Epithelial Specializations Flashcards
What are the four basic cell types in organs?
-Epithelial cells (affected by microtubule targeted treatment)
Protection, absorption, secretion, and more
High mitotic activity - continuously dividing
-Connective tissue
Provide mechanical support & immune surveillance
Variable mitotic activity
-Muscle cells
Specialized for contractility
Mitotically STATIC with some exceptions (uterus- otherwise stem cells are needed)
-Nerve cells
Specialized to conduct electrical impulses
Neurons are mitotically static
What are the characteristics of epithelial cells?
Closely apposed and tightly adherent
* Cell-to-cell adhesion molecules
* Organized into sheets, tubules, or solid
organs
* Functional & morphologic polarity
(usually)
* Apical surface (faces free surface)
* Basal surface (sits on connective tissue)
* Lateral surface
* Avascular (no blood vessels)
* Supported by connective tissue
(Basement membrane)
Where are epithelial cells located
-Cover Body surface (e.g. skin)
-Line closed cavities
*Blood vessels and lymphatics (endothelial cells)
*Body cavities (mesothelial cells)
-Line body tubes
*Alimentary tract
*Respiratory tract
*Gastrointestinal tract
-Form secretory solid organs, glands, and ducts
What are the epithelial specializations of the APICAL Surface?
-Glycocalyx
-Microvilli
-Cilia
- motile
- primary (monocilia)
-Stereocilia
What type of cell line blood vessels and lymphatics*****?
ENDOTHELIAL CELLS, there is LUMENNNNNNN there (so endothelial)
What type of cells lign the body cavities?*****
mesothelial cells
What is glycocalyx and what is their function?and what stain picks up its carbohydrates?
-Gelatinous glycoprotein-polysaccharide (protein) covering the cell membranes of some epithelia; more prominent on apical surface
.
*protection
*permeability barrier
*controls access to cell membrane receptors
*control of fluid and molecule exchange
*cell-cell recognition
*cell adhesion
PAS (PERIODIC ACID SCHIFF)
What are microvilli and what are their function? what stain recognizes them?
-Most numerous and best developed in gastrointestinal & renal epithelial cells
*Increases surface area for absorption or secretion
*May contain specific enzymes
NOT RESOLVABLE in light microscope except AS BRUSH BORDER (like watercolor brush stroke)
What are Microvilli attached to?
- TERMINAL WEB
-In TW, thin filaments (actin) and thick filaments (myosin) run horizontal to the distal surface and perpendicular to the microvilli bundles.
Where are motile cilia (9+2) located?
- THEY BEND
-Resolvable in light microscope with an uneven appearance
*longer, more distinct than microvilli
LOCATED:
-Upper respiratory tract (nasal passage, trachea, bronchi)
-Reproductive tract: oviduct, sperm
Cillia=microtubules= dyneins+ kinesis
How do cilia and flagella bend?
- the movement of dynein motor proteins along microtubule doublets cause them to bend
Where are mono cilia (primary cilia) and what is their function
-IMMOTILE
One per cell – requires electron microscopy
-Mechanoreceptors that monitor fluid flow (open gate on mono cilia when prompted)
THAT IN RETURNS CONTROLS DEVELOPMENT OF THE FOLLOWING:
(kidney, pancreas, liver)
*Kidney: fluid flow bends cilia triggering a signal cascade
*Defect leads to polycystic kidney disease (in cats)
**Specialized primary cilia found in sensory organs (inner ear, retina & nose)
What are stereo cilia and where are they located?
-Elongated, non-motile (MICROVILLI ON STEROIS)
o More like microvilli
o Core of ACTIN filaments
-Much longer than cilia and more
uniformly distributed
-Connections between bases of
adjacent stereocilia give a clumped
appearance
-present in male reproductive tract and inner ear and are MECHANO SENSORY-allowing signal (allows hearing)
within embryonic tissue development, what do Endoderm, Mesoderm, and ectoderm form respectively?
-ECTODERM form SKIN
-MESODERM form MUSCLE, BONE, BODY CAVITIES— no cytokeratin
-ENDODERM form blood vessels and lymphatics
what are the epithelial specializations of the LATERAL surface
-zonula occludens
-zonula adherens
-macula adherens
(aka desmosome)
-gap junctions
What are zonula occludens? and what are their function in epithelial cells?
-tight junctions that work as a selective permeability barrier
-Limits movement of molecules through intercellular space
-Prevent movement of essential integral proteins
Tissue dependent variation in tightness
Brain: very tight junctions
Kidney: somewhat leaky junctions
Anchor proteins link to actin microfilaments
Anchor proteins in epithelium link to actin microfilaments
What are zonula adherents?
