Connective Tissue!!!!!

Good job getting through epithelium and glands! Connective tissue is definitely a lot less material than the last couple of weeks have been. For this section, I would really suggest approaching the histological naming portion thinking about the idea that "form follows function." On the quiz for this week, don't worry about writing out the full histo. name (e.g. dense collagenous connective tissue regularly arranged), the abbreviation is totally fine (e.g. DCCTRA). MAKE SURE to know though what each stands for. This will help you big time in remembering what kind of function it has. Always make sure you know all of the bolded terms in each chapter.

Key things to remember:
-DCCTRA is by far the most common type of connective tissue in the organs that we are studying this week, if you can't remember what kind of connective tissue is present in a specific organ, you're best bet is to go with DCCTRA.
-Make sure you can identify the different fibers in areolar tissue (collagen, elastic) and also be able to ID fibroblasts and know what they secrete. Your manual gives a good explanation of this if you have any q's...
-Hyaline cartilage and elastic cartilage BOTH have chondrocytes, chondroblasts, and a perichondrium (layer on the very outside of the cartilage). The ONLY way to tell them apart is that elastic cartilage has elastic fibers (why it's DECTRA) which are only visible if the cartilage is stained with Orcein-Resorcein/Verheoff's stain. The elastic fibers are very dark because of the stain. Don't get confused though because hyaline cartilage can be stained darker (e.g. purple) too, but it will be a uniform darkness. See below for pics of how elastic fibers cause a non-uniform darkness from the stain.

Examples above are all Elastic cartilage. Notice the contrasting for the elastic fibers and the extracellular matrix.

Hyaline cartilage. Notice how the extracellular matrix (space outside of chondrocytes) is much smoother?? No elastic fibers...

-Fibrocartilage has NO perichondrium, and most often does not have a noticeable chondroblast layer (though it can...). It will have visible chondrocytes if zoomed out, and a meshwork of irreg. fibers if zoomed in. Look in your lab manual for a good example of both. 

Fibrocartilage. Notice the lack of a perichondrium/chondroblasts.

-Know where to find lamina propria! In the intestinal tract (just deep to the epithelium layer before you get to the submucosa) and in the oviduct (also just deep to the epithelium layer). 

-The hepatic/glisson's capsule surrounding the liver is DCCTRA as are almost all capsules. Students are often confused when they see a zoomed out picture of the liver. It has many lobules and they are very noticeable when zoomed out. Don't get confused if you see that!

See the lobules?? 

-Tendons have a general waviness to them which is especially noticeable when zoomed out further than the picture in the lab manual and they help to connect muscle to bone. They can be other colors than pink as is shown in the manual. They have NO horizontal striations which makes them look different than muscle. 

Both photos above are of tendon. Compare them with the one below of skeletal muscle. See the horizontal striations in the one below? That's one key way to tell them apart.

-Ligaments - Don't stress too much about them. Know that they connect bone to bone and that they have elastic fibers (thus DECTRA instead of DCCTRA). What stain would you use to make the elastic fibers visible?

-Know all the terms in the section about bones....

-Make sure you can find endochondral bone formation before your quiz! Each box has an endochondral bone slide, but it is often hard at first to find where in the slide the endo. bone formation is occurring. These are easy points as long as you can find it on your slide!
Remember: Real
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Some hints for each zone: zone of reserve (think reserved people stay by themselves) has mostly single/double cells that are fairly flat. Zone of proliferation (think, they are prolific

and having lots of kids...) shows mostly flat cells, but they are in columns with several others. Zone of hypertrophy, the number of cells in the columns don't change, but they are much bigger (more swollen looking). This layer is probably one of the best landmarks because it is usually the most visible. Zone of calcification is immediately after the zone of hypertrophy where there are no more visible cell membranes because the cells are becoming calcified. If asked to identify it, point immediately after the zone of hypertrophy or else you risk pointing to the zone of resorption. If asked to point to the zone of resorption, make sure you are not right next to the zone of hypertrophy. 

-For the developing tooth, pick a landmark! I like to use dentin as mine. It is often the most recognizable and is always thick and colorful (usually bright pink). Make sure to know that the ameloblasts secrete enamel inward toward the tooth and that odontoblasts secrete the dentin outward. Know what the ameloblasts and odontoblasts are histologically, and make sure that if you are asked to point them out, that you are pointing to the right layer! They are fairly obvious because they are and look like simple columnar!

