In general, epithelial tissues are classified by the number of their layers and by the shape and function of the cells.
Additionally, there are pseudostratified epithelia and transitional epithelia. Examples of Epithelia Simple Epithelium Simple epithelia are made of a single layer of cells that are in direct contact with the basement membrane with a common apical surface.
These cells can be squamous, cuboidal, or columnar. Simple squamous epithelium is found in the alveoli of lungs, and its structure is important for the exchange of gases between the blood and lungs.
Simple cuboidal epithelia line the lumen of collecting ducts in the kidney and are present in the thyroid around the follicles that secrete thyroid hormones.
They protect the underlying structures and have a secretory function such as in the thyroid or absorptive function as in the collecting ducts of the kidney.
Simple cuboidal epithelia line both those structures. Simple columnar epithelia are found in the female reproductive system and in the digestive tract.
The cells in the fallopian tubes are ciliated and involved in the movement of the ovum towards the uterus. Those in the digestive tract are non-ciliated, and instead contain microvilli, which gives the epithelium the appearance of being brush-bordered.
Pseudostratified epithelia are formed of cells that have varying heights and therefore present the illusion of being stratified. However, every cell in this tissue makes contact with the basement membrane, thereby placing it among the simple epithelia.
Stratified Epithelium Stratified epithelia consist of more than one layer of cells and only one layer is in direct contact with the basement membrane.
Similarly, only one layer of cells has the apical surface exposed to the lumen of the organ or to the external environment. These tissues often have a protective role, and the extent of friction or abrasion often determines the number of layers of cells.
Stratified squamous epithelia are found in skin, with many dead, keratinized cells providing protection against water and nutrient loss. Stratified cuboidal epithelia are found surrounding the ducts of many glands, including mammary glands in the breast and salivary glands in the mouth.
Stratified columnar epithelia are rare, found predominantly in some organs of the reproductive system, and in the conjunctiva of the eye. Transitional epithelia are a special subset of stratified epithelia that consist of ovoid cells that can stretch based on the pressure of liquids inside the organ.
They are exclusively found in the excretory system. Characteristics of Epithelial Tissue Epithelial tissues play the role of separating two structures from each other. For instance, the epithelium in a blood vessel demarcates the cells of the blood from those forming the artery or vein.
This allows two organs to remain in close proximity for their function while maintaining separate internal physiology. In order to accomplish this function, however, epithelial tissues need to be tightly attached to each other, forming a mostly impenetrable layer.Classification scheme of epithelial tissue: Typically epithelial tissue is classified on the basis of arrangement and shape of cells.
For naming the tissue types, the arrangement of the cells is stated first, then the shape, and is followed by “epithelium” to complete the naming. Epithelial tissue is a sheet of cells that covers a body surface or lines a body cavity.
Two forms occur in the human body: Two forms occur in the human body: Covering and lining epithelium – forms the outer layer of the skin; lines open cavities of the digestive and respiratory systems; covers the walls of organs of the closed ventral body.
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 .
Epithelial tissue in glands secrete hormones, enzymes, and other substances. Epithelial tissue in the kidneys excrete wastes, and in the sweat glands excrete perspiration.
Epithelial tissue also has a sensory function as it contains sensory nerves in areas such as the skin, tongue, nose, and ears. Classification of Epithelial Tissue study guide by aolinn1 includes 21 questions covering vocabulary, terms and more.
Quizlet flashcards, activities and games help you improve your grades. Thyroid & Salivary epithelial tissue are examples of glandular epithelium, whose function is secretion. -In these glands, cuboidal cells are arranged in small spheres and .