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What is a tissue?
composed of a group of cells with similar structure that perform related functions and are surrounded by extracellular material (non-living)
What are the 4 different tissue types?
- epithelial for covering
- connective for support
- muscle for movement
- nervous for control
What are Epithelial Tissues for?
What are connective tissues for?
What are muscle tissues for?
What are nervous tissues for?
What are epithelial tissues?
serves as a lining for organs that have an opening to the environment
What are the functions of epithelial tissues?
- boundary layer
- interface layer
- transport such as secretion & absorption
What are the special characteristics of epithelia?
- *Cellularity - dense cell areas, multiple points of connection between cells, few extracellular matrix material
- * specialized contacts - multiple cell kjunctions tightly connect neighboring cells
- * polarity - each cell has a distinguishable apical (top) and basal (bottom) side
- * support by connective tissue - an underlying layer of connective tissue supports epithelial tissue
- * avascular but innervated - blood vessels do not cross into epithelial tissue but nerve endings do
- * regenetration - epithelial cells line organs that are exposed to many conditions that destroy the cells & have a great ability to regenerate quickly.
What is simple epithelia?
a single layer of epithelia designed to allow molecules to cross the membrane quickly (ex. capillaries & lungs)
What are the 4 types of simple epithelia?
- simple squamous epithelia
- simple cuboidal epithelia
- simple columnar epithelium
- pseudostratified columnar epithelium
What is simple squamous epithelia?
a flat layer of cells that makes exchange of materials quick & easy.
What are the 2 types of simple squamous epithelia?
Endothelium & Mesothelium
What is Endothelium?
produces a slick slippery surface
What is Mesothelium?
serves as a middle covering as part of serosa found in body cavities
What is simple cuboidal epithelia?
a layer of cube like cells, their height and width are just about equal. it forms gland ducts & tubules
What is simple columnar epithelium?
a layer of tall cells that line the digestive tract & functions in absorption, secretion, & ion movement.
What is pseudostratified columnar epithelium?
a single layer with cells of different heights appearing as if there are different layers.
What do the short & tall cells in pseudostratified columnar epithelium do?
- short cells - undifferentiated & give rise to tall cells
- tall cells - function of scretion & absorption
What is stratified epithelia?
two or more layers of cells, cells rise from basal side. main function is protection
What are the 3 stratified epithelia?
- stratified squamous epithelium,
- stratified cuboidal & columnar epithelium
- transitional epithelium
What is stratified squamous epithelium?
many layers of cuboidal or columnar cells with squamous cells at the surface. It is the best form of protection & lines areas that are often-abraded. This type may be keratinized or not keratinized
What is stratified cuboidal & columnar epithelium?
rare tissue that forms only large ducts of glands
What is transitional epithelium?
lines hollow urinary organs & has the ability to stretch from six to three cells thick
What are the epithelial surface features?
- 1. apical surface features: microvilli & cilia
- 2. lateral surface features: cell junctions
- 3. basal surface features: the basal lamina
What are the epithelial apical surface features?
- plasma membrane extensions on apical side
- microvilli & cilia:
- - microvilli increase the surface area
- - cilia move to push substances in a certain direction with protein structures in it.
What are the epithelial lateral surface features?
cell junctions - cells are held together by proteins that attach the different cell surfaces
What are the epithelial basal surface features?
the basal lamina: thin non-cellular support sheet made up of proteins, controls what enters epithelium, assist in regeneration
What are Glands?
groups of epithelial cells that make & secrete a substance
What can Glands be?
unicellular or multicellular
What are the 2 type of glands?
Exocrine Glands & Endocrine Glands
What are exocrine glands?
substances like mucus, sweat, & saliva are secreted onto body surfaces or cavities. Has ducts
What are endocrine glands?
have no ducts, secrete hormones into blood stream
What has ducts? endocrine glands or exocrine glands?