Epithelial tissues cover the body and line organs

Epithelial tissues are sheets of densely packed, tightly connected cells that cover inner and outer body surfaces. They form the skin and line hollow organs of the body, such as the gut (Figure 41.3). Some epithelial cells have secretory functions; examples are the groups of epithelial cells that secrete hormones, milk, mucus, digestive enzymes, or sweat. Other epithelial cells have cilia to help substances move over surfaces or through tubes. Since epithelial cells create boundaries between the inside and the outside of the body and between body compartments, they frequently have protective as well as absorptive and transport functions. Epithelial cells can also form receptors that provide information to the nervous system. Smell and taste receptors, for example, are epithelial cells that detect specific chemicals.

41.2 Four Types of Tissue All cells can be classified into one of four tissue types. An organ such as the stomach is made up of multiple tissue types.

Cuboidal cells in simple epithelium

Cuboidal cells in simple epithelium

Stomach Epithelial Layer

41.3 Epithelial Tissue (a) A single layer of cuboidal cells forms a simple epithelium lining the collecting ducts of a human kidney. (b) Multiple layers of squamous cells form a stratified epithelium.

Squamous cells

41.3 Epithelial Tissue (a) A single layer of cuboidal cells forms a simple epithelium lining the collecting ducts of a human kidney. (b) Multiple layers of squamous cells form a stratified epithelium.

Epithelial tissues have distinct inner and outer surfaces. The outer surface faces the air, as in the case of the skin and lungs, or a fluid-filled organ cavity, such as the lumen of the gut. These outer surfaces are the apical ends of the epithelial cells, which may have cilia or may be highly folded to increase their surface area. The inner surfaces of an epithelium are the basal ends of the epithelial cells, which rest on an extracellular matrix called a basal lamina (see Figure 4.26).

The skin and the lining of the gut are examples of epithelial tissues that receive much wear and tear. Accordingly, cells in these tissues have a high rate of cell division to replace cells that die and are shed. Dandruff consists of discarded skin cells.

Natural Treatments For Dandruff

Natural Treatments For Dandruff

Stop Your Scalp From Snowing! Finally... A Real Cure for Dandruff! No medication! No weird cures! No messy creams, smelly solutions or strange diets! Are you sick to death of being sold products that could make the problem worse? Are you sick of the shampoos and conditioners that make your head smell like sulphur? If so then try a permanent revolutionary treatment for dandruff!

Get My Free Ebook


Responses

  • danny
    What epithelial tissues are the lining of the guts?
    8 years ago
  • Vito
    What skin cell lines the inner and outer body?
    8 years ago
  • teemu
    Where do epithelial tissues line organs?
    7 years ago

Post a comment