Textus Epithelialis (ghufron_histo@yahoo.co.id). December 12,2008 Tissues are: Collections of specialized cells and cell products organized to perform a limited number of functions The four tissue types are: Epithelial Connective Muscular Nervous

Epithelial tissue Includes glands and epithelium Is avascular Glands are secretory Some characteristics: Is avascular Forms a protective barrier that regulates permeability Cells may show polarity

Functions of epithelium Physical protection Control permeability Provide sensation Produce specialized secretions

The Polarity of Epithelial Cells Figure 4.1

Connections: Cells attach via cell adhesion molecules (CAM) Cells attach at specialized cell junctions Tight junctions Desmosomes Gap junctions List one function for each type of cell junction.

Figure 4.2

Structure of typical epithelium Basal lamina attaches to underlying surface Lamina lucida Lamina densa Germinative cells – Function?

Classification of epithelia Number of cell layers Simple Stratified Shape of apical surface cells Squamous Cuboidal Columnar

Squamous Epithelia Figure 4.3

Cuboidal Epithelia Figure 4.4a

Cuboidal Epithelia Figure 4.4b

Transitional Epithelium Figure 4.4c

Columnar Epithelia Figure 4.5a

Columnar Epithelia Figure 4.5b

Columnar Epithelia Figure 4.5c

Glandular epithelia Exocrine glands Endocrine glands Secrete through ducts onto the surface of the gland Endocrine glands Release hormones into surrounding fluid

Glandular secretions can be: Merocrine (product released through exocytosis) Apocrine (involves the loss of both product and cytoplasm) Holocrine (destroys the cell)

Mechanisms of Glandular Secretion Figure 4.6