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.
Learning Objectives Describe the primary functions and characteristics of epithelial tissue. Key Points Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another.
Epithelial layers are avascular, but innervated. Epithelial cells have two surfaces that differ in both structure and function. Glands, such as exocrine and endocrine, are composed of epithelial tissue and classified based on how their secretions are released. Key Terms epithelium : A membranous tissue composed of one or more layers of cells that form the covering of most internal and external surfaces of the body and its organs. Functions of the Epithelium 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. Elsevier Health Sciences ; Finger-shaped, non-active motile projections on the apical surface of epithelial cells.
Eyelash-shaped, active motile projections on the apical surface of epithelial cells. Inner structure composed of actin filaments Cross-linkage by fimbrin. Inner structure composed of actin filaments.
Inner structure composed of microtubules Anchored in the cytoplasm via basal bodies kinetosomes. Intestine: enterocytes Kidney : epithelium in the proximal tubule.
Inner ear : hair cells of the organ of Corti hearing and the v estibular organ sense of balance Epithelium of the epididymal duct and vas deferens. Respiratory tract : respiratory epithelium Epithelium of the fallopian tubes Epithelium of efferent ducts epididymis.
No active motion possible Flexible passive motion in the inner ear Inflexible rigid in the epididymal duct and vas deferens. Active motion possible through interaction between dynein and microtubules. Increases the absorption surface area of the epithelia. Inner ear Hearing Sense of balance Epididymal duct and vas deferens : secretion and absorption. Ciliary movement Mucociliary clearance of the respiratory tract Transport of oocytes in the fallopian tubes and sperm in the efferent ducts.
Microplicae Small, fold-shaped projections of the apical membrane of epithelial cells comprised of actin filaments very short microvilli Improve adhesion of liquid films. Epithelial cells have two surfaces that differ in both structure and function.
Glands, such as exocrine and endocrine, are composed of epithelial tissue and classified based on how their secretions are released. Key Terms epithelium : A membranous tissue composed of one or more layers of cells that form the covering of most internal and external surfaces of the body and its organs. 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.
Key Terms simple columnar : A columnar epithelium that is uni-layered. Keratinized : To produce or become like keratin. Licenses and Attributions. CC licensed content, Shared previously. Simple squamous epithelium.
Allows materials to pass through by diffusion and filtration, and secretes lubricating substances. Simple cuboidal epithelium. Simple columnar epithelium. Ciliated tissues including the bronchi, uterine tubes, and uterus; smooth nonciliated tissues are in the digestive tract bladder. This membrane is a mixture of carbohydrates and proteins secreted by the epithelial and connective tissue cells.
Epithelial cells may be squamous, cuboidal, or columnar in shape and may be arranged in single or multiple layers. Simple cuboidal epithelium is found in glandular tissue and in the kidney tubules.
0コメント