TISSUES

The “Micro” and “Macro” of Tissues

 

Dissection of the chicken leg/thigh

 

Identify the skin on the surface of the leg/thigh.  The outermost layer of the skin is the epidermis; remember that feathers, like hair, are epidermal derivatives.  The epidermis is a good example of stratified squamous epithelium.

 

Carefully skin the chicken leg.  The deeper layer of the skin is the dermis, which is an excellent example of dense, irregular connective tissue.  The membranous material which may cling to your hands as you work with the chicken skin is loose connective (areolar) tissue.  On most chicken legs you should be able to identify another subcategory of connective tissue.  Adipose tissue is found in the subcutaneous layer (also called the hypodermis) and often around the muscles.

 

Now examine the muscle.  Note that there is a tough membrane, the deep fascia, enclosing each muscle and separating muscle groups; this is another example of dense, irregular connective tissue.  Examine the muscle closely; you should be able to identify the stringy groups of muscle fibers called fascicles. Then follow a muscle to its attachment to a bone.  The tendon, which attaches the muscle to the bone, is composed of dense regular connective tissue.  Remember that bone is also a subcategory of connective tissue.  Depending on the cut of the tissue, you may be able to identify ligaments; these connect bone to bone and are also composed of dense regular connective tissue.  Also, depending on the cut, you may be able to find the menisci in the knee; these are composed of fibrocartilage, just as they are in your knees.  If you have a chicken thigh, you may be able to differentiate the hamstring muscles from the anterior thigh muscle.  If you have chicken leg, the gastrocnemius and soleus muscles are clearly evident as they connect to the Achilles’ tendon.  Recall that cartilage is a subcategory of connective tissue; more cartilage (articular cartilage) can be identified on the chicken leg at the ends of the femur or tibia.   Note the whiteness and translucent appearance of the cartilage and the menisci; this should remind you that cartilage is avascular (it lacks blood vessels).

 

As you try to separate the muscles, look for blood vessels and nerves.  Arteries and veins are composed of epithelial lining, some connective tissue, and smooth muscle.  The blood inside the vessel is also a type of connective tissue.  Arteries have a much thicker smooth muscle layer and more elastic fibers than the accompanying veins.  If a specimen is large enough, it is easy to feel the difference between an artery and a vein by rolling the vessel between your fingers.  The artery will feel much more “springy,” while the vein will readily collapse.  A nerve will appear as a whitish cord-like structure running generally parallel to the vessels.  If you have a chicken thigh, you should be able to identify the sciatic nerve, the largest nerve in the body.

 

After removing all the tissues from the bone, wrap it in a piece of aluminum foil and weigh it.  Then bake the foil-wrapped bone in a 400oF oven for at least 30 minutes.  Let it cool and weigh it again.  The difference is the weight of the water lost during baking.  Then do the calculation:  weight of water lost/weight of the fresh bone x100 = % of bone weight composed of water.  If the bone is left in the oven 5-6 hours, you may have better results.

 

Now using the given slides identify the various tissue types of the chicken leg/thigh under the microscope.

 

 

 

I.  Introduction of Tissues

        Basic characteristics

        Definitions

 

II.  Epithelial tissue

        Features of epithelia

        Special characteristics

                Cellularity, specialized contacts, polarity, basement

                membrane, avascularity, regeneration....

        Classification

                Criteria-- cell shape, cellular arrangement, major classes

                Simple epithelia- simple squamous, cuboidal, columnar,

                  pseudostratified columnar

                Stratified epithelia- st. Squamous, cuboidal, columnar,

                Ttransitional

                Glandular epithelia- endocrine, exocrine glands

 

III.  Connective tissue

        Functions

        Common characteristics- common origin, degrees of vascularity, extracellular matrix

        Structural elements

                Basic characteristics

                Areolar connective tissue

                Ground substance

                Fibers-  collagen, elastic, and reticular

                Cells-

                        Basic characteristics

                        Primary blast cell types

                        Macrophages

 

 

        Types of connective tissue

                Embryonic- mesenchyme, mucous connective tissue

                Connective tissue proper- areolar, adipose, reticular,

                        dense regular, dense irregular

                Cartilage- hyaline, elastic, fibrocartilage

                Bone-

                Blood-

 

IV.  Nervous tissue

        Basic characteristics

        Cell types- neurons, supporting cells

       

V.  Muscle

        Basic characteristics

        Types of muscle tissue- skeletal, cardiac, smooth

 

VI.  Tissue repair

        General mechanisms

        Steps of tissue repair

                Inflammation

                Organization

                Regeneration and/or fibrosis

        Factors affecting the repair process

                General factors

                Tissue type

 

 

THE FLUIDS OF THE BODY:

·        Intracellular

    Fluid within the cells

·        Extracellular

    Fluid outside of cell      

                Plasma

                Tissue fluid