Exam #1: Epithelial Tissue I & II Flashcards
What are the three cell domains of the epithelium?
- Apical
- Lateral
- Basal
What is the epithelial sheet anchored to?
Basal Lamina
What is the only type of epithelium that is vascular?
- Stria Vascularis
- Located in the cochlear duct
- Produces endolymph
Simple Epithelia
One layer w/ all the cells residing on the basement membrane
Stratified Epithelia
- 2 or more strata (layers)
- Only the deepest cells reside on the basement membrane
Pseudostratified Epithelia
- All cells reside on the basement membrane
- Nuclei are located at various levels giving a stratified appearance
Transitional Epithelia
- Urothelium
- Transitions from cuboidal (relaxed) to sqamous when bladder is distended
Keratinized
Outer layer of cells is dead
What are the functions of simple squamous epithelia?
1) BBB
2) Filtration
3) Exchange
Where is simple squamous epithelia found?
- Blood vessels (lining, called endothelium)
- Mesothelium (abdominal cavity)
- Alveolus
What are the functions of simple cuboidal epithelia?
1) Absorption
2) Secretion
3) Barrier
4) Conduit
Where is simple cuboidal epithelia located?
- Thyroid Follicles
- Renal Tubules
- Ducts of glands
What are the functions of simple columnar epithelia?
1) Absorption
2) Secretion
3) Barrier
Where is non-ciliated simple columnar epithelia located?
- Stomach
- Intestines
Where is ciliated simple columnar epithelia located?
Uterine Tubes (helps transport ovulated oocyte)
What are the functions of ciliated pseudostratified columnar epithelia?
1) Secretion
2) Absorption
3) Barrier
4) Transport
Where is ciliated pseudostratified columnar epithelia located?
- Trachea (will have very thick basement membrane)
- Bronchi
- Ducts of male reproductive system (steriocilia)
What are the functions of stratified squamous epithelia?
1) Barrier
2) Protection
Where is nonkeratinzed stratified squamous epithelia located?
- Esophagus
- Distal anal canal
- Vagina
Where is keratinized stratified squamous epithelia located?
Epidermis
Keratin pearls
- Hallmark of a squamous cell carcinoma
- Whirls of keratin deep in the tissue involved
Stratified Cuboidal Epithelium
- Not common
- ## Present in ducts that are in transition from one epithelial type to another
Where is transitional epithelium located?
- Ureters
- Bladder
- Urethra
What is the function of transitional epithelium?
1) Barrier
2) Protection
3) Distension
Transitional Cell Carcinoma
- Stages 0-IV
- Penetrates into the outer layers of the bladder wall
- The deeper the penetration the higher the grade
Metaplasia
- Epithelium changes from one type to a type that is not normally present (can revert back)
- E.g. Trachea & smoking
- Pseudostratified columnar epithelium turns into stratified squamous, which is more protective
- Simultaneous loss of mucous clearance
- Can go back when one stops smoking
Barett’s Esophagus
- GERD
- Constant reflux causes a metaplasia in the distal esophagus
- Stratified squamous turns into protective intestinal type cell with mucous production
- Pre-cancerous
- V. Difficult to reverse
What are the different types of Cilia?
1) Motile
2) Primary (Non-motile)
3) Nodal
Microvilli
- Extensions of the plasma membrane
- Actin microfilaments insert into terminal web
- Cross-linked by actin binding proteins & myosin
- Myosin II present in terminal web, which is motile & causes microvilli to change direction
Stereocilia
- DO NOT RESEMBLE CILIA
- Rather, resemble microvilli– called stereovilli
Motile Cilium
- 9+2 array of MTs
- Contain Dynein ATPase
- Two individual MTs in center
Basal Body
- Base of Motile Cilium
- 9x3 of MTs (like centrioles) NOT 9+2
Primary Monocilium
- Different MT array 9 doublet WITHOUT 2 in center
- Chemosensors, osmoreceptors, & mechanoreceptors
- E.g. kidney & fibroblast
Primary cilium & polycystic kidney disease
- Polycystin 1&2 are involved in Ca++ signaling
- Mutation disrupts signaling and changes orientation of mitotic spindle
- Results in cyst formation
Nodal cilia
- Motile, but MT array is similar to non-motile (9 doublets without two central)
- Direct fluid flow in primitive node from right to left, establishing left/right axis in body
Situs Inversus
- Caused by defect in nodal cilia
- Flipping of internal organ orientation
Microvilli fed state
Spread apart by the action of myosin II in the terminal web
Microvilli in starvation state
Close together by the action of myosin II in terminal web
Brush Border
- Well developed microvilli
- Contains a carbohydrate coat that is Pas + (glycocalyx)
Stereocilia/ stereovilli
- Elongated microvilli
- Actin microfilaments
- Actin binding proteins
- Terminal web
Where are stereocilia located?
