specimens and to appreciate the gift of donors.

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  • This slide gives a very high-level overview of the organization of life and where cells and tissues fit into the picture.

 

  • Notice that tissue is said to be an organized collection of cells with a specialized function. Thus, muscle cells form muscle tissue with the function of contraction and force generation. Neural tissue in the brain is a collection of cells that are specialized in communication with each other and transmitting signals. Liver tissue is composed of cells that specialize in important aspects of metabolism.
  • With this slide, we have the opportunity to see that tissue falls somewhere in the middle of an organizational complexity that is characteristic of all life. As shown here, there are a number of organizational levels below the tissue level: cells, cell organelles, molecules, and atoms. Of course, this series could be taken further to the subatomic and quantum levels. Above cells in this slide, we see organs, organ systems, organisms, populations, and so on to the level of all of the physical and biological components of our planet, the biosphere. We currently do not know if life extends beyond our biosphere.

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  • This slide gives an overview of the light microscope.

Note: You should be very familiar with this important instrument for having used it in the CELL Cellular Organization. Nonetheless, you may wish to review the parts of the light microscope and the proper handling of the microscope and microscope slides at this time.

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  • This is an introductory slide for a brief discussion of the use of human tissues and specimens in scientific research and training.
  • Each of the slides that you will examine in Investigation 1 lab (human skin, lung, and breast tissue) was derived from human cadavers. These are individuals who donated either specific organs or their entire bodies to science.
  • Given the incalculable value that such individuals (organ/body donors) have made to modern science, it is appropriate to devote some thought to the importance of their contribution and its place in the history of scientific discovery and advancement.
  • This slide is of a 1632 painting by Rembrandt entitled “The Anatomy Lesson of Dr. Nicolas Tulp”.

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  • Andreas Vesalius (1514-1564) was a Belgian anatomist and physician. Until his time, much of medicine, and in particular human anatomy, was learned through books based on the dissection of animals. Since the second century AD, western medical education consisted largely of studying the works of the great Greek physician and philosopher Galen. Unfortunately, Galen’s anatomical studies and manuscripts contained little information gained from systematic human dissections.
  • Vesalius, on the other hand, insisted on studying medicine and anatomy with human specimens and in so doing, revolutionized the medical field.
  • In this painting, taken from the National Institutes of Health’s National Library of Medicine, Vesalius is seen preparing to perform an autopsy or dissection. Notice the lack of gloves or protective mask when handling dead and diseased cadavers with sharp instruments! This was certainly dangerous work.

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  • This slide shows Vesalius’ most famous work, De Humani Corporis Fabrica Libri Septem (Latin for “On the fabric of the human body in Seven Books”) which was first published in Basel, Switzerland in 1543.
  • The Corporis is a masterpiece of renaissance publishing in that it is one of the earliest and best examples in which illustrations followed and enhanced the text rather than being included simply for decorative effect.

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  • This slide shows the title front plate of Corporis and one of its most famous illustrations; that of a skeleton contemplating a human skull. It is very clear in works like these the degree to which the sciences and the arts were interwoven in the renaissance.

Note: You may wish to consider the importance of scientific research for medicine and humanity. Once again, you might also discuss the importance of the donors throughout history and even today in advancing science and helping improve the human condition.

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  • The year 1543 was an incredibly important one in the history of science. As we have seen, Vesalius’ work, De Humani Corporis Fabrica Libri Septem was published that year. In addition, Nicolaus Copernicus’ historic work, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) was also published just before his death in 1543 as well. This is the masterpiece of human thought that proposed the heliocentric model of the solar system – that the Sun, not the Earth, was at the center of the solar system and that the other planets revolved around it.
  • 1543: What an important year in the history of science and human thought!

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  • This slide begins our look at normal human tissue. Skin (integumentary system) is the largest organ of the human body. Among its many functions, it keeps the outside world out and the inner environment of the body protected.
  • The average adult human has a skin surface area of roughly 1.75 square meters (19 square feet) and weighs approximately 4.5kg (10 pounds). It is therefore the largest of the body’s organs.
  • Human skin has three characteristic layers. These are, from outside in; the epidermis, dermis, and the hypodermis or subcutaneous layer.

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  • Microscope slides of human skin are almost always sectioned (thinly cut) crosswise through the layers. This slide depicts a micrograph of a slide used by students in Investigation 1 on the left and a pencil drawing on the right.
  • It is not uncommon to use drawings even though photographs are available when studying tissue specimens. This is largely because an artist can include the results of looking at many different microscope fields of view of a particular specimen and produce a composite drawing that depicts all of the relevant details in one image.
  • Much of the subcutaneous layer is composed of fat cells (adipose cells). The roots of hairs can be seen as was as occasional sebaceous glands near the hair follicles. These glands secrete oily material to help lubricate and waterproof the skin. Sometimes sebaceous glands get clogged and infected, causing acne.

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  • This slide introduces lung tissue. In this introductory slide, we see a normal x-ray and gross specimen of the human lung. In anatomy and medicine, the term “gross” refers to macroscopic anatomy as opposed to embryonic anatomy, neuroanatomy, microscopic anatomy, etc. It does not mean gross as in disgusting, rank, or crude as used in the slang of “gross-out”!
  • Interestingly, one of America’s top nineteenth-century surgeons and anatomists was Dr. Samuel D. Gross, who taught and practiced at Jefferson Medical College in Philadelphia and was immortalized by Thomas Eakins 1875 painting The Gross Clinic shown below:

web_EakinsTheGrossClinic

  • In Investigation 3, we will return to lung tissue and show x-ray and gross specimens of both healthy and cancerous lung.

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  • Normal lung tissue, when viewed in the microscope, readily reveals the function of this tissue. Most of what is seen is white air space. These pockets of air are called alveoli and are the location of gas transfer between the blood and the environment. Carbon dioxide (CO2) is released to the outside while oxygen O2 is absorbed from the air and enters the blood.
  • Not surprisingly, in lung sections view in the microscope, we will typically see bronchioles that branch from the bronchial tubes and supply fresh air to the alveoli and remove used gases. Also, we will typically find fields of view that show cross-sections of blood vessels, often packed with red blood cells. Such vessels supply the alveoli with deoxygenated blood, rich in CO2, and drain them of freshly oxygenated blood to be circulated to all the other tissues of the body.

Note: Each student in your group should be sure to see these three structures (alveoli, bronchioles, and blood vessels) and appreciate how the microscopic structure of lung tissue supports the macroscopic function of the lung. In Investigation 3, you will observe how this specialized microscopic tissue structure is completely lost in lung cancers and tumors.

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  • This slide shows normal human breast tissue. Breast tissue was chosen for study because of the prevalence of breast cancer in the population and the importance of early detection. While most breast cancers are associated with middle age or older women, diagnosis of some forms of breast cancer can occur as early as high school, although fortunately, these forms of breast cancer are much, much rarer.  In order to talk about breast cancer scientifically, we must begin with healthy breast tissue for comparison. Nonetheless, we will only depict microscopic sections of breast tissue here – we will not include gross specimens in our study.
  • Notice that we have depicted both active (lactating) and inactive specimens in this slide. This is because the purple-staining cells of the lobe tissue, which are involved in milk production, are often overproduced in certain forms of breast cancer as we will see in Investigation 3.
  • In normal breast tissue, you should be able to identify lobe cells, blood vessels, and large amounts of adipose (fat) cells.

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