Epithelium Flashcards
Basic functional unit of the body
cell
A collection of cells and material between cells that perform specialized functions
tissue
A structure or mass formed by basic tissues to perform specialized functions
organ
A group of organs that work together to perform specialized functions
system
Epithelium traits (2)
Covering and lining of surface
Secretion
Epithelium is derived from
ALL GERM LAYERS
Ectoderm
Mesoderm
Endoderm
Functions of epithelium (7)
- protection
- Transcellular transport (active and passive)
- Secretion
- Absorbtion
- Selective permeability
- Sensory detection
- Contraction (myoepithelial cells)
Characteristics of epithelium (3)
- Composed entirely of cells
- Avascular (no blood vessels)
- Polarity (apical, lateral, basal)
Physical arrangement of epithelium (3)
1-sheets of tightly bound cells (membrane)
2-Glands (single or group secretory)
3-Non-secretory individiul or small clusters of cells
Membrane epithelium arranged:
In sheets to cover body surfaces (inside and outside)
3 criteria for epithelial classification
1-Number of layers of cells
2-Shape of cells in surface layer
3-Special modification of epithelial cells
Number of layers of cells can be
Simple (1 layer of cells)
Stratified (more than 1 layers of cells)
Shape of cells in surface layer
Squamous-flat
Cuboidal-square
Columnar-rectangular
Classes of epithelium in sheets with unique characteristics
Transitional epithelium
Pesudostratified columnar epithelium
3 specialized modifications of epithelial cells
1-Apical cell membrane
2-Basal cell membrane
3-Cytoplasm
Special modification of epithelial cell
Apical cell membrane (3)
- Kinocilia=long, mobile projections-CILIA
- Microvilli=short projections-BRUSH BORDER
- Stereocilia=long, non-mobile projections
Special modification of epithelial cell
Basal cell membrane
Basal infoldings=invagination in basal cell membrane
Special modification of epithelial cell
cytoplasm
Keratinization=deposition of proteinaceous filaments
Psuedostratified columnar epithelium
- simple epithelium
- Variable cell shapes
- All cells attach to basement membrane
- Not all cells reach surface of epithelium
- Common with apical surface modification (cilia or sterocilia)
Transitional epithelium
- stratified epithelium
- shape of surface cells variable
- Can stretch without breaking cell to cell attachment
Apical, basal, lateral polarity arrangement
Apical- toward lumen if present
Basal-attached to basement membrane
Lateral- on sides of cell that aren’t basal or apical
Adhesion of epithelial cells to other things via
Junctional complexes or terminal bars
on apical surface of cell
Glycocalyx and microvilli help
Types of attachments between epithelial cells (4)
Macula-spot
Zonula-girdle or belt
Occludens-tight seal
Adherens-site of adhesion
Desmosome is example of what type of attachement
Macula adherens
Some specialized structures in junctional complexes (2)
Gap juntinos
Hemidesmosomes
Intercellular bridges
desmosomes
Components of basement membrane (2)
1-Basal lamina
2-Lamina relicularis or Lamina fibrorecticularis
Basal lamina
Made by epithelial cells
- ->lamina lucida
- ->lamina densa
Lamina relicularis or lamina fibroreticularis is made by
fibroblasts
Functions of the basement membrane (3)
- Attachment of epithelium
- Filteration
- Direct cell migration during wound healing
Definition of gland
One or more specialized cells that elaborate secretory products (material not related to their ordinary metabolic needs)
Glands originate from
Epithelial cells
Glands are formed by
Projections of epithelium at a surface of the body into underlying mesoderm (primitive CT)
Components of glands (2)
Parenchyma
Stroma
Parenchyma of glands
Secretory epithelial cells
Epithelial cells of ducts
Stroma of glands
CT matrix and cells
Blood vessels
Nerves
To be a gland: 6 criteria
1-presence or absense of a duct
2-Number of secretory cells (exocrine or endocrine)
3-Nature of secretory product of exocrine
4-Mode of release (secretion) of secretory product by cells of exocrine glands
5-Collective shape of groups of secretory cells of exocrine gland
6-Distance endocrine secretory product must travel
Gland with a duct
Exocrine gland: ducts transport secretory product to surface
Gland without duct
Endocrine gland:releases secretory product into blood vessels or tissue fluid for transport carried to other locations in the body
Example of unicellular gland
Goblet cell and APUD cell
Example of multicellular gland
Salivary gland and parathyroid gland
Nature of secretory product of exocrine gland (4)
- Serous secretion
- Mucous secretion
- Mixed secretion
- Sebaceous secretion
Serous secretion product
Watery, rich protein
Mucous secretion product
Viscous, slippery, rich in sugar
Mixed secretion product
Components of serous and mucuos secretions
Sebaceous secretion product
Lipids (oily secretion termed sebum)
Mode of secretion of secretory product by exocrine gland (3)
- merocrine
- apocrine
- holocrine
Merocrine secretion
Secretory product released from secretory granule with NO loss of cytoplasm
Apocrine secretion
Small portion of apical cytoplasm pinched off and released with secretory product
Holocrine secretion
Entire cell released with secretory product
Collective shape of groups of secretory cells of exocrine gland (3)
Tubular (like test tube)
Acinar (berry shaped with tiny lumen)
Aleveolar (big berry with big lumen)
Distance secretory product of endocrine gland can travel (3)
- Autocrine
- Paracrine
- Endocrine
Autocrine
Endocrine glands use this
Secretory product directly acts on same cell
Paracrine
Endocrine glands use this
Secretory products acts on adjacent cells
Endocrine
Endocrine glands use this
Secretory product travels via vasculature to act on distant cells.
Exocrine glands can be classified as (2) depending on duct
- Simple-duct is unbranced
- Compound-if duct does branch
Lobe vs lobule
Lobules are separated by septums (CT wall) WITHIN the lobe. Lobules hold individual secretory acini.
What’s commonly found in the infoldings of basal cell membranes?
Elongated mitochondria to allow E to be used in active membrane transport system.
What will you find on epithelium that is exposed to extensive frction
Keratin. For protection
Classification of epithelium is based on
Morphology (cell layer, shape, special modifications)
Name of epithelium is based on
Specific site in the body
SSE that lines blood vessels, lymphatic vessels, and heart is
endothelium
Glyococalyx
Protective layer of glycoproteins
Goblet cells
- Secrete
- derived
Single cell gland
- secrete mucus–>mucinogen (unhydrated precursor of mucus)
- derived from endoderm
What composes junctional complex
tight junctions (zonular occludens)
zonular adherens
desmosomes (macula adherens)
gap junctions (nexus)
Where can you see mitosis?
Basement membrane
Keratohyalin
Small basophilic granules in cytosplasm that are associated with aggregation of keratin filaments.
Transtional epithelum appearance is due to
Stretching