Connective tissue proper encompasses the types of connective tissue that usually show all three of the defining cellular characteristics of connective tissue with the fewest deviations from those characteristics.
- Dispersed cells
- More extracellular material than cells.
- Extensive protein fibers in the extracellular matrix.
Nonetheless there is still a great variety among the subcategories of connective tissue proper. Some are classified as dense connective tissue proper and have a dense arrangement of extracellular protein fibers that give the tissue strength and toughness. Tendons connecting muscles to bone and ligaments connecting bone to bone are examples of dense connective tissue proper. Other tissues are classified loose connective tissue proper and have fewer extracellular protein fibers and more ground substance (the extracellular material surrounding the protein fibers), making the tissues spongier but more fragile. Areolar tissue, found in the hypodermis of the skin and below the epithelial layers of the digestive, respiratory, and urinary tracts, is a loose connective tissue proper, as is adipose tissue, also known as fat.
Table 5.1 lists some of the subcategories of connective tissue proper, along with some of their characteristics and properties.
In drawing images of connective tissue proper preparations seen under the microscope, it is important to simplify the visuals. Connective tissue preparations are often messy with a number of blotches and shapes irrelevant to the main components of the tissue, which are the cells and the extracellular protein fibers. Especially with connective tissue slides, it is important to make sure you know what you are looking for, find those components, and draw only them in as simple a form as possible, usually with just lines and with minimal shadings or hatchings. Leave out the unnecessary and irrelevant stuff on the slide.
For instance, Figure 5-7 A shows a section of connective tissue taken from just below (deep to) the epithelial layer of the stomach, magnified 40x. Figure 5-7 B illustrates how you should represent that view as a line drawing.
Notice that in the line drawing not every single thick collagen fiber, nor every single thin elastic fiber, not every single fibroblast was drawn. Also notice that some of the out-of-focus, blurry fibers were not drawn at all, rather than draw fuzzy blotches. The key is to get the important structures (once you know what those are) and leave out distracting, non-essential messiness.
Lab 5 Exercises 5.3
- Table 5.1 lists six categories of connective tissue proper. Use the information in that table to identify which category each of the following samples belong to.
- Under each picture, list the evidence that points to the category you choose.
- The key identifying features to look for in each picture are: the type(s) of protein fibers present, the type of cells present, and whether there are significant amounts of ground substance present.
- Collagen protein fibers are thick. Elastic protein fibers are thin. Reticular protein fibers are thin but form a web-like arrangement.
- If there is abundant space between protein fibers, the tissue is likely one of the loose connective tissues. If there is little space between protein fibers, the tissue is likely one of the dense connective tissues.
- Adipose is mainly large adipocyte cells containing a large droplet of lipids and nucleus and cytoplasm crammed into one corner of the cell. There are more adipocytes than extracellular material in adipose.
- The protein fibers in regular dense connective tissue proper will largely parallel each other, but they are often undulate in a wave-like arrangement while being parallel.
A. Source: Stomach wall
B. Joint Capsule
C. Source: Lymph node
D. Source: Fat
E. Source: Aorta Wall
F. Source: Tendon
Lab 5 Exercises 5.4
- Obtain a slide of connective tissue proper from the instructor.
- Follow the checklist in Lab exercise 5.1 to set up your slide for viewing.
- View the slide on the second-highest objective.
- Fill out the blanks next to your drawing.
- In the circle below, draw a representative sample of key features you identified, taking care to correctly and clearly draw their true shapes and directions. Draw your structures proportionately to their size in your microscope’s field of view.