Upload
clinton-white
View
229
Download
2
Tags:
Embed Size (px)
Citation preview
Tissues and a Introduction to the Epithelium
Levels of Organization
atoms→molecules→organelles→cells
→tissues
In the body, tissues can be classified into the following functions:Epithelial – cover 1
Connective – support 2 Movement – muscle 3
Control – nervous 4
Epithelial Tissues
• Epithelial cells can be classified into 2 types, those that cover surfaces and cavities and those that form a glandular function.
Epithelial tissues have the following functions:
• Protection
• Absorption
• Filtration
• Excretion
• Secretion
• Sensory Reception
Characteristics of epithelial tissues:
• Epithelial cells have an upper or free surface.
Characteristics of epithelial tissues:
• Epithelial cells have an upper or free surface.
• This is known as the Apical Surface
Polarity
• The apical surface can be modified by microvilli or cilia.
• Microvilli are seen with cells associated with absorption.
Polarity
• The microvilli can be so thick that it can be described as a brush boarder.
Polarity
• The bottom side of the epithelial cell is called the basal surface.
• It is supported by a non cellular, adhesive sheet called the basal lamina.
Specialized Contacts
• Epithelial cells have contact with each other.
• These lateral contacts are the desmosomes and tight junctions.
Specialized Contacts
• The tight junction forms an impermeable junction between each cell and thus prevents diffusion between the cells.
Specialized Contacts
• The desmosomes help hold the cell’s shape with anchoring junctions scattered between each cell.
Connective Tissue Support
• The basilar surface attached to a connective tissue net work.
• There are two parts. The first is the basal lamina secreted from the epithelial cell.
• The second is the reticular lamina that is made of collagen which is produced by fibroblasts.
Connective Tissue Support
• Together the basal lamina and reticular lamina form the basement membrane.
• This forms the foundations which anchor the epithelial cells.
Avascular but Innervated
• Epithelial cells do not have a blood supply
• They depend on diffusion for the delivery of nutrients and removal of wastes.
• They do have a nerve supply, innervated, for sensory function.
Regeneration
• Do to their protective function; epithelial cells need to be continually replaced.
• Mitotic figures are not uncommon.
Cancer
• Many cancers are of epithelial origin.
• The greater the mitotic index, the greater the chance of cancer.
Cancer Types
Cancer Types
• Lung cancer caused by smoking typically starts in the bronchial epithelium
1 Picture & 1000 words