What is the difference between simple stratified and pseudostratified

These are simple columnar epithelial cells whose nuclei appear at different heights, giving the misleading hence pseudo impression that the epithelium is stratified when the cells are viewed in cross section.

Pseudostratified epithelium can also possess fine hair-like extensions of their apical luminal membrane called cilia. In this case, the epithelium is described as ciliated pseudostratified epithelium. Ciliated epithelium is found in the airways nose, bronchi , but is also found in the uterus and fallopian tubes of females, where the cilia propel the ovum to the uterus.

Stratified epithelium differs from simple epithelium by being multilayered. It is therefore found where body linings have to withstand mechanical or chemical insults. Stratified epithelia are more durable and protection is one their major functions. Since stratified epithelium consists of two or more layers, the basal cells divide and push towards the apex, and in the process flatten the apical cells. Stratified epithelia can be columnar, cuboidal, or squamous type.

However, it can also have the following specializations:. In keratinized epithelia, the most apical layers exterior of cells are dead and lose their nucleus and cytoplasm. They contain a tough, resistant protein called keratin. This specialization makes the epithelium waterproof, and it is abundant in mammalian skin.

The lining of the esophagus is an example of a non-keratinized or moist stratified epithelium. Transitional epithelia are found in tissues that stretch and it can appear to be stratified cuboidal when the tissue is not stretched, or stratified squamous when the organ is distended and the tissue stretches.

It is sometimes called the urothelium since it is almost exclusively found in the bladder, ureters, and urethra. Privacy Policy. Skip to main content. Organization at the Tissue Level.

Search for:. Epithelial Tissue. Characteristics of Epithelial Tissue The human body consists of four types of tissue: epithelial, connective, muscular, and nervous.

Learning Objectives Describe the primary functions and characteristics of epithelial tissue. Answer: Leaky epithelia is found in blood vessels, alveoli, and kidneys to allow for movement of nutrients. Impermeable epithelia is expected in the GI tract.

Answer: Tight junctions form the zonula occludens, which acts as a belt around the cell to prevent proteins from moving from the apical to basolateral surfaces of the membrane. Answer: 1. Stratified squamous keratinizing epithelium. Simple columnar ciliated epithelium. Transitional epithelium. Answer: Integrins are found in hemidesmosomes along the basal surface of epithelial cells.

Dynein is found in cilia where it powers sliding of microtubules. Connexin is found in gap junctions along the lateral surfaces of epithelial cells. Cadherins are found in adhering junctions and desmosomes along the lateral surface of epithelial cells.

Slides Please select whether to view the slides in study mode or quiz mode. In study mode, the images will contain labels and a description. In quiz mode, labels and description will be hidden. Study Mode. Epithelial tissue is one of the four different types of tissues we have. It is important in covering the body, lining the body cavities and composing the glands.

Although the epithelial tissue does not have blood vessels, it is innervated in nature. It comprises cell layers tightly connected together. Epithelium fulfils several different functions in our body.

It protects our body from radiation, desiccation, toxins, and physical trauma. In the digestive tract, epithelium facilitates nutrient absorption. Furthermore, it secretes sweat, mucus, enzymes and other products of ducts. Based on the number of layers, there are three types of epitheliums as simple, stratified and pseudostratified. Overview and Key Difference 2.

What is Simple Epithelial Tissue 3. What is Stratified Epithelial Tissue 4. What is Pseudostratified Epithelial Tissue 5. Simple epithelial tissue contains a single layer of cells resting on a basement membrane, which is a fibrous network. Based on the shape of the cells in simple epithelial tissue, there are three types of simple epithelial tissues as simple squamous epithelial tissue , simple cuboidal epithelial tissue and simple columnar epithelial tissue.

Simple squamous epithelial tissue has a single cell layer composed of flat polygonal or hexagonal shaped cells. For example, the epithelium of the small intestine releases digestive enzymes and cells lining the respiratory tract secrete mucous that traps incoming microorganisms and particles. Epithelial cells are typically characterized by unequal distribution of organelles and membrane-bound proteins between their apical and basal surfaces.

Structures found on some epithelial cells are an adaptation to specific functions. For example, cilia are extensions of the apical cell membrane that are supported by microtubules. These extensions beat in unison, allowing for the movement of fluids and particles along the surface. Such ciliated epithelia line the ventricles of the brain where it helps circulate cerebrospinal fluid and line the respirtatory system where it helps sweep particles of dust and pathogens up and out of the respiratory tract.

Epithelial cells in close contact with underlying connective tissues secrete glycoproteins and collagen from their basal surface which forms the basal lamina. The basal lamina interacts with the reticular lamina secreted by the underlying connective tissue, forming a basement membrane that helps anchor the layers together. Cells of epithelia are closely connected with limited extracellular material present.

Three basic types of connections may be present: tight junctions, anchoring junctions, and gap junctions Figure 4. Epithelial cells are held close together by cell junctions. The three basic types of cell-to-cell junctions are tight junctions, gap junctions, and anchoring junctions. A Tight junction restricts the movement of fluids between adjacent cells due to the presence of integral proteins that fuse together to form a firm seal.

Tight junctions are observed in the epithelium of the urinary bladder, preventing the escape of fluids comprising the urine. An anchoring junction provides a strong yet flexible connection between epithelial cells. There are three types of anchoring junctions: desmosomes, hemidesmosomes, and adherens. Desmosomes hold neighboring cells together by way of cadherin molecules which are embedded in protein plates in the cell membranes and link together between the adjacent cells.

Hemidesmosomes , which look like half a desmosome, link cells to components in the extracellular matrix, such as the basal lamina. While similar in appearance to desmosomes, hemidesmosomes use adhesion proteins called integrins rather than cadherins.

Adherens use either cadherins or integrins depending on whether they are linking to other cells or matrix. These junctions are characterized by the presence of the contractile protein actin located on the cytoplasmic surface of the cell membrane. These junctions influence the shape and folding of the epithelial tissue. In contrast with the tight and anchoring junctions, a gap junction forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between cells.

These junctions thus allow electrical and metabolic coupling of adjacent cells. Epithelial tissues are classified according to the shape of the cells composing the tissue and by the number of cell layers present in the tissue. Figure 4. Similarly, cells in the tissue can be arranged in a single layer, which is called simple epithelium, or more than one layer, which is called stratified epithelium. Transitional describes a form of specialized stratified epithelium in which the shape of the cells, and the number of layers present, can vary depending on the degree of stretch within a tissue.

Epithelial tissue is classified based on the shape of the cells present and the number of cell layers present. Watch this video to find out more about the anatomy of epithelial tissues.

Where in the body would one find non-keratinizing stratified squamous epithelium? The cells in a simple squamous epithelium have the appearance of thin scales. The nuclei of squamous cells tend to appear flat, horizontal, and elliptical, mirroring the form of the cell. Simple squamous epithelium, because of the thinness of the cells, is present where rapid passage of chemical compounds is necessary such as the lining of capillaries and the small air sacs of the lung.

This epithelial type is also found composing the mesothelium which secretes serous fluid to lubricate the internal body cavities. In simple cuboidal epithelium , the nucleus of the box-like cells appears round and is generally located near the center of the cell.