Epithelial Tissue Flashcards
What are the different types of epithelia?
Surface (lining) epithelia
Glandular Epithelia
Germinal Epithelia
What is the function of surface (lining) epithelia?
Form external surface - body and many organs
Form internal lining of hollow tubes - ducts, vessels, tracts
Form internal lining of body cavities
Specialized surface epithelia contain touch receptors and may contain receptors for senses
What is the function of glandular epithelia?
Secrete glandular products exocrine and endocrine
What is the function of germinal epithelia?
Generate gametes and foster their maturation/development (ovaries, testes only)
What epithelia are highly active both metabolically and synthetically?
Glandular and germinal
All epithelia have high ___
Turnover
Where do most tumors derive from?
Epithelial Tissue
What are 3 benign epithelial tumors?
- Adenomas
- Papillomas
- Polyps
What are defining characteristics of epithelia? x 7
Highly cellular - high cells to ECM ratio
Basement Membrane (BM)
Polarity: Apical, Lateral, and Basal Domains
Cell Junctions
Avascular
Intermediate Filaments made of keratin
Often have apical surface modifications - cilia
What is the basement membrane of epithelium?
Interface between epithelium and underlying connective tissue. Most of ECM of epithelia
What are the functions of the basement membrane?
Provides structural support
Physical Barrier
Metabolite diffusion
Helps regulates epithelial growth and differentiation
What are three layers of the basement membrane?
Lamina Lucida
Lamina Densa
Lamina fibroreticularis
What are the characteristics of the lamina lucida?
Multi-adhesive glycoproteins - laminins
Electron lucent
What are the characteristics of lamina dense?
Collagen IV - mesh forming collagen, abundant in basement membrane
GAGs
Electron dense
What are the characteristics of lamina fibroreticularis?
Collagen III fibrils - reticular fibers
Collagen VII - anchoring fibrils. Helps anchor lamina densa to underlying connective tissue
Collagen I - small amounts
What is the basal lamina? What is its function?
Lamina lucida and lamina densa only
Flexible support for overlying epithelium. Anchors cells to basement membrane. Molecular filter
How does the lamina lucida stain?
Laminins - PAS positie
How does the lamina densa stain?
Collagen IV - IHC and PAS positive
Sulfated GAGs - metachromatic and PAS+
How does the lamina fibroreticularis stain?
Collagen III - Argyrophilic and PAS positive
Collagen VII
Collagen I - weakly acidophilic
What are simple epithelia?
1 layer of cells
What are stratified epithelia?
2 or more cell layers
What is pseudostratified epithelia?
Have 1 layer but looks like more than 1 layer
What are the functions and locations of simple squamous epithelia?
Functions - Diffusion, form linings, and secrete serous fluid for lubrication
Locations: Lining body cavities, vessels, alveoli, Bowman’s capsules, and heart chambers
What is the structure and what are the functions and locations of simple cuboidal cells?
Square - as tall as it is wide
Functions - absorption, secretion, and conduits (forms wall of small ducts)
Locations - Ducts in exocrine glands, renal tubes, thyroid follicles
What is the structure, function, and location of simple columnar epithelia?
Appear like columns, taller than they are wide
Functions - absorption, secretion, conduits
Locations (noncilia) - stomach, intestines, gallbladder
Locations (cilia) - Oviducts
What is the structure, function, and location of stratified squamous?
2 or more layers with cells near basal domain being more cuboidal and get flatter as you go towards apical domain.
Functions - barrier and protections and abrasion
Locations (nonkeratinized) - esophagus, vagina, cervix, distal anal canal
Locations (keratin) - epidermis
What is the function and location of stratified cuboidal and columnar epithelia?
Function - barrier and conduit
Locations - largest ducts of exocrine glands, anal-rectal junction
What is the structure, function, and location of transitional (urothelium) epithelia?
Appear pillow-like
Function - stretching and urine-proof barrier, proteins on surface allow it to stretch
Locations - Ureters, urinary bladder, urethra
What is the function and location of pseudostratified columnar?
Functions - secretion, absorption, barrier, conduit
Locations - trachea, bronchi, and ducts of male reproductive system
What are examples of apical surface specialization in the apical end of epithelial tissue?
Keratinization
Goblet cells
What are examples of apical surface specialization in the apical end of individual cells?
Cilia
Microvilli
Stereocillia
Where does keratinization occur and how do they appear in TEM?
Stratified Squamous
Keratinized tissue will have no nuclei in apical most layers and apical layers appear flakey
What are goblet cells? What is their function and where are they located?
Goblet cells are modified simple columnar cells
Function - Secrete mucinogen
Locations - Respiratory tract, Intestinal tract, conjunctiva of eyelid
What are the 3 kinds of cilia?
Motile (M)
Primary (P)
Nodal (N)
What is the function, location, and movement of motile cilia and flagella?
Function - transport (of eggs, mucus, ) and movement (sperm)
Locations - many
Movement - Active, back and forth, synchronous waves, flagella undulate
What is the structure of cilia?
9x2 array with 2 microtubules in middle
Linker proteins
Microtubules - tubulin
Motor proteins - dynein
Basal body - 9x3 array that stabilizes microtubules and secretes tubulin
Striated rootlet - anchors basal body into cytoplasm
What is the structure, function, location, and movement of monocilia?
9x2 microtubule array with no motor proteins. 1 per cell
Function - sensory antenna, role in tissue morphogenesis
Location - nearly every cell
Movement - no active movement, passive bending in fluid
What is the structure, function, location, and movement of nodal cilia?
Structure - 9x2 array with motor proteins (dynein)
Function - helps develop R to L asymmetry of internal organs in the embryo by circulating morphogens (Shh, retinoic acid)
Location - Embryo- gastrulation from primitive node
Movement - Active. Rotate counterclockwise
What is the function, location, and movement microvilli?
Striated border in LM
Function - increase surface area for absorption
Locations - most epithelial cells -> more obvious in LM in kidney tubules and intestine
Movement - nonmotile, can be moved passively by contracting the terminal web
What is the structure of microvilli?
Core of each microvillus has 20-30 vertical and parallel actin (thin) filaments anchored by proteins (fimbrin, espin) to maintain parallel oritentation.
Anchored to cell membrane at tips and sides by villin and myosin I.
No motor proteins.
Myosin II in terminal web - contracts and draws base close together, tips spread, and fluid flow increases between microvilli
What is the structure, function, location, and movement stereocilia?
Structure - Very long microvilli
Function - absorption (male reproductive tract), mechanoreception (ear)
Locations - epididymis, proimal ductus deferens, inner ear
Movement - nonmotile, no motor proteins, no myosin, can be moved passively by fluid flow or fluid vibration