- Male reproductive ducts
- Hair cells in the inner ears (sensory epithelium)
Kartagener’s Triad
1) Chronic sinusitis
2) Bronchiectasis
3) Situs inversus
- Caused by defective cilia
Zonulae Occludens
- Tight Junctions
- Most apical junctional complexes
- Go around the circumference of the cell
Zonulae Adherens
- Just basal to the zonulae occludentes or tight junctions
- Go around the circumference of the cell
Maculae Adherens
- “Spot connection” known as desmosome
- Basal to the Zonula Adherens
Gap Junctions
- Also called nexus
- Communicating junctions
- Pores when open
Hemidesmosomes
- Base of the cell
- Connect the cell to the underlying basal lamina
General Structure of a Junctional Complex
1) Cytoskeletal Elements
2) Intracellular Anchor Proteins
3) Cell Adhesion Molecule (CAM)
Intracellular Anchor Proteins
Link between cytoskeletal element & CAM
Structure of the Zonulae Occludens
1) Cytoskeletal Element= Actin
2) Intracellular Anchor Proteins= ZO proteins (1, 2, &3)
3) Cell Adhesion Molecule (CAM, transmembrane)= Occludin & Claudin, form a tight connection between cell membranes
H. Pylori & Tight Junctions
- Disrupt tight junctions in stomach
- Epithelial cells more susceptible to injury
What are the different disease states that can be caused by claudin mutations?
- Loss of Mg++ in urine
- Brain Cancer
- Deafness
What part of the tight junction does the Cholera toxin disrupt?
ZO protein, intracellular anchor protein
Occludin/ Claudin Ratio
- High Occludin= non-permeable (E.g. BBB)
- High Claudin= permeable
How do tight junctions form functional polarity?
- Restrict the movement of membrane domains
- E.g. Na+/ GLUT transporter
Zonula Adherens Structure
1) Cytoskeletal Elements= Actin
2) Intracellular Anchor Proteins= Catenin & Vinculin
3) Cell Adhesion Molecule (CAM)= E-Cadherin
Macula Adherens Structure
Desmosome
1) Cytoskeletal Elements= Intermediate Filament
2) Intracellular Anchor Proteins
3) Cell Adhesion Molecule (CAM)= Desmocollin & Desmoglein
Stratum Spinosum
- Pink spinous like projects
- Acidophilic
- Points of contact between cells
Pemphigus
- Blistering skin disorder
- Caused by autoantibodies against desmoglein (CAM of desmosome)
Focal Adhesions Structure
1) Cytoskeletal Elements= Actin
2) Intracellular Anchor Proteins= Vinculin, Paxillin, & Talin
3) Cell Adhesion Molecule (CAM)= Integrin
Integrin
CAM that makes focal contacts with ECM (Fibronectin)
Hemidesmosome Structure
1) Cytoskeletal Elements= Intermediate Filaments
2) Intracellular Anchor Proteins
3) Cell Adhesion Molecule (CAM)= Integrin, Type XVII
Bullous Pemphigoid
- Blistering Skin Disorder
- Caused by autoantibodies against Type XVII collagen (CAM of Hemidesmosome)
Gap Junction Structure
- 6x Connexins (transmembrane) form a Connexon
- Connexons oppose each other
Where are gap junctions found?
- Cardiac muscle cells
What are the consequences of mutations in connexons?
- Female infertility
- Neuropathy
- Deafness
- Congenital Cataracts
- Cardiac Arrhythmias
Stippled Epithelial Cells from Vagina
Bacterial Vaginal Infection
What is the first step in malignant transformation & metastasis?
Invasion of basement membrane
What does invasion of basement membrane require in malignancy?
Loosening of junctional complexes
Loosening of junctional complexes
- Cadherin (CAM) loss is most common
- Catenin mutation
- Integrin mutation