 

All pics of developing teeth. Notice how the dentin layer is the most obvious landmark in each?? (Top left=the lighter pink, smooth layer; top right=bright pink thick layer; bottom=bright pink thick layer) I would suggest identifying the dentin layer and then working out/in from there.

-For the spleen, look for a thick capsule with lymphatic nodules as your landmarks. Please do not think that white pulp is what looks white and the red pulp is what's red!!! The white pulp is what is inside the lymph nodules (see the pics below) and the red pulp is everything surrounding the lymph nodules. 

See the thick capsule? The circular parts are the lymph nodules.

-The internal elastic laminae is the squiggly dark line (stained with orcein-resorcein) you see near the lumen of arteries (most obvious on medium sized arteries) and the external elastic laminae is the collection of dark squiggly lines a bit deeper once you get past the smooth muscle. The tunica adventitia is immediately after the external elastic laminae. When the artery is in diastole (relaxed), the squiggly lines are also relaxed and they remain squiggly --> DECTIRA (squiggly lines are irregularly arranged...). When the artery is in systole (blood is higher pressure), the elastic laminae are stretched and are no longer squiggly --> DECTRA (regularly arranged). YOU WILL NEVER see a slide of an internal or external elastic lamina in systole (the animals are no longer living, thus their hearts are no longer pumping... :) ). 

-Finally, make sure you can find some examples of adipose (unilocular adipocytes) on your own slides. Some good places to check are on your parotid slide or around vasculature.

Good luck this week! Let us know if you have any questions.

Connective Tissue Key Terms

Key: Know the anatomical and histological names (including modifications) for the following bolded structures; assume that you will be required to find the structures indicated by * on your own slides.

***This list is not guaranteed to be exhaustive, and only includes terms from this unit. While we will not focus on quiz information from previous weeks, knowledge of previous material may be useful***

Focus on connective tissue histology, but keep in mind all of the following terms.

Basic Connective Tissues

Aerolar Connective Tissue

·       Aeolar connective tissue*

·       Fibroblasts*

·       Collagen fibers*

·       Elastic fibers*

Hyaline Cartilage

·       Hyaline cartilage*

·       Chondroblast layer*

·       Chondrocytes*

·       Nest cells*

·       Perichondrium*

Elastic Cartilage

·       Elastic cartilage*

·       Chondrocytes*

·       Chondroblast layer*

·       Perichondrium*

Fibrocartilage

·       Fibrocartilage*

·       Nest cells*

·       Chondrocytes*

Digestive System

Intestinal Tract

·       Lamina propria*

·       Muscularis mucosa

·       Submucosa*

Liver

·       Glisson’s capsule*

Musculoskeletal System

Tendon

·       Tendon*

·       Collagen fibers*

·       Fibroblast nuclei*

Ligament

·       Ligament

·       Elastic fibers

·       Fibroblast nuclei

Bone

·       Haversion canal*

·       Osteocytes in lacunae*

·       Canaliculi*

·       Concentric lamellae*

·       Interstitial lamellae*

Endochondral Bone Formation

·       Zone of reserve*

·       Zone of proliferation*

·       Zone of hypertrophy*

·       Zone of calcification*

·       Zone of resorption*

·       Perichondrium*

·       Periostium*

Developing Tooth

·       Dental pulp*

·       Odontoblast layer*

·       Predentin*

·       Dentin*

·       Enamel*

·       Ameloblast layer*

Respiratory System

Trachea

·       Chondroblast layer*

·       Perichondrium*

·       Tracheal epithelium

Dermis

·       Dermis*

·       Epidermal epithelium

Lymphatic Tissue

Spleen

·       Splenic capsule*

·       White pulp*

·       Red pulp*

Lymph Node

·       Reticular fibers

·       Dense lymphatic tissue

Cardiovascular

Blood Vessels

·       Internal elastic lamina (systole and diastole)*

·       External elastic lamina (systole and diastole)*

·       Tunica adventitia*

Miscellaneous

Adipose Tissue

·       White adipose cells*

Oviduct

·       Oviduct epithelium

.        Lamina propria*