The most abundant, diverse, and versatile cells in a plant are found in the parenchyma tissue. Parenchyma cells have thin cell walls, and their structure is somewhat non-descript, but tend to be more or less isodiametric equal diameters in all directions. What distinguishes these cells are their many and varied functions.
In general, epithelial tissues are classified by the number of their layers and by the shape and function of the cells. Squamous epithelium has cells that are wider than their height flat and scale-like. This is found as the lining of the mouthoesophagus the blood vessels and in the alveou of the lungs.
Cuboidal epithelium has cells whose height and width are approximately the same cube shaped. Columnar epithelium has cells taller than they are wide column-shaped.
By layer, epithelium is classed as either simple epithelium, only one cell thick unilayered or stratified epithelium as stratified squamous epitheliumstratified cuboidal epitheliumand stratified columnar epithelium that are two or more cells thick multi-layered  and Cells and tissues types of layering can be made up of any of the cell shapes.
This kind of epithelium is therefore described as pseudostratified columnar epithelium. In general, it is found where absorption and filtration occur.
The thinness of the epithelial barrier facilitates these processes.
The four major classes of simple epithelium are: Non-ciliated epithelium can also possess microvilli. Some tissues contain goblet cells and are referred to as simple glandular columnar epithelium. The ciliated type is also called respiratory epithelium as it is almost exclusively confined to the larger respiratory airways of the nasal cavity, trachea and bronchi.
Stratified epithelium[ edit ] Stratified epithelium differs from simple epithelium in that it is multilayered. It is therefore found where body linings have to withstand mechanical or chemical insult such that layers can be abraded and lost without exposing subepithelial layers.
Cells flatten as the layers become more apical, though in their most basal layers the cells can be squamous, cuboidal or columnar. This specialization makes the epithelium waterproof, so is found in the mammalian skin.
The lining of the esophagus is an example of a non-keratinized or "moist" stratified epithelium. These nuclei are pyknoticmeaning that they are highly condensed. Parakeratinized epithelium is sometimes found in the oral mucosa and in the upper regions of the esophagus.
It is sometimes called urothelium since it is almost exclusively found in the bladder, ureters and urethra. Type Description Squamous Squamous cells have the appearance of thin, flat plates that can look polygonal when viewed from above.
The cells fit closely together in tissues; providing a smooth, low-friction surface over which fluids can move easily. The shape of the nucleus usually corresponds to the cell form and helps to identify the type of epithelium.
Squamous cells tend to have horizontally flattened, nearly oval shaped nuclei because of the thin flattened form of the cell. Squamous epithelium is found lining surfaces such as the skinand alveoli in the lungenabling simple passive diffusion as also found in the alveolar epithelium in the lungs.
Specialized squamous epithelium also forms the lining of cavities such as in blood vessels, as endothelium and in the pericardiumas mesothelium and in other body cavities. Cuboidal Cuboidal epithelial cells have a cube-like shape and appear square in cross-section.
The cell nucleus is large, spherical and is in the center of the cell. Cuboidal epithelium is commonly found in secretive tissue such as the exocrine glandsor in absorptive tissue such as the pancreas, the lining of the kidney tubules as well as in the ducts of the glands. The germinal epithelium that covers the female ovaryand the germinal epithelium that lines the walls of the seminferous tubules in the testes are also of the cuboidal type.
Cuboidal cells provide protection and may be active in pumping material in or out of the lumen, or passive depending on their location and specialisation. Simple cuboidal epithelium commonly differentiates to form the secretory and duct portions of glands.
Columnar Columnar epithelial cells are elongated and column-shaped and have a height of at least four times their width. Their nuclei are elongated and are usually located near the base of the cells.All living organisms on Earth are divided into vetconnexx.com main concept of cell theory is that cells are the basic structural unit for all organisms.
Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Tissue, in physiology, a level of organization in multicellular organisms; it consists of a group of structurally and functionally similar cells and their intercellular material..
By definition, tissues are absent from unicellular organisms. Even among the simplest multicellular species, such as sponges, tissues are lacking or are poorly differentiated. Tissue growth and maintenance begin in the womb and continue throughout your life, and nearly 2 trillion new cells are born in your body each day, according to the School of .
Your browser does not support frames. vetconnexx.com Your browser does not support frames. Nerve Cell/Neural. Cell body (site of nucleus and organelles) Contains nucleus and organelles just like any other cell.
Has well-developed RER and golgi (makes a lot of proteins). Epithelium (/ ˌ ɛ p ɪ ˈ θ iː l i ə m /) is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous vetconnexx.comlial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs.
An example is the epidermis, the outermost layer of the skin.