Epithelial Tissue Flashcards
Junctions
A=Tight Junction
B=Adherens
C=Desmosome
D=Gap Junction
E=Hemidesmosome
Simple Squamous
Function: allows passage of materials by diffusion and filtration, secretes lubricating substances
Location: Lining of blood vessels/lymphatics, alveoli, renal glomeruli, heart; serous lining of cavities (mesothelium)
Simple Cuboidal
Function: Secretion and absorption
Location: Renal tubules, ducts and gland
Simple Columnar
Function: protection, lubrication, absorption, secretion
Location: lining of intestine, gallbladder, female reproductive tract
Stratified Squamous
Function: protection, secretion, prevention of fluid loss
Location: skin, mouth, esophagus, larynx, vagina, anus
Stratified Cuboidal
Function: protection, secretion
Location (rare): sweat glands, mammary glands, testes, developing ovarian follicle
Transitional
Structure: top layer made up of dome shaped cells with specialized membrane that allows them to withstand hypertonic effects of urine and protect underlying cells from toxins; cells can adjust their relationships with each other as urinary bladder fills and wall is distended
Function: protection,distensibility
Location: Bladder, ureters, renal calyces
Stratified Columnar
Function: protection, secretion
Location (rare): parts of male urethra, some glands
Pseudostratified
Function: protection, secretion, cilia-mediated transport of mucous and trapped particles
Location: lining of trachea, bronchi, nasal cavity
Endocrine or Exocrine Gland?
Exocrine (duct)
Endocrine or Exocrine Gland?
Endocrine
Tight Junction
- function like the plastic that holds 6 pack of beer together
- Found in epithelia, opposing cell membranes held in tight contact by transmembrane adhesive proteins (claudin ,occludin, junctional adhesion molecule)
- Creates a physical/chemical barrier to control paracellular movement of substances
- Also helps define and maintain separation between apical and basal areas of cell membrane to maintain cell polarity
Epithelial Tissue Function
- Protection
- Transport of nutrients, gases, waste material
- Screte lubricating fluid (serosal surfaces)
- Make up functional tissues of organs and are key elements of many glands
- Specialized epithelail cells serve as sensory receptors
Adherens Junctions
- holds opposing cell membranes together (with thin sliver of intercellular space)
- The intercellular space is bridged by cadherins
- Cadherins attach to cytoplasmic proteins (catenins) which in turn attach to cytoskeletal components (actin filaments, microtubules)
- These transmembrane protein complexes interact with signaling molecules, including tumor suppressor molecules
–Play a role in regulating cell-to-cell contact
(essential for morphogenesis, remodeling of
tissue/organs, controlled proliferation of cells)
Desomosomes
- Anchoring junctions that reinforce cellular adhesion
- Desmosomal cadherins attach to intermediate filaments in cytoskeleton for additional support
- Prominent in tissues under mechanical stress
- dysfunction of desmosoal cadherins associated with cell adhesion cardiomyopathy (arrythmogenic right ventricular dysplasia) blistering diseases (pemphigus vulgaris)
Gap Junctions
- Clusters of intercellular channels that allow rapid transmission of electrical or chemical information from cell to cell
- Intercellular gap spanned by channel forming transmembrane proteins
- connexins form connexons, which aligh with neighboring connexons
Hemidesmosome
- Integrin interacts with laminin to links intermediate filaments of cytoskeleton to extracellular basement membrane
- integrin plays role in cell-cell communication
Basement Membrane
- Macromolecules that bind hormones and other cell signaling molecules
- semi permeable filter for substances coming to cell from underlying tissue
- epithelial cells require contact with basement membrane for normal function and to establish polarity
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