Covering/Lining Epithelial Tissue Flashcards
Describe the characteristics of epithelial cells.
Polarity: apical surface, lateral surface, and basal surface
Closely packed with little intercellular space
Specialized cell-cell junctions
Basal surface attached to basement membrane with underlying connective tissue
Epithelia is avacular but has its own nerve supply
high mitotic rate
What are tight junctions?
these are in the zonula occuldens
Transmembrane linker proteins attach to actin filaments of cytoskeleton
weblike patterns of protein strands peripherally fusing together the outsides of adjacent cell membranes
froms seals between cells which form a diffusion barrier
MOST APICAL OF THE CELL JUNCTIONS, separates apical and basolateral domains
Describe adherens junctions.
Found in zona adherens
INFERIOR TO TIGHT JUNCTIONS
important for lateral adhesion of cells
reach inside adjacent cells to connect cytoskeleton of each
transmembrane proteins attah to actin
stabilize structural cohesion of epithelial sheet
encircle the cell
Describe desmosomes.
Macula adherens
provide spotlike localized adhesions between epithelial cells
do not encircle cell
transmembrane proteins attach to intermediat filaments of the cytoskeleton (keratin, tonofilaments)
Describe gap junctions.
Allow diffusion between cells
Present in lot of different tissues, including smooth and cardiac muscle
hexameric complex of transmembrane channels called connexons that act as hydrophilic channels capable of opening and closing
dont anchor to the cytoskeleton
Describe hemidesmosomes.
found in the basal surface
transmembrane proteins anchor intermediate filaments of cytoskeleton into basal lamina of basement membrane
Describe the basement membrane. What type of collagen are the two layers made of?
Basal (closer to cell): type IV
Reticular (closer to connective tissue): collagen III
difficult to differentiate these layer using LM
Make out layers of basal lamina and reticular fibers of connective tissue.
Can only distinguish basement membrane layers using EM
What are the two ways epithelium can be classified? Describe each.
- Number of layers: Simple = 1 layer, stratified = two or more layers thick
- Shape of cells: squamous = width greater than height, cuboidal = width same as height, columnar = height greater than width.
How do you identify shape of stratified epithelium?
The shape of the most apical layer is what you use.
Is nucleus shape and location a way to indentify type of epithelium?
YES YES YES
What are some examples of functions and where to find:
Stratified squamous
Simple squamous
Simple cuboidal
Transitional
Myoepithelial cells
Pseudostratified columnar
Stratified squamous - mechanical protection - skin
Simple squamous - diffusion/lubrication - lungs
Simple cuboidal - absorption/secretion - kidneys and glands
Transitional - stretch - urinary bladder
Myoepithelial cells - contractility - glands
Pseudostratified columnar - sensation/receptors - nasal cavity
What are the two types of epithelium and some examples of where to find them?
Surface epithelium - covers external surfaces, lines hollow organs, body cavities, and ducts… epidermis of skin, GI and respiratory tract, serous membranes
Glandular epithelium - forms parenchyma of glands, endocrine (ductless) and exocrine glands (unicellular and multicellular types)… may appear pyramidal if encircling a lumen, but still considered CUBOIDAL.
Serous membranes include the pleural, peritoneal, and pericardial lining of body cavities, what does the epithelial portion of these areas be called?
Mesothelium
Lining of cardiovascular system is endothelium
Note the type of epithelium and where it is located.
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What are the three primary germ layers and what they contribute to?
Ectoderm - skin, lining of oral cavity, anal canal
Mesoderm - mesothelium of body cavities, endothelium of blood vessels, epithelium of kidneys
Endoderm - Lining of respiratory tract, lining of most of digestive tract, epithelium of thyroid gland
Where are some more specific areas you might find simple squamous epithelium?
Endothelium of blood vessels
Endocardium lining of inside of heart wall
Mesothelium of body cavities
Bowmans capsules of kidneys
Walls of respiratory spaces in lungs
Where might you find simple columnar epithelium?
Often associated with goblet cells, microvilli, or cilia
stomach, small intestines, colon, gallbladder, fallopian tibe
CT = Connective tissue
GC = Goblet cell
L = Lumen
MV = Brush border
N = Nucleus
rN = Leukocyte
TW = Terminal web
What epithelium is this?
Simple Columnar
What epithelium is this?
Simple Cuboidal
What epithelium is this?
Simple Cuboidal
Where might you encounter pseudostratified columnar epithelium?
Trachea and nasal cavity
What epithelium is this?
Pseudostratified columnar
Where might you find stratified squamous epithelium and what are the two different types? What types in this picture?
Keratinized (right) vs nonkeratinized (left)
Found in epidermis
oral cavity and espohagus
vagina
Where might you find stratified cuboidal epithelium?
Sweat gland ducts
large ducts of exocrine glands
Where might you find stratified columnar epithelium?
Largest ducts of exocrine glands like in salivary glands
Where do you find transitional epithelium?
Renal calyces
ureters
bladder
urethra
