Tissues

There are 4 major types of tissues:  Epithelial, Connective, Muscular, and Nervous.
 

Epithelial Tissues:  Epithelial tissues are characterized by having an attached edge or basilar membrane and a free edge that is exposed to a body cavity or exterior surface.  Epithelial cells are usually packed closely together.  Their major functions are protection and absorption.

We looked at 4 main types of epithelial cells:

Simple Squamous Epithelium - We saw this in a solid sheet of flat cells, on an epithelial "smear" slide, and mixed in among some of the cuboidal cells.

 

Simple Cuboidal Epithelium - We saw these cells in the walls of the renal tubules of the kidney.  The first picture shows cuboidal cells forming the wall of the renal tubules.  These are surrounded by some smaller, thin-walled squamous cells.  The second picture shows the Bowman's Capsule which has a single layer of squamous epithelium surrounding the white space.  The other cells surrounding the Bowman's capsule  are mostly cubodal epithelium.

Simple Columnar Epithelium - We saw these cells lining the edges of the villi (finger-like projections within the intestine).  Be able to identify the tissue, the villi, and the goblet cells.

Pseudostratified Ciliated Columnar Epithelium - This was located on the edge of the piece of tissue containing the cartilage.  These ciliated cells line the windpipe.

Connective Tissues:  Connective tissues vary greatly.  They are the most varied, most abundant, and most widely distributed tissues in the body.  Connective tissues are characterized by widely scattered cells that are embedded in matrix or ground substance that may be liquid, gel-like, or solid.  We looked at 5 major examples.
 

  Adipose tissue - Fat cells

Areolar tissue - (Also called loose connective tissue.  You should be able to identify the tissue as well as the dark elastic fibers,  the faint pink or lavender collagen fibers, and the fibroblast cells.

 
 

Bone tissue - Identify the tissue itself and the center Haversian canal, the dark lacunae that contain the bone cells (osteocytes),  the rings (lamellae) of calcium, and the tiny canaliculi that resemble tiny cracks in the bone.

 
 

Blood tissue - Identify the red blood cells and white blood cells.

 
 

Cartilage - Identify the tissue itself, the gelatinous matrix, and the white lacunae that contain cartilage cells called chondrocytes.

 

Muscle Tissue:  The muscle tissue slides contained 3 pieces of tissue, cardiac muscle, skeletal muscle, and smooth muscle.  Due to the limitations of my digital microscope, computer monitors and TV to display extremely small details, the striations (faint banding patterns) on skeletal and cardiac muscle cannot be seen in pictures at normal magnifcation.

Skeletal Muscle - This muscle tissue is found attached to bones and is controlled voluntarily.  The tissue usually has obvious striations and long straight parallel fibers with many nuclei that are located along the edges of the fibers.   The picture on the right was taken with a much more powerful microscope.

Cardiac Muscle - This tissue is found only in heart tissue and is involuntarily controlled.  The striations are smaller and less distinct.  The muscle fibers are shorter and often branch.  A unique characteristic of cardiac muscle is the structure called an intercalated disk.  These resemble cell walls separating some of the fibers.  They are often faint and hard to see.  The picture on the right was taken from a much more powerful microscope.

 
 

Smooth Muscle - This un-striated muscle tissue is located in the organs and is often called visceral muscle.  It can be seen in the wall of the intestine and in the walls of blood vessels.

 

Nervous Tissue:
The neuron is the best known type of nervous cell.  The cell body and sometimes the axon can be seen surrounded by smaller dark cells called neuroglial cells.  What we call a nerve is actually a bundle of many nerve cells.  Seen in cross section, we can identify bundles of axons.