Tissue

Chapter 4 Study Guide
Bio 169

• Individual body cells are specialized
-Each type performs specific functions that help maintain homeostasis

• Tissues are groups of cells that are similar in structure and perform a common function

• Histology – study of tissues

PRIMARY TISSUE TYPES:
1) Epithelial Tissue (or epithelium) is a sheet of cells that covers a body surface or lines a body cavity
 Forms boundaries
 Occurs in the body as covering and lining epithelium and glandular epithelium
 Covering and lining epithelium forms the outer layer of the skin, and lines the open cavities of the cardiovascular, digestive, and respiratory systems, and covers the walls and organs of the ventral body cavity (internal and external surfaces)
 Glandular epithelium fashions the glands of the body

• Epithelial Tissue Functions:
-Protection
-Absorption
-Filtration
-Excretion
-Secretion
-Sensory reception

• Five Characteristics of Epithelial Tissues:

1) POLARITY
 All epithelia have an apical surface, and upper free surface exposed to the body exterior or the cavity of an internal organ, and a lower attached basal surface. (Both surfaces differ in structure and function)
 Apical surfaces are smooth and slick, and most have microvilli which are fingerlike extensions of the plasma membrane. Microvilli increase the exposed surface area.
 Some epithelia, such as the lining of the trachea, have motile cilia (tiny hairlike projections) that propel substances along their free surface.
 Lying adjacent to the basal surface of an epithelium is a thin supporting sheet called the basal lamina. This noncellular, adhesive sheet consists largely of glycoproteins secreted by the epithelial cells plus some fine collagen fibers. The basal lamina acts a selective filter that determines which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium. The basal lamina also acts as a scaffolding along which epithelial