Cells, Tissues, and Organs

Problem: Can we identify specialized cells under a microscope?

Background Information: You began your life as one cell, the zygote, formed from the union of the sperm and egg (fertilization).  This was a generalized cell; that means that it could become any of the cells in your body.  As mitosis occurs and your cells increase in number, your DNA causes certain cells to become specialized; this means that they become designed for a particular function:

  • Bone cells - to take calcium and phosphorus out of the blood to make what we call bone
  • Muscle cells - to contract or get shorter, thus allowing it to move a bone or organ
  • Epithelial cells - to act as a protective lining inside and out
  • Nerve cells or neurons - to carry an impulse (chemical "message") allowing cells to communicate
  • Red blood cells - to carry oxygen; they are red because they contain the protein hemoglobin.  Hemoglobin contains iron which picks up oxygen like a magnet
  • White blood cells - to digest or break down bacteria and other foreign cells

Groups of these specialized cells working together are called tissues. An organ is 2 or more tissues working together to carry out a specific task.  For example, the heart is an organ made up of several tissues:

  • obviously cardiac muscle tissue
  • an inner and outer lining made up of epithelial tissue
  • vascular tissue (blood) bringing oxygen and nutrients to the muscle cells
  • nervous tissue allowing the brain to communicate and thus control the heart
  • some connective tissue to connect parts allowing the organ to contract

What you will do: For each of the 4 parts below

  1. Find the slide for that tissue or organ, and place it on the microscope stage.
  2. Be very careful; these cells are expensive.
  3. Observe the slide under 100X and then 400X if you can. If you use 400X, DON'T touch the Course Adjustment Knob.
  4. Do a field diagram (6 cm diameter) with title and magnification of the best view.
  5. Label any parts.
  6. Answer the accompanying question in a sentence or two. Do not write out the question. You will lose points for incomplete sentence answers.

A conclusion for this lab is not necessary.



Part 1 - Bone

In the slide, you will see a very obvious pattern.  Bone cells are arranged in concentric circles (around a common center).  At the center is a Haversian canal which carries nerves and blood vessels. The white surrounding the dark cells is the calcium and phosphorus that make up the non-living part of the bone.

1. Is bone living or non-living? Give reasons for your answer.

2. Why are there blood vessels in bone?

3. Is a bone a tissue or an organ? Explain your answer.



Part 2 - Striated (Skeletal) Muscle

In 100X you will clearly see the muscle cells.  Each is a spindle made up of protein that can shorten or contract when a nerve impulse "tells" it to. In 400X, you will see the little bands or "striations" that given striated muscle its name. The book calls this type of muscle skeletal muscle because it attaches to and moves the bones of the skeleton. If this were smooth muscle such as makes up the stomach or an artery, you would not see the striations.

4. What do muscle cells do?

5. Why would every muscle have a nerve and blood vessel running to it?



Part 3 - The Blood

In the slide, you will see red blood cells, white blood cells (stained purple so you can see them), and the clear liquid plasma. There is usually 1 white blood cell for every 600-700 red blood cells unless the person is ill, and then there will be a much greater number of white blood cells.

6. What does the clear plasma do?

7. What cell part is obviously missing from the red blood cells? Why would this be a problem?

8. Is the person, whose blood you are looking at above, a healthy individual? Explain your answer by citing data.



Part 4 - The Alveoli of the Lungs


In the slide, you are looking at a small section of the lung. You notice that it is mostly air.  These pockets of air are surrounded by tiny capillaries containing blood cells; you should be able to see the blood cells.  Each air sac with the capillaries around it is called an alveolus (plural is alveoli).  It is here that oxygen from the air enters the capillary to be carried to the cell.
This section of lung tissue is from a person with lung cancer.  Notice that there are a lot of other cells (cancer cells) filling up a lot of the space. This is a higher magnification; you can tell because the blood cells are larger.

9. What leaves the capillary and enters the air sac in the alveoli?

10. What two tissue types do you think make up most of the lung? Explain.

11. Why would the person above with lung cancer have trouble breathing?


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