write the different types of epithelial tissue write two- two characteristics of each
Answers
Explanation:
Epithelia tissue forms boundaries between different environments, and nearly all substances must pass through the epithelium. In its role as an interface tissue, epithelium accomplishes many functions, including:
Protection for the underlying tissues from radiation, desiccation, toxins, and physical trauma.
Absorption of substances in the digestive tract lining with distinct modifications.
Regulation and excretion of chemicals between the underlying tissues and the body cavity.
The secretion of hormones into the blood vascular system. The secretion of sweat, mucus, enzymes, and other products that are delivered by ducts come from the glandular epithelium.
The detection of sensation.
Characteristics of Epithelial Layers
Epithelial tissue is composed of cells laid out in sheets with strong cell-to-cell attachments. These protein connections hold the cells together to form a tightly connected layer that is avascular but innervated in nature.
The epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. One side of the epithelial cell is oriented towards the surface of the tissue, body cavity, or external environment and the other surface is joined to a basement membrane. The basement layer is non-cellular in nature and helps to cement the epithelial tissue to the underlying structures.
Types of Epithelial Tissue
Epithelial tissues are identified by both the number of layers and the shape of the cells in the upper layers. There are eight basic types of epithelium: six of them are identified based on both the number of cells and their shape; two of them are named by the type of cell (squamous) found in them. Epithelial tissue is classified based on the number of cells, the shape of those cells, and the types of those cells.
Epithelial Tissue Cells
Cells Locations Function
Simple squamous epithelium
the cells are flattened and single-layered
Air sacs of the lungs and the lining of the heart, blood vessels and lymphatic vessels Allows materials to pass through by diffusion and filtration, and secretes lubricating substances
Simple cuboidal epithelium
the cells are cube shaped and single layered
In ducts and secretory portions of small glands and in kidney tubules Secretes and absorbs
Simple columnar epithelium
are rectangular and are attached to the basement membrane on one of their narrow sides, so that each cell is standing up like a column. There is only one layer of cells.
Ciliated tissues including the bronchi, uterine tubes, and uterus; smooth (nonciliated tissues) are in the digestive tract bladder Absorbs; it also secretes mucous and enzymes.
Pseudostratified columnar epithelium
the cells are column-like in appearance, but they vary in height. The taller cells bend over the tops of the shorter cells so that the top of the epithelial tissue is continuous. There is only one layer of cells
Ciliated tissue lines the trachea and much of the upper respiratory tract Secrete mucous; ciliated tissue moves mucous
Stratified squamous epithelium
many layers of flattened cells
Lines the esophagus, mouth, and vagina Protects against abrasion
Stratified cuboidal epithelium
contains many layers of cube-shaped cells
Sweat glands, salivary glands, and mammary glands Protective tissue
Stratified columnar epithelium
many layers of rectangular, column-shaped cells
The male urethra and the ducts of some glands. Secretes and protects
Transitional epithelium
many layers of irregularly shaped cells with diverse sizes
Lines the bladder, urethra and ureters Allows the urinary organs to expand and stretch
Types of Epithelial Tissue
Epithelial tissue is classified by cell shape and the number of cell layers.
LEARNING OBJECTIVES
Classify epithelial tissue by cell shape and layers
KEY TAKEAWAYS
Key Points
There are three principal cell shapes associated with epithelial cells: squamous epithelium, cuboidal epithelium, and columnar epithelium.
There are three ways of describing the layering of epithelium: simple, stratified, and pseudostratified.
Pseudostratified epithelium possesses fine hair-like extensions called cilia and unicellular glands called goblet cells that secrete mucus. This epithelium is described as ciliated pseudostratified epithelium.
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.
In keratinized epithelia, the most apical layers (exterior) of cells are dead and and contain a tough, resistant protein called keratin. An example of this is found in mammalian skin that makes the epithelium waterproof.
Transitional epithelia are found in tissues such as the urinary bladder where there is a change in the shape of the cell due to stretching.