Select the best answer or answers from the choices given: An epithelium that has several layers, with an apical layer of flattened cells, is called (choose all that apply): (a) ciliated, (b) columnar, (c) stratified, (d) simple, (e) squamous.
Select the best answer or answers from the choices given: An epithelium that has several layers, with an apical layer of flattened cells, is called (choose all that apply): (a) ciliated, (b) columnar, (c) stratified, (d) simple, (e) squamous.
The cells are the basic biological unit of life. There are many different types of cells in the body which form various tissues of the human body. The cells which perform similar kinds of functions are involved in the tissue formation. These tissues then come together to give rise to various organs. The tissues present in the human body are classified into four types: the epithelial tissue, the connective tissue, the muscle tissue, and the nervous tissue. Epithelial tissues act as coverings of the organs and control the movement of substances across the surface. Connective tissue is responsible for integrating with the various parts of the body and providing support and protection to organs. Muscle tissues are responsible for the movement of the body. Nervous tissues are responsible for transmission of nerve signals from the brain to other body parts.
The epithelium tissue is one of the primary tissue types present in the body that forms boundaries between different environments. The epithelial tissue is responsible for the formation of a protective covering on the outer side of the organs, lining the inside of body cavities and also for the formation of various glands. The epithelial tissue consists of two types of surface: the apical surface and the basement surface. The apical surface is a free surface that abuts the open space of a gland or hollow organ. The basement surface is an attached surface that lies on the basal lamina.
The cells of the epithelial tissue are laid together to form thin sheets of protective covering. The epithelium can be categorized as: the simple epithelium and the stratified epithelium, based on the number of layers comprising the tissue. Simple epithelium consists of a single layer of cells whereas stratified consists of multiple cell layers. In terms of structure, the cells comprising epithelium tissue can be of 3 types: the squamous, the columnar or the cuboidal.
- Squamous epithelial cells : The squamous cells are flat shaped cells that are found on skin and lung surfaces. Since these cells are typically flattened and thin, the nuclei present in them is also flattened forming a nearly oval shape.
- Cuboidal epithelial cell: The cuboidal cells have cube-like shape and are usually present in the body glands such as exocrine glands and pancreatic glands. Since the shape of the cells is cuboidal, the nuclei present in them are large and spherical. Therefore these epithelial cells form tissue which is actively participating in the process of secretion.
- Columnar epithelial cell: The columnar cells are typically elongated in shape. The nuclei of such cells are usually located at the base. The columnar epithelium can be further classified into ciliated and non-ciliated columnar epithelium based on the presence or absence of cilia.
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