Epithelial tissues are characterized by cellularity, polarity, and rapid regenerative capacity. Basically, epithelial tissues are composed entirely of cells that rapidly replace lost ones through cell division and have apical and basal surfaces.
Finally I get to use my classmates for science. Slowly but surely I'll convince Mr. Ludwig to let me try more radical procedures with them. But I digress, here, my classmates are demonstrating simple squamous cells, or flat cells with disc shaped nuclei. Squamous cells work for diffusion and filtration. They provide a slick lining in the cardiovascular and lymphatic systems. Squamous cells are found in blood vessels, sarosae, the lining of the heart and the kidney glomeruli.
These little squamous cells are pseudostratified, which means that they're almost stacked up like a proper tissue.
This happy group of cells are demonstrating a stratified squamous tissue. Stratified squamous cells form a thick layer that protects whatever is underneath it. Basically, stratified squamous cells form the outer layer of skin, and the lining of the esophagus, mouth, and vagina.
These fellows form a layer of simple cuboidal cells, or cube like cells with spherical nuclei. Cuboidal cells are found on the ovary surface, in kidney tubules, and in ducts and secretory parts of glands. Cuboidal cells are used in areas for secretion and absorption.
Apparently we forgot to do the rest of the cuboidal forms. Here's a picture of some actual pseudo stratified cuboidal cells from imagerepository.net to make up for my error.
This is an actual picture of stratified cuboidal cells under a microscope. Brought to you by some kumc.edu. Stratified cuboidal isn't common in the body but it can be found in some mammary and sweat glands.
My classmates are now demonstrating simple columnar cells. Columnar cells are tall cells with oval nuclei. Many of these cells contain cilia. Those that do contain cilia are found lining the small bronchi and uterine tubes. Columnar cells without cilia line the digestive tract.
Here we have an example of pseudo stratified columnar cells. Pseudo-stratified columnar cells are found in the male sperm-carrying ducts and in your trachea.
And finally the stratified columnar. Columnar cells function in the secretion and propulsion of mucus. Stratified columnar, like stratified cuboidal, aren't found very often in the body. You can find them in the pharynx, male urethra, and lining some glandular ducts.
Ignoring the 'Simple' sign, these classmates are an example of transitional cells. Transitional cells have several layers of different cells, cuboidal cells form the basal layer and the surface layer is composed of dome-shaped cells. Transitional cells line the ureters, bladder, and some parts of the urethra.
Connective tissues are a little different. Connective tissues are characterized by distantly spaced cells in a matrix of some nonliving ground substance and fibers. Connective tissues come from mesenchyme and have varying degrees of vascularity. Connective tissues include cartilage, bone, and blood.
Hyaline cartilage follows a connective pattern, the widely separated cells are surrounded by lacuna. Hyaline cartilage is found in the nose, ribs, trachea, larynx, and caps every joint. Hyaline cartilage is also the hardest to heal because the cells are so few and far apart.
Elastic cartilage has more elastic fibers in it. It's found in the ear, the epiglottis, and in the throat.
Fibrocartilage has a lot of collagen and is in the intervertebral discs, discs of the knee joint, and in pubic symphasis.
Bone consists of cells in a calcified matrix with lots of little blood vessels threading through. These cells function in fat storage and hematapoisis.
Blood is characterized by red and white cells in a fluid matrix, which is the plasma.
And that pretty much covers the tissues. For the next post I'll scan my microscope drawings for the Hyaline lab. I love microscopes...