-ADHESION belts that are responsible for adhesion between cells
-located BENEATH zoned occludes
- numerous filaments are continuous with the ACTIN FILAMENTS of terminal web.
What are Desmosomes (macula adherent) ?
-spot weld/ button between cells
-strong adhesions mediated by INTERMEDIATE FILAMENTS
-important in tissue exposed to STRONG, SHEARING FORCES
(EPIDERMIS/ CARDIAC MUSCLE)
-CELL-CELL COMMUNICATION
-ARTIFACTS HAPPEN bc when cells pull apart during processing, the DESMOSOMES hold cytoplasm from adjacent cells and cause spines between them
What is the order of the tripartite junctional complex found between most glands and cavitary organs?
-Zonula Occludens
-Zonula Adherens
-Macula Adherens
tightest junction nearest to lumen of organ*
What are Gap junctions (macula communicans)?
-Complex of proteins creates permissive communicating channel
-Facilitates transcellular movement of:
*Metabolites/nutrients
*2nd messengers (IP3, cAMP)
*Ions (chemical synapse)
Closure triggered by Ca
A few select locations
Cardiac & smooth muscle
Bone & teeth
What are the epithelial specializations of the basal surface?
-hemidesmosomes
-basal lamina
-basal invaginations
-basal evaginations
What are hemidesmosomes?
-Focal adhesion (½ of a desmosome) on basal membrane of some epithelial cells
-Epithelium: links cytoplasmic intermediate filaments to basement membrane
-WBC: helps them bind to endothelium and leave blood stream.
What is the basal lamina?
-a.k.a Basement membrane
-Physical support for epithelia - may be discontinuous
-Guide for cell adhesion and migration (ex:epithilium migrate when there has been a cut)
-Role in cell signaling
-Filtration barrier (kidney)
what are the components of basal lamina (basement membrane?
-Form wire network
-Collagen
(type IV; some type III)
Glycoproteins
-Laminin
Fibronectin
-Proteoglycans
large molecules; sugars attached to protein core
What are the histologic classifications of epithelial cells?
- SIMPLE (one Layer)
2.STRATIFIED (many layers)
what are the shapes of epithelial cells
how do you figure out the shape of stratified epithelial cells?
-Look at the shape of the TOP layer
What are other descriptor os squamous epithelial cells?
-Nonkeratinized (NUCLEI all the way to the TOP) (presents in protected cells- don’t need that much protection)
-karatenized (DEAD cells scale the SURFACE) present in stronger parts (SKIN)
how yo you identify pseudostratified columbar? THERE IS NO STRATIFIED COLUMBAR IN CLASS/EXAM!!!!!!!!
long cells have multiple levels , but when looked at closely have columbar cells that are squiggly
-All reaching to basal membrane
-Typically has CILIA
-found in upper respiratory track and male reproductive system
example of simple columbar that was cut in a weird plane
What do transitional epithelium (urothelium) look like?
Large surface cells [umbrella cells] specialized to expand or contract; often binucleate.
How does secretion (FROM GLANDS) reach target?
Exocrine type – secrete via ducts opening to a surface
* Endocrine type – secrete into surrounding blood
vessels
What are the classifications for endocrine glands?
Multicellular, simple (unbranched duct)
e.g. dermal sebaceous and sweat glands
Multicellular, compound (branched duct)
Large glands with lobes and lobules
e.g. in pancreas
what does a compound gland look like?
What are the classification of exocrine glands in terms of shape?
-Tubular
Glands and ducts look tubular with parallel sides and a wide lumen
Acinar
-Ducts are tubular but glands have a spherical gland shape with a bulbous end
how can the tubular glands of the EXOCRINE GLANDS be further classified?
what do Acinar glands of the ENDOCRINE glands look like?
Acinus = Latin for berry
Gland terminates in a round cluster of secretory epithelial cell usually with a narrow lumen
Examples:
Exocrine pancreas
Salivary glands
Tracheal glands
what are the classification of exocrine glands in terms of secretory product?
Serous
Watery, opalescent secretion composed of water and proteins
Pink grainy cytoplasm, roundish nuclei
Mucus
Viscous product composed primarily of water and mucin
Pale staining cytoplasm, nuclei pushed against basal membrane.
Cells known as mucous cells
Mixed seromucus glands
What is the only unicellular gland?
Goblet cell
-Produce mucus
-Found in trachea, intestine
Which of these sections is from the respiratory tract?
B- has CILIA and nuclei are pseudo stratified
