Epithelium Flashcards
What are the five levels of organization within the body?
cell–>tissue–>organ–>system–>body
cell: basic functional unit of the body
tissue: a collection of cells and material between cells that perform a specialized function
organ: a structure or mass formed by basic tissues to perform specialized functions
system: a group of organs that work together to perform specialized functions
The four primary tissues and their functions are:
1) epithelium: covering and lining surfaces and secretion
2) connective tissue: support
3) muscle: contraction
4) nervous tissue: impulse conduction
The three germ layers of epithelium are:
ectoderm, mesoderm, endoderm
The seven different functions of epithelium are:
1) Protection: physical, chemical, metabolic
2) Transcellular support: active and passive
3) Secretion: mucous, hormones, enzymes, cytokines
4) Absorption: nutrients, other materials
5) Selective Permeability: between epithelial cells
6) Sensory Detection: taste, hearing, sight
7) Contraction: myoepithelial cells
3 characteristics of epithelium:
1) composed entirely of cells
2) avascular (no blood vessels)
3) polarity (apical, basal, lateral)
3 physical arrangements of epithelium:
1) sheets of tightly bound cells (membrane epithelium)
2) glands
3) non-secretory individual or small clusters of cells
Criteria for classifying epithelium:
1) number of layers
2) shapes of cells
3) Special modifications
What are the different types of layers?
simple, stratified, pseudostratified
What are the different shapes of cells?
Cell shape of epithelium is classified by the surface layer:
squamous (flat), cuboidal (square), columnar (rectangular)
What are the different types of specialized functions?
1) apical cell membrane
a) kinocilia: long, mobile projections that allow movement
b) microvilli: increases surface area; short projections (brush border)
c) stereocilia: increases surface area; long, non-mobile projections
2) basal cell membrane
basal infoldings: invaginations in basal cell membrane
3) cytoplasm
keratinization: only occurs in skin; deposition of proteinaceous filaments
In transitional epithelium…
stratified epithelium, shape of surface cells are variable, can stretch without breaking cell to cell attachment
The apical surface of the cell faces the ________, and the basal surface attaches to the ________ ___________.
lumen, basal membrane
_______ _________ attaches cells together and was later identified as junctional complexes.
terminal bars
What is another name for a desmosome?
macula adherens
What are the components of a junctional complex?
zonula occludens, zonula adherens, macula adherens
What are gap junctions?
channels that allow the passage of material and the communication between cells
________ ________ holds cells together and was later identified as desmosomes.
intercellular bridges
What does the basement membrane do?
acts as glue to hold epithelial tissues to connective tissue; filtration; directs cell migration during healing
What are the two components of the basal membrane?
basal lamina (produced by epithelial cells) and lamina relicularis (lamina fibroreticularis—-> produced by fibroblasts)
What are glands, and where do they originate?
One or more specialized cells that elaborate secretory products (material not related to their ordinary metabolic needs).
They originate from epithelial cells and are formed by projections of epithelium at the surface of a body into underlying mesoderm.
What are the two components of glands?
1) parenchyma: functional components
2) stroma: supporting or structural components
List 6 criteria for classifying glands:
1) presence or absence of duct
2) number of secretory cells
3) nature of secretory product of exocrine glands
4) mode of secretion of product of exocrine glands
5) collective shapes of groups of secretory cells of exocrine glands
6) distance that endocrine secretory product must travel
Differentiate endocrine and exocrine glands
Endocrine glands have no duct and release secretory products into blood vessels or tissue fluid for transport to other locations in the body.
Exocrine glands HAVE a duct that transport secretory product to surface.
Differentiate between unicellular and multicellular glands.
Unicellular glands only have 1 cell (i.e. goblet cell), and multicellular glands have 2 or more cells (i.e. salivary).
Name four and describe different natures of the secretory products of exocrine glands.
1) serous: watery, protein rich
2) mucous: viscous, slippery, rich in sugars
3) mixed: contains serous and mucous components
4) sebaceous: lipids
Name and describe the three different modes of secretion of exocrine glands.
1) merocrine: released from secretory granule with no loss of cytoplasm
2) apocrine: small portion of apical cytoplasm pinched off with secretory product
3) holocrine: entire cell released as secretory product
Name the three shapes of exocrine glands and be able to recognize.
tubular, acinar, alveolar
Differentiate the three different types of secretory distances.
1) autocrine: secretory product directly acts on same cell
2) paracrine: secretory product acts on adjacent cell
3) endocrine: secretory product travels via vasculature and acts on distant cells
Exocrine glands are classified as either:
“simple” if duct is unbranched or “compound” if the duct does branch
What are the types of exocrine glands dependant on?
arrangement of ducts and secretory cells
Differentiate between a lobe and a lobule.
A lobule is a group of parenchyma surrounded by stroma; a lobe is a group of many lobules.
Go through the heirarchy of exocrine glands:
secretory cells—>intercalated duct—>intralobular duct—>interlobular duct—>lobular duct—>main duct
What cells assist with the movement of product out of exocrine glands?
myoepithelial cells
