Epithelium and Glands Flashcards
general functions of epithelial tissue (7)
- protection
- absorption
- transcellular transport
- selective permeability
- surface transport
- secretion (glands)
- sensation
two forms of epithelium
- epithelia
2. glands
epithelia
sheets of adjacent cells
glands
derived from invaginated epithelial cells
specialized forms of epithelium
- mesothelia
- serosa
- endothelia
mesothelia
membranes that line serous body cavities or organs
serosa
membrane that lines many regions of the GI tract and consist of a mesothelium and and underlying connective tissue
endothelia
membranes lining the heart chambers, blood vessels, and lymph vessels
common characteristics of epithelial tissue (lining type) (6)
- form surface sheet
- avascular (rely on diffusion of nutrients form surrounding connective tissue
- tightly packed cells with little extracellular matrix
- dynamic (can respond to environment with some change)
- sheets and individual cells are polarized (have an orientation)
- many have functionally significant cell surface specialization
apical specializations (3)
- microvilli
- celia
- sterocilia
microvilli
- small finger like projections
- covered in carbohydrate rich coating (glycocalyx)
- function in absorption
celiac disease (gluten sensitive enteropathy)
disorder in small intestine in which one the changes is loss of microvilli brush border of absorptive cell
celia
- long, hair like
- in epithelial tissue help with movement of substances across surface epithelium
- sometimes sensory organelles
sterocilia
- in regions of male reproductive system
- found in sensory elements of inner ear
lateral specializations (3)
- tight junctions
- adhering junctions
- gap junctions
tight junctions
- seal adjacent cells
- only in epithelial tissues
- formed by transmembrane junctional proteins
adhering junctions
- provide stability and structural unity
- zonula adherens: formed by transcellular proteins
- macula adherens (desmosomes): formed by plaques and specialized intermediate filaments
gap junctions
-allow cell to cell communication and passage of small molecules
basal specialization
basal membrane
- not part of epithelium tissue (extracellular)
- sheet upon which the epithelial cells rest
- comprised of: the basal lamina and the laminar reticularis
basal lamina
- made by epithelial cells
- type 4 collagen
- hemidesomes: anchor epithelial cells to basal lamina
laminar reticularis
- made by underlying connective tissue cells
- type 3 collagen (some type 1)
basal infolding
- infolding that increase surface area for ion transport
- have mitochondria and ion pumps
- give striated appearance
classification of epithilia
- layers
- shape of cells
layers of epithelia classification (2)
- simple (one layer)
2. stratified (more than one layer)
shape of epithelia classification (3)
- squamous (flat)
- cuboidal (cube)
- columnar (tall column like)
stratified epithelia are classified by
shape of the most superficial cells
if the most apical layer is columnar but the most basal layer is cuboidal the classification would just be columnar
pseudostratified epithelium (general characteristic)
gives stratified appearance but is actually composed of only one layer of cells (all touch the basement membrane)
simple squamous epithelium
- tightly packed, thin cells
- allow exchange of fluid and gases
- nuclei bulge into lumen b/c they are thicker than cytoplasm
special simple squamous epithelium (2)
endothelium: lines the heart, blood vessels, and lymphatic vessels
mesothelium: covers outer surface of organs
simple cuboidal epithelium
- functions in secretion and absorption
- found in many glands
simple columnar epithelium
- functions in absorption, secretion, and protection
- often have microvilli
- found in digestive tract
stratified squamous NON-keratinized
- protection (b/c its stratified)
- maintains a moist surface
- forms lining mucosa in oral cavity
stratified squamous keratinized
- non-nucleated cells filled with keratin on surface
- protection
- ex: skin and surface of the tongue
pseudostratified epithelium
- all cells rest on basal membrane, only columnar reach the apical surface
- often ciliated
- functions for secretion, lubrication, transportation
- found in respiratory system
transitional epithiliym
- have 2 forms: relaxed (more cuboidal) or stretched (more squamous)
- found only in urinary tract
metaplasia
reversible change in which one epithelia type is replaced by another
dysplasia
disordered growth that can lead to neoplasia
neoplasia
new growth
- bening :localized
- malignant: not localized, metastatic
carcinoma
malignant tumor of epithelial tissue
adenocarcinoma
malignant tumor of glandular epithelial tissue
glands
- invaginations of epithelial tissue
- may be unicellular or multicellular
two categories of glands
- exocrine glands
2. endocrine glands
exocrine glands characteristics
- maintain contact with overlying epithelial tissue
- secrete products via ducts onto external or internal epithelial surface from which they originate
- secrete from their apical surface
- ex: submandibular gland, sweat gland
classifications of exocrine secretion (3)
- merocrine: via exocytosis
- apocrine: small portion of apical cytoplasm released with secretory product
- holocrine: secretory cell is destroyed and becomes part of the secretory product
classification based on TYPE of SECRETION for exocrine cells (2)
- serous: watery and often contains enzymes
2. mucous: viscous and has high glycoprotein content
endocrine glands characteristics
- ductless and secrete product into the blood or lymphatic vessel for distribution
- normally secrete basally
